Chapter 6—Housing Structure

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1

New Housing Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1

Old Housing Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6

Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-8

Vapor Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Crawl Space Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Vapor Barriers for Concrete Slab Homes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Wall and Ceiling Vapors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

House Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Foundation Sills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Flooring Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10

Studs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-11

Interior Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-11

Stairways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Doors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-13

Roof Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Rafters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Collar Beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Purlin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Ridge Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Hip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Roof Sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Dormer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Asphalt Shingle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

EPDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-15

Asphalt Built-up Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Coal Tar Pitch Built-up Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Slate Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Tile Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Copper Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Galvanized Iron Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Wood Shingle Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Roof Flashing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Gutters and Leaders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Exterior Walls and Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-16

Putting It All Together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-17

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-21

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-22

Figure 6.1. Housing Structure Terminology, Typical House Built Today . . . . . . . . . . . . . . . . . .6-1

Figure 6.2. Housing Structure Terminology, Typical House Built Between 1950 and 1980 . . . .6-6

Figure 6.3. Foundation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-9

Figure 6.4. Foundation Cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-9

Healthy Housing Reference Manual 1

Contents
Figure 6.5. Interior Stairway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Figure 6.6. Classifications of Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-12

Figure 6.7. Three-dimensional View of a Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-13

Figure 6.8. Window Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-13

Figure 6.9. Wall Framing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-17

2 Contents
Chapter 6: Housing Structure

“The Palace of Fine Arts in Mexico City has sunk more

than 10 feet into the ground since it was built 60 years

ago and the most noticeable effect is that the grand stone

stairway has disappeared and the entrance is now at

street level.” 

C.B. Crawford, 

Canadian Building Digest

Introduction

The principal function of a house is to provide

protection from the elements. Our present society,

however, requires that a home provide not only shelter,

but also privacy, safety, and reasonable protection of our

physical and mental health. A living facility that fails to

offer these essentials through adequately designed and

properly maintained interiors and exteriors cannot be

termed “healthful housing.”

In this chapter, the home is considered in terms of the

parts that have a bearing on its soundness, state of repair,

and safety. These are some of the elements that the

housing inspector must examine when making a

thorough housing inspection.

Figure 6.1 shows a typical house being built and

inspected today and includes a terminology key. Both the

figure and the key are available in an interactive format

in the glossary on the U.S. Inspect Web site [1]. 

Figure 6.2 shows a typical house built between 1950 and

1980 and also includes a terminology key. The figures

show the complexity and the numerous components of a

home. These components form the vocabulary that is

necessary to discuss housing structure inspection issues.

Key to Figure 6.1 (New Housing Terminology)

1. Ash dump (see 35)—A door or opening in the

firebox that leads directly to the ash pit, through

which the ashes are swept after the fire is burned out.

All fireboxes are not equipped with an ash dump.

2. Attic space—The open space within the attic area. 

3. Backfill—The material used to refill an excavation

around the outside of a foundation wall or pipe

trench.

4. Baluster—One of a series of small pillars that is

Figure 6.1. Housing Structure Terminology, Typical House Being Built Today [1]

Healthy Housing Reference Manual 6-1
attached to and runs between the stairs and the

handrails. The spacing between the balusters should

be less than 4 inches to prevent small children from

getting stuck between the balusters. Balusters are

considered a safety item and provide an additional

barrier.

5. Baseboard trim—Typically a wood trim board that is

placed against the wall around the perimeter of a

room next to the floor. The intent is to conceal the

joint between the floor and wall finish.

6. Basement window—A window opening installed in

the basement wall. Basement windows are

occasionally below the finish grade level and will be

surrounded on the exterior by a window well.

7. Blind or shutter—A lightweight frame in the form of

a door located on each side of a window. They are

most commonly constructed of wood (solid or

louvered panels) or plastic. Originally they were

designed to close and secure over the windows for

security and foul weather. Most shutters now are more

likely decorative pieces that are secured to the house

beside the windows.

8. Bridging—Small pieces of wood or metal strapping

placed in an X-pattern between the floor joists at

midspan to prevent the joists from twisting and

squeaking and to provide reinforcement and

distribution of stress.

9. Building paper/underlayment—Building material,

usually a felt paper that is used as a protective barrier

against air and moisture passage from the area

beneath the flooring as well as providing a

movement/noise isolator in hardwood flooring.

10. Ceiling joist—A horizontally placed framing

members at the ceiling of the top-most living space of

a house that provides a platform to which the finished

ceiling material can be attached.

11. Chair rail (not shown)—Decorative trim applied

around the perimeter of a room such as a formal

dining room or kitchen/breakfast nook at the

approximate same height as the back of a chair. It is

sometimes used as a cap trim for wainscoting (see

wainscoting).

12. Chimney—A masonry or in more modern

construction wood framed enclosure that surrounds

and contains one or more flues and extends above the

roofline. 

13. Chimney cap—The metal or masonry protective

coveringat the top of the chimney that seals the

chimney shaft from water entry between the chimney

enclosure and the flue tiles. 

14. Chimney flues—The space or channel in a chimney

that carries off the smoke and other combustion gases

to the outside air. Most homes will have a terra cotta

tile flue or a metal flue.

15. Collar beam/tie—A horizontal piece of framing

lumber that provides intermediate support for

opposite rafters. They are usually located in the

middle to upper third portion of the rafters. It is also

known as a collar beam or collar brace.

16. Concrete slab floor—Typically approximately

4 inches thick, the concrete slab floor provides a

number of uses. It creates a solid level surface to walk

and work on. It provides a separation between the

grade/soil and a potentially livable area. It also

provides lateral compression resistance for the

foundation walls, preventing soil pressure from

outside the foundation from pushing the foundation

walls and footings inward. 

17. Corner brace—Diagonal braces placed at the corners

of framed walls to stiffen them and provide extra strength.

18. Cornice—An overhang of a pitched roof at the eave

line that usually consists of a fascia board, a soffit, and

any appropriate moldings or vents.

19. Cornice molding—The individual pieces of wood

trim that are applied to the cornice area at the eaves.

20. Door casing/trim—The finish trim details around the

perimeter of the door on the interior finished wall.

21. Door frame/jamb—The top and sides of the door to

include the wall framing as well as the actual door

frame and trim. 

22. Downspout—A pipe, usually of metal or vinyl, that is

connected to the gutters and is used to carry the roofwater runoff down and away from the house. 

23. Downspout gooseneck—Segmented section of

downspout that is bent at a radius to allow the

6-2 Housing Structure
downspout to be attached to the house and to follow

the bends and curves of the eaves and ground. 

24. Downspout shoe—The bottom downspout

gooseneck that directs the water from the downspout

to the extension or splash block at the grade. 

25. Downspout strap—Strap used to secure the

downspout to the side of the house. 

26. Drain tile—A tube or cylinder that is normally

installed around the exterior perimeter of the

foundation footings that collects and directs ground

water away from the foundation of the house. The tile

can be individual sections of clay or asphalt tubing or,

in more recent construction, a perforated-plastic drain

tile that is approximately 4 inches in diameter. The

drain tile leads either towards a sump or to an exterior

discharge away from the house. 

27. Entrance canopy—A small overhanging roof that

shelters the front entrance.

28. Entrance stoop—An elevated platform constructed of

wood framing or masonry at the front entry that

allows visitors to stand above or out of the elements.

The platform should be wide enough to allow

someone to stand on the platform while opening an

outward swinging door such as a storm door even if

one is not present. 

29. Exterior siding—The decorative exterior finish on a

house. Its primary function is to protect the shell of

the house from the elements. The choice of siding

materials varies widely to include wood, brick, metal,

vinyl, concrete, stucco, and a variety of manufactured 

compositions such as compressed wood, compressed

cellulose (paper), fiber-reinforced cement, and

synthetic stucco. 

30. Fascia—The visible flat front board that caps the

rafter tail ends and encloses the overhang under the

eave that runs along the roof edge. The gutter is

usually attached at this location. 

31. Fascia/rake board—The visible flat front board that

caps the rafter tail ends and encloses the overhang

under the eave that runs along the roof edge and at

the edge of the roofing at the gables. The gutter is

usually attached to this board at the eaves. 

32. Finish flooring (not shown)—The final floor covering

inside the living space of a house. The most common

types of finishes are carpeting; hardwood flooring;

ceramic, composite, or laminate stone tile; parquet

panels; or vinyl sheet flooring.

33. Finished grade line—A predetermined line indicating the

proposed elevation of the ground surface around a

building.

34. Firebox—The cavity in the open face of the fireplace

in which the fire is maintained. The firebox leads

directly to the fireplace flue. The firebox is constructed of

fire or refractory brick set in fireclay or reinforced

mortar in traditional masonry fireplaces. The firebox

may also be constructed of metal or ceramic-coated

metal panels in more modern prefabricated fireplaces.

The walls of the firebox are usually slanted toward the

living space both to direct smoke up toward the flue

and to reflect heat into the room.

35. Fireplace cleanout door—The access door to the ash

pit beneath the fireplace. On a fireplace that is located

inside the house, the cleanout door is usually located

in the lowest accessible level of the house such as the

basement or crawl space. On a fireplace that is located

at the outside of the house, the cleanout door will be

located at the exterior of the chimney. Not all

fireplaces are equipped with a cleanout door.

36. Fireplace hearth—The inner or outer floor of a

fireplace, usually made of brick, tile, or stone.

37. Flashing (not shown)—The building component

used to connect and cover portions of a deck, roof, or

siding material to another surface such as a wall, a

chimney, a vent pipe, or anywhere that runoff is

heavy or where two dissimilar materials meet. The

flashing is mainly intended to prevent water entry and

is usually made of rubber, tar, asphalt, or various metals.

38. Floor joists—The main subfloor framing members

that support the floor span. Joists are usually made of

engineered wood I-beams or 2×8 or larger lumber. 

39. Foundation footing—The base on which the

foundation walls rests. The foundation is wider than

the foundation wall to spread out the load it is

bearing and to help prevent settling.

40. Foundation wall—The concrete block, concrete slab

or other nonwood material that extends below or

Healthy Housing Reference Manual 6-3
partly below grade, which provides support for

exterior walls and other structural pans of the building. 

41. Framing studs—A 2×4 or 2×6 vertical framing

member used to construct walls and partitions,

usually spaced 12 to 24 inches apart. 

42. Gable framing—The vertical and horizontal framing

members that make up and support the end of a building

as distinguished from the front or rear side. A gable is

the triangular end of an exterior wall above the eaves.

43. Garage door—The door for the vehicle passage into

the garage area. Typical garage doors consist of

multiple jointed panels of wood, metal, or fiberglass. 

44. Girder—A large beam supporting floor joists at the same

level as the sills. A larger or principal beam used to support

concentrated loads at isolated points along its length.

45. Gravel fill—A bed of coarse rock fragments or

pebbles that is laid atop the existing soil before

pouring the concrete slab. The gravel serves a dual

purpose of breaking surface tension on the concrete

slab and providing a layer that interrupts capillary

action of subsurface moisture from reaching the

concrete slab. Typically, a polyethylene sheeting will

be installed between the gravel fill and the concrete

slab for further moisture proofing.

46. Gutter—A channel used for carrying water run-off.

Usually located at the eaves of a house and connected

to a downspout. The primary purpose of the gutters

and downspouts is to carry roof water run-off as far

away from the house as possible. 

47. Insulation—A manufactured or natural material that

resists heat flow that is installed in a house’s shell to

keep the heat in a house in the winter and the

coolness in the house in the summer. The most

common form of insulation is fiberglass, whether in

batts or blown-in material, along with cellulose, rigid

foam boards, sprayed-in foam, and rock wool.

48. Jack/king stud—The framing stud, sometimes called

the trimmer, that supports the header above a

window, door, or other opening within a bearing wall.

Depending on the size of the opening, there may be

several jack studs on either side of the opening.

49. Mantel—The ornamental or decorative facing around

a fireplace including a shelf that is attached to the

breast or backing wall above the fireplace.

50. Moisture/vapor barrier—A nonporous material, such

as plastic or polyethylene sheeting, that is used to

retard the movement of water vapor into walls and

attics and prevent condensation in them. A vapor

barrier is also installed in crawl space areas to prevent

moisture vapor from entering up through the ground.

51. Newel post—The post at the top and bottom of the

handrails and anywhere along the stair run that

creates a directional change in the handrails is called

the newel post. The newel post is securely anchored

into the underlying floor framing or the stair stringer

to provide stability to the handrails.

52. Reinforcing lath—A strip of wood or metal attached

to studs and used as a foundation for plastering,

slating or tiling. Lath has been replaced by gypsum

board in most modern construction.

53. Ridge board/beam—The board placed on edge at the

top-most point of the roof framing, into which the

upper ends of the rafters are joined or attached.

54. Roofing—The finished surface at the top of the house

that must be able to withstand the effects of the

elements (i.e., wind, rain, snow, hail, etc.). A wide

variety of materials are available, including asphalt

shingles, wood shakes, metal roofing, ceramic and

concrete tiles, and slate, with asphalt shingles making

up the bulk of the material used.

55. Roof rafters—Inclined structural framing members

that support the roof, running from the exterior wall

the to the ridge beam. Rafters directly support the

roof sheathing and create the angle or slope of the roof. 

56. Roof sheathing—The material used to cover the

outside surface of the roof framing to provide lateral

and rack support to the roof, as well as to provide a

nailing surface for the roofing material. This material

most commonly consists of plywood OSB or

horizontally laid wood boards. 

57. Sidewalk—A walkway that provides a direct, allweather approach to an entry. The sidewalk can be

constructed of poured concrete, laid stone, concrete

pavers, or gravel contained between borders or curbs.

6-4 Housing Structure
58. Sill plate—The horizontal wood member that is

anchored to the foundation masonry to provide a

nailing surface for floors or walls built above.

59. Silt fabric—A porous fabric that acts as a barrier

between the backfilled soil (see backfill) and the gravel

surrounding the drain tile. This barrier prevents soil

particles from blocking the movement of groundwater

to the drain tile.

60. Soffit/lookout block—Rake cross-bracing between

the fly rafters and end gable rafters that the soffit is

nailed to.

61. Stair rail—A sturdy handhold and barrier that follows

the outside, and sometimes inside, perimeter of the

stairs. The stair rail is used to prevent falls and to

provide a means of additional support when walking

up or down the stairs.

62. Stair riser—The vertical boards that close the space

between each stair tread on a set of stairs (see stair

stringer and stair tread).

63. Stair stringer—The supporting members in a set of

stairs that are cut or notched to accept the individual

treads and risers (see stair riser and stair tread).

64. Stair tread—The horizontal board in a stairway that

is walked upon (see stair riser and stair stringer).

65. Subfloor—Boards or plywood, installed over joists,

on which the finish floor rests. 

66. Support post—A vertical framing member usually

designed to carry or support a beam or girder. In

newer construction a metal lally (pronounced “lolly”)

column is commonly used, as well as 4×4- or 6×6-

inch wood posts.

67. Tar—Otherwise known as asphalt, tar is a very thick,

dark brown/black substance that is used as a sealant or

waterproofing agent. It is usually produced naturally

by the breakdown of animal and vegetable matter that

has been buried and compressed deep underground.

Tar is also manufactured—a hydrocarbon by-product

or residue that is left over after the distillation of

petroleum. It is commonly used as a sealant or patch for

roof penetrations, such as plumbing vents and chimney

flashing. Tar is also used as a sealer on concrete and

masonry foundation walls before they have been

backfilled.

68. Termite shield—A metal flashing that is installed

below the sill plate that acts as a deterrent to keep

termites from reaching the sill plate. 

69. Top plate—The topmost horizontal framing members

of a framed wall. Most construction practices require

the top plate to be doubled in thickness.

70. Wainscoting—The wooden paneling of the lower

part of an interior wall up to approximately waistheight or between 36 and 48 inches from the floor.

71. Wall insulation—A manufactured or natural material

that resists heat flow that is installed in a house’s shell

to keep the heat in a house in the winter and the

coolness in the house in the summer. Fiberglass batts

are the most common form of wall insulation.

72. Wall sheathing—The material used to cover the

outside surface of the wall framing that provides lateral

and shear support to the wall as well as a nailing

surface for the exterior siding.

73. Window casing/trim—The finish trim details around

the perimeter of the window on the interior finished wall. 

74. Window cripple—Short studs placed between the

header and a top plate or between a sill and sole plate.

75. Window frame/jamb—The top and sides of the

window, to include the wall framing and the actual

window frame and trim.

76. Window header—A beam placed perpendicular to

wall studs above doors, windows, or other openings to

carry the weight of structural loads above the window

or door. 

77. Window sash—The framework that holds the glass in

a door or window.

78. Window well (not shown)—An excavation around a

basement window that prevents the surrounding soils

from collapsing into the window. The window well

surround is normally constructed of formed

corrugated galvanized metal, built-up masonry, or

pressure-treated wood. 

Healthy Housing Reference Manual 6-5
Key to Figure 6.2 (Old Housing Terminology)

Fireplace

1. Chimney—A vertical masonry shaft of reinforced

concrete or other approved noncombustible, heat

resisting material enclosing one or more flues. It

removes the products of combustion from solid,

liquid or gaseous fuel.

2. Flue liner—The flue is the hole in the chimney. The

liner, made of terra cotta or metal, protects the brick

from harmful smoke gases.

3. Chimney cap—This top is generally of concrete. It

protects the brick from weather.

4. Chimney flashing—Sheet metal flashing provides a

tight joint between chimney and roof.

5. Firebrick—An ordinary brick cannot withstand the

heat of direct fire, and so special firebrick is used to

line the fireplace. In newer construction, fireplaces are

constructed of prefabricated metal inserts.

6. Ash dump—A trap door to let the ashes drop to a pit

below, where they may be easily removed.

7. Cleanout door—The door to the ash pit or the bottom of

a chimney through which the chimney can be cleaned.

8. Chimney breast—The inside face or front of a

fireplace chimney.

9. Hearth—The floor of a fireplace that extends into the

room for safety purposes.

Roof

10. Ridge—The top intersection of two opposite

adjoining roof surfaces.

11. Ridge board—The board that follows along under

the ridge.

12. Roof rafters—The structural members that support

the roof.

6-6 Housing Structure

Figure 6.2. Housing Structure and Terminology, Typical House Built Between 1950 and 1980 [2]
13. Collar beam—Not a beam at all; this tie keeps the

roof from spreading and connects similar rafters on

opposite sides of the roof.

14. Roof insulation—An insulating material (usually rock

wool or fiberglass) in a blanket form placed between

the roof rafters to keep a house warm in the winter

and cool in the summer.

15. Roof sheathing—The boards that provide the base

for the finished roof. In newer construction, roof

sheathing is composed of sheets of plywood, or

oriented strand board (OSB).

16. Roofing—The wood, asphalt or asbestos shingles—or

tile, slate, or metal—that form the outer protection

against the weather.

17. Cornice—A decorative element made of molded

members, usually placed at or near the top of an

exterior or interior wall.

18. Gutter—The trough that gathers rainwater from a roof.

19. Downspout—The pipe that leads the water down

from the gutter.

20. Storm sewer tile—The underground pipe that

receives the water from the downspouts and carries it

to the sewer. In newer construction, plastic-type

material have replaced tile. 

21. Gable—The triangular end of a building with a

sloping roof.

22. Barage board—The fascia or board at the gable just

under the edge of the roof.

23. Louvers—A series of slanted slots arranged to keep

out rain, yet allow ventilation.

Walls and Floors

24. Corner post—The vertical member at the corner of

the frame, made up to receive inner and outer covering

materials.

25. Studs—The vertical wood members of the house,

usually 2×4s at minimum and spaced every 16 inches.

26. Sill—The board that is laid first on the foundation,

and on which the frame rests.

27. Plate—The board laid across the top ends of the

studs to hold them even and tight.

28. Corner bracing—Diagonal strips to keep the frame

square and plumb.

29. Sheathing—The first layer of outer wall covering

nailed to the studs.

30. Joist—The structural members or beams that hold up

the floor or ceiling, usually 2×10s or 2×12s spaced 

16 inches apart.

31. Bridging—Cross-bridging or solid. Members at the

middle or third points of joist spans to brace one to

the next and to prevent them from twisting.

32. Subflooring—Typically plywood or particle wood

that is laid over the joists.

33. Flooring paper—A felt paper laid on the rough floor

to stop air infiltration and, to some extent, noise.

34. Finish flooring—Hardwood, of tongued and grooved

strips, carpet, or vinyl products (tile, linoleum).

35. Building paper or sheathing—Paper or plasticized

material placed outside the sheathing, not as a vapor

barrier, but to prevent water and air from leaking in.

Building paper is also used as a tarred felt under

shingles or siding to keep out moisture or wind.

36. Beveled siding—Sometimes called clapboards, with a

thick butt and a thin upper edge lapped to shed

water. In newer construction, vinyl, aluminum, or

fiber cement siding and stucco are more prevalent.

37. Wall insulation—A blanket of wool or reflective foil

placed inside the walls.

38. Metal lath—A mesh made from sheet metal onto

which plaster or other composite surfacing materials

can be applied. In newer construction, plaster

sheetrock 4-×8-foot sheets have replaced lath.

Foundation and Basement 

39. Finished grade line—The top of the ground at the

foundation.

40. Foundation wall—The wall of poured concrete

(shown) or concrete blocks that rests on the footing

and supports the remainder of the house.

Healthy Housing Reference Manual 6-7
41. Termite shield—A metal baffle to prevent termites

from entering the frame.

42. Footing—The concrete pad that carries the entire

weight of the house upon the earth.

43. Footing drain tile—A pipe with cracks at the joints,

or perforated plastic pipe to allow underground water

to drain away before it gets into the basement.

44. Basement floor slab—The 4- or 5-inch layer of

concrete that forms the basement floor.

45. Gravel fill—Placed under the slab to allow drainage

and to guard against a damp floor.

46. Girder—A main beam upon which floor joists rest.

Usually of steel, but also of wood.

47. Backfill—Earth, once dug out, that has been replaced

and tamped down around the foundation.

48. Areaway—An open space to allow light and air to a

window. Also called a light well.

49. Area wall—The wall, of metal or concrete, that forms

the open area.

Windows and Doors

50. Window—An opening in a building for admitting

light and air. It usually has a pane or panes of glass

and is set in a frame or sash that is generally movable

for opening and shutting.

51. Window frame—The lining of the window opening.

52. Window sash—The inner frame, usually movable,

that holds the glass.

53. Lintel—The structural beam over a window or door

opening.

54. Window casing—The decorative strips surrounding a

window opening on the inside.

Stairs and Entry

55. Entrance canopy—A roof extending over the

entrance door.

56. Furring—Falsework or framework necessary to bring

the outer surface level to the inner surface.

57. Stair tread—The horizontal part of a step that the

foot hits when climbing up or down the stairs.

58. Stair riser—The vertical board connecting one tread

to the next.

59. Stair stringer—The sloping board that supports the

ends of the steps.

60. Newel—The post that terminates the railing.

61. Stair rail—The bar used for a handhold when using

the stairs.

62. Balusters—Vertical rods or spindles supporting a rail.

Foundation

The word “foundation” is used to mean

• construction below grade, such as footings, cellar,

or basement;

• the composition of the earth on which the

building rests; and

• special construction, such as pilings and piers used

to support the building.

The foundation bed may be composed of solid rock,

sand, gravel, or unconsolidated sand or clay. Rock, sand,

or gravel are the most reliable foundation materials.

Figure 6.3 shows the three most common foundations for

homes. Unconsolidated sand and clay, though found in

many sections of the country, are not as desirable for

foundations because they are subject to sliding and

settling [1]. Capillary breaks have been identified as a key

way of reducing moisture incursion in new construction [3].

The footing distributes the weight of the building over a

sufficient area of ground to ensure that the foundation

walls will stand properly. Footings are usually concrete;

however, in the past, wood and stone have been used.

Some older houses were constructed without footings.

Although it is usually difficult to determine the condition

of a footing without excavating the foundation, a footing

in a state of disrepair or lack of a footing will usually be

indicated either by large cracks or by settlement in the

foundation walls. This type of crack is called a “Z” crack.

Foundation wall cracks are usually diagonal, starting from

the top, the bottom, or the end of the wall (Figure 6.4).

6-8 Housing Structure
Cracks that do not extend to at least one edge of the wall

may not be caused by foundation problems. Such wall

cracks may be due to other structural problems and

should also be reported. 

The foundation walls support the weight of the structure

and transfer this weight to the footings. The foundation

walls may be made of stone, brick, concrete, or concrete

blocks. The exterior should be moisture proofed with

either a membrane of waterproof material or a coating of

portland cement mortar. The membrane may consist of

plastic sheeting or a sandwich of standard roofing felt

joined and covered with tar or asphalt. The purpose of

waterproofing the foundation and walls is to prevent

water from penetrating the wall material and leaving the

basement or cellar walls damp. 

Holes in the foundation

walls are common in many

old houses. These holes

may be caused by missing

bricks or blocks. Holes and

cracks in a foundation wall

are undesirable because

they make a convenient

entry for rats and other

rodents and also indicate

the possibility of further

structural deterioration.

Basement problems are a

major complaint of

homeowners [4–9].

Concrete is naturally

porous (12%–18% air).

When it cures, surplus

water creates a network of

interconnected capillaries.

These pores let in liquid

water, water vapor, and

radon gas. Like a sponge,

concrete draws water from

several feet away. As concrete ages, the pores get bigger as

a result of freezing, thawing, and erosion.

Concrete paints, waterproofing sealers, or cement coatings

are a temporary fix. They crack or peel and cannot stop

gases such as water vapor and radon.

Damp basement air spreads mold and radon through the

house. Efflorescence (white powder stains) and musty

odors are telltale signs of moisture problems. 

Basement remodeling traps invisible water vapor, causing

mold and mildew. Most basements start leaking within

10 to 15 years. The basement walls and floors should be

sealed and preserved before they deteriorate. The basement

floor should be concrete placed on at least 6 inches of

gravel. The gravel distributes groundwater movement

under the concrete floor, reducing the possibility of the

water penetrating the floor. A waterproof membrane, such as

plastic sheeting, should be laid before the concrete is

placed for additional protection against flooding and the

infiltration of radon and other gases.

The basement floor should be gradually, but uniformly,

sloped from all directions toward a drain or a series of

drains. These drains permit the basement or cellar to drain if

it becomes flooded.

Healthy Housing Reference Manual 6-9

Figure 6.4. Foundation Cracks [4]

Figure 6.3. Foundation [3]
Water or moisture marks on the floor and walls are signs

of ineffective waterproofing or moisture proofing. Cellar

doors, hatchways, and basement windows should be

weather-tight and rodent-proof. A hatchway can be inspected

by standing at the lower portion with the doors closed; if

daylight can be seen, the door needs to be sealed or repaired.

Vapor Barriers

Crawl Space Vapor Barriers

Throughout the United States, even in desert areas, there

is moisture in the ground from groundwater being

absorbed. Even in an apparently dry crawl space, a large

amount of water is entering. The moisture is drying out

as fast as it is entering, which causes high moisture levels

in the crawl space and elsewhere in the house. A solid

vapor barrier is recommended in all crawl spaces and

should be required if moisture problems exist [10]. This

vapor barrier, if properly installed, also reduces the

infiltration of radon gas. Of course, if the moisture is

coming from above ground, a vapor barrier will collect

and hold the moisture. Therefore, any source of moisture

must be found and eliminated. The source may be as

obvious as sweating pipes, or may be more difficult to

spot, such as condensation on surfaces. The solution can

be as simple as applying insulation to exposed sections of

the piping or complex enough to require power exhaust

fans and the addition of insulation and vapor barriers. 

The more common causes of moisture problems in a new

home are moisture trapped within the structure during

construction and a continuing source of excess moisture

from the basement, crawl space, or slab. To resolve this

potential problem, 6-mil plastic sheets should be laid as

vapor barriers over the entire crawl space floor. The sheets

should overlap each other by at least 6 inches and should

be taped in place. The plastic should extend up the

perimeter walls by about 6 inches. The plastic sheets

should be attached to the interior walls of the crawl space

with mastic or batten strips. All of the perimeter walls

should be insulated, and insulation should be between the

joists at the top of the walls. Vents, which may need to be

opened in the late spring and closed in the fall, should

not be blocked. If not properly managed, moisture

originating in the crawl space can cause problems with

wood flooring and create many biologic threats to health

and property. A properly placed vapor barrier can prevent

or reduce problem moisture from entering the home. 

Vapor Barriers for Concrete Slab Homes

Strip flooring and related products should be protected

from moisture migration by a slab. Proper on-grade or

above-grade construction requires that a vapor barrier be

placed beneath the slab. Moisture tests should be done to

determine the suitability of the slab before installing

wood products. A vapor barrier equivalent to 4- or 6-mil

polyethylene should be installed on top of the slab to further

protect the wood products and the residents of the home.

Wall and Ceiling Vapor Barriers

Wall and ceiling vapor barriers should go on the heated

side of the insulation and are necessary in cold climates.

Water vapor flows from areas of high pressure (indoors in

winter) through the wall to an area of low pressure

(outdoors in winter). People and their pets produce

amazing quantities of water vapor by breathing. Additional

moisture in considerable quantities is created in the home

from everyday activities such as washing clothes, cooking,

and personal hygiene. The purpose of the vapor barrier is

to prevent this moisture from entering the wall and freezing,

then draining, causing damage. In addition, wet insulation has

very little insulating value. Insulation with the vapor

barrier misplaced will allow the vapor to condense in the

insulation and then freeze. In cold climates, this ice can

actually build up all winter and run out on the floor in

the spring. Such moisture buildup blisters paint, rots

sheathing, and destroys the insulating value of insulation. 

House Framing

Many types of house-framing systems are found in

various sections of the country; however, most framing

systems include the elements described in this section.

Foundation Sills

The purpose of the sill is to provide support or a bearing

surface for the outside walls of the building. The sill is the

first part of the frame to be placed and rests directly on

the foundation wall. It is often bolted to the foundation

wall by sill anchors. In many homes, metal straps are

cemented into the foundation wall that are bent around

and secured to the sill. It is good practice to protect the

sill against termites by extending the foundation wall to at

least 18 inches above the ground and using a noncorroding

metal shield continuously around the outside top of the

foundation wall.

Flooring Systems

The flooring system is composed of a combination of

girders, joists, subflooring, and finished flooring that may

be made up of concrete, steel, or wood. Joists are laid

perpendicular to the girders, at about 16 inches on center, and

the subflooring is attached to them. If the subfloor is wood, it

may be nailed, glued, or screwed at either right angles or

diagonally to the joists. Many homes are built with wood

I-joists or trusses rather on than solid wood joists.

6-10 Housing Structure
In certain framing systems, a girder supports the joists

and is usually a larger section than the joists it supports.

Girders are found in framing systems where there are no

interior bearing walls or where the span between bearing

walls is too great for the joists. The most common application

of a girder is to support the first floor. Often a board known

as a ledger is applied to the side of a wood girder or beam

to form a ledge for the joists to rest upon. The girder, in

turn, is supported by wood posts or steel “lally columns”

that extend from the cellar or basement floor to the girder.

Studs

For years, wall studs were composed of wood and were

2×4 inches; but, with the demand for greater energy

efficiency in homes, that standard no longer holds true.

Frame studs up to 6 inches wide are used to increase the

area available for placing insulation material. The

increased size in the studs allow for larger spaces between

joists.

There are now alternatives to conventional wood studs,

specifically, insulated concrete forms, structural insulated

panels, light-gauge steel, and combined steel and wood

[11–13]. The advantages of light-gauge steel include the

following: 

• weighs 60% less than equivalent wood units and

has greater strength and durability; 

• is impervious to termites and other damagecausing pests; 

• stays true and does not warp; 

• is noncombustible; and 

• is recyclable. 

The disadvantages of steel include these: 

• steel is an excellent thermal conductor and

requires additional external insulation; 

• as a new product, it is unfamiliar to craftsmen,

engineers, and code officials; and 

• a different type of construction tools are required. 

The combined steel and wood framing system includes

light-gauge steel studs with 6-inch wooden stud pieces

attached to the top and bottom to allow easy attachment

to traditional wood frame materials. 

There are two types of walls or partitions: bearing and

nonbearing. A bearing wall is constructed at right angles

to support the joists. A nonbearing wall, or partition, acts

as a screen or enclosure; hence, the headers in it are often

parallel to the joists of the floor above.

In general, studs, like joists, are spaced 16 inches on

center. In light construction, such as garages and summer

cottages, wider spacing on studs is common.

Openings for windows or doors must be framed in studs.

This framing consists of horizontal members (headers)

and vertical members (trimmers or jack studs). 

Because the vertical spaces between studs can act as flues

to transmit flames in the event of a fire, fire stops are

important in preventing or retarding fire from spreading

through a building by way of air passages in walls, floors,

and partitions. Fire stops are wood obstructions placed

between studs or floor joists to block fire from spreading

in these natural flue spaces.

Interior Walls

Many types of materials are used for covering interior

walls and ceilings, but the principal type is drywall. The

generic term “drywall” is typically used when talking

about gypsum board. It is also called wallboard or referred

to by the brand name Sheetrock. Gypsum board is a sheet

material composed of a gypsum filler faced with paper. In

drywall construction, gypsum boards are fastened to the

studs either vertically or horizontally and then painted.

The edges along the length of the sheet are slightly

recessed to receive joint cement and tape.

Drywall finish, composed of gypsum board, is a material

that requires little, if any, wait for application. Other

drywall finishes include plywood, fiberboard, or wood in

various sizes and forms. Plaster was once quite popular for

interior walls. Plaster is a mixture (usually of lime, sand,

and water) applied in two or three coats to lath to form a

hard-wall surface. A plaster finish requires a base on

which plaster can be spread. Wood lath at one time was

the plaster base most commonly used, but today gypsumboard lath is more popular. Gypsum lath may be

perforated to improve the bond and thus lengthen the

time the plaster can remain intact when exposed to fire.

Building codes in some cities require that gypsum lath be

perforated. Expanded-metal lath also may be used as a

plaster base. Expanded-metal lath consists of sheet metal

slit and expanded to form openings to hold the plaster.

Plaster is applied over the base to a minimum thickness of

1⁄2 inch. Because wood-framing members may dry after

Healthy Housing Reference Manual 6-11
the house is completed, some shrinkage can be expected,

which, in turn, may cause plaster cracks to develop

around openings and in corners. Strips of lath embedded

in the plaster at these locations prevent cracks. Bathrooms

have unique moisture exposure problems and local code

approved cement board should be used around bath and

shower enclosures.

Stairways

The purpose of stairway dimension standards is to ensure

adequate headroom and uniformity in riser and tread size.

Interior stairways (Figure 6.5) should be no less than

44 inches wide. The width of a stairway may be reduced

to 36 inches when permitted by local or state code in

one- and two-family dwellings. Stairs with closed risers

should have maximum risers of 81⁄4 inches and minimum

treads of 9 inches plus 1 inch nosing. Basement stairs are

often constructed with open risers. These stairs should

have maximum risers of 81⁄4 inches and minimum treads

of 9 inches plus 1-inch nosing. The headroom in all parts

of the stair enclosure should be no less than 80 inches.

Dimensions of exterior stairways should be the same as

those of interior stairways, except that the headroom

requirement does not apply.

Staircases should have handrails that are between 11⁄4 and

25/8 inches wide, particularly if the staircases have more

than four steps. Handrails should be shaped so they can

be readily grasped for safety and placed so they are easily

accessible. Handrails should be 41/8 inches from the wall

and be 34 to 38 inches above the leading edge of the

stairway treads. Handrails should not end in any manner

or have projections that can snag clothing. 

Windows

The six general classifications of windows (Figure 6.6) are

as follows [1]:

• Double-hung sash windows that move up or

down, balanced by weights hung on chains, ropes,

or springs on each side;

• Casement sash windows that are hinged at the side

and can be hung so they will swing out or in; 

• Awning windows that usually have two or more

glass panes that are hinged at the top and swing

out horizontally; 

• Sliding windows that usually have two or more

glass panes that slide past one another on a

horizontal track; 

• Fixed windows that are generally for increased

light entry and decorative effect; and

• Skylight windows for increased room illumination

and decoration that can be built to open.

The principal parts of a window, shown in threedimensional view in Figure 6.7 and face-on and side view

in Figure 6.8, are the following: 

6-12 Housing Structure

Figure 6.6. Classifications of Windows [1]

Figure 6.5. Interior Stairway [4]
Drip cap—A separate piece of wood projecting over the

top of the window; a component of the window casing.

The drip cap protects against moisture.

Window trough—The cut or groove in which the sash of

the window slides or rests. 

Window sill—The shelf on the bottom edge of a

window, either a projecting part of the window frame or

the bottom of the wall recess that the window fits into. The

sill contains the trough and protects against moisture. 

Recent technological advancements—new materials,

coatings, design, and construction features—make it

possible to choose windows that allow you to balance

winter heating and summer cooling needs without

sacrificing versatility or style. To ensure that windows,

doors, or skylights selected are appropriate for the region

in which they are to be installed, Energy Star

Certification labels include a climate region map.

Some window glass is made of tempered glass to resist

breakage. Some windows are made of laminated glass,

which resists breakage, but if broken produces glass shards

too small to cause injury [14]. The glazing, or glass, can

be a solid glass sheet (single glazed) or have two layers of

glass (double glazed) separated by a spacer. Air trapped

between the glass layers provides some insulation value.

Triple-glazed windows have three pieces of glass, or two

layers of glass with a low

emissivity film suspended

between them. Tripleglazed windows have

advantages where

extremes in weather and

temperature are the

norm. They also can

reduce sound

transmission to a greater

degree than can single- or

double-glazed windows.

Doors

There are many styles of

doors both for exterior

and interior use. Exterior

doors must, in addition

to offering privacy,

protect the interior of the

structure from the

elements. Various parts of

a door are the same as the

corresponding parts of a

window. A door’s

function is best

determined by the material

from which it is made, how it looks, and how it operates.

When doors are used for security, they are typically made

from heavy materials and have durable, effective locks and

hinges. A door that lets in light or allows people to look

out onto the yard, such as a sliding glass door or a french

door, will have multiple panes (also called lights) or be made

almost completely of glass.

Houses have many exterior and interior door options.

Exterior doors are typically far sturdier than interior doors

and need to be weather tight and ensure security for the

home. Exterior doors are also more decorative than most

interior doors and may cost a considerable amount.

Typical exterior doors include front entry doors, back

doors, french doors, dutch doors, sliding glass doors,

patio doors, and garage doors.

French doors and sliding doors are examples of the two

primary ways doors open. French doors swing on hinges;

sliding doors glide along a track. Some doors, such as

dutch doors, have tops and bottoms that swing open

independently.

Most doors are made of wood or materials made to look

like wood. Fiberglass composite and steel doors often have

Healthy Housing Reference Manual 6-13

Figure 6.8. Window Details [3]

Figure 6.7. Three Dimensional View of a Window [1]
polymer or vinyl coatings embossed with wood grain;

some even have cellulose-based coatings that can be

stained like wood doors. Wood doors are made from

every kind of wood imaginable, hardwoods being the

most durable and elegant. Wood doors insulate better

than glass; composite and steel doors provide even more

insulation and durability, as well as better security than

does wood.

Garage Doors

Garage doors open in almost any configuration needed

for the design of the home. Installing most garage doors is

complex and dangerous enough that only a building

professional should attempt it. Garage doors often include

very strong springs that can come loose and severely

injure the unsuspecting installer. Garage door springs are

under extreme tension because of the heavy loads they

must lift, which makes them dangerous to adjust. A

garage door may suffer from any of several problems. The

most common problem is that the door becomes difficult

to lift and lower. This may be something that can be

resolved with simple adjustments, or it may be more

serious. If the door is connected to an electric opener, the

opener mechanism can be disconnected from the door by

pulling the release cord or lever. If the door then works

manually, the problem is with the electric opener. A door

that seems unusually hard to lift may have a problem with

spring tension. Wood doors should be properly painted or

stained both outside and inside. If only the outside of a

garage door is finished, the door may warp and moisture

may cause the paint to peel.

Rules issued by the Consumer Product Safety

Commission on December 3, 1992, specify entrapment

protection requirements for garage doors [15]. 

The rules require that residential garage door openers

contain one of the following: 

• An external entrapment protection device, such as

an electric eye that sees an object obstructing the

door without having actual contact with the

object. A door-edge sensor is a similar device. The

door-edge sensor acts much like the door-edge

sensors on elevator doors.

• A constant contact control button, which is a

wall-mounted button requiring a person to hold

in the control button continuously for the door to

close completely. If the button is released before

the door closes, the door reverses and opens to the

highest position. 

• A sticker on all newly manufactured garage door

openers warning consumers of the potential

entrapment hazard. The sticker is to be placed near

the wall-mounted control button. 

The variety of exterior door systems has increased

significantly over the past 5 to 10 years. Many combine

several different materials to make a realistic, if not actual

wood, door that provides both beauty and enhanced security.

Exterior House Doors

Exterior door frames are ordinarily of softwood plank,

with the side rabbitted to receive the door in the same

way as casement windows. At the foot is a sill, made of

hardwood or other material, such as aluminum, to

withstand the wear of traffic and sloped down and out to

shed water. Doors often come equipped with door sweeps

to conserve energy. 

The four primary categories of modern exterior doors are

steel, fiberglass, composites, and wood.

Steel—The most common exterior door sold today is

steel. Humidity will not cause a steel door to warp or twist.

Steel doors often have synthetic wood-grain embossed

finishes that accept stain. Just about every steel exterior door

is filled with some type of foam. This foam allows the doors

to achieve R-values almost five times that of an ordinary

wood door. Metal is often used as a veneer frame. In general,

the horizontal members are called rails and the vertical

members are called stiles. Every door has a top and

bottom rail, and some may have intermediate rails. There

are always at least two stiles, one on each side of the door.

Fiberglass—The second most frequently selected exterior

door is fiberglass. Fiberglass doors are similar to steel doors,

but tend to be much more resistant to denting. (Steel

doors can be dented quite easily.) Fiberglass doors also are

stainable and have rich, realistic wood graining. Fiberglass

doors are insulated with foam and have high R-values.

Composite materials—The third most common exterior

door is made of composite materials. These doors often

are of two materials blended together. Their composite

fiber-reinforced core can be twice as strong as wood. This

composite core will not rot, warp, or twist when subjected

to high levels of humidity.

Wood—The last major category of doors is wood. Solid

wood doors range from inexpensive to true works of art.

Their downside is that they can warp and bow if not sealed

properly from humidity and will then fit poorly in their frames. 

6-14 Housing Structure
Other types of wooden doors are described below.

• Batten doors are often found on older homes.

They are made of boards nailed together in

various ways. The simplest is two layers nailed to

each other at right angles, usually with each layer

at 45° to the vertical. Another type of batten door

consists of vertical boards nailed at right angles to

several (two to four) cross strips called ledgers,

with diagonal bracing members nailed between

the ledgers. If vertical members corresponding to

ledgers are added at the sides, the verticals are

called frames. Batten doors are often found in

cellars and other places where appearance is not a

factor and economy is desired.

• Solid flush doors are perfectly flat, usually on both

sides, although occasionally they are made flush

on one side and are paneled on the other. Flush

doors sometimes are solid planking, but they are

commonly veneered and possess a core of small

pieces of white pine or other wood. These pieces 

are glued together with staggered end joints. Along

the sides, top, and bottom are glued 3⁄4 inch edge

strips of the same wood, used to create a smooth

surface that can be cut or planed. The front and

back faces are then covered with a 1/8-inch to

1⁄4-inch layer of veneer. Solid flush doors may be

used on both the interior and exterior.

• Hollow-core doors, like solid flush doors, are

perfectly flat; but, unlike solid doors, the core

consists mainly of a grid of crossed wooden slats

or some other type of grid construction. Faces are

three-ply plywood instead of one or two plies of

veneer, and the surface veneer may be any species

of wood, usually hardwood. The edges of the core

are solid wood and are made wide enough at the

appropriate places to accommodate locks and

butts. Doors of this kind are considerably lighter

than solid flush doors. Hollow-core doors are

usually used as interior doors.

Many doors are paneled, with most panels consisting of

solid wood or plywood, either raised or flat, although

exterior doors frequently have one or more panels of glass.

One or more panels may be used, although some have as

many as nine panels. Paneled doors may be used both on

the interior or exterior.

The frame of a doorway is the portion to which the door

is hinged. It consists of two side jambs and a head jamb,

with an integral or attached stop against which the

door closes.

Roof Framing

Rafters

One of a series of structural roof members spanning from

an exterior beam or a ridge board. Rafters serve the same

purpose for the roof as joists do for floors, that is,

providing support for sheathing and roofing material.

They are typically placed on 16-inch centers. 

Collar Beam

Collar beams are ties between rafters on opposite sides of

the roof. If the attic is to be used for rooms, the collar

beam may double as the ceiling joist. 

Purlin

A purlin is the horizontal member that forms the support

for the rafters at the intersection of the two slopes of a

gambrel roof.

Ridge Board

A ridge board is a horizontal member that forms a lateral

tie to make rafters secure.

Hip

A hip is like a ridge, except that it slopes. It is the intersection

of two adjacent, rather than two opposite, roof planes.

Roof Sheathing

The manner in which roof sheathing is applied depends

upon the type of roofing material. Roof boards may vary

from tongue-and-groove lumber to plywood panels.

Dormer

The term “dormer window” is applied to all windows in

the roof of a building, whatever their size or shape.

Roofs

Asphalt Shingle

The principal damage to asphalt shingle roofs is caused by

strong winds on shingles nailed close to the ridge line of

the roof. Usually the shingles affected by winds are those

in the four or five courses nearest the ridge and in the

area extending about 5 feet down from the edge or rake of

the roof.

EPDM

Ethylene propylene diene monomer (EPDM) is a singleply roofing system. EPDM allows extreme structural

movement without splitting or cracking and retains its

pliability in a wide range of temperatures.

Healthy Housing Reference Manual 6-15
Asphalt Built-up Roofs

Asphalt roofs may be unsurfaced (a coating of bitumen

being exposed directly to the weather) or surfaced (with

slag or gravel embedded in the bituminous coating).

Using surfacing material is desirable as a protection

against wind damage and the elements. This type of roof

should have enough pitch to drain water readily.

Coal Tar Pitch Built-up Roofs

This type of roof must be surfaced with slag or gravel. A

coal tar pitch built-up roof should always be used on a

deck pitched less than 1⁄2 inch per foot; that is, where

water may collect and stand. This type of roof should be

inspected on completion, 6 months later, and then at least

once a year, preferably in the fall. When the top coating

of bitumen shows damage or has become badly

weathered, it should be renewed.

Slate Roofs

The most common problem with slate roofs is the

replacement of broken slates. Otherwise, slate roofs

normally render long service with little or no repair.

Tile Roofs

Replacement of broken shingle tiles is the main

maintenance problem with tile roofs. This is one of the most

expensive roofing materials. It requires very little maintenance

and gives long service.

Copper Roofs

Usually made of 16-ounce copper sheeting and applied to

permanent structures, copper roofs require practically no

maintenance or repair when properly installed. Proper

installation allows for expansion and contraction with

changes in temperature.

Galvanized Iron Roofs

The principal maintenance for galvanized iron roofs

involves removing rust and keeping the roof well painted.

Leaks can be corrected by renailing, caulking, or replacing

all or part of the sheet or sheets in disrepair. 

Wood Shingle Roofs

The most important factors of wood shingle roofs are their

high pitch and exposure, the character of wood, the kind of

nails used and the preservative treatment given the

shingles. At one time these roofs were treated with

creosote and coal tar preservatives. Because they are made

from a flammable material, insurance companies

frequently have higher rates for wood shingle roofs.

Roof Flashing

Valleys in roofs (such as gambrel roofs, which have two

pitches designed to provide more space on upper floors

and are steeper on their lower slope and flatter toward the

ridge) that are formed by the junction of two downward

slopes may be open or closed. In a closed valley, the slates,

tiles, or shingles of one side meet those of the other, and

the flashing below them may be comparatively narrow. In

an open valley, the flashing, which may be made of zinc,

copper, or aluminum, is laid in a continuous strip,

extending 12 to 18 inches on each side of the valley, while

the tiles or slates do not come within 4 to 6 inches of it.

The ridges built up on a sloping roof where it runs down

against a vertical projection, like a chimney or a skylight,

should be weatherproofed with flashing. Failure of roof

flashing is usually due to exposed nails that have come

loose. The loose nails allow the flashing to lift, resulting

in leakage. Flashings made of lead or coated with lead

should not be used. 

The use of a thin, self-sticking rubber ice and water shield

under flashings and on the edge of roofs is now common

practice. The shield helps reduce leakage and ice backup

in cold climates, preventing serious damage to this part of

the home. 

Gutters and Leaders

Gutters and leaders should be of noncombustible

materials and should not be made of lead, lead-coated

copper, or any other formulation containing lead. They

should be securely fastened to the structure and spill into

a storm sewer, not a sanitary sewer, if the neighborhood

has one. When there is no storm sewer, a concrete or

stone block placed on the ground beneath the leader

prevents water from eroding the lawn. This stone block is

called a splash block. Gutters should be checked every

spring and fall and cleaned when necessary. Gutters must

be placed or installed to ensure that water drainage is

taken away from the foundation of the house. Soil around

the home should be graded in a manner that also drains

the water away from the foundation of the home.

Exterior Walls and Trim

Exterior walls are enclosure walls whose purpose is not

only to make the building weather tight, but to also allow

the building to dry out. In most one- to three-story

buildings they also serve as bearing walls. These walls may

be made of many different materials (Figure 6.9). 

Brick is often used to cover framed exterior walls. In this

situation, the brick is only one course thick and is called a

brick veneer. It supports nothing but itself and is kept

6-16 Housing Structure
from toppling by ties

connected to the frame

wall. 

In frame construction,

the base material of the

exterior walls is called

sheathing. The sheathing

material may be squareedge, shiplap,

tongue-and-groove

boards, or plywood or

oriented strand board

(OSB). Sheathing, in

addition to serving as a

base for the finished

siding material, stiffens

the frame to resist sway

caused by wind. It is for

this reason that sheathing

is applied diagonally on

frame buildings. Its role

is to brace the walls

effectively to keep them

from racking.

Many types of sidings,

shingles, and other

exterior coverings are applied over the sheathing. Vinyl

siding; wood siding; brick, cedar, and other wood shingles

or shakes; asphalt; concrete; clapboard; common siding

(called bevel siding); composition siding; cement shingles;

fiber cement (e.g., Hardiplank); and aluminum siding are

commonly used for exterior coverings. In older homes,

asbestos-cement siding shingles can still be found as an

exterior application or underneath various types of

aluminum or vinyl siding. 

Clapboard and common siding differ only in the length

of the pieces. Composition siding is made of felt, grit,

and asphalt, which are often shaped to look like brick.

Asbestos and cement shingles, which were used until the

early 1970s, are rigid and produce a siding that is fireresistant, but also a health hazard. Cedar wood shingles

and aluminum are manufactured with a backer board that

gives insulation and fire-resistant qualities. Vinyl siding is

manufactured from polyvinyl chloride (PVC), a building

material that has replaced metal as the prime material for

many industrial, commercial, and consumer products.

PVC has many years of performance as a construction

material, providing impact-resistance, rigidity, and

strength. The use of vinyl siding is not without controversy,

because PVC is known to cause cancer in humans.

Accidental fires in vinyl-sided buildings are more dangerous

because vinyl produces toxic vapors when heated.

Putting It All Together

The next section shows a home being built by Habitat for

Humanity. 

This small, one-family home represents all of the

processes that would also be used for a far more expensive

and elaborate dwelling. The homebuilding demonstrated

by the following pictures was by an industrial arts class to

educate and train a new generation of construction specialists

and homebuilders. 

A. 

The foundation trench for a new home has horizontal metal

rods, also called reinforcement rods or rebar, to increase the

strength of the concrete. After the concrete hardens, a

perforated pipe 4 to 6 inches in diameter is placed beside it

to collect water and allow it to drain away from the

foundation. This pipe is the footing drain, and the poured

concrete beside it is the footer. The footing drain is

important in removing water from the base of the home. It

also serves the secondary purpose of moisture control in the

home and provides a venting route for radon gas. The holes

dug near the legs of the workers will be filled with concrete

and form the footer that will hold up the porch of the home. 

To assist in preventing capillary action from wicking water

from the foundation to the wooden structure, a polyethylene

sheet is placed over the footer before pouring the concrete

foundation, or building a cinderblock foundation.

Healthy Housing Reference Manual 6-17

Figure 6.9. Wall Framing [4]
6-18 Housing Structure

E. 

Gravel fill is placed outside the finished poured concrete

foundation. This ensures that moisture does not stand

around the foundation for any time. The moisture is routed

to the footing drain for fast dispersal.

B. 

The concrete on top of the footer is leveled to establish a

surface for the foundation of the home. Once the footer has

hardened, the perforated drainage pipe will be laid on the

outside of the poured foundation wall. The reinforcing rods

were positioned in the trench before pouring the concrete.

C. 

Concrete will be poured into this form on top of the footer

to create the foundation of the home. Again, reinforcing rods

are added to ensure that the concrete has both lateral

strength, as well as the strength to support the home. Once

the concrete has hardened and becomes seasoned, the forms

will be removed to reveal the finished poured concrete

foundation over the perforated drainage pipe. Not shown is a

newer technique of using insulating polystyrene forms and

ties in a building foundation.

D. 

Foundations are not always poured concrete, but are often

cinderblock or similar materials that are cemented in place

to form the load-bearing wall. The arrow shows the concrete

chute delivering concrete into the form. Long poles are

pushed into the freshly poured concrete to remove air

pockets that would weaken the foundation. 

Care must be taken to ensure that the forms are

appropriately supported before pouring the concrete. Often

tar, plastic, or other waterproof materials are placed on the

outside of the foundation to the ground level to further

divert moisture from the house to the footing drains.
Healthy Housing Reference Manual 6-19

F. 

A termite shield is established on top of the concrete wall

(foundation) just below the sill of the home. The sill is

typically made of pressure- and insecticide-treated wood to

ensure stability and long life. 

A cinderblock foundation will be used to support the storage

shed attached to the house. Note the potential for

inadvertent sabotage of the termite shield if a shield is not

installed on the top of the cinder block foundation. 

G. 

OSB subfloor, the joist supporting the floor, and the metal

bridging that is used to keep the joist from twisting can be

seen from the crawl space under the home.

If the material used for the flooring or external sheathing of

the home is made of plywood or a composition that is not

waterproof, the material must be protected from rain to

prevent deterioration and germination of mold spores. Some

glues or resins release toxic vapors for years if deterioration

is allowed to begin.

H. 

The flooring material of the

first floor of the home is OSB

applied to the subfloor with

both glue and wood screws.

Where possible, the screws

should extend into the subfloor

and the joist below the subfloor to prevent squeaking.

J. 

The exterior wall

framing is composed of

studs that are 2x6-inch

boards. The horizontal

member extending from

one exterior wall to the

other is called a girder

and is a prime support

for the second floor of the home. The larger studs in the

exterior wall are used both for greater strength and to provide

greater energy efficiency for the home.

The lintels above the windows and doors distribute the

weight of the second floor and roof across the studs that are

located on each side of the openings in the frame.

K. 

The joists above the first floor

are connected to the central

girder of the home by steel

brackets. These brackets

provide a far more effective

alternative than does

toenailing nails to hold the joists in place or to notching the

girder to hold them.

I. 

The interior wall framing is

composed of studs

traditionally referred to as

2×4s. The horizontal member

at the top of the studs is

called a girt or a ribbon. In

this case the builders

have used two 2×4s, placing

one on top of the other.

Because the outside walls

have used studs that are 2×6-inch boards, the girts or

ribbons on top of these are also double 2×6-inch boards.
6-20 Housing Structure

L. 

The subroof or roof

sheathing is applied from

the bottom up with

temporary traction boards

nailed to the subroof to

allow safe installation of the

material. 

The subroof is placed on the rafters up to the ridge board of

the roof. A waterproof material will be added to the subroof

before installing the final roofing material.

M. 

An interior wall is

installed to create

second-floor rooms. 

The subroof has been

installed.

The exterior wood of

the home has been

covered with plastic

sheathing or a

housewrap to protect it

from moisture.

N. 

Flashing material, such

as sheet metal, is

installed at critical

locations to make sure

that water does not

enter the home where

the joints and angles of

a roof meet:

• where the dormer roof meets the roof and the walls 

of the dormer meet the roof,

• where windows penetrate the walls,

• where the vent stack penetrates the roof,

• where the porch roof meets the front wall,

• skylights, and 

• eaves of the house.

O. 

A safety scaffold is standing at the rear of the home, and the

final roofing material has been applied, in addition to the

exterior vinyl siding.
References

1. US Inspect. Glossary of terms. Chantilly, VA: US

Inspect; no date. Available from URL:

http://www.usinspect.com/Glossary/glossary.asp.

2. Center for Disease Control. Housing construction

terminology. In: Basic housing inspection. Atlanta:

US Department of Health and Human Services;1976.

3. Building Science Corporation. Read this before

you design, build, or renovate. Westford, MA:

Building Science Corporation; 2004. 

4. Center for Disease Control. Basic housing

inspection. Atlanta: US Department of Health

and Human Services; 1976.

5. Wagner JD. Drying out a wet basement. New

York: This Old House Ventures, Inc.; no date.

Available from URL: http://www.thisoldhouse.com/

toh/knowhow/interiors/article/

0,16417,220912,00.html.

6. Friedman D. Inspecting foundations for structural

defects. Poughkeepsie, NY: Daniel Friedman;

2001. Available from URL: http://www.inspectny.com/structure/foundation.htm.

7. Association of Bay Area Governments. Foundations:

section 5. Oakland, CA: Association of Bay Area

Governments; 1998. Available from URL:

http://www.abag.ca.gov/bayarea/eqmaps/

fixit/ch5.

8. Crawford CB. CBD-148: foundation

measurements. Ottawa, Ontario, Canada:

National Research Council; 1972. Available from

URL: http://irc.nrc-cnrc.gc.ca/cbd/cbd148e.html.

9. Hamilton JJ. CBD-184: foundations on swelling

or shrinking subsoils. Ottawa, Ontario, Canada:

National Research Council; 1977. Available from

URL: http://irc.nrc-cnrc.gc.ca/pubs/

cbd/cbd184_e.html.

10. US Department of Housing and Urban

Development. Basements and crawl spaces.

Washington, DC: US Department of Housing

and Urban Development; 2000. Available from

URL: http://www.hud.gov/offices/hsg/sfh/

ref/sfhp1-25.cfm.

11. Bateman BW. Light-gauge steel verses

conventional wood framing in residential

construction. J Construction Educ

1997;2(2):99–108.

12. National Association of Home Builders Research

Center. Integrated steel/wood combination

framing. Upper Marlboro, MD: National

Association of Home Builders; no date. Available

from URL: http://www.toolbase.org/

tertiaryT.asp?DocumentID=

4249&CategoryID=1142.

13. Steel Wood Studs. Why use steel wood studs?

Reno, NV: Steel Wood Studs; 2001. 

14. Canadian Mortgage and Housing Corporation.

Understanding window terminology. Ottawa,

Ontario, Canada: Canadian Mortgage and

Housing Corporation; no date. Available from

URL: http://www.cmhc-schl.gc.ca/

en/burema/gesein/abhose/abhose_061.cfm.

15. US Consumer Product Safety Commission. Safety

commission publishes Final Rules for automatic

garage door openers. Washington, DC: US

Consumer Product Safety Commission; 1992.

Available from URL: http://www.cpsc.gov/

cpscpub/prerel/prhtml93/93024.html.

Healthy Housing Reference Manual 6-21

P. 

The front porch of the home is constructed of pressuretreated, insect-resistant lumber. The use of such lumber

should be carefully evaluated with respect to what chemicals

have been used and the potential for human exposure to the

treated wood. Composite wood products and plastic decking

materials, collectively called Trex, are available as an

alternative to pressure-treated wood. A proper hand railing

and balusters will be installed.
Additional Sources of Information

Carmody J, Christian J, Labs K, editors. Builder’s

foundation handbook. Oak Ridge, TN: Oak Ridge National

Laboratory; 1991. 

US Department of Housing and Urban Development.

Basements and crawl spaces. Washington, DC: US

Department of Housing and Urban Development; 2000.

Available from URL: http://www.hud.gov/offices/

hsg/sfh/ref/sfhp1-25.cfm.

6-22 Housing Structure