Category Construction

The roof is the part of the wood-frame structure that varies most widely across the country. This is because the roof plays the most active role of all the parts of a building in protecting against the weather, and in the United States, variations in weather are extreme. Some roofs protect primarily against the heat of the sun; others must shelter the inhabitants under tons of snow.

SELECTION OF ROOF SLOPE

One of the most obvious variations of roof form has to do with the slope or pitch of the roof. The main factors affecting the slope of a roof are stylistic considerations, the type of roofing material to be used, and the space desired beneath the roof. The climate also has a strong influence on roof slope. Areas of significant rainfall have roofs pitched to shed the rain, while warm, arid climates tend to favor flatter roofs.

The slope or pitch of a roof is measured as a propor­tion of rise to run. A roof that rises 4 in. in 1 ft. (12 in.) is said to have a 4-in-12 pitch (or 4:12). The second number in the roof-pitch proportion is always 12.

4

the shape of roofs

Roof shapes tend to have a regional character that reflects not only climatic variation, but also historical and material influences. All roof forms are derived from four basic roof shapes shown below: the flat roof, the shed roof, the gable roof, and the hip roof.

12 iN

12 iN

12-iN-12 PiTCH

ROOFS

Introduction

DUTCH GABLE GAMBREL

(HIP + GABLE) (2 SLOPES OF GABLE)

HALF HIP MANSARD

(hip + gable) (2 slopes of hip)

Virtually any roof form may be made by combining the four basic shapes with the connections illustrated in this chapter. Some of these composite shapes are so common they have their own names. For example, the hip and gable shapes can combine to form a Dutch gable. Two different slopes of gable roof can combine to form a gambrel roof. A shed dormer may be added to a gable roof, and so forth. Four common combina­tions are shown above.

Stick framing— One advantage of stick framing is that the space within the roof structure can become living space or storage. Vaulted (cathedral) ceilings, half-story living spaces on upper floors, and true storage attics are all examples. A second advantage is that complex roofs may be stick-framed more economi­cally than truss-framed. For owner-builders who need not include the cost of labor, stick framing is especially attractive.

Truss framing— Trusses can span much farther than stick-framed roofs, leaving large open areas below them or permitting partition walls to be relocated without consideration for the roof structure above. Trusses go up quickly, usually resulting in a cost saving over stick­framed roofs on simply shaped buildings. A big disad­vantage of trusses is that the truss roof is almost impos­sible to remodel, since trusses should never be cut.

WALLS

Rigid insulation, with a potential R-value approxi­mately double that of batt insulation, is a very attractive alternative for upgrading the thermal performance of walls. The material is easy to install in large lightweight sheets, has sufficient strength to support most siding and interior finish materials, and can double as an air/ vapor barrier in some cases. Its disadvantages are high cost and potential for toxic offgassing in a fire.

Rigid insulation is most effective when used on the exterior of the building because it covers the entire skin of the building continuously without the interruption of floors or interior partitions. It can act as the backing for siding but does not provide the strength to act as structural sheathing. Alternative methods of bracing the building, such as structural sheathing (see 78A) or let-in bracing (see 77B & C), must therefore be used. Hybrid systems, in which structural sheathing is used only at necessary locations with rigid insulation elsewhere, can also provide cost effective insulation upgrades.

When applied to the exterior of buildings in cold cli­mates, the low permeability of rigid insulation can trap vapor in the stud cavities, causing structural damage. The reverse can be true in warm climates. It is there-

FURRING SAME THICKNESS AS RIGID INSULATION AT WINDOW & DOOR OPENINGS AND AS REQUIRED FOR NAILING OF Siding

vapor retarder LOcATED AT INTERIOR face of 2×6 stud wall

floor structure with insulation and continuous AIR/vAPOR BARRIER SEE 61-62

RIGID INSuLATION may Be continuous over wall or foundation below

practicality of specific types of insulation with local professionals.

Used on the interior of a building in a cold cli­mate, rigid insulation can perform three functions at once: insulation, vapor retarder, and air barrier. To accomplish this, a foil-faced insulation board carefully taped at all seams and caulked and/or gasketed at top, bottom, and openings would be used.

fore advisable to carefully coordinate the use of rigid insulation with a high-permeability vapor retarder based on the specific climatic zone and to verify the

The use of interior rigid insulation requires deep electrical boxes and the need for extra-wide backing at corners and at the top plate.

@ RIGID INSULATION

roof or upper floor structure with insulation and continuous air/vapor barrier see 197 QR 63

single 2X6 top plate

structural sheathing or other bracing batt insulation in 2X6 stud WALL

STRAPPING for NAILING around openings

horizontal 2X3 STRAPPING AT 24 IN. o. c. NAILED To studs horizontal batt insulation between

STRAPPING vapor retarder located at interior face of 2X6 stud WALL

WIRING AND PLuMBING

located within

STRAPPING LAYER

Strapping consists of horizontal nailing strips attached to the inside of a stud wall. The strapping touches the studs only at the intersection between the two, so thermal bridging is virtually eliminated. Strapping is used extensively in energy-efficient buildings. With 2×6 studs and 2×3 strapping, an R-25 value can be achieved.

The advantages of the system are that it is simple and straightforward and uses a minimal amount of extra framing materials. With two-thirds of the insula – tive value in the (2×6) stud cavities, an air/vapor barrier can be located at the inside face of the framed wall, thus eliminating the need to puncture it with services. In addition, the plumbing and electrical work itself is simplified by the creation of horizontal chases on the walls.

Strapping must be fastened securely to the studs to prevent rotation, but interior finish panels will ulti­mately tie the strapping together to keep it in place.

double strapping for

BASE TRIM NAILING floor structure WITH insulation and continuous air/vapor BARRIER SEE 61-62

Extra strapping is usually required for nailing at cor­ners, at window and door openings, and at the base of the wall (see drawing above). In addition, vertical blocks are required for the attachment of electrical boxes.

Strapping may also be applied to the exterior of a building. In this case, the strapping is more easily installed, but the advantage of a horizontal chase inte­rior of the vapor retarder is lost. Furthermore, the strapping insulation must be installed from the exterior, exposed to the weather.

SHEATHING 2X4 STUDS AT 24 IN. O. C. WITH BATT INSULATION AND ALIGNED WITH OUTER EDGE OF PLATE

2X4 studs AT 24 IN. o. c. with batt insulation aligned with inner edge of plate & offset from outer studs

vapor retarder 2×8 or 2×10 PLATE

Staggered-stud framing is essentially a double stud wall framed on a single wide plate with the studs offset from one another so that there is negligible thermal bridging. The system is appreciated by builders for its minimal deviation from standard frame construction. Staggered-stud framing is substantially the same as platform framing, and subcontractors are sequenced in the same order as standard construction. With this technique, insulative values of R-.30 or more can be attained. A 2×8 or 2×10 plate with staggered 2×4 studs at 24 in. o. c. is most common.

Because there are effectively two separate walls, this system offers a special opportunity at windows and doors to splay the opening.

roof or upper floor structure with insulation and continuous air/vapor BARRIER see 197 QR 63

single top 2X top plate

plywood gusset ties stud walls at openings

STAGGERED 2X4 STuD WALLS FILLED WITH BATT insulation

vapor RETARDER located at interior FACE oF INNER FRAMED WALL SINGLE 2X SoLE PLATE

floor structure with insulation and continuous air/vapor BARRIER SEE 61-62

By increasing the rough-opening size at the “inner wall,” the opening will be more generous from the inside and reflect light better into the room.

The disadvantages of the system also stem from its similarity to standard platform frame construction. Unlike strapping systems or double wall systems, stag – gered-stud systems have the air/vapor barrier located on the inside (warm) face of the wall, with the atten­dant problems of sealing perforations of the barrier from plumbing and electrical services.

Double wall framing is capable of achieving the highest insulation values of all the upgraded framing techniques. Values of R-40 are common. Slightly more framing materials and considerably more labor (than strapping or staggered stud) are required for the increased performance.

The outer framed wall is most commonly used as the bearing wall. This strategy has two advantages: The insulation and the inner wall can be installed under the roof out of the weather, and the shear walls are most easily installed and logically located at this (outer wall) location. However, finish detailing at the wall/ceiling joint is complicated if the inner wall is nonstructural, and the continuity of the air/vapor barrier is somewhat

S3

difficult to achieve at the wall/floor intersection.

can be located within the inner wall without having to

Less common (and not illustrated) is the use of the
penetrate the barrier. To get the air/vapor barrier into

inner wall as the bearing wall. This system avoids the minor disadvantage of the outer bearing wall system, but has two major disadvantages: it requires support of the outer wall beyond the edge of the foundation and the outer wall and the extra insulation must be installed from the outside of the building, exposed to the weather.

The ability to locate an air/vapor barrier at the out-
side surface of the inner wall contributes significantly to

this position is simple with an interior bearing wall, but somewhat involved with an exterior bearing wall. It can be accomplished, however, by fastening the barrier to the (outer face of the) inner wall before it is tipped into place. The cavity can be filled with horizontal batts tied to the exterior wall before the inner wall is positioned or insulation can be blown in afterward through holes predrilled in the top plywood gusset.

@ DOUBLE WALL FRAMING

WALL cap + 2 IN. 2 IN.

this horizontal joint is best protected with A flashing made to fit over the sheathing and moisture BARRIER of THE framed wall.

wood cap with sloped top p. t. furring screwed to underside of wood cap

DRIP trim fastened through siding to furring & WALL siding moisture barrier continuous over top of wall sheathing WALL FRAMING

WIDTH of FRAMED WALL

note this detail has a continuous moisture BARRIER oVER THE TOP oF THE WALL WITHouT penetrations. the moisture BARRIER MAy BE replaced with metal flashing.

WALL cAP see 1050

WINDOW HEAD SEE 103B & C

TOP EDGE SEE 107B

BOTTOM EDGE SEE 107C

TOP EDGE SEE 107B

INSIDE CORNER SEE 104C

Many of today’s common exterior wall finishes have been protecting walls from the weather for hundreds of years. Others such as plywood, hardboard, and vinyl have been developed more recently. Regardless of their history, when applied properly, each is capable of pro­tecting the building for as long as the finish material itself lasts.

If possible, the best way to protect both the exte­rior finish and the building from the weather is with adequate overhangs. But even then, wind-driven rain will occasionally get the building wet. It is important, therefore, to detail exterior wall finishes carefully at all but the most protected locations.

The introduction of effective moisture barriers under the siding has the potential to prolong the life of walls beyond the life of the siding alone. While the siding is still the first line of defense against weather, it is possible to view one of its primary functions as keeping sunlight from causing the deterioration of the moisture barrier, which ultimately protects the walls of the building.

Where the moisture barrier stops—at the edges and the openings through the wall—special attention must be paid to the detailing of exterior wall finishes.

Sealants—In this country alone, there are more than 200 manufacturers of 20 different types of caulks and sealants. However, the appropriate use of sealants for wood-frame buildings is limited for two reasons. First, sealants are not really needed—there are 200-year-old wooden buildings still in good condition that were built without the benefit of any sealants. Second, the lifespan of a sealant is limited—manufacturers claim only 20 to 25 years for the longest-lasting sealants. Therefore, it is best practice to not rely heavily on the use of sealants to keep water out of buildings.

However, some situations in wood-frame construc­tion do call for the use of a sealant or caulk. These are mostly cases where the sealant is a second or third line of defense against water intrusion or where it is used to retard the infiltration of air into the building. In all instances, it is recommended that the caulk or sealant not be exposed to the direct sunlight.

@ EXTERIOR WALL FINISHES

A VERTICAL EDGE IS A LIKELY PLACE FOR WATER TO LEAK AROUND THE EXTERIOR WALL

finish into the structure of a building. a continuous moisture barrier behind the vertical joint is crucial. a sealant can help deter the moisture, but will deteriorate in the ultraviolet light unless placed behind the wall finish,

WHERE IT WILL BE PRoTEcTED.

AT THE upper edges of WALL FINisHEs (AT eaves & rakes, under windows & doors & at other horizontal breaks), direct moisture away from the top EDGE of THE finish MATERIAL To THE face of the wall.

if siding is to be painted.
Horizontal Material Change	Sills, Eaves & Other Overhangs
EXTERIOR WALL FINISHES At Vertical Edges	EXTERIOR WALL FINISHES At Top Edges

the bottom edge of the wall finish is more

LIKELY to GET WET THAN THE TOP. ALLoW WATER

to fall from the bottom edge of the wall finish in a way that avoids capillary action.

6

porch

: .. or deck

I

I

! s

foundation roof

or other

MATERIAL

EXTERIOR WALL FINISHES

At Bottom Edges

Horizontal wood siding is common in both historic and modem buildings. The boards cast a horizontal shadow line unique to this type of siding.

Materials—Profiles (see below right) are commonly cut from 4-in., б-in., and 8-in. boards. Cedar, redwood, and pine are the most typical. Clear grades are avail­able in cedar and redwood. Many profiles are also made from composite hardboard or cementboard. These materials are much less expensive than siding milled from lumber and are almost indistinguishable from it when painted.

A HORIZONTAL SIDING

Drop Shiplap T & G Bevel

Horizontal Siding Profiles

Types—Siding joints may be tongue and groove, rabbeted, or lapped. Common profiles (names may vary regionally) are illustrated at bottom right.

Application—Boards are typically applied over a moisture barrier and sheathing, and should generally be back-primed before installation. Boards are face – nailed with a single nail near the bottom of each board but above the board below to allow movement. Siding is joined end to end with miter or scarf joints and sealant over a stud.

Finish—Horizontal wood siding is usually painted or stained. Clear lumber siding is sometimes treated with a semitransparent stain.

Rain Screen Siding—Rain screen siding strategy recognizes that some moisture will penetrate the wall and provides an easy path for this moisture to escape the wall assembly. A rain screen wall can be understood as two layers of protection with an air space in between.

An outer layer sheds most of the weather, and an inner layer takes care of what little moisture gets through.

The critical element—one that is not present in (most) other siding systems—is the air space between the two layers. This air space provides a capillary break and promotes the rapid escape of moisture with a clear path to the base of the wall for water to drain by gravity and by allowing ventilation to remove moisture in the form of water vapor.

Materials—The inner layer can be made of the same materials as the moisture barrier in most siding systems: tar paper, building wrap, or rigid foam insula­tion in conjunction with flashing (and tape or sealant). The air space is created by vertical furring strips, usu­ally 3/8 in. to У2 in. thick aligned over the studs. The
outer layer is usually made with horizontal wood siding (clapboards), but can be made of any material that sheds water and is capable of spanning between the ver­tical furring strips. Screening is required at the top and bottom of the wall to keep insects out of the air space.

Application—Materials are applied with nails or staples as with standard siding materials. Special care should be taken that materials lap properly to shed water. The inner layer, called the drainage plane, must be especially carefully detailed and constructed to keep moisture out of the framing. Back-priming and end­priming of wood siding materials is very important to prolong the life of the material and of the finish.

Finish—Rain screen siding can be finished with any paint or stain designed for use on standard siding. Because the system breathes and does not trap mois­ture within the wall, finishes will typically outlast the same finish applied to a standard wall.

@ RAIN SCREEN SIDING

trim may BE ELIMINATED at horizontal TOP

EDGES If SIDING IS OIT cAREFuLLY TO FIT UNDER SILLS OR EAVES.

OR

matched SIDING MAY BE TRIMMED

with second

LAYER, OR BOARD SIDING WITH HORIZONTAL BATTEN.

top edges (soffit trim, eave TRIM & under SILLS) TRIMMED WITH under SILL TRIM INTO WHicH SIDING SLIDES. SPEQAL TooL

punches tabs at cut top

EDGE oF SIDING; TABS Lock

into trim, which may need to be furred depending on location of horizontal cut

IN SIDING.

Vinyl sidings were developed in an attempt to elimi­nate the maintenance required of wood sidings. Most aluminum-siding manufacturers have moved to vinyl.

Material—There are several shapes available. Most imitate horizontal wood bevel patterns, but there are some vertical patterns as well. Lengths are generally about 12 ft., and widths are 8 in. to 12 in. The ends of panels are factory-notched to allow for lapping at end joints, which accommodates expansion and contraction. Color is integral with the material and ranges mostly in the whites, grays, and imitation wood colors. The vinyl will not dent like metal, but will shatter on sharp
impact, especially when cold. Most manufacturers also make vinyl soffit material, and some also make decora­tive trim. Vinyl produces extremely toxic gasses when involved in a building fire.

Installation – Vinyl has little structural strength, so most vinyl sidings must be installed over solid sheathing. Proper nailing with corrosion-resistant nails is essential to allow for expansion and contrac­tion. Because vinyl trim pieces are rather narrow, many architects use vinyl siding in conjunction with wood trim, as suggested in the isometric drawing above.

@ VINYL SIDING

TOP EDGES ARE SOMETIMES LEFT WITHOUT TRIM BECAUSE THEY CAN EASILY BE CUT TO A CLEAN SQUARE EDGE THAT IS BUTTED AGAINST A SoFFIT, EAvE, or other horizontal surface, or trim may be added.
horizontal joints between siding PANELS oR between PANELS & oTHER MATERIAL SHoULD BE blocked if they do not occur over a plate or floor framing.
LAP PANELS To FoRM A DRIP EDGE oR	BUTT PANELS AND FLASH WITH METAL z FLASHING, SEE 104A
vertical joints BETWEEN SIDING PANELS SHoULD ALWAYS FALL ovER A STUD.
manufactured LAP joiNT
butt joint covered WITH BATTEN

Materials— Plywood siding is available in 4-ft.-wide panels, 8 ft., 9 ft., and 10 ft. tall. Typical thicknesses are 3/s in., V’2 in. and 5/s in. The panels are usually installed vertically to avoid horizontal joints, which require blocking and flashing. Textures and patterns can be cut into the face of the plywood to resemble vertical wood­siding patterns.

Installation—Manufacturers suggest leaving a Vs-in. gap at panel edges to allow for expansion. All edges should be treated with water repellent before
installation. It is wise to plan to have window and door trim because of the difficulty of cutting panels precisely around openings. Fasten panels to framing following the manufacturer’s recommendation.

Single-wall construction—Since plywood, even in a vertical orientation, will provide lateral bracing for a building, it is often applied as the only surface to cover a building. This is called single-wall construction and has some unique details (see 80 and 113).

Most of the details for double-wall plywood con­struction also apply to single-wall construction. But with single-wall construction, the moisture barrier is applied directly to the framing, making it more difficult to achieve a good seal. The wide-roll, polyolefin mois – ture/air infiltration barriers work best (see 88B). Also, the bottom edge of the plywood is flush against the foundation, so a drip detail is impossible (see right).

Flashing—Windows and doors that are attached through the casing and need head flashing because of exposure to rain or snow are very difficult to flash. As shown in the drawings below, a saw kerf must be cut into the siding at the precise location of the flashing. The flashing and siding must be installed simultane­ously before the door or window is attached.

Flashing a Header

COVER HORIZONTAL EDGES WITH TRIM FASTENED TO A SPACER. LOCATE SHINGLE FASTENERS VERY HIGH ON LAST cOuRSE	NOTE SHORT HORIZONTAL EDGES SUCH AS APRONS MAY BE COVERED WITH A PIECE OF TRIM FASTENED TO THE SLOPED SURFACE OF THE SHINGLES. FOR RAKE TRIM. SEE 115A & B
FASTENERS 1 IN. (MIN.) ABOVE COURSE LEVEL OF NEXT COURSE
shingles butt TO VERTICAL TRIM
JOINTS BETWEEN SHINGLES OFFSET 11/2 IN. (MIN.) FOR THREE ADJACENT COURSES.
1A-IN. SPACE BETWEEN ADJACENT SHINGLES IN FIELD (NOT AT CORNERS OR EDGES)
DOUBLE BOTTOM COURSE PROJECTS 1/2 IN. BELOW SHEATHING TO FORM DRIP.
OUTSIDE CORNERS ARE WOVEN SO ALTERNATE ROWS HAVE EDGE OF SHINGLE EXPOSED. EDGE IS TRIMMED FLUSH WITH ADJACENT SHINGLE ON OPPOSITE FACE OF CORNER. CORNER BOARDS CAN ALSO BE USED AS TRIM AT OUTSIDE CORNERS. SEE 110 .
INSIDE CORNERS ARE WOVEN LIKE OUTSIDE CORNERS. SHINGLES ARE TRIMMED TO BUTT AGAINST SHINGLE ON OPPOSITE FACE. TOP SHINGLE ALTERNATES FROM ROW TO ROW. CORNERBOARDS CAN ALSO BE USED AS TRIM AT INSIDE CORNERS. SEE 110

Shingles are popular because they can provide a durable, low-maintenance siding with a refined natural appearance. Shadow lines are primarily horizontal but are complemented with minor verticals. Material costs are relatively moderate but installation costs may be very high.

Materials—Shingles are available in a variety of sizes, grades, and patterns. The most typical is a western red cedar shingle 16 in. long. Redwood and cypress shin­gles are also available. Because shingles are relatively small, they are extremely versatile, with a wide variety of coursings and patterns.

Installation—Shingles are applied over a moisture barrier to a plywood or OSB wall sheathing so at least two layers of shingles always cover the wall. Standard

coursing allows nail or staple fasteners to be concealed by subsequent courses. With shingles there is less waste than with other wood sidings.

Finish—Enough moisture gets between and behind shingles that paint will not adhere to them reliably.

Left unfinished, they endure extremely well, but may weather differentially, especially between those places exposed to the rain and those that are protected.

Stains and bleaching stains will produce more even weathering.

Preassembled shingles—Shingles are also avail­able mounted to boards. These shingle boards increase material cost, decrease installation cost, and are most appropriate for large, uninterrupted surfaces. Corner boards are required at corners.

@ WOOD SHINGLE SIDING

CEDAR SHINGLES

MITER TOP TRIM PIECE.

SECOND PIECE OVERLAPS FIRST.

START AT BOTTOM OF RAKE WITH BOARD RIPPED TO THIcKNESS of butt end of shingles. TOP END is cut level & FITS uNDER SHINGLE (SEE ISOMETRIc AT RIGHT).

Elevation

ONE Method OF FINISHING THE TOP EDGE OF A SHINGLE wALL IS TO LAP THE SHINGLE cOuRSES wiTH TRIM PIEcES RIPPED FROM A cEDAR 2x. IF THE cOuRSING IS EQuAL, ALL THE TRIM PIEcES, ExcEPT FOR THE MITERED TOP PIEcES, wILL ALSO BE EQuAL.

SHINGLE SIDING AT RAKE Lapped Trim

THE BASE Layer IS NOT ExPOSED & THEREFORE can be a lower-grade SHINGLE.

FINISH-LAYER SHINGLE projects about 1/2 IN. BELOw BASE LAYER TO FORM A DRIP.

RIP SHINGLES TO DESIRED wIDTH & APPLY AT SAME cOuRSING AS

NAILING MuST BE EXPOSED FOR THIS cOuRSING.

NOTE FOR PREPAINTED OR PRIMED SHINGLES, LEAVE NO SPAcE BETwEEN FINISH LAYER SHINGLES.

DOuBLE cOuRSING, AN ALTERNATIVE cOuRSING METHOD, cALLS FOR TwO LAYERS APPLIED AT THE SAME cOuRSE. A PREPAINTED OR PRIMED SHINGLE cALLED SIDEwALL SHAKE IS cOMMONLY uSED.

Shingled Trim

SHINGLE SIDING AT RAKE

DOUBLE-COURSED SHINGLES

Shingled & IxTrim

Brick veneer covers wood-frame construction across the country. Where it is not subjected to moisture and severe freezing, it is the most durable exterior finish.

Materials—Bricks come in a wide variety of sizes, with the most common (and the smallest) being the modular brick (2>4 in. by 35/s in. by 75/s in.). These bricks, when laid in mortar, can follow 8-in. modules both horizontally and vertically. Colors vaiy from cream and yellows to browns and reds, depending on the clay color and method of firing. Bricks should be selected for their history of durability in a given region.

Installation— Bricks are laid in mortar that should be tooled at the joints to compress it for increased resis­tance to the weather. Because both brick and mortar are porous (increasingly so as they weather over the years), they must be detailed to allow for ventilation and drainage of the unexposed surface. A 1-in. air space between the brick and the wood framing, with weep holes located at the base of the wall, typically suf­fices (see 117B). It is important to keep this space and the weep holes clean and free of mortar droppings to ensure proper drainage.

TOP OF WALL IS DETAILED TO KEEP WATER OFF THE HORIZONTAL SuRFAcE OF THE TOP BRIcK. THIS cAN

usually be accomplished with the detailing OF

THE ROOF ITSELF. cOvER THE JOINT BETWEEN BRIcK & ROOF WITH WOOD TRIM. cAuLK THE jOINT AS FOR vERTicAL jOINTS, BELOW.

RAKE TRIM LAPS BRIcK

SEALANT BETWEEN WOOD & BRIcK

RAKE IS uSuALLY TRIMMED WITH WOOD

sufficiently WIDE TO cover the stepping OF brick caused BY SLOPE. DETAIL AS FOR TOP OF WALL.

SHEATHING AIR SPAcE brick BAcKER ROD SEALANT vertical casing OR TRIM OF WOOD OR OTHER MATERIAL

vERTicAL jOINTS Such AS WINDOW & DOOR cASINGS AND AT TRANSITIONS TO OTHER MATERIALS MuST BE cAREFuLLY cAuLKED TO SEAL AGAINST THE WEATHER. BAcKPRIME WOOD cOvERED BY OR

in contact with brick.

Finish – A number of clear sealers and masonry paints can be applied to the finished masonry to improve weather resistance, but reapplication is required eveiy few years.

@ BRICK VENEER

BOTH INSIDE & OUTSIDE CORNERS CAN BE MADE SIMPLY WITH THE BRICKS THEMSELVES.

Brick Corner

IF WooD

Brick and Siding Corners

BRICK VENEER

Corners

sill preprimed on underside if wood

sealant between SILL and brick.

rowlock brick sloped at angle of SILL

FLASHING coNTINuouS to back of SILL

SHEATHING 15-LB. FELT 1-IN. AIR SPAcE

BRICK VENEER AT WINDOW/DOOR Attachment to Casing & Sill

CONTROL JOINT ORIENTED HORIZONTALLY OR VERTICALLY &

LOCATED OVER STRUCTURAL MEMBERS & DIAPHRAGMS BREAKS STUCCO PANELS INTO 18-FT. (MAX.) DIMENSIONS (OR LENGTH-TO-WIDTH RATION OF 2.5И). ——

SELF-FURRING GALVANIZED 17-GAUGE 11/2-IN. MESH STUCCO WIRE (SHOWN) OR GALVANIZED EXPANDED METAL LATH

15-LB. FELT BOND BREAK

Stucco is made of cement, sand, and lime. It is usu­ally applied in three coats, building to a minimum thickness of 3/4 in. Cost may be moderate in areas with high use, but high where skilled workers are few.

Materials— Reinforcing materials through which the plaster is forced are either stucco wire or metal lath. This reinforcing is fastened either to sheathing or directly to the framing (without sheathing). When sheathing is used, it must be rigid enough to remain stiff during the process of applying the stucco—5/s-in. plywood is typical.

A double-layer moisture barrier between the rein­forcing and the framing is important because the stucco will bond with the outer layer of barrier, destroying its ability to repel water. The outer layer forms a bond

break so that the inner layer will remain intact to pro­tect the framing. The inner layer performs best if it is thick, with drainage channels.

Application – The first (scratch) coat has a raked finish, the second (brown) coat has a floated finish, and the final (color) coat may have a variety of finishes. Applying stucco takes skill, so stucco is the least appro­priate of all the exterior wall finishes for owner-builders to attempt.

Finish—Textures ranging from smooth to rustic are achieved by troweling the final coat. Color may be integral in the final coat or may be painted on the sur­face. Stucco is not very moisture resistant and must be sealed or painted.

CASING BEAD AT TOP,

SIDE, OR RAKE EDGES

OR

WRAPPED BASE COAT WITH FIBERGLASS MESH

FINISH COAT WITH INTEGRAL COLOR

BASE COAT WITH EMBEDDED FIBERGLASS MESH

RIGID INSULATION

with grooved back

OR

Synthetic stucco looks like traditional stucco but is really a flexible acrylic coating applied over rigid insu­lation. Called EIFS (Exterior Insulation and Finish

Systems), synthetic stucco is more flexible than stan­dard stucco and more moisture resistant. This moisture resistance, which certainly is a strength of the system, worked against early versions of its application when imperfect detailing led to moisture being trapped inside the wall behind the impermeable EIFS layer. With updated water-managed EIFS, it is now assumed that some moisture will penetrate the surface, and therefore a drainage path is provided for this moisture to escape.

Materials—There are several manufacturers of water – managed EIFS. Each starts with rigid insulation, fas­tened to the framing with nails fitted with large plastic washers designed to prevent crushing of the insulation. The insulation is protected from impact by a stucco
base made of acrylic cement reinforced with fiberglass mesh. An acrylic finish coat with integral color provides moisture protection.

Application—All systems start with an effective mois­ture barrier applied to the wall sheathing. The next layer is a drainage plane that provides a clear path for moisture to escape. This drainage plane can be a sepa­rate plastic drainage mat or vertical grooves integrated into the back side of the rigid insulation, which is the following layer. The base coat of stucco is troweled directly onto the insulation, reinforced with mesh, and then another layer of base coat. The final coat is troweled over the hardened base coat.

Finish—There are a variety of common troweled finish textures. Color is integral in the final coat, so painting is unnecessary, but inspection and repair of sealant joints every few years is highly recommended.

Wall insulation is typically provided by fiberglass batts. Building codes in most climates allow 2×4 walls with ЗУ2 in. of insulation (R-ll) or 2×6 walls with 5V2 in. of insulation (R-19).

Vapor retarder—Vapor retarders are installed in con­junction with wall insulation. The purpose of a vapor retarder, a continuous membrane located on the warm side of the insulation, is to prevent vaporized (gaseous) moisture from entering the insulated wall cavity, where it can condense, leading to structural or other damage.

Common vapor retarders include 4- or 6-mil polyeth­ylene film applied to the inside of framing or specially formu­lated paint or primer applied to the surface of chywall.

Rigid insulation with taped

, , , RETARDER WARM

joints may also be used.

Various vapor retarder materials have different rates of permeability (see 88A), and, because moisture can enter a wall assembly from either side, it is wise to use the most permeable material proven to be effective in a given region so as not to trap moisture within the assembly.

The vapor retarder should always be located on the warm side of the insulation. In a cold, chy climate the
retarder goes on the inside of the wall. But in mixed climates the migration of vapor can reverse in the summer. For this reason, building scientists recom­mend against using low-permeability materials on the inside of air-conditioned walls.

The location of the vapor barrier may be adjusted in upgraded applications provided that two-thirds or more of the insulative value of the wall remains to the cold side of the barrier.

АІГ barrier— An air barrier is intended to control the migration of air through the insulated envelope of a building. Standard construction practices allow voids and breaks in the building envelope that can leak up to two times the total air volume of the building per hour—accounting for up to 30% of the total heat loss (or gain) of the building. Upgrading the envelope can cut this air leakage to one-third of an air change per hour and can thus have significant consequences for energy bills in most climates.

An effective air barrier combines a continuous mem­brane with tight seals around openings such as windows where the membrane is penetrated. It may be made of a variety of materials and may be located either inside or outside of the insulation. When inside the insulation, the barrier may be chywall, rigid insulation, or the same film that forms a vapor retarder. Outside the insulation, building wrap, rigid insulation, or sheathing may be used. In each case, joints are taped or overlapped and caulked, and tight seals are made with floor and ceiling air barriers. Windows, doors, electrical, plumbing, and other services that penetrate the membrane are sealed with expansive foam, caulk, and/or special tape.

It is important to consider that the reduced ventila­tion rate due to control of air leakage can lower indoor air quality. The provision of controlled ventilation with simple energy-saving devices such as air-to-air heat exchangers can alleviate this problem.

Unfaced batts—The most common method of insulating walls is to use unfaced batts that are fitted between studs. A vapor retarder is applied to the warm side of the wall in the form of a vapor retarding paint or primer or a 4-mil polyethylene film. Properly detailed, this vapor retarder can serve as the air barrier.

Faced batts – Batt insulation is often manufactured with a paper facing that, in cold climates, serves as both vapor retarder and means of attachment. For attach­ment, the facing material has tabs that are stapled in place between the studs.

To use the facing as a vapor retarder, it is better to staple the tabs to the face of the studs to make a better seal. However, this interferes with the installation of interior finish materials because the tabs build up unevenly on the face of the studs.

Rigid insulation—In

standard construction, rigid insulation is generally used only in extreme situations where wall depth is limited but a code-prescribed R-value is required. Examples of such situations include headers (see 76A & B) and loca­tions where heat ducts, vents, or plumbing must be in exterior walls. In upgraded framing systems, however, rigid insulation is used extensively (see 122A).

Spray-foam insulation—It can cost many times as much as competing insulations, but spray-foam insu­lation can equal the R-value of the best rigid foam, double as a vapor retarder, and fully fill the most awk­wardly shaped framing cavity. Except for its high cost, it is a nearly ideal insulating material for mixed climates where warm and cold sides of the envelope reverse during the year.

In climatic zones with extremely cold or hot weather (or high utility rates), there is special incentive to insulate buildings beyond code minimums. A decision to super – insulate affects the construction of walls more than floors or roofs because walls are generally thinner (being constructed of 2x4s or 2x6s rather than 2x10s or 2x12s). Walls are also in direct contact with the ambient air because they do not have a crawl space or attic to inter­vene as a buffer.

The most direct way to increase the insulative capacity of walls is to make them thicker. A 2×4 framed wall upgraded to 2×6, for example, will increase from a com­bined (batt plus framing) R-value of 9.0 to a value of R-15.1. But increasing wall thickness alone is only effec­tive to a point because a significant part of the wall (about 9% of a wall framed at 24 in. o. c.) is composed of studs, plates, etc., which conduct heat at about three times the rate of insulative batts. When headers and other extra framing are considered, walls often have as much as 20% of their area devoted to framing. The conductance of heat through this framing is called thermal bridging.

There are two strategies for decreasing the effects of thermal bridging. The first is to reduce the quantity of framing members and is called advanced framing (see 74). The second strategy is to insulate the framing mem­bers that remain so that they do not “bridge” between the cold and warm sides of the wall. Several ways to insulate framing members are discussed on the following pages.

Rigid insulation—Rigid insulation added to the exterior or interior of a framed wall can typically add an R-value of 7 to 14 at the same time that it interrupts thermal bridging (see 122).

Strapping—Horizontal nailing strips are attached to the inside of a stud wall. Insulative values of R-25 are easily attainable (see 123).

Staggered-stud framing—A double offset stud wall framed on a single, wide plate. Combined insulative values of R-30 are common (see 124).

Double wall framing—A duplicate (redundant) wall system with R-values of up to 40 is easily reached (see 125).

THE BEST HEAD FLASHING IS SOLDERED AT THE END SO THAT THE END PROFILE MATCHES THE SIDE PROFILE. LOWER EDGE OF FLASHING ExTENDS PAST HEAD cASING AT LEvEL OF DRIP. casing

FLASHING

NOTE THE DETAIL AT RIGHT IS PREFERRED TO THE DETAIL AT LEFT BECAUSE IT IS LESS SUSCEPTIBLE TO PHYSICAL DAMAGE.

FLASHING DRIPS

Soldered Head Flashing

TWO MORE practical solutions ARE TO cut THE FLASHING FLuSH WITH THE cASING, OR, BETTER, TO TRIM & FOLD THE FLASHING ON SITE, AS SHOWN BELOW.

SIDE OF cASING.

FOLD HORizONTAL PART OF FLASHING DOWN OvER SIDE OF cASING.

SuRFAcE OF SIDING TO BE APPLIED LATER.

Folded Head Flashing

Section

WIND0W/D00R HEAD FLASHING

WIND0W/D00R HEAD FLASHING

At End of Flashing

SIDING PANEL

CONTINUOUS HORIZONTAL Z METAL FLASHING WITH 2-IN. (MIN.) OVERLAPS At

joints.

siding panel

moisture barrier continuous under

Isometric horizontal

siding joint

sheathing (OR stud wall for single-wall construction)

continuous moisture barrier

z METAL flashing siding panels

Section

NOTE

IT is prudent to cover the vertical END OF the flashing with a small piece of moisture barrier OR A DAB OF sealant TO MINIMizE THE POTENTIAL FOR LEAks.

HORIZONTAL WALL FLASHING

Corner Details

Any horizontal member such as a handrail, a trellis, or a joist that butts into an exterior wall poses an inher­ently difficult flashing problem at the top edge of the abutting members. Where such a connection is likely to get wet, the best approach is to avoid the problem by supporting the member independent of the wall. A handrail, for example, could be supported by a column near the wall but not touching it. A trellis could be self-supported.

If a horizontal member must be connected to a wall in a location exposed to the weather, two things can be done to protect the structure of the wall. First, do not puncture the surface of the siding with the member, and do everything possible to attach the member to the surface of the siding with a minimum number of fas­teners. Second, place an adequate gasket, such as 30-lb. or 90-lb. felt, behind the siding at the location of the attachment. This will help seal nails or screws that pass through the siding to the structure of the wall.

TRADITIONAL WOOD SILL WITH DRIP SLOPES AT 10° & REQUIRES THAT TOP OF RIM JOIST & COMMON JOISTS BE SHAVED OFF FOR INSTALLATION. SILL EXTENDS TO OUTSIDE EDGES OF DOOR CASINGS.

EXTRUDED SILLS OF ALUMINUM OR POLYCARBONATE ARE THE MOST COMMON FOR ALL MODERN DOORS. THE THRESHOLD IS INTEGRAL. THE SILL MUST BE SUPPORTED AT OuTER Edge. ExTRuDED SILLS May ALSO Be USED IN Slab-On-Grade cONSTRUcTION.

FLATTENED WOOD SILL SLOPES AT 7° & IS INSTALLED ON TOP OF JOIST SYSTEM. OUTSIDE EDGE IS FLUSH WITH JAMB (SHOWN) OR CASING.

NOTES

ADJUST PROFILE OF SILLS FOR OUTSWINGING DOORS.

WEATHERSTRIP BOTTOM OF DOOR.

WOOD SILLS ARE NOT COMPATIBLE WITH SLAB SUBFLOORS.

EXTRUDED SILLS

INTERIOR Flange cOORDINATES wiTH SILL & FINISH FLOOR.

BOTTOM FLANGE OF PAN LAPS SHEATHING & DOOR wRAP.

NOTE MOISTURE BARRIER (NOT SHOwN FOR cLARITY) cONTINUOUS AROUND SIDES OF ROUGH OPENING & LAPS SIDES OF SILL PAN, SEE 89.

AT DOOR LOcATIONS ExPOSED TO THE wEATHER, A GALvANIzED METAL DOOR-SILL PAN FIT INTO THE DOOR ROUGH OPENING wILL PROTECT THE STRUCTURE OF A wOODEN FLOOR SYSTEM BELOw.

^ WOOD SILLS

Residential garage doors have evolved from swinging and sliding types to almost exclusively the overhead variety. They are manufactured primarily with a solid – wood frame and plywood or particleboard panels. Paneled metal, fiberglass, and vinyl doors are avail­able in some regions. There are two operating types, sectional and one-piece, both which can be manual or fitted with automatic openers.

Sectional doors— Sectional doors are by far the more common (see 101B). They are hinged horizontally— usually in four sections—and roll up overhead. The advantages are that a sectional door is totally protected by the structure when in the open position, and that it closes to the inside face of the jamb, making the design of the jamb opening somewhat flexible.

One-piece doors – One-piece doors pivot up. The door fits within the jamb and extends to the outside of the building when in the open position. This exposes the open door to the weather. The advantage of this type of door over a sectional door is the greater design flexibility afforded by the single-piece door. Hardware for this type of door is not usually available locally.

Flashing is essential to keeping water away from the structure and the interior of a building. It is used wher­ever there is a horizontal or sloped penetration of the outer building skin or a juncture of dissimilar materials that is likely to be exposed to the weather. Flashing provides a permanent barrier to the water and directs it to the outer surface of the building, where gravity carries the water down to the ground. Of course, the best protection against water penetration of walls is an adequate eave, but wind-driven rain may make this strategy occasionally unreliable.

Wall flashing, which provides the first line of defense against water, should be taken very seriously, especially because walls, unlike roofs, are not intended to be replaced regularly. Wall flashing is likely to be in place for the life of the building.

Two physical properties affect the flow of water on vertical surfaces. The first property, gravity, can be used to advantage in directing water down the wall of a building. The other property, surface tension, cre­ates capillary action that results in water migrating in all directions along cracks in and between materials. In

many cases, the negative effects of surface tension can be avoided by the proper use of a drip.

A drip is a thin edge or undercut at the bottom of a material placed far enough away from the building surface so that a drop of water forming on it will not touch the wall but will drop away (see 103A). Drips may be made of flashing or may be cut into the building material itself.

In the case of vertical joints, a sealant may be required to counter the effects of surface tension. Except for vertical joints that cannot be flashed effec­tively, a well-designed flashing (see 103-105) is always preferable to a bead of sealant.

Common flashing materials include galvanized steel, baked enamel steel, aluminum, copper, stainless steel, and lead. Because flashing materials may be affected in different ways by different climates, air pollutants, and building materials, the selection of appropriate mate­rials is specific to each job. It is also important to isolate different metals when flashing to prevent corrosive interaction (galvanic action) between them. Consult with local sheet-metal shops for appropriate materials for specific applications.

HEADER SET HIGHER THAN STANDARD TO ALLOW FOR TRACK.

INTERIOR FINISH JAMB CASING PROJECTS BELOW HEAD Jamb & IS Fitted with trim to cover track hardware.

adjustable track HARDWARE

Head Jamb

Pocket doors – Pocket doors slide on a track attached to the head jamb and are sold as a kit, with the door and pocket separate and the pocket broken-down for ease of transport. The pocket is assembled at the site, and the head jamb (which much be set higher than 6 ft. 8 in. to allow for the track) is leveled, shimmed, and attached to the frame of the building. Next the pocket itself and the opposite jamb are shimmed and nailed. The heavier and wider the door and the better the quality of the hardware, the less likely the door is to derail. Pocket doors can’t be made to seal as tightly as hinged doors. The walls are flimsy at the pocket, and wiring or plumbing can’t be put in this section of wall.

Bypass doors—Bypass doors, such as sliding closet doors, slide on a track, like pocket doors, but have a double track and two doors that are not concealed in a pocket in the wall. Nylon guides on the floor keep the bottom of the doors in line. As with pocket doors, the header of a bypass door should be set higher than normal, and the casing should be designed to cover the track hardware. The jambs are like those for hinged doors but without stops.

Bifold doors—Bifold doors have two hinged halves that fold to one side, with a track at the top. Installation notes for bypass doors apply, except that casing trim must be kept above the top of the doors to allow the doors to fold.

Because they do not have to be sealed against the weather, interior doors are much simpler than exterior doors. Interior doors are used primarily for privacy and to control air flow. The doors themselves are typi­cally made of wood or composite wood products. They are 1% in. thick, and have either panels, like the one shown above, or a flush plywood veneer over a hollow core or solid core.

Hinged interior doors are usually prehung on a jamb without casings. The jamb on the hinged side is first nailed to the frame of the building, using shims to make it plumb. The jambs at the head and opposite side are then shimmed for proper clearance and nailed.

Some doors are hinged to a split jamb that will expand to accommodate some variation in wall thick­ness. Interior doors do not have sills and rarely have a threshold unless the floor material changes at the door.

Sliding doors, whether they are wood, vinyl, fiber­glass, or aluminum, fasten to a building more like a window than like a hinged door. Because the weight of a sliding door remains within the plane of the wall, there is no lateral loading on the jamb of the door unit. Sliding doors are therefore supported on the sill and can be attached to the building like windows—through the casing or with a nailing fin. As with sliding windows most sliding-door manufacturers recommend not fastening the nailing fin at the head because header deflection can impede door operation.

Sliding doors are trimmed to the finish materials of the wall in the same way as swinging doors and win­dows (see 92-94).

HEADER SEE 68-70 SHEATHING

DOOR WRAP IF EXPOSED TO WEATHER SEE 89

NAILING Fin on

sheathing & under moisture BARRIER

SIDING

caulk SEE 106

flashing if exposed to weather SEE 103b & c

insulate rough-opening cavity.

jamb extender to make jamb flush with interior

WALL FINISH

Storm sash made today are usually fitted to aging single-glazed windows. The storm sash protects the existing window from the weather and also improves the thermal performance of the window.

Usually made of aluminum, storm sash are custom fit to the exterior face of the existing window. Many are operable from the interior and are fitted with screens. Depending on how they are installed, storm sash can either significantly extend the useful life of old windows or actually contribute to their deterioration. A proper installation depends on numerous factors including the climate and the detailing of the original window.

New custom wood windows can be manufactured with single glazing if fitted with storm sash. This can be useful for historic work or when attempting to make simple inexpensive sash for a microclimate that requires them. The storm sash provide the thermal performance required by code at the same time they protect the most precious part of the assembly—the sash itself—from the weather. Storms located at fixed sash can be left in place year-round, while storms at operable windows can be exchanged for screens during the summer.

WALLS

Doors

HEAD

Traditional Exterior Door

Modern doors have been derived from traditional prototypes; they are better insulated and better sealed, and usually require less maintenance than their ances­tors. Exterior hinged doors are made of wood (ply­wood, composite, or solid wood), fiberglass (fiberglass skin over a wood frame with a foam core), or insulated steel. Wood is the most beautiful, fiberglass the most durable, steel the most inexpensive.

Most exterior doors swing inward to protect them from the weather. Nearly all manufacturers sell their doors prehung (hinged to a jamb and with exterior casing attached). Sills and thresholds are the most vari­able elements in manufactured prehung doors. Most doors come with an extruded metal sill and integral threshold, which is installed on top of the subfloor (see 100B). Wood sills must be thicker than metal for strength, so they work best with finish flooring materials that are 3/4 in. thick or more (see sill drawing at right).

Because of the torsional forces exerted by the hinges on the jamb when the door is open, doors that swing need to have their jambs fastened directly and securely to the buildings frame. The best way to accomplish this is to nail the jamb directly to the supporting stud, using shims to make the jamb plumb. It is common practice to attach a prehung door through the casing with long screws through the hinge and jamb into the stud.

plastic or sheet-metal sill PAN provides alternative moisture protection in severe conditions. fasten pan only through sides and face flanges and lap sides with peel-and-stick flashing.

WINDOW/DOOR ROUGH-OPENING WRAP

Alternative Details for Severe Exposure to Rain

Modern windows derive from the traditional wooden window shown above. Older windows have a wooden sash that holds the glass, which is usually divided into small panes by muntin bars. This sash is hinged or slides within a wooden frame that is fixed to an opening in the wall. At the bottom of the frame is a wood sill, sloped to shed water. The sides and top of the frame are called jambs.

These components and their terminology have been handed down to the modern window, but modern win­dows are better insulated and better sealed, and usually need less maintenance than the traditional prototypes.

Today’s window is made in a factory and is shipped ready to install in a rough opening. Several popular types, classified by their method of operation, include casement, double-hung, sliding, hopper, awning, and fixed. Each of these types is made in wood, vinyl, metal, fiberglass, or a combination of these materials. Sizes and details vary with the manufacturer. Double-hung, sliding, and fixed windows are generally made in larger sizes than the hinged types. Optional trim packages are available with most.

@ WINDOW TERMINOLOGY

SHEATHING EXTERIOR WALL FINISH FLASHING SEE 103B & C

CASING

HEADER SUPPLIES STRUCTURE TO WALL ABOVE WINDOW OPENING. SEE 68-70

insulation fills IN void between window jamb & rough opening to insulate better &

TO RETARD AIR INFILTRATION.

SASH

SuPPORT WINDOW ON

framing according to manufacturer’s

SPECIFICATIONS.

moisture-barrier

WRAP PROTECTS

framing from water

LEAKS AROuND WINDOW. SEE 89

All windows require a coordinated installation in wood-frame walls, as follows:

Header— Size the header so that loads from above do not bear on the window itself, restricting operation.

Window wrap—Wrap the framing at the rough opening with a moisture barrier to protect it from any leaks around the edges of windows and doors.

Sill pan— At windows exposed to severe weather, add under the window a continuous metal or plastic pan that drains to the exterior (see 89B).

Shim and support – Shim the window at the sill and affix the shims to the framing so that the window is level and rests firmly on the framing.

Insulation—Place batt or spray foam insulation around the edges of the installed window to reduce both heat loss and air infiltration.

Air barrier—An air barrier, if used, must be sealed to the window unit. The moisture/air barrier may be sealed to the window nailing flange at the wall’s outside surface, or the vapor/air barrier may be sealed to the jamb’s inside edge at the wall’s inside surface.

Wood windows—Wood windows (see 92-95) are pleasing for their warm, natural look. Along with the excellent thermal properties of wood, the aesthetic appeal of the wood window is its strongest asset.

The major disadvantages of wood windows are the initial high cost and the ongoing need for maintenance. Wood is susceptible to deterioration from the weather, so periodically refinishing the exterior surfaces is neces­sary. Every effort should be made to protect all-wood windows from rain by locating them under overhangs.

Wood windows clad with aluminum and vinyl were developed to minimize maintenance. The cladding decreases their need for maintenance yet retains the aesthetic advantages of wood on the interior.

Vinyl windows—Made of extruded PVC that is either screwed or heat-welded at mitered corners, vinyl windows (see 93B and 94B) have come to dominate the window market. Their cost and expected maintenance are low, while their insulative properties are relatively high. They are available in all typical operating types.

Vinyl windows are not available with exterior cas­ings, but decorative casings are often added (see 93B). One disadvantage of vinyl windows is the limited range of available colors. The vinyl cannot be painted, and only very light colors such as white and tan are available because dark colors tend to absorb heat, causing warping.

Fiberglass windows—Newly developed fiberglass windows have none of the disadvantages of competing materials, but they are currently quite expensive. Fiberglass does not deteriorate in the weather like wood and does not expand with heat like vinyl. It is a relatively good insulator and is so durable that manu­facturers offer lifetime warranties. Fiberglass windows have factory-applied finishes, ranging from light to very dark, and can be painted.

Metal windows—Until recently, aluminum windows were the most common low-cost window. But energy codes and the popularity of vinyl windows have virtu­ally eliminated aluminum windows from the residential market except in very mild climates. Aluminum is still available for commercial applications. The ubiquitous storefront windows are available in polished aluminum, anodized bronze, and a spectrum of baked-enamel colors.

Unclad wood windows are attached to the building through the casing. This is the traditional way that win­dows have been fastened to wood buildings. The nail holes are typically filled, and the casings painted. It is also possible to cover the nails with a dripmold or with a backband that may be nailed from the side or the face, depending on the profile of the backband. The backband is mitered at the corners and dies on the sill.

When attaching a window through the casing, it is important to support the weight of the window unit from below. Shim the sill and/or the extensions of the side jambs below the sill.

Some manufacturers also recommend blocking and nailing the units through the jamb. In this case, the nails can be covered by the stops.

Typical Backband Profiles

HEADER

SHEATHING

SIDING

FLASHING AT HEAD DRIP

BACKBAND BACKBAND NAIL CASING NAIL CASING

URETHANE-FOAM OR BATT INSULATION

SASH

NOTE

BACKBAND COVERS THE CASING Nail IN THIN, Flat

casing & allows various widths of SIDING TO BuTT AGAINST IT. COvER BACkBAND NAILS WITH SIDING OR FILL NAIL HOLES.

HEADER SHEATHING SIDING FLASHING WITH DRIP (OPTIONAL) WOODEN Dripmold CASING NAIL CASING uRETHANE-FOAM OR BATT insulation SASH
NOTE WOODEN DRIPMOLD CAN Take THE PLACE OF FLASHING DRIP AT THE HEAD OF WINDOWS & DOORS. IT MAY ALSO BE uSED in conjunction WITH FLASHING. IT IS OFTEN uSED WITH SHINGLE SIDING.
OR SIDING TO BuTT AGAINST IT.
Brickmold Casing	Dripmold at Head

дЛ WOOD WINDOWS

HEADER SEE 68-70 SHEATHING WINDOW WRAP SEE 89 SIDING	MODERN WINDOWS ARE uSuALLY MANuFAcTuRED WITH NAILING FINS THAT ACT AS FLASHING & PROviDE NAILING FOR ATTAcHING THE WINDOW TO THE BuiLDING. WINDOWS WITH NAILING FINS cAN BE uSED BOTH with & without casings. HEADER
SHEATHING SIDING MOISTURE BARRIER LAPS NAILING FIN AT HEAD (FIN LAPS MOISTURE BARRIER AT SIDES & SILL). FLASHING WITH DRIP NAIL THROUGH FIN INTO FRAMING.
FLASHING IF EXPOSED TO WEATHER SEE 103B & C CASING SEE 92
Head Jamb
URETHANE-FOAM OR ВАТТ INSULATION
SIDING SHEATHING WINDOW WRAP SEE 89
METAL. VINYL. OR WOOD JAMB & SASH(CLAD WOOD SHOWN)
CAULK SEE 106 CASING SEE 92
HEADER SHEATHING SIDING FLASHING WITH DRIP AT HEAD decorative casing RABBETED OvER NAILING FIN moisture BARRIER LAPS NAILING FIN AT HEAD (FIN LAPS moisture BARRIER AT SIDES & SILL). secondary FLASHING OR DRIP IN cASING AT HEAD NAIL THROuGH FIN INTO FRAMING. uRETHANE-FOAM OR BATT INSuLATION METAL, viNYL, OR WOOD JAMB & SASH (cLAD WOOD SHOWN)
Side Jamb
WINDOW WRAP SEE 89 SHEATHING
Sill
Nailing Fin with Casing
B WOOD, METAL, OR VINYL WINDOWS ‘ Attachment through Nailing Fin
UNCLAD WOOD WINDOWS Attachment through Casing

HEADER SEE 68-70

SHEATHING

WINDOW WRAP SEE 89

SIDING

NAILING FIN ATTACHED

to frame of building

Head Jamb
SHEATHING
window WRAP SEE 89 SIDING NAILING FIN ATTAcHED to frame of building
caulk AT jamb SEE 106
Side Jamb
shim window to bottom of rough opening for leveling & support.
SIDING
NAILING FIN ATTAcHED to frame of building window wrap SEE 89
NAILING FIN ATTAcHED to frame of building
SHEATHING
window WRAP SEE 89 SIDING	SHEATHING SIDING

д CLAD WOOD WINDOWS

Where fixed windows are acceptable, a great deal of expense may be saved by custom-building the win­dows on the job without sash. In this case, the glass is stopped directly into the window frame, and caulk or glazing tape seals the glass to the casing just as it would to the sash. Ventilation must be provided for the space by means other than operable windows.

When designing and installing site-built fixed windows, the following guidelines are useful:

1. Allow Vs in. minimum clearance at the top and sides of the glass.

2. Rest the base of the glass on setting blocks spaced one-quarter of the width from each end.

3. Glass can be set closer to the interior of the building than shown in 95A by using exterior stop.

U. Support the sill of wide or heavy windows by shimming it from the framing.