50 PRESERVATION 

BRIEFS 

Lightning Protection 

for Historic Structures 

Charles E. Fisher 

National Park Service 

U.S. Department of the Interior 

Technical Preservation Services 

Introduction 

The loss of historic buildings as a result of lightning 

strikes makes local front page news every year. 

Lightning strikes make no distinction between historic 

properties and other types of structures. Historic 

barns, churches, museums, homes, stores, factories, 

lighthouses, schools, and other buildings, as well 

as structures such as tall monuments, may be at 

unnecessary risk of damage or loss as a result of a strike 

by lightning. 

The insurance industry reports that 5% of all claims 

are lightning-related in the U.S., with annual building 

damage estimated as high as $1 billion according 

to Underwriters Laboratories, Inc. Certain types 

of structures are especially susceptible to damage, 

particularly churches where lightning accounts for 

nearly one-third of all church-building fires each year 

(Fig.1). 

Lightning protection systems in the United States date 

back to colonial days and the time of Benjamin Franklin. 

Figure 1. Saved from a wrecking ball and renovated in 1970 by a 

70-person congregation, the Sanctuary of the Holy Spirit church 

was the oldest operating place of worship in Winder, Georgia. 

Just five years later, the 1904 church was destroyed by fire, having been struck by lightning during a violent thunderstorm. 

Photo: Paul Brennen/shutterstock.com.

Old systems that have survived in whole or in part on 

historic structures may be historic features in their own 

right and deserve preservation. Such historic lightning 

protection systems may still be operating properly 

or can be repaired and upgraded. Some old systems 

simply are too deteriorated, incomplete, or archaic to 

repair and make fully functional, raising the question 

whether they should be saved in place or removed 

in whole or in part for safety. For historic structures 

that have none and are located in areas that are prone 

to lightning strikes, or are of special significance and 

deemed irreplaceable, a modern lightning protection 

system may merit installation. 

This Preservation Brief is designed for owners, property 

managers, architects, contractors, and others involved 

in the preservation of historic structures. It includes 

information on the care, maintenance, and repair 

of historic and older lightning protection systems; 

discusses factors to consider in assessing the need for 

a lightning protection system where none exists; and 

includes historic preservation guidance on the design 

and installation of new systems. 

What Causes a Lightning Strike? 

During violent storms, ice particles form in the 

atmosphere and collide with each other, resulting in a 

transfer of negative ions among ice particles. Smaller ice 

particles or crystals tend to lose negative ions, becoming 

positively charged, and are then carried through 

updrafts to the upper levels of the clouds. Heavier ice 

particles gain negative charges and settle below within 

the clouds. Lightning is produced when these oppositecharged cloud values create high electric fields—nature’s 

way of reducing the imbalance. 

The more tyical negative electrical charges travel 

in leaders or about 150-foot segments. During 

thunderstorms, bursts of negative charges extend closer 

to the ground. Under such conditions, higher exposed 

objects on the ground in turn may send positively 

charged leaders upward. When two oppositely charged 

1 
leaders connect, a massive stroke of current travels to the 

ground along one or more paths of low resistance (Fig. 

2). Usually several strokes occur in rapid succession, 

appearing to the human eye as a single lightning bolt to 

the ground. 

The mechanical force of this enormous energy flow can 

have a blast effect on a structure, exploding, for example, 

a large chimney, parapet or corner of a building. Heat up 

to 50,000°F generated along its path through wood and 

other building material can result in fire and considerable 

damage. Besides the risk of injury and loss of human life, 

irreparable damage to cultural resources can occur as a 

consequence of a lightning strike. 

Figure 2. Positive and negative electrical charges occur naturally 

under certain weather conditions, causing imbalances. When a 

downward stream of strong negative charges in the air meets with a 

shorter leader of positive charges that have accumulated on, and are 

arising from a building, tree, or object, the resulting flash is lighting. 

The drawing shows a building with a lightning protection system 

providing a safe path for the lightning to travel to the ground rod 

beneath the soil. Courtesy: Cornell Agricultural Safety and Health 

Program, Jim Houghton, illustrator. 

Components of Conventional 

(Traditional) Systems 

The function of a conventional lightning protection 

system is not to prevent lightning from striking a 

structure, but rather to provide a specific path of low 

resistance for lightning current to travel to the ground 

that will result in no damage or injury. Since the 18th 

century, it has proven effective. 

There are three principal components of a conventional 

system: the lightning rod (air terminals), conductor, 

and ground (Fig. 3). Besides these three traditional 

components, a system includes the bonding of other 

metal features of a building considered to be a lightning 

hazard and, particularly today, the use of surge 

suppressors. 

The lightning rod (air terminal) typically is the most 

prominent visual component of the system, and in 

its older, more traditional form could appear as an 

ornamental feature on a structure. In most cases, rods 

are used at prescribed locations and distances, joined 

together by connecting wires to conductors. In today’s 

contemporary applications, the lightning rods are very 

simple in design, most often consisting of utilitarian air 

terminals measuring 10 to 12 inches in height, although 

certain conditions may require taller terminals. By 

contrast, lightning rods of the late 19th and early 20th 

century were usually taller, typically four to six feet in 

height, and often had a more decorative appearance 

with embellishments, such as a weather or directional 

vane or glass balls (Fig. 4). 

Each lightning rod must be attached to the grounding 

system through horizontal roof cables and vertical 

conductors. Cables are used to join individual lightning 

rods, most often in loops or series, and then in turn 

attached to two or more main conductors running 

to metal grounds. One major exception occurs in 

structures with structural steel where, under certain 

conditions, lightning rods may be tied directly to 

the steel frame. The steel needs to be continuously 

connected, since it must serve as the conductor and be 

tied to the ground for the lightning protection system to 

be complete. 

Cables vary by weight and number of strands of wire, 

with heavier cables required for use on structures taller 

than 75 feet. The number of required main conductors 

depends in part on the perimeter length of the structure. 

Even on smaller historic buildings, two or more down 

conductors are needed to help diffuse the electrical 

charge from a lightning strike along its path to the 

ground. 

The grounding system usually consists of long solidmetal grounding rods driven into the soil, usually to 

a depth of at least 10 feet, to which the down cables 

Conductor 

Lightning rod 

(air terminal) 

Ground rods 

Cable under eave 

Figure 3. Conventional lightning protection systems consist of three 

principal components: the lightning rods, which are connected by 

cables to the system; two or more down conductors, which connect 

the lightning rods to the grounding system; and the ground rods. 

Adapted from a 1950 U. S. Department of Agriculture illustration. 

2 
Figure 4. The most common historic lightning rods of the late 19th to 

early 20th century consisted of a lightning rod or air terminal, glass 

Bayonet-style tip 

Lightning rod 

Glass ball with 

metal collars 

Stand 

ball, and a stand attached to the roof. These rods tended to run four 

to six feet in height and were quite prominent on the roof. Courtesy: 

Charles Fisher Collection. Drawing: New Old Products, Inc. 

are attached at one end using special connectors. On 

buildings today, the most commonly used grounding 

rod is an 8 to 10-foot copper, copper-clad steel, or 

stainless steel rod. Depending on the soil condition, 

depth of soil, and presence of bedrock near the surface, 

additional grounding rods may be needed or may need 

to be placed in a different manner. In some cases, an 

alternate grounding system is needed altogether. Other 

grounding systems, such as those used for electrical, 

telephone service, or a satellite dish, need to be 

connected to the lightning protection ground. 

Whenever a structure has metal gutters and 

downspouts, metal roof vents, large metal awnings or 

other conductive objects that contribute to lightning 

hazards, these objects need to be bonded to the lightning 

protection system. On the inside of a building, copper 

and galvanized-iron water lines as well as steam or 

hot water heating systems with metal pipes must be 

connected to the ground conductors. Bonding of these 

objects to the lightning protection system through use of 

metal conductors deters an electrical charge caused by 

a lightning strike from seeking alternative paths to the 

earth. Bonding also deters side flashing whereby current 

otherwise could jump from components of the lightning 

protection system to nearby conductive objects. As it 

is impractical to bond all metal objects, such as each 

steel or aluminum window on a building, only objects 

considered more hazardous are usually bonded to the 

lightning protection system (Fig. 5). 

Lightning damage to a structure can occur from 

lightning striking distant or nearby power lines. 

Resulting power surges can affect not only sensitive 

electronic equipment, such as computers and security 

systems, but also common household items such as 

land-line telephones, electric appliances, and home 

entertainment centers. There is always the human safety 

risk as well from such power surges, thus the adage stay 

off the phone (land-line) during an electrical storm. For 

safety and to protect against excess voltage, different 

types of surge protective devices (SPD) are used. 

History 

Lightning strikes have mystified man since the 

beginning of time. While it has been observed long ago 

that lightning tends to strike tall objects, not until the 

mid-1700s did there emerge a general understanding of 

lighting and how to prevent damage to structures. 

In the late 1740s and early 1750s, interest in static 

electricity led Benjamin Franklin to investigate the 

nature of electricity, including lightning. In a series 

of letters to Peter Collinson, a Fellow of the Royal 

Figure 5. Bonding of conductive material on a structure to the 

lightning protection system is important to deter damage from side 

flashing. In this drawing, the metal downspout has been bonded to 

the down conductor. Unless bonded, metal gutters and downspouts 

provide a good path for an electrical discharge to side flash and cause 

damage to a building. Drawing: English Heritage© 

3 
Society of London, Franklin described his experiments 

and observations on electricity. Published together in 

London in 1751, these letters soon led Thomas-Francois 

Dalibard and a colleague, collaborating in Paris, to 

experiment with a tall metal rod that was insulated in 

the ground. Their experiment in May 1752 was based 

on a proposal described by Franklin in his letters and 

succeeded in drawing sparks, helping to confirm that 

thunderclouds are electrified.

Franklin probably conducted his famous kite 

experiement shortly thereafter, unaware at that point of 

the earlier french experiment. He did publish in his Poor 

Richard’s Almanac a description of a lightning protection 

system in 1753, and, in the same year, he was awarded 

the prestigious Copley Gold Metal by the Royal Society 

of London for his “curious experiments and observations 

on electricity.” Franklin had envisioned a means to 

protect a structure from being struck by lightning. Yet 

he soon came to realize that rather than preventing 

strikes, lightning protection systems functioned to 

provide a safe path of travel for the electrical discharge. 

In a letter written in 1762, Franklin provided a detailed 

description of a lightning protection system: 

Prepare a steel rod 5 or 6 feet long, half an Inch thick at its 

biggest End, and tapering to a sharp Point; which Point 

should be gilt to prevent its rusting. Let the big End of the 

Rod have a strong Eye or Ring of half an inch Diameter: 

Fix this Rod upright to the Chimney or highest Part of the 

Building, by means of Staples, so as may be kept steady. Let 

the pointed End be upwards, and rise three or four Feet above 

the Chimney or Building that the Rod is fix’d to. Drive into 

the Ground an Iron Rod of about an Inch Diameter, and ten 

or twelve feet long, that has also an Eye or Ring in the upper 

End. It is best that the Rod should be at some Distance from 

the Foundation of the Building, not nearer than ten feet, if 

your Ground will allow so much. Then take as much Length 

of Iron Rod of about half an Inch Diameter, as will reach from 

the Eye in the Rod above to that in the Rod below; and fasten 

it securely to those Rods, by passing its Ends thro’ the Rings, 

and bending those Ends round till they likewise form Rings. 

This Length of Rod may be in one or several Pieces. If in 

several, let the Ends of the Pieces be also well hooked to each 

other. Then close and cover every Joint with Lead...that there 

should be considerable Quantity of metalline Contact between 

Piece and Piece: For if they were only hook’d together, and 

so touch’d each other but in Points, the Lightning in passing 

thro’ them might melt and break where they join. The Lead 

will also prevent the Weakening of the Joints by Rust. To 

prevent the Shaking of this Rod by the Wind, you may secure 

it by a few Staples to the Building till it comes down within 

ten feet of the Ground, and thence carry it off to your Ground 

Rod; near to which should be planted a Post, to support the 

Iron Conductor above the heads of the people walking under it. 

In such a remarkable short time, the basics of today’s 

lightning protection system for ordinary structures were 

in place, and this invention became popularly known as 

the Franklin system. It is still the most commonly used 

lightning protection system for structures throughout 

the world. Yet even Franklin acknowledged that he and 

his colleagues benefited from some luck in arriving so 

quickly at a lightning protection system that worked. 

In the second half of the 18th century, lightning 

protection systems were being installed from Boston 

to South Carolina. Yet this was a pioneering period 

and installations were far from common. Relying 

principally on descriptions provided by Franklin rather 

than first-hand experience, early installers operated 

with some trial and error. A number of the known early 

installations seem to have worked reasonably well in 

providing a safe path to the ground for the charge from 

an electrical strike, establishing for the first time that 

buildings could be protected from significant damage 

caused by lightning. 

When strikes to a protected structure occurred, damage 

to the lightning protection system still could result 

due to material deficiencies or improper installation. 

The “Electric Rod and Conductor” on Christ Church 

in Philadelphia was struck by lightning in June 1777, 

and rendered useless, although additional damage to 

the church seemingly did not occur. System damage 

reported at other buildings included the narrower 

pointed end of the rod at times melting and needing 

to be replaced; large metal staples securing a down 

conductor to the building dislodging and having to 

be reattached; and down conductor sections joined 

with hook and eye connections needing to be rejoined. 

Failures did occur as a result of undersized conductors, 

too few lightning rods, or lack of bonding to nearby 

metal objects, with resulting damage to buildings. It 

soon became clear that thicker conductors needed to be 

used; connectors needed to be more secured and, where 

possible, reduced in numbers; and, to avoid damage to 

foundations, more extensive grounding was required, 

depending upon soil condition. 

Evidence of late eighteenth-century installations have 

survived, including ones in Franklin’s hometown. A 

section of a hand-forged, wrought-iron conductor 

remains inside the stair tower of Independence Hall 

and would have been joined in a series of sections using 

hook-and-eye connections to form the down conductor. 

In Portsmouth, New Hampshire, a system was installed 

in 1767 on the Warner House, purportedly under the 

personal inspection of Franklin. An early system still 

survives on the Warner House, consisting of a long 

forged-welded piece of wrought iron (Fig. 6). A hookand-eye section of the ground has even survived and is 

now on display inside the building. 

In Europe, individuals that shared Franklin’s scientific 

interest in lightning protection helped to guide early 

installations on buildings. Despite some initial 

resistance on religious grounds, lightning rods soon 

appeared on many larger steeple-topped churches 

that had a propensity for being struck by lightning. 

4 
Figure 6. Lightning protection was installed on the Warner House 

in Portsmouth, New Hampshire, in 1767, purportedly under the 

personal inspection of Benjamin Franklin. An early system still 

survives on the building, consisting of a long forged-welded rod of 

wrought iron which extended up and above the chimney, comprising 

both the conductor and the air terminal. The conductor was joined 

to a separate, buried, iron ground rod by a forged hook and eye 

connector. Photo: Peter Michaud. 

Specialized applications soon followed such as for 

powder magazines and lighthouses. 

The installation by 1788 of the lightning rod on the dome 

of the Maryland State House in Annapolis, Maryland, 

represented a superb example of a building-specific 

application of the Franklin system. Still in place and 

fully functional, the historic wrought-iron lightning rod 

measures 28 feet in height and is 2 1/2 inches square 

at its base, its thickest point. This lightning rod has a 

decorative flare, including a weathervane toward the top 

and an acorn and pedestal at its base. As part of a 18thcentury renovation of the State House, Joseph Clark, a 

local architect and builder, erected the large dome and 

installed the lightning protection system, essentially 

using the Franklin system (Fig. 7). 

Despite no real manuals or standards, the early 

installations of the “Franklin rod” often proved effective. 

The experience derived from the early applications 

provided for an enlightened learning process. Still, there 

were failures that reinforced the belief among some that 

lightning rods actually attracted lightning and should 

not be used. 

By at least the early 19th century, individuals were 

marketing lightning protection, sometimes with little or 

no understanding of the working of the Franklin system. 

In 1824, the newspaper New England Farmer reprinted a 

letter attributing many of the recent failures to improper 

grounding and installation, stating that "Lightning 

rods are generally made and put up by persons wholly 

unacquainted with the principles of electricity and what is 

necessary to constitute a safe conductor." 

The letter goes on to provide instructions for proper 

installation that include the use of five or more points at 

the end of the rod, with points sharpened, tipped with 

silver, and elevated five or six feet above the highest part 

of the building. The writer specified that the rod (and 

conductor) should be at least 3⁄4 inch in diameter, with 

a continuous weld rather than linked where possible, 

and should terminate in the earth six or seven feet deep, 

set in a bed of two or three bushels of wet charcoal. 

The letter’s author noted that the expense for one rod 

on a two-story building would not exceed $50, still a 

considerable sum for the time 

Figure 7. The c. 1788 wrought-iron lightning rod on the Maryland 

State House dome measures 28 feet in height, 2-1/2 inches square at 

its base, and is pointed at its top. The rod passes through a decorative 

copper-paneled wood acorn that is nearly 4 feet in diameter. The 

acorn helps provide stability to the rod that, in turn, is secured 

to the pedestal or base of the acorn. While based on the Franklin 

system, this rod had a decorative flare, including a weathervane 

and ornamental base. Prominently located in Annapolis along the 

Chesapeake Bay, an area of frequent summer lightning storms, the 

building has been struck by lightning as recently as 2016, surviving 

undamaged. Photo by Niagara (Own work) [CC BY-SA 3.0 (http://

creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons. 

5 
According to the writer of the aforementioned letter, 

a single rod could protect a building for 20 feet on 

each side. Practice and observation were still guiding 

lightning protection work. 

As to the number and placement of the lightning rods, 

in 1823 the French Academy of Sciences carried out 

scientific investigations and proposed that the protection 

zone (cone of protection) of an air terminal was a radius 

twice its height. This provided a framework needed to 

determine the placement and number of air terminals. 

Included along with other detailed information in the 

report entitled “Instruction sur les paratonneres,” it was 

adopted by the French government and gained wide 

distribution in the United States. 

Information on how to protect structures from lightning 

was shared through newspapers and other means, 

reaching not only an urban audience but farmers as 

well. Because of their typical large size, location in 

open areas, and their use to store flammable hay and 

Figure 8. Church steeples, roof turrets, and chimneys were 

identified early on as being susceptible to lightning strikes. Finials, 

weathervanes, and other such ornamentation in these locations could 

often serve as lightning rods when connected to down conductors and 

grounds. The cupula on the Home Moravian Church in WinstonSalem, North Carolina, is an excellent example. Old Salem, Inc., has 

a number of Moravian buildings where early lightning protection 

systems are still in place. Photo: Sunni L. Goodson. 

grains, barns were recognized as being high risks for 

lightning strikes. A description for proper installation of 

lightning protection on a New England barn appearing 

in an 1848 issue of The Cultivator, a New England farm 

journal, reflects the prevailing view that multiple rods/

terminals and ground components were needed for most 

structures. 

In applying the conductor to the barn, begin at the northwest 

corner, by inserting the rod far enough into the ground to 

always insure its contact with the moist ground; carry it along 

the gable end to one end of the ridge pole, thence along the 

ridge pole to the other end of the ridge pole, thence along the 

other gable end, and down the southwest corner continuing 

into the ground....There should be a point at the eaves on each 

corner, and one on each side of the ridge pole, which should 

be covered with a coating of silver to prevent them from 

rusting.... 

It was common practice to locate the conductor on the 

outside since most systems were installed on existing 

buildings. However, installations that ran down the 

interior still were occurring. An 1847 article in the 

Burlington Gazette refers to a church in Philadelphia that 

recently was destroyed as a result of lightning: "It was 

provided with a conductor, but it ran down from the 

steeple inside the church!.... Such blundering ignorance 

as that of setting a rod to conduct the lightning into the 

house, we have seldom heard of. The precise reason for 

the failure was not stated." 

By the mid-19th century, the collegial nature of the 

pioneers of early lightning protection system was giving 

way to a competitive field and proprietary products. 

This change came at a time that fostered a growth in 

the marketing and sales of lightning protection across 

an expanding country. New lightning protection 

products and patented systems could get ready 

exposure as a result of the proliferation of newspapers 

and manufacturing trade catalogues. The New York 

firm of Marshall Lefferts & Brothers, manufacturers 

of galvanized and iron building products, marketed 

in their 1854 trade catalog the sale of galvanized iron 

for lightning protection systems that eliminated the 

degrading effects of rusting. Galvanized steel soon 

became, along with copper, the common materials used 

for components. 

About the same time, David Munson of Indianapolis, 

Indiana, purportedly invented a copper tubular spiral 

lightning rod, using copper because of its greater 

conductivity than iron. Made of sheet copper for 

affordability, the distinctive tubular spiral shape 

provided needed rigidity and became a popular type for 

years. In the 1858 publication, A Chapter on Thunder and 

Lightning, Their Causes and Effects, numerous advantages 

of the Munson Rod were touted, including that it did 

not rust. Conducting rods came in 5-foot lengths with 

connections made by lapping and wiring. The lightning 

rod also was made of copper with a terminal consisting 

of multiple points. 

6 
Figure 9. While plain round, 4-inch to 5-inch, color-glass lightning 

rod balls were most common in the late nineteenth and early 

twentieth centuries, balls also came in more decorative patterns and 

shapes such as the pleated round balls shown here in a variety of 

colors. Courtesy: Ferdinand Meyer Collection. 

By the 1850s, patents were appearing for glass insulators 

to secure cables running between air terminals and 

to secure the main conductors, enabling cables not to 

directly touch the building. The use of different styles of 

glass and porcelain insulators became common, all in a 

perceived effort to help direct a lightning discharge. 

With the Industrial Revolution, lightning protection 

products became mass-produced at affordable prices 

and shipped by railroad across the country. For the 

Franklin system, there now were many different parts 

that were available, such as specialized insulators and 

connectors, and a variety of shapes and sizes available 

for air terminals—some utilitarian and others quite 

decorative. 

The westward movement onto the Great Plains 

following the Civil War contributed to the Golden 

Age of lightning protection, as this included areas 

thought particularly prone to turbulent lightning. The 

long stretches of flat land made buildings on isolated 

farmsteads and grain storage containers along railroad 

sidings at risk. 

A 4-inch to 5-inch glass or ceramic ball became a 

common feature on many late 19th and early 20thcentury rods. They came in different patterns, colors, 

and shapes, with plain round colored balls dominating 

the landscape. Balls could be added to one or more of 

the lightning rods on the roof. Folklore has it that the 

balls were functional, designed to break when lightning 

struck, thus giving notice to the building owner that the 

system both had worked and should be inspected for 

any possible damage. In fact, the glass balls were purely 

decorative and intended to aid sales (Fig. 9). Additional 

decoration could be added to a lightning rod. Multiple, 

color glass balls and custom-crafted metalwork were 

two ways to accent it. A directional weather vane 

attached to one of the rods could in turn be embellished 

with colored glass or a metal animal or sailboat, 

reflecting the building use or owner’s interest.

The longer length of air terminals of this period typically 

required a sturdy stand for stability and attachment 

to the roof. The height of these stands varied widely, 

commonly ranging from one to three feet, meaning that 

the rods could measure as high as five feet or more. 

Three-foot stands with five-foot rods were the most 

prevalent size. The rod would usually have a point, 

with common shapes being a shell point or a bayonet 

shape. A rounded point was also available, though not 

as popular in the U.S. as in Europe. 

In an unusual application, and the first use of aluminum 

as part of a lightning protection system, a pyramidshaped cast of aluminum was selected to be the top of 

the Washington Monument and was installed in 1884. It 

was later augmented with lightning rod points (Fig. 10). 

By the 1880s, the commonly accepted measurement 

that helped determine the number and placement of 

Figure 10. When the Washington Monument was completed in 1884, 

it was capped with a pyramid made of aluminum. Though intended to 

function as a lightning rod, it proved within the year to be deficient. 

After lightning struck, a crack appeared under the top stone. As a 

remedy, copper rods attached to a copper band were placed around 

the base of the aluminum apex. The band was directly connected 

to the iron elevator shaft inside the monument that was part of the 

rest of the otherwise functioning system. The cap is the first use of 

aluminum as a lightning rod in the United States. Photo: Theodor 

Horydczak, Library of Congress. 

7 
lightning rods was a cone of protection served by each 

air terminal that had a radius of the circle at the base 

measuring the same height as the air terminal—a 1:1 

ratio. At such a ratio, more lightning rods were typically 

needed than was common prior to the Civil War. 

Scientific investigation in lightning protection continued 

throughout this time along with a growing need 

for professional standards. In Great Britain, "rules 

[recommendations] for those who installed lightning 

protection systems" was published in 1882 in The Report 

of the Lightning Rod Conference. One of the conclusions of 

the conference was that there was "no authentic case on 

record where a properly-constructed conductor failed to 

do its duty." 

In the United States, the National Fire Protection 

Association (NFPA) drew upon this report when 

they developed and published in 1904 Specifications 

for Protection of Buildings against Lightning. Though 

more conservative than the British report in terms of 

the ability of a properly installed lightning protection 

system to be effective in all cases, they concluded that 

lightning protection systems materially reduced the risk 

of fire loss to structures where prone to such damage. 

They noted that within a 5-year period, 3,842 dwellings, 

9,375 barns, 328 churches, and 59 ice houses had losses 

from fires due to lightning.

By 1908, the Underwriters Laboratories in the United 

States began the independent testing and certifying 

of certain lightning protection equipment. Such 

specifications and quality assurance were sorely needed. 

Traveling salesmen hawking lightning protection 

to unsuspecting homeowners, farmers, and small 

merchants too often were more interested in a quick sale 

rather than whether the system was properly installed. 

Figure 11. Two salesmen kits used by F. B. Renak operating out of 

Racine, Wisconsin. He was a reputable agent for several companies 

including the Security Lightning Rod Company, which offered a 

reasonable 10-year guarantee upon installation at a time when some 

unscrupulous companies offered essentially worthless hundredyear or lifetime guarantees. The kits included sectional pieces of a 

twisted copper conductor and two styles of air terminals--one was a 

bayonet shape and the other came in a shell or bullet shape. The shell 

terminals were available in several materials, including copper and 

nickel-coated copper. Courtesy: Charles Fisher Collection. 

In many communities, particularly in the Midwest, 

popular opinion turned against the salesman and the 

potential benefits of lightning protection. Ironically, 

this came at a time when there was general support 

among the scientific community as to the effectiveness of 

properly installed lightning protections (Fig. 11). 

Using scare techniques, parlor tricks to simulate 

lightning, testimonials, and flashy advertising, 

unscrupulous traveling salesmen frequently gave little 

consideration as to whether a structure was at risk and 

merited lightning protection. Going hand-in-hand 

with aggressive sales techniques was often over-priced, 

shoddy work. Where grounds were not functional or 

conductors improperly connected, flashy air terminals 

on a roof provided no protection and written guarantees 

were of little value. 

The "Golden Age" of lightning protection came to an 

end by the 1930s, a victim of the excesses of so many 

traveling salesmen and the Great Depression. Many 

of the lightning protection manufacturers ceased 

production. Fortunately, a few of the companies did 

survive and continue today to offer various traditional 

components that meet modern standards. 

In the decade after World War II, a number of important 

changes occurred. Aluminum became an alternative 

to the use of more expensive copper for terminals and 

cables and remains, along with copper, one of the 

two most common materials available today. Since 

aluminum is a better conductor than galvanized steel, 

does not rust, and was competitively priced, it generally 

replaced the use of galvanized steel. 

The older method of determining placement of air 

terminals—the “cone of protection”—became less used. 

The 150-ft Rolling Sphere Model, developed in the 1950s, 

has gained more common acceptance. Except for some 

historic reproductions, air terminals are now shorter 

than many of their predecessors and are available in 

both pointed and blunted (rounded) tips. 

“Surge protectors” or surge protective devices (SPD) 

have become a significant part of modern lightning 

protection work, reflecting our increased reliance on 

electronics and technology (Fig. 12). Besides providing 

for surge protection at the main electrical service box, 

second-stage or point-of-use surge protectors are needed 

to protect sensitive electrical devices such as computers. 

These surge protectors must be rated for lightning 

protecttion. With the proliferation of service lines to a 

structure, proper bonding of these service lines to the 

common ground of the lightning protection system 

remains important. 

Risk Assessment 

The majority of buildings in this country neither 

have existing lightning protection nor may they be 

8 
Figure 12. A surge 

protector covering the 

electrical lines in a house, 

barn, or other such 

structure is relatively 

inexpensive to have 

installed. With two or more 

electrical service boxes, each 

will need one. The surge 

protector includes one or 

more LED lights which 

indicate whether or not it 

is properly functioning. 

In areas of frequent 

thunderstorms, the unit 

may need to be replaced 

after a severe or repeated 

number of power surges in 

the line. Photo: Independent 

Lightning Protection 

Company. 

in real need of such protection. Nevertheless, there 

are significant number of structures, including many 

historic ones, at risk of loss or damage due to lightning 

strikes and which merit protection. Local building 

codes or fire marshals may require certain buildings 

being rehabilitated or undergoing a change in use to 

install lightning protection. In most cases, the decision 

to install or maintain an existing lightning protection 

system for a historic building is voluntary. If an owner 

elects to install one, many local building codes do set 

forth installation standards, often drawing upon the 

National Fire Protection Association’s Standard for 

Installation of Lightning Protection Systems (NFPA 780). 

The frequency of lightning strikes varies considerably 

across the country (Fig 13). Coastal areas in the 

southeast are particularly prone to high numbers of 

lightning strikes, while the west coast has few. Even 

within a single state, the number of lightning events 

each year can vary considerably by location. Lightning 

activity and lightning strikes are tracked on a continuing 

basis by companies providing fee services for weather 

forecasts, insurance claims, and other business purposes. 

These companies are the best source of data for a specific 

area where such information is not publicly available. 

In Annex L to NFPA 780, information on lightning 

risk assessment is provided. The described method 

takes into account the building environment, type of 

construction, structure occupancy, structure contents, 

and lightning stroke consequences. Among the 

examples that NFPA 780 cites, and where the need 

for protection should be given serious consideration 

regardless of the outcome of the risk assessment, 

are structures located where there is high lightning 

frequency, tall isolated structures, buildings containing 

explosive or flammable materials, and buildings 

containing irreplaceable cultural heritage. While 

most historic structures by their very nature may be 

considered irreplaceable, practical constraints, including 

financial ones, often result in an informed owner having 

Figure 13. The frequency of lightning strikes varies considerably across the country and is tracked and reported nationwide. States with a high 

number of cloud-to-ground flashes in 2016 included Louisiana and Kansas with over one million each; states with a low number included Maine and 

New Hampshire with each around 10,000. Ben Franklin's home state of Pennsylvania had 182,071 cloud-to-ground flashes in 2016 while across the 

country, California had 48,958. Courtesy of Vaisala. 

9 
to weigh the risks of not installing a lightning protection 

systems—in other words, the likelihood of lightning 

striking a building and the resulting damage and 

potential loss of life that could occur. 

Buildings with towers or spires such as historic 

courthouses and churches are at greater risk because of 

their height and since they are often the most prominent 

buildings within a small community. On the other 

hand, a downtown historic building, even one with 

a tower such as a firehouse, set among much taller, 

newer buildings, is less likely to be struck by lightning. 

Structures such as lighthouses that are tall and in 

exposed locations are at high risk when located where 

lightning strikes occur. Similarly, an isolated building 

on a hilltop is more prone to a lightning strike than a 

rowhouse in an urban district. 

The type of construction is another factor taken into 

account, particularly the structural framework and 

the roof type. For example, a wood roof has a higher 

risk value than a fiberglass shingle roof because of its 

greater flammability; a structural steel-frame building 

with a metal roof that is electrically continuous is at a 

lower risk than a concrete building with a composition 

roof. Another factor is the occupancy use and damage 

that may occur. With theaters, schools, and large retail 

stores, a lightning strike may cause both fire and panic 

with loss of life. For farms, there is the risk of fire and 

loss of business, and for museums there is the additional 

irreplaceable loss of cultural heritage. 

A lightning risk assessment should be undertaken by a 

qualified, experienced individual, usually an architect 

or engineer, who operates independent of any lightning 

protection company. For structures that have been 

previously struck by lightning, and where conditions 

have not changed that otherwise would significantly 

lower risk, remember that lightning can and has struck 

twice in the same place. 

Inspection, Evaluation, and Maintenance 

Whether old or quite recent, lightning protection 

systems need to be periodically inspected and 

maintained. Systems can be impacted by changes to a 

structure, as with an addition of a dormer, attachment 

of a new metal blade sign, or installation of a new roof. 

Fasteners and certain other components degrade over 

time, requiring cleaning, securing, or replacement. 

Components may also suffer from man’s careless or 

unintentional actions. While performing as intended, a 

system might even incur some damage, such as to the 

tip of an air terminal or damage to a surge protector, as a 

result of a lightning strike. 

The inspection should either ensure that the system is 

fully functional or identify components that are broken, 

dislodged, or otherwise deficient (Fig. 14). Historic 

components needing conservation work should be 

identified. While today’s lightning protection standards 

Figure 14. Lightning protection systems should be visually inspected 

every year and once every five years be inspected by an experienced 

professional. Note the break in the down conductor at the top of the 

photograph and the lack of a bonded connection to the cable at the 

bottom, which goes to one or more grounds. The old ground rod 

should be bonded to the new ground. Photo by author. 

do not classify older systems as obsolete, even functional 

systems may merit some upgrading, and this should be 

noted in the inspection. 

The recommended number and placement of air 

terminals needed for coverage today usually will exceed 

that of older systems. Also, some old lightning rods may 

be connected to only one conductor, rather than today’s 

required two or more conductors and grounds. It is 

important to check whether pertinent objects and service 

lines are properly bonded to the lightning protection 

system. As part of the inspection and evaluation 

process, existing surge suppressors and arresters should 

be checked, and those locations lacking adequate surge 

protections should be identified. 

On older systems, new ground rods usually need to be 

installed and connected to the old ground rod. Even 

under normal conditions, grounding components decay 

and usually will need replacement within 30 years or 

less, depending upon soil conditions (Fig. 15). The 

inspection should also indicate whether additional 

ground rods need to be installed. Particular attention 

should be placed on recent site work, such as trenching 

for cable lines or installation of landscape features like 

10 
 

Figure 15. Ground rods decay and may need replacement within 30 

years or less depending upon soil conditions. Ground rods should be 

copper-clad steel, solid copper, or stainless steel. They should be 8 feet 

long and no less than 1/2 inch in diameter. Reprinted with permission 

from NFPA Standard 780, 2017, Standard for the Installaton of 

Lightning Protection Systems, Copyright © 2016, National Fire 

Protection Association, Quincy, MA. This reprinted material is 

not the complete and official position of the NFPA on the referenced 

subject, which is represented only by the standard in its entirety. 

a metal flagpole, which may have cut or otherwise 

disturbed a previously functioning ground. 

Besides visual inspection, a ground resistance test can 

help establish if an existing ground is working properly. 

If a visual inspection of certain components is not 

possible, as with concealed conductors, a continuity test 

can be run instead. A visual inspection by an individual 

familiar with lightning protection systems should 

take place annually and at least every five years be 

undertaken by a professional who also tests the ground 

and the system’s conductivity. Where roof replacement 

or repairs to chimneys, parapets, or similar features has 

occurred, a visual inspection should immediately follow. 

With an older system, an assessment should be made 

at the outset as to its overall historic significance and 

that of individual components. A lightning rod with a 

colorful glass ball and crafted weathervane dating to the 

turn-of-the-twentieth century can easily be appreciated, 

yet early connectors, conductors, and glass insulators, 

while more utilitarian in function, may be significant as 

well and merit preservation considerations. 

There are additional considerations when an older 

system is determined to be a historic feature of a 

building. If a lightning rod is rare or quite distinctive 

and exhibits deterioration, it may be appropriate in some 

cases, particularly with museums and public buildings, 

to replace it with a replica, conserving and retaining the 

original piece for display or storage inside. Examples 

include a deteriorated rod that exhibits high quality 

craftsmanship and specifically designed for a structure; a 

rod that is of unusual design and is considered valuable 

folk art; or a surviving 18th-century lighting rod. 

Where historic lightning rods and other components 

can function properly and are in fair to good condition, 

identifying steps to conserve and secure them in place 

is usually the preferred preservation approach. When 

repairs are necessary, finding certain parts for old 

systems may be more difficult and may necessitate 

utilizing reproduction parts that may not have been ULcertified, but are otherwise serviceable. If the existing 

system is in poor condition and needs substantial 

upgrading, replacement may be the only alternative. 

Recommendation of the inspector should be explained 

in the evaluation, including a discussion of alternatives. 

With serviceable pre-Civil War lightning rods, and 

even with more common decorative rods of the Golden 

Era, special attention is needed where there is a risk of 

vandalism or theft. If a building is being mothballed 

or is undergoing major repairs and is not in a secured 

location, historic lightning rods with any decoration 

usually should be temporarily removed. If the risk is 

high for lightning strike, an interim system with modern 

terminals may need to be installed. 

Traditionally, the most common threat of vandalism is 

due to a glass ball or weathervane being used for target 

purposes, particularly on vacant and isolated buildings. 

While rarely preventable, glass balls broken as a result 

of vandalism can often be replaced, since a number of 

the common designs and colors are still available today 

as moderately priced reproductions using original tools 

(Fig. 16). Theft occurs as well, since historic lightning 

rods with glass balls or decorative weathervanes are 

Figure 16. This three-piece vintage mold for a round pleated-glass 

lightning rod ball is still used to make accurate reproductions today. 

Photo by author. 

11 
valued by collectors, and copper conductors can be sold 

for scrap metal. 

Proper maintenance of historic lightning protection 

systems includes some similar tasks associated with 

modern systems. Attachment hardware and connectors 

may become loose and simply need to be retightened. 

On a common tripod stand, excessive rust on a steel or 

iron screw, or water leakage where the screw is attached 

through the roof, will over time cause one or more of the 

legs of the stand to detach from the roof. As a result, the 

rod usually will bend or deflect to one side. Thus, it is 

important to re-secure the stand and ensure that the roof 

is watertight at the connection. 

Historic hardware may need to be cleaned to ensure 

proper function and longer wear. Where historic 

hardware is severely corroded or broken, has suffered 

from past abuse, or is otherwise seriously deficient, 

replacement parts should be used. 

With replacement hardware even as simple as screws, 

care must be taken to avoid use of dissimilar metals 

that have different electrical properties which can 

result in galvanic corrosion. If the existing conductors 

are copper, the connectors should be copper or brass. 

Similarly, only aluminum connectors should be used 

with aluminum conductors. Because of appearance 

and durability, plastic anchors and connectors should 

generally be avoided for historic buildings. Parts 

designed for lightning protection installations should be 

used in replacement work. 

It may be necessary to clean iron and steel parts 

of the lightning rod. Particularly with decorative 

weathervanes and directional signs, care must be taken 

to avoid unnecessary damage when cleaning. Where 

the object appears to be discolored, this can be the result 

of a natural patina that provides some protection, and 

the object may be prized for this visual quality and 

undisturbed nature. With copper and brass, cleaning 

to an as-new appearance should generally be avoided 

except where repairs are made at connectors. 

Decorative objects, such as a fish or horse on a 

weathervane, were typically formed from relatively 

thin sheet metal, as opposed to heavier weight castings 

that also were sometimes used. Where cleaning is 

appropriate, use the gentlest means possible, avoiding 

unnecessary abrasion or etching. The best cleaning 

approach is to use methods suitable for the cleaning of 

similar art and historic objects. If the decorative objects 

have vestiges of early paint, it may be appropriate to 

take steps to conserve the paint since it adds to the 

historical value. More than one metal material may 

be used in a single lightning rod assembly, so it is 

important to identify the metals on each part and to use 

an appropriate cleaning method for each type. 

Iron and later steel used for stands to support a lightning 

rod are somewhat more forgiving in terms of cleaning 

methods than softer metals like aluminum, copper, 

nickel, bronze, and brass, which generally should not be 

cleaned. Gentle hand scraping, soft wire brushing, and 

sanding with medium grit emery paper can remove rust 

on iron and steel, except for where fine detail requires 

more delicate work. Because iron and steel easily rust, 

support stands and applied decorative objects that are 

to be painted should be cleaned and treated with a 

zinc-based metal primer on the same day. Air terminal 

stands, connectors, and cables can be painted without 

impeding the flow of electricity in case of a lightning 

strike. 

Historic and reproduction glass balls are a fragile 

component of the lightning rod and should be handled 

carefully. Glass can inadvertently be scratched or etched 

when in contact with certain metal cleaners used on 

adjacent metal parts. Cleaning to remove bird waste and 

other harmful residue should be done by washing with 

a soft cloth, warm water, and a mild non-ionic detergent. 

Because of their outdoor exposure, cleaning glass to an 

as-new appearance is not recommended so as to avoid 

unnecessary risk of breakage. 

Glass and porcelain insulators used to fasten cables to 

a building are no longer made for lightning protection 

work. The cable typically ran through or was secured 

to the side of a glass insulator, which came in a wide 

range of colors. The insulator was in turn attached 

to the building in a variety of ways, typically with 

a metal bracket or ring. By the early 20th century, 

porcelain insulators became prevalent, replacing 

the glass insulator. They can still be used in place 

when maintaining or upgrading older systems (Fig. 

17). Where existing insulators have major cracks, are 

broken, or missing altogether, they can be replaced 

with appropriate metal fasteners. As historic insulators 

Figure 17. Glass insulators were attached to a structure in a variety 

of ways using metal rings, staples, wire, or similar fasteners. Where 

old insulators are damaged and no longer functional, they can be 

replaced with appropriate metal fasteners. Photo by author. 

1212 
are replaced, samples should be retained for record 

purposes and future reference. 

Conductors can be cleaned and painted to inhibit 

corrosion or reduce their visibility. Since the exterior 

walls of many historic buildings were periodically 

painted, special cable mounts were often used in the past 

that allowed the cable to be secured approximately one 

inch off the wall. 

Repair 

Repairing and augmenting an existing lightning 

protection system on a historic building follows some 

of the same basic principals, whether the system is 

historic or more contemporary, yet there are also some 

key differences. With historic systems, there is a greater 

emphasis on retaining old materials through repairs 

and, where necessary, augmentation. An 1870 system 

that has survived on a building would most likely be 

considered deficient today in terms of the number and 

placement of air terminals. For example, there is the 

current requirement that one or more terminals be used 

at each chimney, depending upon chimney size—a 

practice not always common in the past. 

Historic lightning rods can often be repaired and 

coverage augmented where needed with smaller, plain 

contemporary air terminals. The taller lightning rods 

typically used in the past were usually set on individual 

stands. Misshapen or bent stands can usually be 

straightened, while fasteners securing the legs of the 

stand to the roof often need to be replaced. It is also 

important to check that the roof is sound where the legs 

are attached and to correct any wood rot or other roof 

decay prior to reattaching the stands. Where lightning 

rods are partially concealed in the roof, it is important to 

renew seals where they penetrate the roof (Fig. 18). 

Particularly on late 19th-and early 20th-century buildings, 

accurate reproduction lightning rods often can be used 

where a historic terminal is missing or to augment for 

proper coverage where historic ones exist. There are 

both some age-old companies as well as newer ones 

that not only manufacture a number of the traditional 

lightning rods, but also offer cables, connectors, and 

other hardware for lightning protection systems that are 

very similar, and at times, a true match to various older 

designs. Besides cost, factors influencing the decision 

whether to use traditional replacement parts or those 

of more modern design include the historic significance 

of the existing system; the preservation approach as to 

whether maintain, restore, or rehabilitate a building; and 

the visibility of a particular component. 

Where historic lightning rods are of galvanized steel or 

iron, it is possible to retain them in place, depending 

upon condition. These rods usually were connected in 

the past to conductors of the same or similar material. 

While iron or steel does not meet code today for 

conductors and rods, there are tests that can be run 

Figure 18. With concealed lightning protection systems, cable wire 

connecting lightning rods and conductors are partially or totally 

concealed on the exterior by running most of the lines within the 

structure. Where the lightning rod stand is attached to the roof, as 

well as where the concealed cable is attached on the outside to the 

lightning rod, are all areas that need to be routinely inspected and 

repaired as needed. The roof seal at the junction of the cable through 

the roof will need to be replaced over time. Drawing: Courtesy of 

Independent Lightning Protection Company. 

for continuity in a circuit (but not for capacity). As in 

the case of the Maryland State House, the historic iron 

lightning rod was repaired and retained as an essential 

part of a functioning system. 

Where historic lightning rods and conductors are 

determined to be comparable or equivalent with modern 

ones in terms of functionality, they can be treated as 

intergral to the lightning protection system. Where 

functionally deficient, they can be retained in place and 

bonded to the updated system. Such old terminals or 

conductors would thus not be essential to the system, 

but rather retained as a historic feature. 

Where one or more existing terminals are connected by 

a cable to only one down conductor, installing a second 

path to an additional ground is important. In the case 

of old conductors, an inspection may find that they 

are not working properly. Historic conductors may be 

undersized, frayed, or otherwise degraded and need to 

be replaced with appropriately-sized modern wire cable 

that is U.L.-approved for lightning protection. 
Case Study 

Upgrading old lightning protection on a 

historic building 

Mumma House, Antietam National 

Battlefield, Sharpsburg, Maryland

Located within the Antietam National Battlefield, 

the historic Samuel Mumma farm house had 

lightning protection devices installed some years 

after the Civil War. As part of an exterior stabilization of the wood-framed residence in the 1990s, the 

National Park Service also provided for a newlyfunctioning lightning protection system. 

The existing system, which appeared to date to the 

late 1800s, included four tall ornamented lightning 

rods on the terne-metal roof, each consisting of a 

galvanized- steel point with a sunburst air terminal 

on top. The tall rods had been bent over time 

and the three-legged galvanized steel braces were 

twisted and loose from the roof. The two original 

steel down conductors, consisting of twisted 

section rods, were still in place and connected to 

ground rods. There were several above-grounds 

breaks in the down conductors, rendering the 

system inoperable. Most of the original glass 

insulators used to attach the down conductors to 

the masonry walls remained, though a number 

were broken or missing altogether. 

For its time, the original protection system would 

have been considered a proper functioning 

system with a correct placement of lightning rods, 

use of two down conductors securely attached 

to grounds, and cables correctly connecting to 

lightning rods appropriately sized. While this 

building feature had acquired historic significance 

over time and was visually prominent on the 

roofline, it no longer served its intended function. 

Besides breaks in the conductors and damage to 

the lightning rods, there were other deficiencies 

by today’s standards, including the lack of air 

terminals at the chimneys and the distance 

between existing terminals being too great. 

Furthermore, replacement steel air terminals and 

steel conductors are no longer used. 

In assessing whether the system should be repaired 

and upgraded or be replaced altogether, a number 

of factors were considered. After the National Park 

Service was in contact with a long-established, 

Figure A. Rear view of the Mumma House showing three of 

the four tall reproduction lightning rods placed close to the 

same locations as the historic ones, which were too deteriorated 

to reuse. Running down the left side of the house below the 

chimney is one of the two historic down conductors, which were 

saved in place and bonded to the new system. Photo by author. 

Figure B. Photo shows one of the reproduction tall lightning 

rods being secured in place. New cables connected the 

reproduction lightning rods and the modern air terminals to the 

down conductors that lead to the grounds. Photo: Independent 

Lightning Protection Company. 

Figure C. The historic down conductor with its original insulator 

attached to the house just above the stone foundation is still connected to 

the old ground while bonded to the new conductor and new ground rod. 

Photo by author. 

14 
lightning protection manufacturer in Goshen, 

Indiana, it was determined that the historic air 

terminals and a number of the connectors could 

still be easily replicated using old molds that the 

company had for casting of new parts. Since the 

historic terminals were in poor condition and 

mounted high on the roof, it was decided to replace 

the four lightning rods with matching designs. 

Replacement steel terminals were not considered a 

suitable option, so lead-coated copper was selected 

for its durability and similar coloration to the 

original terminals. 

Figure E. Plan for the 

installation of the new 

system. Note that the 

historic systems did not 

include any lightning rods 

at the chimneys, while 

today’s code requires two 

air terminals on each side 

of this size chimney. The 

required new air terminals 

were much smaller than 

the historic ones and were 

relatively inconspicuous 

along the ridge of the roof. 

Drawing: courtesy of the 

Independent Lightning 

Protection Company. 

The four reproduction lightning rods were installed 

close to the original locations. To augment and 

ensure proper coverage, additional contemporary 

terminations were installed. There was no effort to 

conceal the new connecting cables since visibility 

was a historic feature of the old system. New copper 

down conductors were placed at needed locations, 

including where two historic steel conductors 

existed. The new conductors were connected to 

new grounding rods. Both of the historic down 

conductors with their glass insulators were retained 

in place and bonded to adjacent new conductors, 

providing an informative way to preserve in place 

part of the old system. 

Upon completion of the work, the visual prominence 

of the historic lightning rods had been re-established 

while integrating non-obtrusive additions to the 

system in order to meet code. A distinctive rooftop 

feature, the large reproduction lightning rods are part 

of a fully-functional lightning protection system. 

Figure D. Tall lightning rods once again stand out on the Mumma 

House. These reproduction rods along with retention of the historic 

down conductors have been incorporated into the modern lightning 

protection system that was installed. Much smaller, contemporary air 

terminals located on the roof are barely discernable from below. 

Photo by author. 

15 
Depending upon age and significance, if a historic down 

conductor or the cables connecting the air terminals are 

to be replaced, one or more sections should be saved; 

tagged as to its function, location, and date of removal; 

and stored with the structure’s historic artifacts for 

future reference. Remember, it may be possible to retain 

in place an inadequate historic down conductor by 

simply bonding it to a new down conductor (see case 

study on page 14). 

When installing new down conductors, each should be 

fitted with a purpose-made test clamp at an accessible 

location to permit periodic testing. Where conditions 

permit, new ground conductors on masonry structures 

should be attached only at joints rather than to masonry 

units (Fig. 19). 

Any sharp bends in conductors require attention since 

they raise the risk of flashover problems. Sharp bends 

can be either reworked so as to form a minimum bend 

radius of eight inches, or, if that is not possible, the 

Figure 19. Placement of down conductors along inside corners 

or adjacent to downspouts helps minimize their visibility. This 

conductor has been placed on an inside corner. Other good 

installation practices shown in the drawing include the use of clamps 

to attach the conductor at mortar joints, rather than damaging 

the stones; the avoidance of sharp bends in the conductor; and 

provisions for a test clamp and an inspection pit accessing the ground 

connection which can be used during periodic inspections of the 

system. Drawing: English Heritage©. 

section of the conductor should be replaced and the 

alignment changed. 

In most cases, repair work involving neglected 

systems includes new ground rods being installed. 

Most old grounding rods do not merit special historic 

preservation considerations and can be left in place and 

bonded to the new ground rods. When installing new 

grounding rods, avoid where possible any archeological 

resources. All service lines should be bonded to the new 

lightning grounds. 

Surge protective devises that are not functioning 

properly should simply be replaced with modern units 

and, where lacking, new ones should be added. Metal 

objects and features at risk that lack proper bonding to 

the lightning protection system should be connected as 

well. 

Installing a New System 

Installing a new system on a historic structure requires 

a number of special considerations. Depending upon 

the nature of the structure, such as its height, complexity 

of the roof, internal access, type of structure, historic 

significance, and use, the decision has to be made 

whether to conceal as much as possible or surface mount 

the new terminals and conductors. On a high-rise 

building with a continuous steel structure, it is common 

practice to tie the lightning protection system to the steel 

structure. High-rise buildings are prone to be stuck by 

lightning (Fig. 20). The Empire State Building in New 

York City is struck on the average of more than 20 times 

a year. Small modern air terminals mounted on a high 

rooftop usually have little visual impact from below. 

Most historic buildings, however, are much lower in 

height and their roofs are often readily seen. For these 

buildings, the decision as to the extent of concealment 

may involve consideration of two or more possible 

options, with the most common options being: 

1. Elect to place modern air terminals and conductors in 

a manner that minimizes their visual impact yet remains 

fully exposed on the outside. 

2. Select an installation approach that conceals within 

the structure as much of the lightning protection system 

as possible. 

3. Choose to install reproduction lightning rods 

appropriate to the period and type of the structure, 

augmenting with contemporary terminals as needed, 

and elect not to conceal the system. 

Some of the earliest 18th-century installations concealed 

part of the down conductor within the building such as 

at Independence Hall and Christ Church in Philadelphia. 

This approach fell out of favor for a number of years, as 

systems generally were surface mounted on the outside. 

Since the Golden Age, there are a multitude of products 

16 
and installation techniques that permit concealment 

of the conductors or cables connecting lightning rods. 

Current standards and building codes generally allow 

the use of either exposed or concealed systems. 

With concealed systems, the exposed air terminals run 

through the roof and are typically attached below to a 

ridge board or other part of the inside roof structure, 

permitting the connecting conductors to run inside 

the roof. The terminals require a good weather seal at 

the roof. The connecting conductors can be attached 

to outside ground conductors or to concealed ground 

conductors that are either set in a wall cavity on finished 

interiors or, on some utilitarian structures, left partially 

exposed on the interior side of outside walls. At grade, 

the inside ground conductors can then be run to the 

outside and be joined to the grounding rods. 

Concealment applications exist for specialty features 

even as mundane as metal rooftop ventilators commonly 

found on small manufacturing buildings and barns. 

Figure 20. High-rise buildings in cities 

such as New York, Chicago, and Atlanta 

have a higher risk of being struck by 

lightning, and it is not uncommon for 

some structures to be hit multiple times 

during a year. Multiple strokes from a 

single lightning occurrence can strike 

more than one building at the same 

time as shown in this photograph of the 

Atlanta skyline during a thunderstorm. 

Photo: David Selby©. 

With ventilators, the air terminal would extend from 

inside the vent up through the center top and be secured 

inside the vent to the conducting cables. 

One of the factors when considering concealment 

methods is how much initial disturbance is required on 

the interior of a structure. For historic buildings, such 

an approach may not be advisable if historic interior 

finishes and distinctive features are adversely impacted. 

On the other hand, if such disturbance is not necessary 

or the interior is undergoing considerable work, 

concealment techniques are a plausible option. 

In many cases, the most practical approach is to design 

a modern system that is largely an outside mount, but 

where special attention is placed on utilizing appropriate 

techniques and materials that help minimize the visual 

impact of the cabling and multiple air terminals. 

Fortunately, today’s smaller air terminals accommodate 

simple, unobtrusive attachment methods, unlike the 

taller stands commonly used in the past. While roof 

Reroofing a Structure that has Lightning Protection

Most reroofing work necessitates temporary removal of portions of the lightning protection system. With some small 

simple roofs, a roofer may be capable of undertaking the reinstallation work, subject to an inspection by a qualified 

lightning protection professional upon completion of the work. In most cases, however, the removal and reinstallation 

should be done by a qualified lightning protection contractor. If the work must be undertaken during a season of high 

lightning risk, every effort should be made to closely coordinate the overall work in order to minimize the time when 

the building is left unprotected. 

While reroofing, it is often important that certain aspects of the lightning protection systems unaffected by the roof 

work remain functional. This particularly applies to surge protection. Where there is a high risk, any components 

of the lightning protection system remaining in place during the roof work should not create unintended paths for 

electrical discharge from a potential lightning strike. If the reroofing stems in part from related new construction that 

will affect the design of the existing lightning protection systems, as with the construction of a large addition or a new 

dormer, services of a qualified lightning protection professional should be used. 

17 
Common Questions about 

Lightning Protection Systems

By installing a lightning protection system is 

there a greater risk of a lightning strike? No. 

Is a licensed contractor required for installation? 

Even though many of the components of a traditional 

lightning protection system are readily available to 

the public and contractors, licensed and certified 

installers should be used in most cases. 

In a lightning-prone region should a weathervane on a building be bonded to a lightning 

protection system? Yes. Where no system exists, 

it may be best to leave the weathervane ungrounded 

rather than undertake a do-it-yourself project. 

What to do with an old decorative rod on a 

building where the system has not been functional for years? If the building is considered to be 

at risk, repair and upgrade the lightning protection 

or remove the rod and store for possible later reuse. 

If the area is not highly prone to lightning and the 

building risk is low, probably no immediate action is 

needed. 

What about the use on a historic building of 

one of the non-conventional types of lightning 

protection systems that have been marketed in 

recent years? NFPA and UL safety standards for 

lightning protection only apply to the widely accepted Franklin system. The conventional/traditional 

Franklin system remains effective and has stood the 

test of time. 

With a working lightning protection system, 

are there any precautions to be taken during a 

lightning storm? There are still the normal precautions to be taken such as avoiding metal water pipes 

(no baths) for personal safety, disconnecting sensitive 

electronics when possible, and staying indoors. 

Can landscape features like trees be protected 

from lightning damage? Yes. Lightning protection 

can be installed on trees. 

mounted terminals are typically connected by conductor 

wires running along the roof top, down conductors 

can often be placed at inside corners, beside or behind 

downspouts, or on less prominent elevations for reduced 

visibility. On chimneys and rooftop features such as 

parapets, the small terminals can be placed on the least 

prominent side or in a way that best minimizes their 

visual impact while providing the necessary protection. 

Both lightning protection systems that primarily use 

copper components and ones that use aluminum are 

available today. With copper terminals and cables, 

some of the connectors and fasteners usually are made 

of bronze. For historic buildings, copper systems often 

are preferred because they have been traditionally used 

in the past and may be a good visual match where 

replication is desired. While copper is more costly, 

aluminum as a material is a slightly poorer conductor, 

requiring heavier gauge cables and components. As 

a replacement for galvanized cables and terminals, 

aluminum or sometimes lead-coated copper may be 

preferred over copper for a closer color match. 

The choice as to whether to use copper or aluminum 

is at times dictated by the existing roofing material. 

Copper should not be used for lightning protection 

on old galvanized steel or corrugated iron roofs, as it 

will tend over time to stain and erode the roofing due 

to galvanic corrosion. Aluminum should also be used 

on steel, iron, and zinc roofs. For such commonlyfound historic roofing materials as slate, wood, asphalt 

shingles, and rolled roofing, either copper or aluminum 

may be used. 

While the installation of lightning protection should 

always be done by a certified lightning protection 

contractor, there are projects where a roofing contractor 

needs to be involved as well. Such close coordination 

is important, especially on membrane roofs, to ensure 

both that the lightning protection is properly installed 

and that the integrity of the roofing and flashing is 

not impaired. The appropriate means of attaching air 

terminals to the roof and securing the connecting cables 

without reducing the service life of the roof depends 

on a variety of factors. The use of specific sealants, 

adhesives, cap sheet materials, and metal fasteners to 

secure cables and terminals to the roof depends in part 

on the type of roof, roofing material, and other building 

specific conditions. Fasteners must be attached in a 

manner that minimizes the risk of future water leaks. 

For smaller historic structures such as most residences 

and barns, there is the option of installing a new system, 

utilizing period reproduction air terminals where 

appropriate and augmenting with modern smaller 

air terminals at chimneys and other locations where 

dictated by today’s standards (Fig. 21). This approach 

can be used to replace a missing system, or where it is 

simply the preference of the property owner, providing 

the intent is not to create a major new visual feature 

where one did not historically exist. Care should be 

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taken to select a design that is compatible with the 

historic character of the building, especially in regards 

to any ornamentation. Because of availability, the 

best building candidates for reproduction terminals 

are those dating to the Golden Age. Even some of the 

manufacturers’ cables and connectors available today for 

general installations are a match to historic ones. 

Although lightning protection can be added to a 

structure anytime, the best time is when a roof is being 

replaced. Existing surge protection that is deficient 

should be upgraded or replaced whenever needed. For 

building uses such as museums with special climate 

controls, businesses with vital data equipment, or even 

homes with expensive home entertainment centers, upto-date protection from power surges is important. Such 

surges may be caused not only by lightning but also by 

electrical malfunctions. If the installation of a traditional 

lightning protection is being postponed or because 

of low risk not being considered, appropriate surge 

protective devices still should be installed and care be 

taken that electrical service, cable, and similar systems 

are properly grounded. 

The locations for down conductors are usually derived 

as a result of requirements of standards and codes and 

aesthetic considerations. For historic buildings of special 

significance, particular care in the installation of the 

grounds should be taken so as to minimize disturbance 

and risks to historic landscape features and damage to 

any archeological resources. Furthermore, location of 

drain pipes and underground utility lines should be 

marked prior to grounds being installed. 

Codes, Standards, and Contracts 

For large or complex structures, special applications, 

certain uses, or buildings of high historic significance, 

the services of an architect or engineer experienced with 

lightning protection is usually desirable to assist with 

major upgrades or new installations. A number of the 

major manufacturers of lightning protection systems 

Figure 21. Small air terminals have been used in this more recent 

installation and have little visual impact. If a partially concealed 

system was desired, the cable and the mount for two of the air 

terminals could have been concealed within the ventilators. 

Photo by author. 

also provide helpful design assistance. In more common 

building cases where design services independent of 

the installation contractor are not used, the property 

representative needs to check with the local building 

department as to relevant code provisions. While 

the National Electrical Code, which includes general 

references to lightning protection may be cited, the most 

commonly referred to safety standard specifically for 

lightning protection work is that issued by the National 

Fire Protection Association and entitled, NFPA 780 

Standard for Installation of Lightning Protection Systems. 

The Underwriters Laboratories, Inc. (UL), has a 

similar standard covering the installation of lightning 

protection, UL 96A Standard for Installation Requirements 

for Lightning Protection Systems. In addition, UL has 

requirements that cover the components used in 

the system, UL 96 Standard for Lightning Protection 

Components. These standards can be specified in a 

contract document along with NFPA 780. 

Where a historic system is being repaired or undergoing 

upgrades using specialty reproduction parts, all 

functional replacement parts, unlike ornamental 

pieces, should be UL-listed products. UL-listed 

products help provide quality assurance, but it does 

not necessarily mean that non-UL-approved parts 

are unsafe to use. For new installations and for some 

older systems, UL also offers an optional Inspection 

Certificate Program through UL-listed installers. A UL 

Certificate assures that a lightning protection system 

installed on a structure has been inspected by a UL-field 

representative and is in compliance with UL, NFPA, or 

U.S. government standards. 

The Lightning Protection Institute (LPI) is a voluntary 

membership association for lightning protection 

manufacturers and contractors that provides training 

and certifications for designers and installers. They 

offer different levels of certifications for installers. A 

membership list can be found on their website. The 

Institute also administers a quality assurance program 

that certifies an installation meets their quality assurance 

program through a third-party inspector. 

For most projects, competitive proposals from 

experienced lightning protection installers are desirable. 

However, with historic systems, the choice of installers 

may be more limited. Depending upon the historic 

resource and conditions, it may be important to use a 

contractor both with experience in lightning protection 

systems and historic buildings. Work on historic 

buildings often requires knowledge of older building 

materials and construction; an appreciation of the 

importance of installing a lightning protection system 

that does not unnecessarily impact the structure’s 

historic appearance or damage historic materials; and a 

commitment to the highest quality of work. 

The cost of a new system varies according to many 

factors such as the size of a structure, roof type, and 

19 
materials. Features that require individual protection, 

such as dormers, chimneys, and metal skylights, will 

add to the cost. Porches and lower additions to a 

building may necessitate additional work to ensure full 

protection coverage. The type of materials to be used 

affects costs, with copper and copper alloys being more 

expensive than aluminum. Copper cannot be used on 

structures with aluminum siding or most metal roofs, 

and similarly aluminum cannot be used on a copper 

roof. The extent of required bonding of nearby objects 

and the level of surge protection coverage desired are 

also cost factors. 

The cost of a new system installed on a simple 

monument, house, or barn with a small footprint and 

plain roofline tends to be relatively inexpensive. A new 

system on a medium-sized residence or commercial 

building with multiple dormers, chimneys, and 

numerous features that need to be bonded to the system 

will cost considerably more. Among some other factors 

affecting costs are whether conductors are concealed 

or run exposed, the ease of access to the building, and 

where the building is located. 

Summary 

The use of lightning protection systems to protect 

structures and provide for public safety is scientifically 

accepted. Various government entities require such 

installations on their buildings and local building codes 

in areas of frequent lightning may require such systems 

depending upon the use of a structure. While there are 

no special requirements simply because a building is 

historic, as an irreplaceable cultural resource, historic 

structures at risk of damage or loss from a lightning 

strike merit protection. 

Acknowledgements 

Charles Fisher, Technical Preservation Services, National 

Park Service, has over 44 years of experience in historic 

building conservation and rehabilitation. 

The author would like to thank the assistance of Robert 

E. Cripe, Sr. and Jan Yoder, Independent Protection 

Company; Doug Franklin, retired president, Thompson 

Lightning Protection; Terry Portfleet, Michigan Lightning 

Protection; Sandy Easley, New Old Products, Inc.; Sunni 

L. Goodson, historic preservation consultant; Bruce Gill, 

Christ Church in Philadelphia; and Peter Michaud, New 

Hampshire Division of Historical Resources. 

Special thanks go to Dr. E. Philip Krider, University of 

Arizona. Assistance provided by Kaaren Staveteig and 

Brian Goeken, Chief, Technical Preservation Services, of 

the National Park Service, are gratefully acknowledged. 

This publication has been prepared pursuant to the 

National Historic Preservation Act, which directs the 

Secretary of the Interior to develop and make available 

information concerning historic properties. Additional 

information offered by Technical Preservation Services is 

available on our website at www.nps.gov/tps. Comments 

about this publication should be made to: Technical 

Preservation Services, National Park Service, 1849 C 

Street NW, Washington, DC 20240. 

This publication is not copyrighted and can be 

reproduced without penalty. Normal procedures for 

credit to the author and the National Park Service are 

appreciated. Except for the photographs by the author, 

illustrations used in this publication may not be used in 

other print or electronic media without permission of the 

owners. Photographs by the author should be credited 

with author’s name, National Park Service. 

October 2017 

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