PRESERVATION 

BRIEFS 

The Preservation and Repair of 

Historic Stucco 

Anne Grimmer 

u.s. Department of the Interior 

National Park Service 

Preservation Assistance Division 

The term "stuccd' is used here to describe a type of 

exterior plaster applied as a two-or-three part coating 

directly onto masonry, or applied over wood or metal 

lath to a log or wood frame structure. Stucco is found 

in many forms on historic structures throughout the 

United States. It is so common, in fact, that it frequently goes unnoticed, and is often disguised or used 

to imitate another material. Historic stucco is also 

sometimes incorrectly viewed as a sacrificial coating, 

and consequently removed to reveal stone, brick or 

logs that historically were never intended to be exposed. Age and lack of maintenance hasten the deterioration of many historic stucco buildings. Like most 

historic building materials, stucco is at the mercy of the 

elements, and even though it is a protective coating, it 

is particularly susceptible to water damage. 

Stucco is a material of deceptive simplicity: in most 

cases its repair should not be undertaken by a property 

owner unfamiliar with the art of plastering. Successful 

stucco repair requires the skill and experience of a professional plasterer. Therefore, this Brief has been prepared to provide background information on the nature 

and components of traditional stucco, as well as offer 

guidance on proper maintenance and repairs. The Brief 

will outline the requirements for stucco repair, and, 

when necessary, replacement. Although several stucco 

mixes representative of different periods are provided 

here for reference, this Brief does not include specifications for carrying out repair projects. Each project is 

unique, with its own set of problems that require individual solutions. 

Historical Background 

Stucco has been used since ancient times. Still widely 

used throughout the world, it is one of the most common of traditional building materials (Fig. 1). Up until 

Fig. 1. These two houses in a residential section of Winchester, Virginia, illustrate the continuing popularity of stucco (a) from this 

early 19th century, Federal style house on the left, (b) to the English Cotswold style cottage that was built across the street in the 

1930's. Photos: Anne Grimmer. 
the late 1800's, stucco, like mortar, was primarily Iimebased, but the popularization of portland cement 

changed the composition of stucco, as well as mortar, 

to a harder material. Historically, the term "plaster" has 

often been interchangeable with "stucco"; the term is 

still favored by many, particularly when referring to the 

traditional lime-based coating. By the nineteenth century "stucco," although originally denoting fine interior 

ornamental plasterwork, had gained wide acceptance 

in the United States to describe exterior plastering. 

"Render" and "rendering" are also terms used to describe stucco, especially in Great Britain. Other historic 

treatments and coatings related to stucco in that they 

consist at least in part of a similarly plastic or malleable 

material include: parging and pargeting, wattle and 

daub, "cob" or chalk mud, pise de terre, rammed 

earth, briquete entre poteaux or bousillage, halftimbering, and adobe. All of these are regional variations on traditional mixtures of mud, clay, lime, chalk, 

cement, gravel or straw. Many are still used today. 

The Stucco Tradition in the United States 

Stucco is primarily used on residential buildings and 

relatively small-scale commercial structures. Some of 

the earliest stucco buildings in the United States include examples of the Federal, Greek and Gothic Revival styles of the eighteenth and the nineteenth 

centuries that emulated European architectural fashions. Benjamin Henry Latrobe, appointed by Thomas 

Jefferson as Surveyor of Public Buildings of the United 

States in 1803, was responsible for the design of a number of important stucco buildings, including St. John's 

Church (1816), in Washington, D.C. (Fig. 2). Nearly 

half a century later Andrew Jackson Downing also advocated the use of stucco in his influential book The 

Architecture of Country Houses, published in 1850. In 

Downing's opinion, stucco was superior in many respects to plain brick or stone because it was cheaper, 

warmer and dryer, and could be "agreeably" tinted. As 

a result of his advice, stuccoed Italianate style urban 

and suburban villas proliferated in many parts of the 

country during the third quarter of the nineteenth 

century. 

Revival Styles Promote Use of Stucco 

The introduction of the many revival styles of architecture around the turn of the twentieth century, combined with the improvement and increased availability 

of portland cement resulted in a "craze" for stucco as a 

building material in the United States. Beginning about 

1890 and gaining momentum into the 1930's and 1940's, 

stucco was associated with certain historic architectural 

styles, including: Prairie; Art Deco, and Art Moderne; 

Spanish Colonial, Mission, Pueblo, Mediterranean, 

English Cotswold Cottage, and Tudor Revival styles; as 

well as the ubiquitous bungalow and "four-square" 

house (Fig. 3). The fad for Spanish Colonial Revival, 

and other variations on this theme, was especially important in furthering stucco as a building material in 

the United States during this period, since stucco 

clearly looked like adobe (Fig. 4). 

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Fig. 2. St. John's Church, Washington, D. c., constructed of 

brick and stuccoed immediately upon completion in 1816, 

reflects the influence of European, and specifically English, 

architectural styles. Photo: Russell Jones, HABS Collection. 

Fig. 3. The William Gray and Edna S. Purcell House, 

Minneapolis, Minnesota, was designed in 1913 by the 

architects Purcell and Elmslie in the Prairie style. Stuccoed 

in a salmon-pink, sand (float) finish, it is unusual in that it 

featured a 3-color geometric frieze stencilled below the eaves of 

the 2nd story. The Minneapolis Institute of Art has removed 

the cream-colored paint added at a later date, and restored the 

original color and texture of the stucco. Photo: Courtesy 

MacDonald and Mack Partnership. 
Although stucco buildings were especially prevalent in 

California, the Southwest and Florida, ostensibly because of their Spanish heritage, this period also 

spawned stucco-coated, revival-style buildings all over 

the United States and Canada. The popularity of stucco 

as a cheap, and readily available material meant that by 

the 1920's, it was used for an increasing variety of 

building types. Resort hotels, apartment buildings, 

private mansions and movie theaters, railroad stations, 

and even gas stations and tourist courts took advantage 

Fig. 4. The elaborate Spanish Colonial Revival style of this 

building designed by Bertram Goodhue for the 1915 Panama 

California Exposition held in San Diego's Balboa Park 

emphasizes the sculptural possibilities of stucco. Photo: C. W 

Snell, National Historic Landmark Files. 

of the "romance" of period styles, and adopted the 

stucco construction that had become synonymous with 

these styles (Fig. 5). 

A Practical Building Material 

Stucco has traditionally been popular for a variety of 

reasons. It was an inexpensive material that could simulate finely dressed stonework, especially when 

"scored" or "lined" in the European tradition. A stucco 

coating over a less finished and less costly substrate 

such as rubblestone, fieldstone, brick, log or wood 

frame, gave the building the appearance of being a 

more expensive and important structure. As a weatherrepellent coating, stucco protected the building from 

wind and rain penetration, and also offered a certain 

amount of fire protection. While stucco was usually 

applied during construction as part of the building 

design, particularly over rubblestone or fieldstone, in 

some instances it was added later to protect the structure, or when a rise in the owner's social status demanded a comparable rise in his standard of living. 

Composition of Historic Stucco 

Before the mid-to-Iate nineteenth century, stucco consisted primarily of hydrated or slaked lime, water and 

sand, with straw or animal hair included as a binder. 

Natural cements were frequently used in stucco mixes 

after their discovery in the United States during the 

1820's. Portland cement was first manufactured in the 

United States in 1871, and it gradually replaced natural 

cement. After about 1900, most stucco was composed 

primarily of portland cement, mixed with some lime. 

With the addition of portland cement, stucco became 

even more versatile and durable. No longer used just 

as a coating for a substantial material like masonry or 

log, stucco could now be applied over wood or metal 

lath attached to a light wood frame. With this increased 

strength, stucco ceased to be just a veneer and became 

a more integral part of the building structure. 

Fig. 5. During the 19th and 20th centuries stucco has been a popular material not only for residential, but also for commercial 

buildings in the Spanish style. Two such examples are (a) the 1851 Ernest Hemingway House, Key West, Florida, built of stuccoed 

limestone in a Spanish Caribbean style; and (b) the Santa Fe Depot (Union Station), San Diego, California, designed by the 

architects Bakewell and Brown in 1914 in a Spanish Colonial Revival style, and constructed of stucco over brick and hollow tile. 

Photos: (a) J.F. Brooks, HABS Collection, (b) Marvin Rand, HABS Collection. 

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Today, gypsum, which is hydrated calcium sulfate or 

sulfate of lime, has to a great extent replaced lime. 

Gypsum is preferred because it hardens faster and has 

less shrinkage than lime. Lime is generally used only 

in the finish coat in contemporary stucco work. 

The composition of stucco depended on local custom 

and available materials. Stucco often contained substantial amounts of mud or clay, marble or brick dust, 

or even sawdust, and an array of additives ranging 

from animal blood or urine, to eggs, keratin or gluesize 

(animal hooves and horns), varnish, wheat paste, 

sugar, salt, sodium silicate, alum, tallow, linseed oil, 

beeswax, and wine, beer, or rye whiskey. Waxes, fats 

and oils were included to introduce water-repellent 

properties, sugary materials reduced the amount of 

water needed and slowed down the setting time, and 

alcohol acted as an air entrainer. All of these additives 

contributed to the strength and durability of the stucco. 

The appearance of much stucco was determined by the 

color of the sand-or sometimes burnt clay, used in the 

mix, but often stucco was also tinted with natural pigments, or the surface whitewashed or colorwashed 

after stuccoing was completed. Brick dust could provide color, and other coloring materials that were not 

affected by lime, mostly mineral pigments, could be 

added to the mix for the final finish coat. Stucco was 

also marbled or marbleized-stained to look like stone 

by diluting oil of vitriol (sulfuric acid) with water, and 

mixing this with a yellow ochre, or another color (Fig. 

6). As the twentieth century progressed, manufactured 

or synthetic pigments were added at the factory to 

some prepared stucco mixes. 

Methods of Application 

Stucco is applied directly, without lath, to masonry 

substrates such as brick, stone, concrete or hollow tile 

(Fig. 7). But on wood structures, stucco, like its interior 

counterpart plaster, must be applied over lath in order 

to obtain an adequate key to hold the stucco. Thus, 

when applied over a log structure, stucco is laid on 

horizontal wood lath that has been nailed on vertical 

wood furring strips attached to the logs (Fig. 8). If it is 

applied over a wood frame structure, stucco may be 

applied to wood or metal lath nailed directly to the 

wood frame; it may also be placed on lath that has 

been attached to furring strips. The furring strips are 

themselves laid over building paper covering the wood 

sheathing (Fig. 9). Wood lath was gradually superseded by expanded metal lath introduced in the 

late-nineteenth and early-twentieth century. When 

stuccoing over a stone or brick substrate, it was customary to cut back or rake out the mortar joints if they 

were not already recessed by natural weathering or 

Fig. 6. Arlington House, Arlington, Virginia, was built between 1802-1818 of brick covered with stucco. It was designed by George 

Hadfield for George Washington Parke Custis, grandson of Martha Washington, and was later the home of Robert E. Lee. This 

photograph taken on June 28, 1864, by Captain Andrew f. Russell, a U. S. Signal Corps photographer, shows the stucco after it had 

been marbleized during the 1850's. Yellow ochre and burnt umber pigments were combined to imitate Sienna marble, and the stucco, 

with the exception of the roughcast foundation, was scored to heighten the illusion of stone. Photo: National Archives, Arlington 

House Collection, National Park Service. 

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Fig. 7. Patches of stucco have fallen off this derelict 19th 

century structure exposing the rough-cut local stone 

substrate. The missing wood entablature on the side and the 

rough wood lintel now exposed above a second-floor window, 

offer clues that the building was stuccoed originally. Photo: 

National Park Service Files. 

Fig. 8. Removal of deteriorated stucco in preparation for 

stucco repair on this late-18th century log house in 

Middleway, West Virginia, reveals that the stucco was 

applied to hand-riven wood lath nailed over vertical wood 

strips attached to the logs. Photo: Anne Grimmer. 

Fig. 9. This cutaway drawing shows the method of 

attachment for stucco commonly used on wood frame or 

balloon frame structures from the late-19th to the 20th 

century. Drawing: Brian Conway, "Illinois Preservation 

Series Number 2: Stucco. " 

erosion, and sometimes the bricks themselves were 

gouged to provide a key for the stucco. This helped 

provide the necessary bond for the stucco to remain 

attached to the masonry, much like the key provided 

by wood or metal lath on frame buildings. 

Like interior wall plaster, stucco has traditionally been 

applied as a multiple-layer process, sometimes consisting of two coats, but more commonly as three. 

Whether applied directly to a masonry substrate or 

onto wood or metal lath, this consists of a first 

"scratch" or "pricking-up" coat, followed by a second 

scratch coat, sometimes referred to as a "floating" or 

"brown" coat, followed finally by the "finishing" coat. 

Up until the late-nineteenth century, the first and the 

second coats were of much the same composition, generally consisting of lime, or natural cement, sand, perhaps clay, and one or more of the additives previously 

mentioned. Straw or animal hair was usually added to 

the first coat as a binder. The third, or finishing coat, 

consisted primarily of a very fine mesh grade of lime 

and sand, and sometimes pigment. As already noted, 

after the 1820's, natural cement was also a common 

ingredient in stucco until it was replaced by portland 

cement. 

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A B 

I --- ~ 

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c o 

Fig. 10. (a) Tudor Place, Washington, D.C. (1805-1816), was designed by Dr. William Thornton. Like its contemporary, Arlington 

House, it is stuccoed and scored, with a roughcast base, but here the stucco is a monochromatic sandstone color tinted by sand and 

mineral pigments (b). Although the original stucco was replaced in the early-20th century with a portland cement-based stucco, the 

family, who retained ownership until 1984 when the house was opened to the public, left explicit instructions for future stucco 

repairs. The mix recommended for repairing hairline cracks (c), consists of sharp sand, cement and lime, burnt umber, burnt sienna, 

and a small amount of raw sienna. Preparation of numerous test samples, the size of "a thick griddle cake," will be necessary to 

match the stucco color, and when the exact color has been achieved, the mixture is to be diluted to the "consistency of cream," 

brushed on the wall and rubbed into the cracks with a rubber sponge or float . Note the dark color visible under the eaves intended to 

replicate the stronger color of the originallimewashed stucco (d). Photos: Anne Grimmer. 

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Both masonry and wood lath must be kept wet or 

damp to ensure a good bond with the stucco. Wetting 

these materials helps to prevent them from pulling 

moisture out of the stucco too rapidly, which results in 

cracking, loss of bond, and generally poor quality 

stuccowork. 

Traditional Stucco Finishes 

Until the early-twentieth century when a variety of 

novelty finishes or textures were introduced, the last 

coat of stucco was commonly given a smooth, troweled 

finish, and then scored or lined in imitation of ashlar. 

The illusion of masonry joints was sometimes enhanced by a thin line of white lime putty, graphite, or 

some other pigment. Some nineteenth century buildings feature a water table or raised foundation of 

rough-cast stucco that differentiates it from the stucco 

surface above, which is smooth and scored (Fig. 10). 

Other novelty or textured finishes associated with the 

"period" or revival styles of the early-twentieth century 

include: the English cottage finish, adobe and Spanish, 

pebble-dashed or dry-dash surface, fan and sponge 

texture, reticulated and vermiculated, roughcast (or wet 

dash), and sgraffito (Fig. 11). 

Repairing Deteriorated Stucco 

Regular Maintenance 

Although A. J. Downing alluded to stuccoed houses in 

Pennsylvania that had survived for over a century in 

relatively good condition, historic stucco is inherently 

not a particularly permanent or long-lasting building 

material. Regular maintenance is required to keep it in 

good condition. Unfortunately, many older or historic 

buildings are not always accorded this kind of care. 

Because building owners knew stucco to be a protective, but also somewhat fragile coating, they employed a 

variety of means to prolong its usefulness. The most 

common treatment was to whitewash stucco, often 

annually. The lime in the whitewash offered protection 

and stability and helped to harden the stucco. Most 

importantly, it filled hairline cracks before they could 

develop into larger cracks and let in moisture. To improve water repellency, stucco buildings were also 

sometimes coated with paraffin, another type of wax, 

or other stucco-like coatings, such as oil mastics. 

Assessing Damage 

Most stucco deterioration is the result of water infiltration into the building structure, either through the 

roof, around chimneys, window and door openings, or 

excessive ground water or moisture penetrating 

through, or splashing up from the foundation. Potential causes of deterioration include: ground settlement, 

lintel and door frame settlement, inadequate or leaking 

gutters and downspouts, intrusive vegetation, moisture 

migration within walls due to interior condensation 

and humidity, vapor drive problems caused by furnace, 

bathroom and kitchen vents, and rising damp resulting 

from excessive ground water and poor drainage around 

the foundation. Water infiltration will cause wood lath 

to rot, and metal lath and nails to rust, which eventuFig. 11. The Hotel Washington, Washington, D. C. 

(1916-1917), is notable for its decorative sgraffito surfaces. 

Stucco panels under the comice and around the windows 

feature classical designs created by artists who incised the 

patterns in the outer layer of red-colored stucco while still 

soft, thereby exposing a stucco undercoat of a contrasting 

color. Photo: Kaye Ellen Sill1onson. 

ally will cause stucco to lose its bond and pull away 

from its substrate. 

After the cause of deterioration has been identified, 

any necessary repairs to the building should be made 

first before repairing the stucco. Such work is likely to 

include repairs designed to keep excessive water away 

from the stucco, such as roof, gutter, downspout and 

flashing repairs, improving drainage, and redirecting 

rainwater runoff and splash-back away from the building. Horizontal areas such as the tops of parapet walls 

or chimneys are particularly vulnerable to water infiltration, and may require modifications to their original 

design, such as the addition of flashing to correct the 

problem. 

Previous repairs inexpertly carried out may have 

caused additional deterioration, particularly if executed 

in portland cement, which tends to be very rigid, and 

therefore incompatible with early, mostly soft limebased stucco that is more "flexible ." [ncompatible 

7 
repairs, external vibration caused by traffic or construction, or building settlement can also result in 

cracks which permit the entrance of water and cause 

the stucco to fail (Fig. 12). 

Before beginning any stucco repair, an assessment of 

the stucco should be undertaken to determine the extent of the damage, and how much must be replaced 

or repaired. Testing should be carried out systematically on all elevations of the building to determine the 

overall condition of the stucco. Some areas in need of 

repair will be clearly evidenced by missing sections of 

stucco or stucco layers. Bulging or cracked areas are 

obvious places to begin. Unsound, punky or soft areas 

that have lost their key will echo with a hollow sound 

when tapped gently with a wooden or acrylic hammer 

or mallet. 

Identifying the Stucco Type 

Analysis of the historic stucco will provide useful information on its primary ingredients and their proportions, and will help to ensure that the new replacement 

stucco will duplicate the old in strength, composition, 

color and texture as closely as possible. However, unless authentic, period restoration is required, it may not 

be worthwhile, nor in many instances possible, to attempt to duplicate all of the ingredients (particularly 

some of the additives), in creating the new stucco mortar. Some items are no longer available, and others, 

notably sand and lime-the major components of traditional stucco-have changed radically over time. For 

example, most sand used in contemporary masonry 

work is manufactured sand, because river sand, which 

was used historically, is difficult to obtain today in 

many parts of the country. The physical and visual 

qualities of manufactured sand versus river sand, are 

quite different, and this affects the way stucco works, 

as well as the way it looks. The same is true of lime, 

which is frequently replaced by gypsum in modern 

stucco mixes. And even if identification of all the items 

in the historic stucco mix were possible, the analysis 

would still not reveal how the original stucco was 

mixed and applied. 

There are, however, simple tests that can be carried out 

on a small piece of stucco to determine its basic makeup. A dilute solution of hydrochloric (muriatic) acid 

will dissolve lime-based stucco, but not portland cement. Although the use of portland cement became 

common after 1900, there are no precise cut-off dates, 

'as stuccoing practices varied among individual plasterers, and from region to region. Some plasterers began 

using portland cement in the 1880's, but others may 

have continued to favor lime stucco well into the earlytwentieth century. While it is safe to assume that a 

late-eighteenth or early-nineteenth century stucco is 

lime-based, late-nineteenth or early-twentieth century 

Fig. 12. (a) Water intrusion caused by rusting metal, or (b) plant growth left unattended will gradually enlarge these cracks, 

resulting in spalling, and eventually requiring extensive repair of the stucco. Photos: National Park Service Files. 

8 
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Fig. 13. (a) In preparation for repainting, hairline cracks on this Mediterranean style stucco apartment building were filled with a 

commercial caulking compound; (b) dirt is attracted and adheres to the texture of the caulked areas, and a year after painting, these 

inappropriate repairs are highly obvious. Photos: Anne Grimmer. 

stucco may be based on either lime or portland cement. 

Another important factor to take into consideration is 

that an early lime-stucco building is likely to have been 

repaired many times over the ensuing years, and it is 

probable that at least some of these patches consist of 

portland cement. 

Planning the Repair 

Once the extent of damage has been determined, a 

number of repair options may be considered. Small 

hairline cracks usually are not serious and may be 

sealed with a thin slurry coat consisting of the finish 

coat ingredients, or even with a coat of paint or whitewash. Commercially available caulking compounds are 

not suitable materials for patching hairline cracks. Because their consistency and texture is unlike that of 

stucco, they tend to weather differently, and attract 

more dirt; as a result, repairs made with caulking compounds may be highly visible, and unsightly (Fig. 13). 

Larger cracks will have to be cut out in preparation for 

more extensive repair. Most stucco repairs will require 

the skill and expertise of a professional plasterer (Fig. 

14). 

In the interest of saving or preserving as much as possible of the historic stucco, patching rather than wholesale replacement is preferable. When repairing heavily 

textured surfaces, it is not usually necessary to replace 

an entire wall section, as the textured finish, if wellexecuted, tends to conceal patches, and helps them to 

blend in with the existing stucco. However, because of 

the nature of smooth-finished stucco, patching a number of small areas scattered over one elevation may not 

be a successful repair approach unless the stucco has 

been previously painted, or is to be painted following 

the repair work. On unpainted stucco such patches are 

hard to conceal, because they may not match exactly or 

blend in with the rest of the historic stucco surface. For 

Fig. 14. This poorly executed patch is not the work of a 

professional plasterer. While it may serve to keep out water, it 

does not match the original surface, and is not an appropriate 

repair for historic stucco. Photo: Betsy Chittenden. 

this reason it is recommended, if possible, that stucco 

repair be carried out in a contained or well-defined 

area, or if the stucco is scored, the repair patch should 

be "squared-off" in such a way as to follow existing 

scoring. In some cases, especially in a highly visible 

location, it may be preferable to restucco an entire wall 

section or feature. In this way, any differences between 

the patched area and the historic surface will not be so 

readily apparent. 

Repair of historic stucco generally follows most of the 

same principles used in plaster repair. First, all deteriorated, severely cracked and loose stucco should be removed down to the lath (assuming that the lath is 

securely attached to the substrate), or down to the masonry if the stucco is directly applied to a masonry 

substrate. A clean surface is necessary to obtain a good 

9 
bond bet\'veen the stucco and substrate. The areas to be 

patched should be cleaned of all debris with a bristle 

brush, and all plant growth, dirt, loose paint, oil or 

grease should be removed (Fig. 15). If necessary, brick 

or stone mortar joints should then be raked out to a 

depth of approximately 5/8" to ensure a good bond 

between the substrate and the new stucco. 

To obtain a neat repair, the area to be patched should 

be squared-off with a butt joint, using a cold chisel, a 

hatchet, a diamond blade saw, or a masonry bit. Sometimes it may be preferable to leave the area to be 

patched in an irregular shape which may result in a 

less conspicuous patch. Proper preparation of the area 

to be patched requires very sharp tools, and extreme 

caution on the part of the plasterer not to break keys of 

surrounding good stucco by "over-sounding" when 

removing deteriorated stucco. To ensure a firm bond, 

the ne~ patch must not overlap the old stucco. If the 

stucco has lost its bond or key from wood lath, or the 

lath has deteriorated or come loose from the substrate, 

a decision must be made whether to try to reattach the 

old lath, to replace deteriorated lath with new wood 

lath, or to leave the historic wood lath in place and 

supplement it with modern expanded metal lath. Unless authenticity is important, it is generally preferable 

(and easier) to nail new metal lath over the old wood 

lath to support the patch. Metal lath that is no longer 

securely fastened to the substrate may be removed and 

replaced in kind, or left in place, and supplemented 

with new wire lath . 

When repairing lime-based stucco applied directly to 

masonry, the new stucco should be applied in the same 

manner, directly onto the stone or brick. The stucco 

will bond onto the masonry itself without the addition 

of lath because of the irregularities in the masonry or 

those of its mortar joints, or because its surface has 

been scratched, scored or otherwise roughened to provide an additional key. Cutting out the old stucco at a 

diagonal angle may also help secure the bond between 

the new and the old stucco. For the most part it is not 

advisable to insert metal lath when restuccoing historic 

masonry in sound condition, as it can hasten deterioration of the repair work. Not only will attaching the lath 

damage the masonry, but the slightest moisture penetration can cause metal lath to rust. This will cause 

metal to expand, eventually resulting in spalling of the 

stucco, and possibly the masonry substrate too. 

If the area to be patched is properly cleaned and prepared, a bonding agent is usually not necessary. However, a bonding agent may be useful when repairing 

hairline cracks, or when dealing with substrates that do 

not offer a good bonding surface. These may include 

dense stone or brick, previously painted or stuccoed 

Fig. 15. (a) After reattaching any loose wood lath to the furring. strips underneath, the a:ea to be patched has been cleaned, the lath 

thoroughly wetted, and (b) the first coat of stucco has been applzed and scratched to provide a key to hold the second layer of stucco. 

Photos: Betsy Chittenden. 

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masonry, or spalling brick substrates. A good mechanical bond is always preferable to reliance on bonding 

agents. Bonding agents should not be used on a wall 

that is likely to remain damp or where large amounts 

of salts are present. Many bonding agents do not survive well under such conditions, and their use could 

jeopardize the longevity of the stucco repair. 

A stucco mix compatible with the historic stucco 

should be selected after analyzing the existing stucco. It 

can be adapted from a standard traditional mix of the 

period, or based on one of the mixes included here. 

Stucco consisting mostly of portland cement generally 

will not be physically compatible with the softer, more 

flexible lime-rich historic stuccos used throughout the 

eighteenth and much of the nineteenth centuries. The 

differing expansion and contraction rates of lime stucco 

and portland cement stucco will normally cause the 

stucco to crack. Choosing a stucco mix that is durable 

and compatible with the historic stucco on the building 

is likely to involve considerable trial and error, and 

probably will require a number of test samples, and 

even more if it is necessary to match the color. It is 

best to let the stucco test samples weather as long as 

possible-ideally one year, or at least through a change 

of seasons, in order to study the durability of the mix 

and its compatibility with the existing stucco, as well as 

the weathering of the tint if the building will not be 

painted and'color match is an important factor. If the 

test samples are not executed on the building, they 

should be placed next to the stucco remaining on the 

building to compare the color, texture and composition 

of the samples with the original. The number and 

thickness of stucco coats used in the repair should also 

match the original. 

After thoroughly dampening the masonry or wood 

lath, the first, scratch coat should be applied to the 

masonry substrate, or wood or metal lath, in a thickness that corresponds to the original if extant, or generally about 1/4" to 3/8" . The scratch coat should be 

scratched or cross-hatched with a comb to provide a 

key to hold the second coat. It usually takes 24-72 

hours, and longer in cold weather, for each coat to dry 

before the next coat can be applied. The second coat 

should be about the same thickness as the first, and 

the total thickness of the first two coats should generally not exceed about 5/8". This second or leveling coat 

should be roughened using a wood float with a nail 

protruding to provide a key for the final or finish coat. 

The finish coat, about 1/4" thick, is applied after the 

previous coat has initially set. If this is not feasible, the 

base coat should be thoroughly dampened when the 

finish coat is applied later. The finish coat should be 

worked to match the texture of the original stucco (Fig. 

16). 

Colors and Tints for Historic Stucco Repair 

The color of most early stucco was supplied by the 

aggregate included in the mix-usually the sand. 

Sometimes natural pigments were added to the mix, 

and eighteenth and nineteenth-century scored stucco 

was often marbleized or painted in imitation of marble 

or granite. Stucco was also frequently coated with 

whitewash or a colorwash. This tradition later evolved 

into the use of paint, its popularity depending on the 

vagaries of fashion as much as a means of concealing 

repairs. Because most of the early colors were derived 

from nature, the resultant stucco tints tended to be 

mostly earth-toned. This was true until the advent of 

brightly colored stucco in the early decades of the 

twentieth century. This was the so-called "Jazz Plaster" 

developed by O.A. Malone, the "man who put color 

into California," and who founded the California 

Stucco Products Corporation in 1927. California Stucco 

was revolutionary for its time as the first stucco/plaster 

to contain colored pigment in its pre-packaged factory 

mix. 

When patching or repairing a historic stucco surface 

known to have been tinted, it may be possible to determine through visual or microscopic analysis whether 

the source of the coloring is sand, cement or pigment. 

Although some pigments or aggregates used traditionally may no longer be available, a sufficiently close 

color-match can generally be approximated using sand, 

natural or mineral pigments, or a combination of these . 

Obtaining such a match will require testing and comparing the color of dried test samples with the original. 

Successfully combining pigments in the dry stucco mix 

prepared for the finish coat requires considerable skill. 

The amount of pigment must be carefully measured for 

each batch of stucco. Overworking the mix can make 

the pigment separate from the lime. Changing the 

amount of water added to the mix, or using water to 

apply the tinted finish coat, will also affect the color of 

the stucco when it dries. 

Generally, the color obtained by hand-mixing these 

ingredients will provide a sufficiently close match to 

cover an entire wall or an area distinct enough from the 

rest of the structure that the color differences will not 

be obvious. However, it may not work for small 

patches conspicuously located on a primary elevation, 

where color differences will be especially noticeable. In 

these instances, it may be necessary to conceal the 

repairs by painting the entire patched elevation, or 

even the whole building. 

Many stucco buildings have been painted over the 

years and will require repainting after the stucco repairs have been made. Limewash or cement-based 

paint, latex paint, or oil-based paint are appropriate 

coatings for stucco buildings. The most important factor to consider when repainting a previously painted or 

coated surface is that the new paint be compatible with 

any coating already on the surface. In preparation for 

repainting, all loose or peeling paint or other coating 

material not firmly adhered to the stucco must be removed by hand-scraping or natural bristle brushes. The 

surface should then be cleaned. 

Cement-based paints, most of which today contain 

some portland cement and are really a type of limewash, have traditionally been used on stucco buildings. 

The ingredients were easily obtainable. Furthermore, 

the lime in such paints actually bonded or joined with 

the stucco and provided a very durable coating. In 

many regions, whitewash was applied annually during 

spring cleaning. Modern, commercially available premixed masonry and mineral-based paints may also be 

used on historic stucco buildings. 

11 
Fig. A Fig. B 

.. 

Fig. C Fig. 0 

Fig. 16. (a) In preparation for stucco repair, this plasterer is mixing the dry materials in a mortar box with a mortar hoe (note the 2 

holes in the blade), pulling it through the box using short choppy strokes. After the dry materials are thoroughly combined, water 

is added and mixed with them using the same choppy, but gradually lengthening stokes, making sure that the hoe cuts completely 

through the mix to the bottom of the box. (b) The deteriorated stucco has been cut away, and new metal lath has been nailed to the 

clapboarding in the area to be patched. (Although originally clapboarded when built in the 19th century, the house was stuccoed 

around the turn-of-the-century on metal lath nailed over the clapboard.) (c) The first, scratch coat and the second coat have been 

applied here, and await the spatterdash or rough-cast finish of the final coat (d) which was accomplished by the plasterer using a 

whisk broom to throw the stucco mortar against the wall surface. This well-executed patch is barely discernable, and lacks only a 

coat of paint to make it blend completely with the rest of the painted wall surface. Photos: Anne Grimmer. 

12 
If the structure must be painted for the first time to 

conceal repairs, almost any of these coatings may be 

acceptable depending on the situation. Latex paint, for 

example, may be applied to slightly damp walls or 

where there is an excess of moisture, but latex paint 

will not stick to chalky or powdery areas. Oil-based, or 

alkyd paints must be applied only to dry walls; new 

stucco must cure up to a year before it can be painted 

with oil-based paint. 

Contemporary Stucco Products 

There are many contemporary stucco products on the 

market today. Many of them are not compatible, either 

physically or visually, with historic stucco buildings. 

Such products should be considered for use only after 

consulting with a historic masonry specialist. However, 

some of these prepackaged tinted stucco coatings may 

be suitable for use on stucco buildings dating from the 

late-nineteenth or early-twentieth century, as long as 

the color and texture are appropriate for the period and 

style of the building. While some masonry contractors 

may, as a matter of course, suggest that a waterrepellent coating be applied after repairing old stucco, 

in most cases this should not be necessary, since colorwashes and paints serve the same purpose, and stucco 

itself is a protective coating. 

Cleaning Historic Stucco Surfaces 

Historic stucco buildings often exhibit multiple layers of 

paint or limewash. Although some stucco surfaces may 

be cleaned by water washing, the relative success of 

this procedure depends on two factors: the surface 

texture of the stucco, and the type of dirt to be removed. If simply removing airborne dirt, smooth unpainted stucco, and heavily-textured painted stucco 

may sometimes be cleaned using a low-pressure water 

wash, supplemented by scrubbing with soft natural 

bristle brushes, and possibly non-ionic detergents. 

Organic plant material, such as algae and mold, and 

metallic stains may be removed from stucco using poultices and appropriate solvents. Although these same 

methods may be employed to clean unpainted roughcast, pebble-dash, or any stucco surface featuring exposed aggregate, due to the surface irregularities, it 

may be difficult to remove dirt, without also removing 

portions of the decorative textured surface. Difficulty in 

cleaning these surfaces may explain why so many of 

these textured surfaces have been painted. 

When Total Replacement is Necessary 

Complete replacement of the historic stucco with new 

stucco of either a traditional or modern mix will probably be necessary only in cases of extreme deteriorationthat is, a loss of bond on over 40-50 per cent of the 

stucco surface. Another reason for total removal might 

be that the physical and visual integrity of the historic 

stucco has been so compromised by prior incompatible 

and ill-conceived repairs that patching would not be 

successful. 

When stucco no longer exists on a building there is 

more flexibility in choosing a suitable mix for the replacement. Since compatibility of old and new stucco 

will not be an issue, the most important factors to consider are durability, color, texture and finish . Depending on the construction and substrate of the building, 

in some instances it may be acceptable to use a relatively strong cement-based stucco mortar. This is certainly true for many late-nineteenth and early-twentieth 

century buildings, and may even be appropriate to use 

on some stone substrates even if the original mortar 

would have been weaker, as long as the historic visual 

qualities noted above have been replicated. Generally, 

the best principle to follow for a masonry building is 

that the stucco mix, whether for repair or replacement 

of historic stucco, should be somewhat weaker than the 

masonry to which it is to be applied in order not to 

damage the substrate. 

General Guidance for Historic Stucco Repair 

A skilled professional plasterer will be familiar 

with the properties of materials involved in stucco 

repair and will be able to avoid some of the pitfalls that would hinder someone less experienced . 

General suggestions for successful stucco repair 

parallel those involving restoration and repair of 

historic mortar or plaster. In addition, the following principles are important to remember: 

• Mix only as much stucco as can be used in one 

and one-half to two hours. This will depend on 

the weather (mortar will harden faster under hot 

and dry, or sunny conditions); and experience is 

likely to be the best guidance. Any remaining 

mortar should be discarded; it should not be 

retempered. 

• Stucco mortar should not be over-mixed. (Hand 

mix for 10-15 minutes after adding water, or machine mix for 3-4 minutes after all ingredients are 

in mixer.) Over-mixing can cause crazing and 

discoloration, especially in tinted mortars. Overmixing will also tend to make the mortar set too 

fast, which will result in cracking and poor bonding or keying to the lath or masonry substrate . 

• Wood lath or a masonry substrate, but not metal 

lath, must be thoroughly wetted before applying 

stucco patches so that it does not draw moisture 

out of the stucco too rapidly. To a certain extent, 

bonding agents also serve this same purpose. 

Wetting the substrate helps retard drying. 

• To prevent cracking, it is imperative that stucco 

not dry too fast. Therefore, the area to be stuccoed should be shaded, or even covered if possible, particularly in hot weather. It is also a good 

idea in hot weather to keep the newly stuccoed 

area damp, at approximately 90 per cent humidity, 

for a period of 48 to 72 hours. 

• Stucco repairs, like most other exterior masonry 

work, should not be undertaken in cold weather 

(below 40 degrees fahrenheit, and preferably 

warmer), or if there is danger of frost. 

13 
14 

Historic Stucco Textures 

Most of the oldest stucco in the U.S. dating prior to 

the late-nineteenth century, will generally have a 

smooth, troweled finish (sometimes called a sand or 

float finish), possibly scored to resemble ashlar masonry units. Scoring may be incised to simulate masonry joints, the scored lines may be emphasized by 

black or white penciling, or the lines may simply be 

drawn or painted on the surface of the stucco. In 

some regions, at least as early as the first decades of 

the nineteenth century, it was not uncommon to use 

a roughcast finish on the foundation or base of an 

otherwise smooth-surfaced building (Fig. a). Roughcast was also used as all overall stucco finish for 

some outbuildings, and other less important types 

of structures. 

A wide variety of decorative surface textures may be 

found on revival style stucco buildings, particularly 

residential architecture. These styles evolved in the 

late-nineteenth century and peaked in popularity in 

the early decades of the twentieth century. Frank 

Lloyd Wright favored a smooth finish stucco, which 

was imitated on much of the Prairie style architecture inspired by his work. Some of the more picturesque surface textures include: English Cottage or 

English Cotswold finish; sponge finish (Fig. b); fan 

texture; adobe finish (Fig. c), and Spanish or Italian 

---

Fig. A Fig. B 

Fig. 0 Fig. E 

finish. Many of these finishes and countless other 

regional and personalized variations on them are 

still in use. 

The most common early-twentieth century stucco 

finishes are often found on bungalow-style houses, 

and include: spatter or spatterdash (sometimes 

called roughcast, harling, or wetdash), and pebbledash or drydash. The spatterdash finish is applied 

by throwing the stucco mortar against the wall using 

a whisk broom or a stiff fiber brush, and it requires 

considerable skill on the part of the plasterer to 

achieve a consistently rough wall surface. The mortar used to obtain this texture is usually composed 

simply of a regular sand, lime, and cement mortar, 

although it may sometimes contain small pebbles or 

crushed stone aggregate, which replaces one-half 

the normal sand content. The pebbledash or drydash finish is accomplished manually by the plasterer throwing or "dashing" dry pebbles (about 1/8" 

to 1/4" in size), onto a coat of stucco freshly applied 

by another plasterer. The pebbles must be thrown at 

the wall with a scoop with sufficient force and skill 

that they will stick to the stuccoed wall. A more 

even or uniform surface can be achieved by patting 

the stones down with a wooden float. This finish 

may also be created using a texturing machine (Figs. 

d-f illustrate 3 versions of this finish. Photos: 

National Park Service Files). 

Fig. C 

Fig. F 
Summary 

Stucco on historic buildings is especially vulnerable not 

only to the wear of time and exposure to the elements, 

but also at the hands of well-intentioned "restorers;' 

who may want to remove stucco from eighteenth and 

nineteenth century structures, to expose what they 

believe to be the original or more "historic" brick, 

stone or log underneath. Historic stucco is a characterdefining feature and should be considered an important historic building material, significant in its own 

right. While many eighteenth and nineteenth century 

buildings were stuccoed at the time of construction, 

others were stuccoed later for reasons of fashion or 

practicality. As such, it is likely that this stucco has 

acquired significance over time, as part of the history 

and evolution of a building. Thus, even later, nonhistoric stucco should be retained in most instances; 

and similar logic dictates that new stucco should not be 

applied to a historic building that was not stuccoed 

previously. When repairing historic stucco, the new 

stucco should duplicate the old as closely as possible in 

strength, composition, color and texture . 

Mixes for Repair of Historic Stucco 

Historic stucco mixes varied a great deal regionally, depending as they did on the availability of 

local materials. There are probably almost as 

many mixes that can be used for repair of historic 

stucco as there are historic stucco buildings. For 

this reason it is recommended that at least a rudimentary analysis of the existing historic stucco be 

carried out in order to determine its general proportions and primary ingredients. However, if 

this is not possible, or if test results are inconclusive, the following mixes are provided as reference. Many of the publications listed under 

"Selected Reading" include a variety of stucco 

mixes and should also be consulted for additional 

guidance. 

Materials Specifications should conform to those 

contained in Preservation Briefs 2: Repainting Mortar 

Joints in Historic Brick Buildings, and are as follows: 

• Lime should conform to ASTM C-207, Type S, 

Hydrated Lime for Masonry Purpos~s. 

• Sand should conform to ASTM C-144 to assure 

proper gradation and freedom from impurities. 

Sand, or other type of aggregate, should match 

the original as closely as possible. 

• Cement should conform to ASTM C-lS0, Type 

II (white, non-staining), portland cement. 

• Water should be fresh, clean and potable. 

• If hair or fiber is used, it should be goat or cattle 

hair, or pure manilla fiber of good quality, 1/2" 

to 2" in length, clean, and free of dust, dirt, oil, 

grease or other impurities. 

• Rules to remember: More lime will make the 

mixture more plastic, but stucco mortar with a 

very large proportion of lime to sand is more 

likely to crack because of greater shrinkage; it is 

also weaker and slower to set. More sand or 

aggregate, will minimize shrinkage, but make 

the mixture harder to trowel smooth, and will 

weaken the mortar. 

Soft Lime Stucco (suitable for application to 

buildings dating from 1700-1850) 

A.f. Downing's Recipe for 50ft Lime Stucco 

1 part lime 

2 parts sand 

(A.J. Downing, "The Architecture of Country Houses," 1850) 

Vieux Carre Masonnj Maintenance Guidelines 

Base Coats (2): 

1 part by volume hydrated lime 

3 parts by volume aggregate [sand]-size to match original 

6 pounds/cubic yards hair or fiber 

Water to form a workable mix. 

Finish Coat: 

1 part by volume hydrated lime 

3 parts aggregate [sand]-size to match original 

Water to form a workable mix. 

Note: No portland cement is recommended in this mix, but if 

it is needed to increase the workability of the mix and to decrease the setting time, the amount of portland cement added 

should never exceed 1 part to 12 parts lime and sand. 

("Vieux Carre Masonry Maintenance Guidelines;' June, 1980.) 

"Materials for 50ft Brick Mortar and for 50ft Stucco" 

5 gallons hydrated lime 

10 gallons sand 

1 quart white, non-staining portland cement (1 cup only for 

pointing) 

Water to form a workable mix. 

(Koch and Wilson, Architects, New Orleans, Louisiana, February, 1980) 

Mix f9r Repair of Traditional Natural Cement or Hy- draulic LIme Stucco 

part by volume hydrated lime 

2 parts by volume white portland cement 

3 parts by volume fine mason's sand 

If hydrauliC lime is available, it may be used instead of limecement blends. 

("Conservation Techniques for the Repair of Historical Ornamental Exterior Stucco, January, 1990) 

Early-twentieth century Portland Cement Stucco 

1 part portland cement 

21 /2 parts sand 

Hydrated lime = to not more than 15% of the cement's volume 

Water to form a workable mix. 

The same basic mix was used for all coats, but the finish coat 

generally contained more lime than the undercoats. (" lIIinois 

Preservation Series No.2: Stucco," January, 1980) 

American Portland Cement Stucco Specifications 

(c. 1929) 

Base Coats: 

5 pounds, dry, hydrated lime 

1 bag portland cement (94 lbs.) 

Not less than 3 cubic feet (3 bags) sand (passed through a IR 

screen) 

Water to make a workable mix. 

Finish Coat: 

Use WHITE portland cement in the mix in the same proportions as above. 

To color the stucco add not more than 10 pounds pigme nt for 

each bag of cement contained in the mix. 

15 
Selected Reading 

Ashurst, john, and Nicola Ashurst. Practical Building Conservatioll, 

[IISlisli Heritas" Tecllllical Halld/1ook, Volullle 3. Mortars, Plasters and 

~elld('Ys. New York: Halsted Press, 1988. 

Conway, Brian D. Illinois Preservatiol1 Series Number 2: Stucco. 

Springfield, IL: lIIinois Department of Conservation, Division of 

Historic Sites, 1980. 

Grimmer, Anne E. Keeping it Cleal1: Removil1g Exterior Dirt, Pail1t, 

Staills alld Graffiti from Historic Masol1nj Buildil1gs. Washington, 

D.C.: National Park Service, U.S. Department of the Interior, 1988. 

Hodgson, Frederick T. Plaster al1d Plasteril1g. Mortars al1d Cements, How 

to Make, ulld How to Use ... with An Illustrated Glossary of Terms. 

New York: The Industrial Publication Company, 1901. 

johnson, leRoy, jr. (editor). Handbook of Maintenance Techniques for 

Buildillg Conservation in the Strand Historic District, Galveston, Texas. 

(Revised edition originally published in 1980 as Preservation 

Maintenance Handbook, prepared by Michael Emrick, AlA, for the 

Galveston Historical Foundation.) Austin, TX: Texas Historical 

Commission, 1984. 

jowers, Walter. " Bungalow Building Materials: How to Repair 

Stucco." The Old-House Jou mal. Vol. XIII, No. 4 (May 1985), pp. 

80-83. 

MacDonald, Marylee. Preservation Briefs 21: Repairing Historic Flat 

Plaster-Walls and Ceilings. Washington, D.C.: National Park Service, 

U.S. Department of the Interior, 1989. 

Mack, Robert c., AlA, de Teel Patterson Tiller, and James S. Askins. 

Preservation Briefs 2: Repointing Mortar Joints in Historic Brick 

Buildings. Washington, D.C.: National Park Service, U.S. 

Department of the Interior, 1980. 

McKee, Harley J., FAIA. Introduction to Early American Masonry-Stone, 

Brick, Mortar alld Plaster. Washington, D.C.: National Trust for 

Historic Preservation and Columbia University, 1973. 

Matero, Frank G., Mary Hardy, Antonio Rava and Joel Snodgrass. 

Conservation Techniques for the Repair of Historical Ornamental Exterior 

Stucco. (With a Case Study for the Repair of the Cabildo Pedimental 

Sculpture). Report prepared for the Division of Historic 

Preservation, Office of Cultural Development, Louisiana 

Department of Culture, Recreation and Development by The 

Center for Preservation Research, Columbia UniverSity, New York. 

january 1990. 

16 

Portland Cement Plaster (Stucco) Manual. Skokie, IL: Portland Cement 

Association, 1980. 

Van Den Branden, E, and Thomas L. Hartsell. Plastering Skills. 

Second edition. Homewood, IL: American Technical Publishers, 

Inc., 1984. 

Vieux Carre Masonry Maintenance Guidelines. Revised from the initial 

report prepared by Mary L. Oehrlein in 1977. New Orleans, LA: 

Vieux Carre Commission, 1980. 

Whitewash & Coldwater Paints. Bulletin No. 304-G. Washington, D.C.: 

National Lime Association, 1955. 

Worsham, Gibson. "Exterior Plaster Restoration at the Lord Morton 

House, Lexington, Kentucky." Association for Preservation Technology 

Bulletin. Vol. XIII, No. 4 (1981), pp. 27-33. 

Acknowledgements 

The author gratefully acknowledges the technical expertise contributed to the 

preparation of this publication by Gilbert Wolf, National Plastering Industries; 

Walter Jowers; Brian Conway, Michigan Bureau of History; and master 

plasterer, Lawrence Ring, Sr. In addition, invaluable comments were provided 

by Michael Auer, Charles Fisher, Lauren Meier, Sharon Park, and Kay Weeks, 

professional staff of the Technical Preservation Services Branch, National Park 

Service; professional staff of the Cultural Resources program, Mid-Atlantic 

Regional Office, National Park Service; and S. Elizabeth Sasser of the 

Williamsport Preservation Training Center, National Park Service. 

This publication has been prepared pursuant to the National Historic 

Preservation Act of 1966, as amended, which directs the Secretary of the 

Interior to develop and make available information concerning historic 

properties. Comments on the usefulness of this publication may be directed to 

H. Ward Jandl, Chief, Technical Preservation Services Branch, Preservation 

Assistance Division, National Park Service, P.o. Box 37127, Washington, D.C. 

20013-7127. 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. 

October 1990 

Cover Photograph: St. James Church, Goose Creek, Berkeley 

County, South Carolina (1713-1719), is constructed of brick 

covered with stucco. Although much restored, it is notable 

for its ornamental stucco detailing, including rusticated 

quoins, cherub head "keystones" above the windows, flaming 

hearts, and a pelican in piety-symbol of the sacrament, in 

the pediment over the front door. Photo: Gary Hume.