Category Construction

 

WALL SHEATHiNG FLASHiNG FiNiSH WALL AND MOiSTURE BARRiER LAP FLASHiNG AT WALL. KEEP SiDiNG NAiLS OUT OF FLASHiNG TO ALLOW VERTiCAL ADJUSTMENT WHEN REROOFiNG.

 

FLASHiNG ExTENDS 3 IN. (Min.) up WALL AND 4 IN. (Min.) ONTO ROOF.

 

FLASHiNG LApS 2 iN. (Min.) AT sidewalls

 

step FLASHiNG (before IT is covered ву next course OF ROOFING)

 

NAIL NEAR TOp EDGE ABOVE pREViOuS FLASHiNG. ROOF cOuRSES LAID OVER EAcH cOuRSE OF STEp FLASHiNG

 

FLASHiNG

 

ROOFING

 

SHEATHiNG

 

NOTES STEp-FLASHiNG piEcES ARE 2 IN. LONGER THAN ROOF cOuRSING exposure AND ARE INSTALLED WITH THE ROOFING MATERIAL, ONE cOuRSE AT A TIME. ExTERIOR WALL FiNiSH AND MOISTuRE BARRiER WILL LAp STEp FLASHiNG. FLASHiNG DIMENSIONS DEpEND ON ROOFING MATERIAL AND piTCH.

 

LAP FLASHiNG WITH MOiSTURE BARRIER AND WALL FINISH (NOT SHOWN). –

LEVEL wALL

flashing, see 169D,

notched for step or

SIDEWALL FLASHING
vertical leg of step or sidewall

FLASHING ExTENDS

below corner, as allowed By

SIDING.

Lapped Flashing for Moderate Weather	Lapped Flashing for Moderate Weather

bottom EDGES of soldered corner flashing

AND LEVEL WALL FLASHING LAp

roofing.

SIDEWALL

of step

FLASHING

laps

soldered

corner

FLASHING.

note

roofing (not shown) laps

SIDEWALL oR STEp FLASHING AND

soldered corner

FLASHING.

Soldered Flashing for Extreme Weather

дЛ OUTSIDE CORNER FLASHING

INSIDE CORNER FLASHING

Lapped Flashing for Moderate Weather

The flashing detail at left applies to both reduced pitch (shown) and increased pitch. Reduced pitch – change flashing can be avoided in favor of a cleaner detail by bending asphalt shingles or by soaking or steaming and bending wood shingles. The pitch change can also be made gradual by adding a strip of sheathing at the bend in the roof (see below) so that stiffer roofing materials such as wood shingles and shakes, tiles and slates can make the transition without flashing.

EXTRA

TRUSS WITH OVERHANGING EAVE

Exposed or Boxed-ln Eave

ENGINEERED HEEL TIED TO WEB SYSTEM OF TRUSS ALLOWS DEEP CEILING INSULATION SEE 198-199

TRUSS WITH SOFFITED EAVE

TRUSS WITH SOFFITED EAVE

Because roofs are the highest part of a building and are the least weighted down by other parts of the build­ing, they are the most vulnerable to the effects of wind. In areas prone to high winds, the design and detailing of roofs is one of the most critical concerns for the longevity of a building. The bracing of buildings to resist lateral wind forces is discussed in Chapter 3 (see 77 & 82).

Wind generally moves horizontally to impose lateral forces on buildings, much as earthquakes do. But wind flows in complex shifting patterns around a building, creating pressures on some surfaces and suction on others. Thus it can create vertical forces that actually lift the roof off a building.

These vertical forces can be created in three ways. First, they may be produced as a negative pressure (suction) if developed on the leeward side of a building. In the case of a pitched roof, this condition theoreti-

A second way for wind to exert a vertical force on a roof is for the wind to catch a protrusion such as an eave or rake overhang. In this case, the force of the wind is localized at the edge of the roof.

Finally, wind can lift the roof structure from the inside of the building. This generally occurs as a weak point in the shell of the building such as a window or garage door giving way to the pressure of the wind. The wind suddenly enters the structure, pressur­izing it and forcing the roof up.

To resist the force of high winds on roofs, several strategies may be employed. Some involve design decisions to minimize the impact of high winds in the first place, others involve strengthening what is built to minimize damage.

Design strategies—One basic strategy to increase a roof’s chance of survival in high winds is to keep the roof pitch low. High-pitch roofs extend higher into the sky, where wind velocity is greater, and present a greater surface area than do low-pitched roofs. Pitches between 2:12 and 7:12 are recommended for high-wind areas.

The shape of the roof also has a large impact on its durability in a windstorm. Generally, hip roofs fare the best because their geometry makes them self-bracing, and they have low eaves with no tall walls. Gable roofs present a weak point at the gable end itself, which is a tall vertical surface.

The width of overhangs at both eave and rake are important considerations for high-wind zones. Many buildings have been destroyed by winds that catch the underside of the eave and lift it off the building. Eaves of 8 in. or less are recommended for high-wind areas unless special measures are taken to anchor them.

Anchoring strategies—Assuming the building is shaped appropriately to withstand the force of high wind, it is still necessary to reinforce it beyond typical code standards. Framing members must be anchored to resist uplift and overturning, sheathing must be stronger, and fasteners must be increased. These mea­sures are illustrated on the following page.

ROOF FRAMING FOR HIGH WIND

HIGH-WIND RAKE

Balloon Frame to Sheathing

HIGH-WIND RAKE

Balloon Frame with Lookouts

NOTE

TOENAiLiNG (OR MORE FRAMiNG ANCHORS) TiE ROOF FRAMiNG TO DOUBLE TOP PLATE TO RESiST SHEAR FORCES PARALLEL AND PERPENDiCULAR TO WALL.

Platform Frame

Roof sheathing attaches to the surface of the raf­ters or trusses to form the structural skin of the roof.

It spans the rafters to support the roofing and, in the case of panel sheathing such as plywood or OSB, it acts with the walls to resist horizontal loads. Roof-sheathing material must be coordinated with the roofing itself, since each type of roofing has special requirements.

At exposed roof overhangs, the sheathing must be rated for exposure to the weather. The everyday sheathing used on the body of a roof is not rated for weather exposure, so when exposed eaves and/or rakes occur at the perimeter, a different (more expen­sive) weather-rated grade of plywood or OSB must be used. Solid board sheathing may also be used at these exposed locations.

The two basic types of sheathing are solid sheathing and open sheathing.

Solid Sheathing— Solid sheathing provides a con­tinuous surface at the plane of the roof. This type of sheathing is necessary for composition roofing and built-up roofing, which have no structural capacity themselves. Metal, tile, and shingle roofing may also be applied to solid sheathing. For economic and structural (lateral-load) reasons, solid sheathing is almost always plywood, OSB, or other structural panels (see 163).

The structural panels act as a diaphragm to transfer lateral loads at the plane of the roof to the walls. When an exposed ceiling is desired, solid sheathing may
also be constructed of solid-wood tongue-and-groove boards. Tongue-and-groove sheathing, however, does not act as a diaphragm, so other methods of providing lateral-load stability, such as diagonal bracing, must be employed.

Open sheathing—Open sheathing, also called skip sheathing, is composed of boards spaced apart (see 166). This type of roof sheathing is used under wood shingles and shakes, which usually require ventilation on both sides of the roofing material. Open sheathing may also be chosen for economic reasons, but only if used with roofing systems such as metal or tile, which have the structural capacity to span between sheathing boards. Alternative methods of providing a roof dia­phragm, such as diagonal bracing, must be used with open sheathing.

Combinations, of course, are also possible and often appropriate. For example, solid sheathing at exposed overhangs is often combined with open sheathing on the rest of the roof.

Recommendations—Sheathing recommendations for roofs by roofing types are as follows:

Composition and built-up roofing must be applied to solid sheathing because these roofing materials do not have the structural capacity to span between the boards of open sheathing.

Wood shingle and shake roofing is best applied over open sheathing because the spacing between the open sheathing allows the roofing to breathe from both sides, prolonging its life. Shingle and shake roofs may also be applied to solid sheathing at exposed eaves and rakes and similar locations. In some regions, the common practice is to place a moisture barrier over open sheathing to keep out wind-driven rain. In very windy areas, solid sheathing is often used. Consult with local codes and builders for the accepted practice.

Metal and tile roofing may be applied to either solid or open sheathing. Both roofing materials have the strength to span across open sheathing, but there is no advantage for either in having them breathe from both sides.

ROOF SHEATHING

Introduction

NOTE

most manufacturers specify a 1/8-in. space

BETWEEN THE EDGES OF pANELS TO ALLOW FOR

expansion. panels sized

FOR THIS Spacing ARE AVAILABLE. the gap may BE OMITTED IN VERY DRY climates., check WITH local codes & builders FOR accepted practice IN your area.

Panel installation—Low cost and ease of installation make plywood or OSB panels the sheathing of choice for most modern roofs. The system provides a struc­tural diaphragm and is appropriate for all but wood shingle or shake roofing, which requires ventilation.

The standard panel size is 4 ft. by 8 ft., so rafter or truss spacing that falls on these modules is most practical. Care must be taken to protect panel edges from the weather by the use of trim or edge flashing (see 169C). Sheathing at exposed overhangs must be exterior or exposure 1-rated and must be thick enough to hold a nail or other roof fastener without penetration of the exposed underside.

Recommended fastening—Recommended fas­tening is 6 in. o. c. at edges and 12 in. o. c. in the field (6 in. in the field for supports at 48 in. o. c.). For sheathing spans greater than 24 in., tongue-and – groove edges, lumber blocking, or panel edge clips are required at edges between supports. Use two clips for spans of 48 in.

12 / 0 5/i6 in. 12 in. 16 / 0 5/i6 in. to 3/8 in. 16 in. 24 / 0 3/8 in. to У2 in. 24 in. 32 / 16 15/32 in. to 5/8 in. 32 in. 48 / 2 4 23/32 in. to 7/8 in. 48 in.

Notes—Values in the table above are based on APA – rated panels continuous over two or more spans with the long dimension of the panel perpendicular to sup­ports. Verify span with panel rating. (For the APA rating stamp, see 48.)

Spans are based on a 30-lb. live load and 10-lb. dead load, the minimum rated by the APA—The Engineered Wood Association. Check local codes and with design professionals for higher loading such as greater snow loads or higher dead loads of concrete tiles or other heavy roofing. These ratings are minimum. For a more solid roof, reduce spans or increase thickness.

SOLID ROOF SHEATHING Plywood & Non-Veneered Panels

NOTE

JOiNTS MAY BE MADE AT MiD-SPAN FOR SOME END-MATCHED DEckiNG. VERiFY NAiLiNG WiTH MANUFACTURER’S SpEcS. TOENAiLiNG AT MiD­span iS REquiRED for longer spans. VERiFy with manufacturer.

T&G sheathing (decking) is most often used for exposed ceiling applications. It can also be used selec­tively at exposed eaves or overhanging rakes. Rafters are spaced at wide centers since the decking will span more than 24 in. in most cases (see the table at right). Because this sheathing material does not provide a dia­phragm at the plane of the roof, other means of bracing the roof against horizontal loads must usually be employed. For example, the roof may be braced with metal straps applied to the top of the sheathing or with a layer of plywood or OSB over the decking.

Insulation for an exposed ceiling must be located above the sheathing. Insulation will vary with climate and with roofing material. Rigid insulation is usually the most practical because of its thin profile, but it is more expensive than batt insulation. Batts are often chosen for colder climates, where the thickness of either type

EXPOSED T&G DECKiNG SPANS 1
Nominal thickness	Approximate span
2 in.	6.0 ft.
3 in.	10.5 ft.
4 in.	13.5 ft.
5 in.	17.0 ft.

of insulation (rigid or batts) requires adding a second level of structure above the decking to support the roof.

This table assumes a 30-lb. live load for Douglas – fir or southern pine species. The table is for com­parison and approximating purposes only. The actual span capacity depends on roof pitch, species, live-load values, and end-joint pattern.

SOLID ROOF SHEATHING

Exposed T&G Decking

RIGID INSULATION OVER TEMPERATURE-CONTROLLED SPACE

T&G EXPOSED DECKING

insulation frieze block

NAILING BLOcK FOR FINISH wALL

Metal or composition roofing may be applied directly over rigid insulation on T&G sheathing. For this construction, fasteners must be sized to penetrate through the insulation but not through the decking.

Preformed metal roofing—Preformed metal roofing may be applied directly to the insulation over a layer of 15-lb. or 30-lb. felt. If the insulation is more than ЗУ2 in. thick, wooden nailers equal to the thickness of the insulation and parallel to the decking are recom­mended to provide a stable surface for roof fasteners. Nailers should be located 3 ft. to 5 ft. o. c., depending on the profile of the metal roofing.

Composition roofing—Composition roofing may also be applied directly if the insulation board is strong enough to withstand the rigors of the roofing process. Most asphalt-shingle manufacturers, however, will not honor their warranty unless the shingles are applied to a ventilated roof. Unventilated shingles can get too hot and deteriorate prematurely. The addition of vertical furring strips and sheathing over the insulation with vents at the top and bottom of the assembly will satisfy the requirement for ventilation.

EXPOSED T&G DECKING AT EAVE

Metal or Composition Roof

Wood or tile roofing requires another layer of mate­rial over the insulation. In some cases, it may be more economical to substitute nonrigid insulation.

Wood shingles or shakes—Wood shingles and shakes last longer it they are allowed to breathe from both sides, so they should be raised on furring strips above the level of the insulation. The furring strips may be nailed through the rigid insulation to the decking, or they may be attached directly to the decking between rows of insulation. The spaces and cracks between the shakes or shingles will usually provide adequate ventilation.

Despite the advantages of breathing, shingles should be installed over solid sheathing and underlayment in areas with extreme wind-driven rain or snow or if the roof pitch is as low as 3-in-12 or 3l/2-in-12.

Ceramic or concrete tiles—Ceramic and concrete tiles, like shingles, commonly require furring strips.

The furring strips should be spaced according to the length of the tiles (see 187B, 188, and 189).

EXPOSED T&G DECKING EAVE

Wood or Tile Roof

Open, or skip, sheathing is usually made with 1×4 or 1×6 boards nailed horizontally to the rafters with a space between the boards. Since this sheathing material does not provide a diaphragm at the plane of the roof, other means of bracing the roof against hori­zontal loads must be employed. Let-in wooden bracing or metal strap bracing applied to the top or bottom surface of the rafters will suffice in most cases. This bracing must be engineered in seismic or high-wind zones or for very large roofs. Bracing may sometimes be omitted on hip roofs because the shape of the roof provides the bracing.

Spacing for open sheathing depends on the type of roofing. The ability of the sheathing to span between
supports depends on the spacing and on the type of roofing applied over it. Check with local codes and with roofers for accepted local practices.

Wood shingles or shakes require spacing equal to the exposure of the shingles or shakes—usually about 5 in. for shingles to 10 in. for shakes. The sheathing is usually 1×4.

Concrete tiles, depending on the type, may be installed on open sheathing spaced in the 12-in. to 14-in. range. The roofing material is heavy, so 1×6 or 1×8 or 2×4 sheathing is practical.

Preformed metal roofing is lightweight and runs continuously in the direction of the rafters. In most cases, 1×6 sheathing at 24 in. o. c. is adequate.

@ OPEN ROOF SHEATHING

Flashing is a necessary component of most roofing systems. Flashing makes the roof watertight at edges, openings, and bends in the roof where the roofing material cannot perform the job alone.

Flashing materials and details must be coordinated with the roofing material to make a durable and water­proof roof. Although design principles are transferable from one type of roofing to another, proportions of materials may vary. For example, the details drawn in this section show a thin-profile roofing material such as asphalt or wood shingles, but flashing for thicker roofing materials such as tile or shake will have dif­ferent proportions. Some of these special flashings can be found with the details for the particular roofing type.

You may want to use different flashing materials for roofs than for walls, because roofs are constantly exposed to the weather and, in most cases, are replaced much more frequently than walls. (For a discussion of wall flashing materials, see 102.) Moreover, roof flashing itself is not always replaced at the same time as the roof. Chimney or wall flashing may not be easily changed when the building is reroofed, so it should be made of materials like copper or stainless steel, which can last as long as the building. Valley or pitch-change
flashing will be easy to replace at the time of reroofing if the original roof is removed. This flashing may be made of material with a life span equivalent to the roof itself.

The flashing and its fasteners must be compatible with each other and with the roofing material itself. For example, flashing and fasteners for metal roofs must be compatible with the roofing metal to avoid galvanic cor­rosion. Flashing may be isolated from other materials with 30-lb. felt or bituminous paint.

The basic principle of roof flashing is to have the roofing, the flashing, and other materials overlap one another like shingles. Water running down the surface of the roof should always be directed by the flashing across the surface of the roof. Gravity will then work to direct water down the roof, away from the gaps cov­ered by the flashing. This way, only wind-driven rain can force water through the roofing to the waterproof underlayment (see 177), which acts as a second line of defense. Each detail may have local variations to account for such weather-related factors. All flashing materials, therefore, should be discussed with local sheet-metal contractors or roofers.

ROOF FLASHING

Introduction

Hemmed edges—One very important detail for roof flashing is the hemmed edge, which folds back on itself about V2 in.

— –

This fold makes the flashing thicker at the edge, which, aside from forming a stronger and neater edge when exposed, helps control the flow of water on roofs, as shown in the drawings on this page. Tucked under roofing, the tumed-up hemmed edge creates an air gap that prevents moisture from migrating between the roofing and flashing by capillary action.

A hemmed edge also works when it is horizontal, as in sidewall flashing (see 171A & B), where the hemmed edge not only resists capillary action but also forms a barrier to water running down the flashing and thus keeps it from running onto the roof sheathing.

Turned down and lapped over roofing, the hemmed edge creates an air gap under the flashing that discour­ages capillary action. The hemmed edge can also form a seal on smooth surfaces such as skylight glass, which is only made more complete by the presence of water adhering by surface tension to the two surfaces.

Fasteners—Flashing is usually nailed to the struc­ture. Nails are located at the edge of the flashing to avoid punctures in the flashing where it is designed to keep moisture from entering. Care must be taken to select nails that will not cause galvanic corrosion.

Another method of attaching flashing is the cleat, a small metal clip usually made of the same material as the flashing itself. Cleats fasten flashing to the roof without puncturing the flashing and allow for expansion and contraction of flashing metal without dislodging of

used to make concealed

FLASHiNG

ROOF FLASHING

Hemmed Edges & Fasteners

ROOFiNG

FELT uNDERLAYMENT LAPS OVER METAL EAVE FLASHiNG.

SHEATHiNG

METAL EAVE FLASHiNG WiTH DRIP LAPS FASCiA

(& gutter).

LEVEL WALL FLASHING

Valleys on roofs, like valleys in the landscape, col­lect the runoff of all the slopes above them. To handle such a concentration of water, valleys must be carefully flashed. Except when using roofing materials that can bend, such as asphalt shingles or roll roofing, valleys are usually flashed with metal flashing.

Open valley flashing is the most common and may be used with virtually all roofing materials. An open valley allows the runoff water to flow within the con­fines of the exposed metal flashing rather than over the roofing material itself.

NOTE BITUMINOUS SHEET WATERPROOFING LAPS VALLEY FLASHING IN LOCATIONS WITH SEVERE WEATHER. SEE SECTION A-A AT LOWER RIGHT.

VALLEY FLASHING EXTENDS FULL LENGTH OF VALLEY.

UNDERLAYMENT ROOFING

■VALLEY BETWEEN ROOFING IS WIDER AT EAVE THAN AT TOP. ESPECIALLY IN AREAS OF EXTREME COLD. TYPICAL VALLEY IS 5 IN. TO 6 IN. WIDE AT TOP AND INCREASED AT Vs IN. PER LINEAR FOOT OF VALLEY.

NOTES

FOR VALLEY FLASHING OF ASPHALT SHINGLES.

SEE 183B & C

FOR ROLL ROOFING WITHOUT FLASHING. SEE 181B

Cleats at 2 ft. o. c. fasten valley flashing to the roof without puncturing the flashing and allow for expansion and contraction of flashing metal without dislodging fasteners (see 168). Without cleats, flashing is wider and is nailed at the outer edges.

iN LOCATiONS WiTH SEVERE WEATHER, BiTUMiNOUS SHEET WATERPROOFiNG iS LAPPED OVER VALLEY FLASHiNG AT Both Sides FOR LENGTH OF valley.

1-IN. cRIMp IN FLASHING IF ROOF

planes discharge unequal amounts

OF RAINWATER DuE TO

unequal pitches or unequal areas OF watershed.

Section A-A

Sidewall flashing is a single-piece flashing installed before the roofing to create a flashing channel against the wall (see 171B). This type of flashing is adequate for most situations and allows easy reroofing.

Step flashing is a multiple-piece flashing that is woven in with the courses of roofing material (see 171C). This flashing is best for severe weather condi­tions. It may present some reroofing difficulties,

дЛ SIDEWALL & STEP FLASHING -—’ Introduction	A HIP FRAMING WITH TRUSSES Posted by admin on 23/ 11/ 15 Framing a valley with trusses is a simple matter of attaching a series of progressively smaller trusses to the top chords of the trusses of the main roof. The main-roof trusses do not have to be oversize since the only extra weight they will cany is the dead weight of the jack trusses themselves. Simple as this system is, many builders still prefer to frame these roof inter­sections as a farmers valley (see 137) with solid-sawn lumber. VALLEY FRAMING WITH TRUSSES Valley Jack Trusses Rectangular openings for skylights or chimneys may be constructed in a truss roof. Small openings less than one truss space wide may be simply framed between trusses as they would be in a rafter-framed roof (see 135-136). Openings up to three truss spaces wide are made by doubling the trusses to either side of the opening and attaching header and mono or other special trusses to the doubled trusses. Larger openings (more than three truss spaces wide) require specially engineered trusses in place of the doubled trusses. Obviously, it is most efficient if the width and place­ment of the opening correspond to truss spacing. OPENINGS IN TRUSS ROOF Headers between Double Trusses   WITH SHEATHiNG   RAFTER DIES ON ROOF Posted by admin on 23/ 11/ 15
Framing
ROOFiNG SHEATHiNG
SUPPORT TO RAKE.
CUT ON FASCiA iS MADE AT PiTCH OF ROOF & ABOVE LEVEL OF ROOFING; FASciA IS SuppORTED ву RAFTERS & sheathing.
SHEATHiNG
Elevation
——- ROOFING
SHEATHING FASCIA
	FASCIA DIES ON ROOF

ROOF SHEATHiNG

END RAFTER

common RAFTER

EDGE FLASHiNG

VERGE RAFTER OR TRiM BOARD CONTiNUOUS TO FASCiA

WALL sheathing

furring continuous behind VERGE RAFTER SEE 150A

FURRiNG ALLOWS VERGE RAFTER OR TRiM BOARD TO ACT AS DRiP.

double top plate

VERGE RAFTER OR TRiM BOARD

SiDiNG TRiMMED TO cONTiNuOuS FuRRiNG

corner OF WALLS BELOW—–

fascia shown MITERED TO VERGE; IT MAY ALSO BE square-cut & covered WITH TRiM OR GuTTER.

ExTERiOR wALL FINISH

WALL SHEATHiNG

(Q ABBREVIATED RAKE

ABBREVIATED RAKE/EAVE

Corner Framing

siding

WALL SHEATHING

flashing

NAILING BLOcK

ROOF SHEATHING

ROOFING

2X LEDGER NAILED TO STuDS

2X PuRLiNS

perpendicular TO rafters provide 1V2-IN. AIR space FOR LATERAL AIR MOVEMENT. provide INTAKE & exhaust vents. see 201

Shed Roof with Continuous Vent Strip

The strength, precision manufacturing, and long lengths that make engineered lumber appropriate for floor framing (see 43A) also indicate its use for roof framing. I-joists used as rafters constitute the bulk of engineered lumber used for roof framing; and they are stiffer, stronger, and lighter than their solid-sawn counterparts, but they also cost more, and their appear­ance is not generally satisfactory if exposed.

Despite the many advantages, engineered lumber as roof framing has not seen the explosive growth that has been the case with floor framing. Part of the reason is that roof framing with engineered lumber is hardware intensive. Virtually every connection must be made with a metal connector, and most also require the addition of two web stiffeners, one on each side of the I-joist rafters. This adds considerable time and labor cost to the task of roof framing.

Another difference between framing roofs with solid-sawn or engineered lumber is that engineered lumber almost always requires a structural ridge beam.

This means that roof loads must usually be carried down to the foundation through the core of the building.

The cost/benefit ratio for framing roofs with engi­neered lumber favors its use only for simple gable or shed roof forms. However, many builders have found ways to combine the advantages of both solid-sawn and engineered lumber on the same building. In these hybrid roofs, engineered lumber is used for the basic forms, and solid-sawn lumber is employed for the smaller-scale parts and the more complicated forms. This mixing of materials is practical for roof construc­tion where differential shrinkage is not usually a signifi­cant problem.

The general framing principles that apply to roof framing with solid-sawn lumber also hold true for engineered lumber. To perform as designed, however, engineered lumber roof components must be installed completely in accordance with the individual manufac­turer’s instructions. The drawings in this section there­fore emphasize roof framing conditions that are specific to engineered lumber.

l-JQIST RAFTERS

Introduction

WEB STIFFENER AT EACH

I-JOIST RAFTER AT EAVE

With Beveled Bearing Plate

I-JOIST RAFTER AT EAVE

With Metal Connector

MOST i-JOiST MANUFACTURERS DO NOT SUPPORT THiS DETAiL.

NOTE

BLOCK ALL RAFTERS WiTH i-JOiST OR LSL FRiEZE BLOCK. EXTEND wEB STiFFENERS iNTO EAVE AS REQuIRED FOR

structure.

I-JOIST RAFTER/CEILING JOIST

With Bird’s Mouth

ROOF SHEATHING

RAFTERS ATTACHED TO EACH OTHER WITH 3A-IN. PLYWOOD GUSSETS ON BOTH SIDES.

DOUBLE-BEVELED WOOD FILLER PLATE

STRUCTURAL RIDGE BEAM

ROOF SHEATHiNG METAL STRAP i-JOiST RAFTER

WEB STiFFENER METAL RAFTER HANGER STRUCTURAL RiDGE BEAM

дЛ I-JOIST RAFTER/STRUCTURAL RIDGE BEAM

structural rafter

OF LVL, LSL, OR DOUBLE I-JOISTS ® SIDE OF DORMER. SKYLIGHT. OR OTHER ROOF OPENING

STRUCTURAL RAFTER/HEADER

I-joiST RAFTER
roofing
roofing
i-JOiST RAFTER
roof SHEATHING
WEB STiFFENERS AT BOTH SiDES PER MANUFACTURER’S SPECS –
WEB STIFFENER AT BoTH SiDES pER manufacturer’s specs for deep RAFTERS
roof sheathing
NAILING block for SuBFASciA
bird’S-mouth cut at lower FLANGE oF RAFTER MuST HAVE FuLL BEARING oN plate.
LSL rim or blocking
BiRD’S-MOUTH CUT AT LOWER FLANGE oF RAFTER MuST have full bearing on plate.
exterior finish WALL WITH trim
ceiling joist SEE 132
VENTED soffit SEE 202B, c & 203A
ceiling joist SEE 132
double top plate of stud wall note block all rafters with I-joist or LSL frieze BLocK
WALL SHEATHING
double top plate of stud wall
WALL SHEATHING
note dummy rafter laps I-joist RAFTER 11/2 x distance of overhang.
roofing
align top of dummy rafter
roofing
roof sheathing
roof sheathing
(VENTED) frieze block SEE 202A
dummy rafter nailed to web STiFFENERS i-joist rafter
. i-joist rafter
web stiffener
web stiffener
dummy RAFTER
double top plate of stud wall
bird’S-mouth cut at lower FLANGE oF RAFTER MuST HAVE FuLL bearing on plate. double top plate of stud wall
exterior WALL finish
Section Parallel to Eave
WALL SHEATHING

Roof trusses, like floor trusses, are a framework of small members (usually 2x4s) that are connected so that they act like a single large member. They are always engineered by the manufacturer.

Engineered roof trusses can span much greater distances than the stick-framed rafter-and-tie system. Long spans (over 40 ft.) are possible with simple trusses so that large open rooms may be designed with roof loads bearing only on the perimeter walls. Interior walls may simply be partition walls and may be repositioned without compromising the roof structure.

A second advantage of roof trusses is the reduction in roof framing labor. Trusses are typically set in place

by the delivery truck and may be positioned and fas­tened in a fraction of the time it would take to frame with rafters and ties.

One major disadvantage of roof trusses is the dif­ficulty of adapting them to complex roof forms. Roofs with numerous hips, valleys, or dormers are usually less expensive to build if they are framed with rafters.

Another disadvantage of roof trusses is that the webs of the truss occupy space that could be available for storage or as a full-size attic. Furthermore, these webs cannot be cut for any future remodeling purposes.

Five common roof truss types are shown in the drawings below.

A gable-end truss transfers the load of the roof to the wall on which it bears through 2×4 struts at 24 in. o. c. The standard gable-end truss is the same size as a standard truss. A gable-end truss can be used with a rake overhang of 12 in. or less when the barge rafter is supported by the roof sheathing. It can also be used with flat 2×4 lookouts let into the truss above the struts. A dropped gable-end truss (see 156B) is shorter than a standard truss by the depth of the lookouts.

ROOFiNG ROOF SHEATHiNG

TOP CHORD OR GABLE-END TRUSS

EXTERiOR WALL FiNiSH WALL SHEATHiNG

BOTTOM CHORD OF GABLE-END TRuSS

cEiLiNG NAiLER

iNTERiOR FiNiSH

double top plate

Truss/Gable-End Wall

дЛ STANDARD GABLE-END TRUSS

lookouts BEAR ON TOp cHORD OF dropped truss to support rake

OVERHANG.

SEE DETAIL ON RIGHT

Truss/Gable-End Wall

DROPPED GABLE-END TRUSS

There are several ways to frame a hip roof using trusses. None is simple, so many builders elect to frame hips (even on a truss roof) with rafters (see 138).

The most common method of framing a hip with trusses is called the step-down system. A series of progressively shallower trusses with flat tops is used to create the end roof pitch of the hip roof. The last of these trusses is the girder truss, which carries the weight of short jack trusses or rafters that complete the roof.

Section

EXPOSED RAKE WITH TRIM BOARD

Detail at Eave

The transition from soffited eave to rake can demand some carpentry heroics. Only when the soffit is ter­minated at the plane of the end wall is the detailing reasonably direct, requiring only that the end of the soffit space be finished. This situation may occur with an abbreviated rake (see below) or with an overhanging rake (see below and 148B). As shown below, the end of the soffit space may be finished with a pork chop or with a layered gable—a continuation of the gable-wall finish over the end of the soffit.

PORK CHOP WiTH ABBREVIATED RAKE (ALSO USED WITH OVERHANGING RAKE); VERGE RAFTER oR Trim BoARD LApS pork chop. chop covers end of soffit space.

When the soffit extends beyond the plane of the end wall, the rear side of the soffited space (opposite the fascia) must be finished as well as the end. As shown in the drawings below, this may be accomplished most elegantly with a Greek return, or with a simpler soffit return.

barge rafter DIES on roof. SEE 149B framing details SEE 149A GREEK RETuRN ExTENDS soffit around corner of building & covers it with a small hip roof. fascia mitered at corners follows edge of hip roof & DIES into END WALL.

pork chop AT END

LAYERED GABLE WITH ABBREVIATED RAKE (ALSo uSED WITH oVERHANGING RAKE); GABLE-WALL FINISH ExTENDS To cover end of soffit space. VERGE RAFTER oR TRIM BoARD LApS FINISH & FINISH May LAp second wall finish below.

soffit return takes the direct approach to cover both THE END & REAR oF the soffited space. this DETAIL MAY BE uSED WITH boxed-in or with exposed RAKE.

FRAMING DETAILS SEE 149c

NOTE

Elevation

дЛ GREEK RETURN

EXPOSED RAKE WITH TRIM BOARD Posted by admin on 22/ 11/ 15 Corner Framing EXPOSED RAKE WITH VERGE RAFTER Posted by admin on 22/ 11/ 15 Section COMMON RAFTER   end rafter same as common RAFTERS   FASCiA SQUARE CUT (AS SHOWN) & COVERED WiTH BARGE TRiM, oR MiTERED To barge RAFTER   BARGE RAFTER   corner of walls   EXPOSED RAKE WITH VERGE RAFTER Posted by admin on 21/ 11/ 15 Corner Framing NOTE cOORDiNATE Flashing & TRiM with gutter AND FASciA. ExTERiOR-RATED ROOF SHEATHiNG AT ExpOSED pORTiON OF ROOF OTHER CONSIDERATIONS Posted by admin on 21/ 11/ 15 In addition to the choices about pitch, shape, and structure discussed above, many other decisions con­tribute to the overall performance of the roof. These include selection of sheathing, underlayment, and roofing material; eave, rake, and flashing details; gutters and downspouts; and insulation and ventilation of the roof assembly. All of these issues are discussed in this chapter. Rafter sizes are usually 2×6, 2×8, 2×10 or 2×12, and spacing is usually 16 in. or 24 in. o. c. Species of wood vary from region to region. Rafter sizing depends pri­marily on span, spacing, roof loads, and sometimes on required insulation depth. For a rafter-span table, see 131A. @ ROOF FRAMING Stick-framed rafters may be supported by the walls of the building, by a structural ridge beam, or by purlins. Simple-span roof – The simplest sloped roof—the shed roof—has rafters that span from one wall to another, as shown at right. These rafters must be strong enough to cany the dead-load weight of the roof itself and subsequent layers of reroofing, plus the live-load weight of snow. The rafters must usually be deep enough to contain adequate insulation. The total roof load is transferred to the ends of the rafters, where it is supported by the walls. In the simple example at right, each wall carries part of the roof load. Triangulated roof – Common (full-length) rafters are paired and usually joined to a ridge board, as shown in the drawing at right. Each rafter spans only half the distance between the two walls (the gable roof, shown in the drawing at right, is the simplest version). Horizontal ties—either ceiling joists or collar ties— form a triangle with the rafters. Ceiling joists are gener­ally located on the top plate of the walls but may also be located higher to form a partially vaulted ceiling. Collar ties are usually nailed near the top of the roof between opposing rafters and spaced at 4 ft. o. c. Collar ties are not sufficient by themselves to resist the out­ward thrust of the rafters. Rafters in triangulated roofs are shallower than those in shed roofs of equal width because they span only half the distance of the shed rafters and because they do not usually contain insulation. Structural ridge beam—The horizontal ties that are required in a triangulated roof may be avoided if the rafters are attached at the ridge to a structural ridge beam (or a wall), which effectively changes the triangu­lated roof into two simple-span roofs, as shown in the drawing below. NONSTRUCTURAL RiDGE BOARD SEE 133B COLLAR TiE RAFTER Purlin—A purlin is a horizontal member that sup­ports several rafters—usually at midspan. Purlins were commonly used to help support the long slender rafters of pioneer houses and barns. Today they are also used occasionally to reduce the span of a set of rafters, but the purlins must themselves be supported by the frame of the structure, as shown in the drawing below. the NAME "PURLiN" iS ALSO GiVEN TO A Member That SPANS across RAFTERS TO SUPPORT ROOF DECKiNG. SEE 150C ALLOWABLE RAFTER SPANS IN FEET Rafter size, Joist spacing (ft.) species, and grade 12 in. o. c 16 in. o. c. 24 in. o. c. 2×6 spruce-pine-fir #2 12.1 11.0 9.0 2×6 Douglas fir #2 12.6 11.3 9.2 2×8 spruce-pine-fir #2 15.9 14.1 11.5 2×8 Douglas fir #2 16.5 14.3 11.6 2×10 spruce-pine-fir #2 19.9 17.2 14.0 2×10 Douglas fir #2 20.1 17.4 14.2 9.5 x 2.06-inch I-joist 21.4 19.4 16.8 2×12 spruce-pine-fir #2 23.0 19.9 16.3 2×12 Douglas fir #2 23.4 20.2 16.5 11.9 x 2.06-inch I-joist 25.5 23.1 19.0 This table compares two species of sawn lumber and one I-joist for use as rafters on a roof with a 30-psf live load. The table is for estimating purposes only. For a roof-sheathing span table, see 163. RIP RiDGE BOARD iF iNTERiOR finish meets Common Rafters AT RIDGE. slightly undercut the plumb CUT ON BARGE OR VERGE RAFTERS IF LuMBER IS GREEN; THE BoARDS will shrink to MEET at centerline. NAIL iNTo RiDGE BoARD NEAR BoTToM of RAFTERS; uPPER NAILS MAY BE ADDED AFTER lumber DRIES. Ceiling joists are very similar to floor joists. In fact, the second-floor joists of a two-story building act as the ceiling joists for the story below. Ceiling joists are dis­tinguished from floor joists only when there is no floor (except an attic floor) above the joists. Ceiling joists are sized like floor joists. The span of the joists depends on spacing and whether the attic above the joists will be used for storage. ALLOWABLE CEILING JOIST SPANS iN FEET Joist size, Joist spacing (ft.) species, and grade 12 in. o. c 16 in. o. c. 24 in. o. c. 2×6 spruce-pine-fir #2 12.9 11.7 10.2 2×6 Douglas fir #2 13.5 12.2 10.7 2×8 spruce-pine-fir #2 17.0 15.4 13.5 2×8 Douglas fir #2 17.8 16.1 14.1 2×10 spruce-pine-fir #2 21.7 19.7 17.2 2×10 Douglas fir #2 22.7 20.6 18.0 9.5 x 2.06-inch I-joist 22.8 20.6 17.9 2×12 spruce-pine-fir #2 26.4 24.0 20.6 2×12 Douglas fir #2 27.6 25.1 20.8 11.9 x 2.06-inch I-joist 27.2 24.6 21.4 This table is based on a light attic load of 20 psf and a deflection of L/360. The table is for estimating pur­poses only. The joists can function as ties to resist the lateral forces of rafters. For this purpose, it is important to attach the joists securely to the rafters. ANGLE NAiLS THROUGH JOiSTS iNTO RAFTERS TOWARD CENTER OF BUiLDiNG. The underside of ceiling joists is often furred down with a layer of 1x lumber to resist plaster or drywall cracking due to movement of the joists. The drawing below illustrates furring parallel to the joists to resist cracking along a beam that interrupts the continuity of the joists. Furring perpendicular to the joists, usually called strapping, is also common. At walls or beams that support them at the eave, rafters are cut at the point of support with a notch called a bird’s mouth. BiRD’S MOUTH CUT EAVE STUD WALL The width of the bird’s mouth is equal to the width of the sheathed stud wall (or unsheathed wall if sheathing is to be applied later). The underside of the rafters should meet the inside corner of the top of the wall. This is especially important if the ceiling is vaulted and a smooth transition between wall and ceiling is desired (see below). BLOCKING pREVENTS rotation of rafters & allows ventilation of roof. note for rafter support at rake WALL, SEE 1340. Wherever the pitch of a roof changes from shallow to steep (as in a gambrel roof) or from steep to shallow (as in a shed dormer) the two ends of the rafters must be supported. If the pitch change occurs over a wall, the wall itself will provide the support. If the pitch change does not occur over a wall, the support will have to be provided by a purlin or a beam (header). ROOFING & SHEATHING LOW-PITCH & HIGH-PITCH RAFTERS LAP/ BOTH BEAR ON SUPPORT. BEAM. PURLIN. OR WALL ROOFING & SHEATHING LOW-PITCH & HIGH-PITCH RAFTERS LAP.- BOTH BEAR ON SUPPORT. BEAM. PURLIN. OR WALL Pitch Changes with Support Below DouBLE 2X HEADER up-slope RAFTER on joist hanger – – FINISH CEILING Pitch Changes without Support Below ROOF/WALL Rafters Parallel to Wall The end rafters of a gable or a shed roof are sup­ported by the walls under them, called rake walls. The framing of the rake should be coordinated with the detailing of the rake. Of the three drawings below, the first example is the simplest method of support and is used with all types of rake, often in conjunction with an unfinished attic. The second example is best for sup­porting lookouts for an exposed or boxed-in rake. The third example provides nailing for a boxed-in rake or an exposed ceiling. Elements from the three examples may be combined differently for specific situations. For rake-wall framing, see 72A, B & C. ROOFiNG ROOF SHEATHiNG RAKE TRiM SEE 146-147 END Rafter Balloon OR platform-framed rake wall SEE 72B Framing the elements that project through the roof of a building—skylights, chimneys, and dormers— begins with a rectangular opening in the framing. For openings in a single roof plane framed entirely with common rafters, framing is relatively easy. An opening three rafter spaces wide or less can be made by heading off the interrupted rafters and doubling the side rafters, as shown below. Obviously, it is more efficient if the width and placement of the opening cor­respond to the rafter spacing. Larger openings should be engineered. Openings that straddle hips, valleys, or pitch changes must have special support, special framing, and special flashing. RiDGE DOUBLED COMMON RAFTER AT SiDES OF OPENiNG TOP & BOTTOM RAFTER HEADER (OFTEN DOUBLED) Headers for simple openings are, in most cases, either plumb or perpendicular to the rafters, as shown in the drawing below. Plumb openings require a header deeper than the rafters. FOR dormer OpENiNGS SEE 135B. FOR skylight OpENiNGS SEE 136A & B. FOR chimney openings SEE 1360. Dormers are often more than three rafter spaces wide so their structure cannot be calculated by rules of thumb. The opening in the roof may be structured to support all or part of the loads imposed by the dormer. The dormer walls and roof are framed like the walls and roof of the main building. If the dormer walls do not extend below ceiling level, the roof structure at the edge of the opening must support the dormer. DORMER WALL SUPPORTED ON ROOF FRAMING ROOF SHEATHING ENGINEERED RAFTERS AT SIDE OF DORMER OPENiNG ■ "" If the dormer has side wails that extend to the floor, the floor may be used to support the dormer, and the rafters at the side of the opening may be single. ROOF OPENINGS General   DORMER OPENING   ROOFiNG SHEATHiNG RAFTER 2X HEADERS SKYLiGHT SEE 175B & C, 176 iNSULATED stud wall between roof rough opENiNG & OEiLiNG RouGH opENiNG LiNE oF FiNiSH OEiLiNG дЛ SKYLIGHT OPENING Vaulted Ceiling The inside corner of two intersecting roof planes is called a valley. In most cases, valleys are supported by a valley rafter that extends from the outside wall of the building to the ridge or to a header. These valley rafters support large loads and should be engineered. Jack raf­ters support the area between the valley rafter and the ridge or header. TOP EDGE OF JACK FAFTERS ALiGN WiTH CENTER OF VALLEY RAFTER. bottom edge of valley rafter must be flush with bottom of jack rafters WHEN interior surface is to be finished or it may project below jacks when no interior finish is required, or if jack rafters are furred. As shown at right, valley rafters can be supported at the top by a ridge or by a header. The ridge support system is more practical when the ridges of the inter­secting roofs are close together; however, the header support system is better when the lower ridge inter­sects the main roof near or below the center of the rafter span. Where headroom is not required between intersecting roofs, a simpler “farmer’s valley” or “California valley” may be constructed. This valley is made without a valley rafter. One roof is first built entirely of common rafters without any special valley framing. Then 2x sleepers are installed over the rafters or over the sheathing of the first roof, and jack rafters are attached to the sleepers. . ІАГІ^ 2x sleeper common RAFTER @ VALLEY FRAMING RiDGE DOUBLE Top plate bird’s mouth   common rafters jack rafters   OF HiP AND JACK RAFTERS, SEE BELOW.   A hip is the outside comer where two planes of a roof meet. It is composed of a hip rafter at the comer and jack rafters from the hip to the eave. The hip rafter is supported at its lower end by the wall at plate level (or by a post) and at its upper end by the ridge (or by a wall). Most codes require that the hip rafter project below the bottom edge of the jack rafters (see the top drawing at right). This is not veiy logical because, unlike a valley rafter, a hip rafter does not support much roof load. The extra depth presents no problem in an attic space, but if the inside face of the roof is to be made into a finish ceiling, the hip rafter will have to be ripped to allow the planes of the finish ceiling to meet (middle drawing at right). If codes will not permit ripping the hip rafter, furring may be added to the underside of the jack and common rafters to allow the finish ceiling to clear the hip rafter. The top ends of the jack rafters may be cut off to permit venting at the top of the hip roof (bottom drawing at right). ) HIP FRAMING The framing of a flat roof is more like a floor than it is like a pitched roof. The joists are level or nearly level and support the ceiling below and the live loads above. Connections to walls are like those for floors (see 32), as are the framing details for openings (see 38B) and canti­levers (see 39A). As for floors, the structure of a flat roof may be a joist system (dimension lumber or I-joists), a girder system, or a truss system. Blocking and bridging (see 38A) must be considered at the appropriate locations. Flat roofs are unlike floors, however, in that they are not really flat. They might be more properly called “low – slope” roofs because they must slope at least Vi in. per ft. in order to eliminate standing water. This minimal slope may be achieved in several ways: 1. The joists themselves may slope if the ceiling below does not have to be level, or if the ceiling is furred to level. 2. Trusses may be manufactured with a built-in slope. 3. Shims may be added to the top of the joists. 4. Tapered rigid insulation may be added to the top of the sheathing. 5. The joists may be oversize and tapered on top. 6. Sloped rafters can be scabbed alongside level ceiling joists. The easiest and most direct way to support an overhang at the corner of a flat roof is with a beam below the joists cantilevered from the top of a bearing wall, as shown in A traditional framing method for a cantilevered corner without a beam is with joists that radiate from a doubled central diagonal joist, as shown below. A strong fascia board is advisable here, as with all framing using cantilevered joists. A third option for framing a cantilevered comer is shown below. All methods illustrated should be engi­neered by a professional. NOTE USE RAFTER-SPAN TABLE FOR FLAT-FOOR JOiST SPANS, SEE 131A. ^ FLAT-ROOF FRAMING Designing the basic shape of the roof and designing the configuration of eaves and rakes are the most crit­ical tasks in roof design. Stylistically, the selection of eave and rake types should complement both the roof form and the roofing material. Functionally, the eave and rake should help protect the building from the elements. The shape of the roof will suggest certain eave and/or rake shapes (see 140B), and certain eave types work best with particular rake types (see 141). Eave— The eave is the level connection between the roof and the wall. Eaves are common to all sloped roofs and often to flat roofs. There are four basic types of eave (see 141). For eave details, see 142 and 143A & B. Rake- The rake is the sloped connection between the roof and the wall. Only shed and gable roof types and their derivatives have a rake. There are three basic types of rake (see 141). For rake support and rake details, see 144-147. The way in which one edge of a EAVES & RAKES Introduction The basic shape and structure of a roof system need to be coordinated with the finish of the roof at the edges. The shape of the roof affects the treatment of the edges, and vice versa. A hip roof, for example, is easier to finish with a soffited eave than is a gable roof. The basic roof shapes are best suited for the following finish treatment at the edges: SHED ROOFS HAVE BOTH A RAKE & AN EAVE. ALL EAVE TYPES EXCEPT FOR SOFFiTS CAN BE COMBiNED wiTH all rake types. a special EAVE Detail IS REQuIRED FOR The top edge. SEE 143B   FLAT ROOFS HAVE NO RAKES. OVERHANGING EAVES CAN BE DETAILED WITH A SOFFIT OR WITH EXPOSED RAFTERS. WHEN THERE ARE О OVERHANGS. THERE IS AN ABBREVIATED EAVE OR A PARAPET. SEE 72D   GABLE ROOFS, LIKE SHED ROOFS, HAVE BOTH EAVES & RAKES. Except FOR SOFFITED EEAVES, ALL EAVE & RAKE TYpES cAN BE cOMBINED. A special detail is required AT THE RIDGE, wHERE THE TwO RAKES Meet. SEE 131B & 1440   COMBINATION ROOF TYPES USUALLY HAVE BOTH RAKES & EAVES. THEY FOLLOW THE GUIDELINES OF THE INDIVIDUAL ROOF TYPES.   Combination Types   ^ ROOF SHAPE & EAVE/RAKE SELECTION roof is finished affects the detailing of the other edges. For example, a soffited eave on a gable-roofed building is easier to build with an abbreviated rake than with an exposed rake. The designer should attempt to match the level edge of the roof (the eave) to the sloped edge (the rake). In examining the details of the eave and rake, there­fore, the two must be considered as a set. It is logical to start with the eave, because all sloped roof types have eaves, but not all have rakes. There are four basic sloped-roof eave types. All four types are appropriate for hip roofs, and all but the sof – fited type can make a simple and elegant transition from eave to rake on gable and shed roofs. The eave types and their most appropriate companion rakes are diagrammed below. RAKES   OVERHANGiNG RAKES SEE 141-147   Exposed Rake Boxed-In Rake SEE 146, 147A, B, D, 148 SEE 147D   Abbreviated Rake SEE 150   EAVES   Overhanging Eaves SEE 142 Exposed Eave SEE 142a goes with shed, gable, hip roofs equally well.   very common; simple to build. SEE 146, 147A, B, c   awkward to detail & build.   not common, but could be built with simple details.   LESS common; easier to build SEE 148 & slightly less clunky than soffited eave with boxed-in RAKE.   common & fairly simple construction, but not elegant. SEE 148B   common combination, can be built in two basic ways. SEE 148A   Soffited Eave SEE 142B & c works best on hip (or flat) roofs with no RAKE; often used on gable roofs as well.   awkward to detail & build.   very common for this type of EAVE; VERY simple construction.   not common, but could be built with simple details.   Boxed-In Eave SEE 142D goes with shed, gable, hip roofs equally well.   Abbreviated Eave SEE 143A goes with shed, gable, hip roofs equally well.   VERY common; simple construction. SEE 150B   awkward to detail & build.   awkward to detail & build.   ^ EAVE/RAKE COMBINATIONS ^ EXPOSED EAVE   SOFFITED EAVE   NOTE THiS DETAiL WORKS WELL ON STEEP ROOFS, WHERE A FASCiA MAY APPEAR TOO BULKY. NOTE no gutter shown. hang gutter from strap SEE 1950 OR USE VERTiCAL FASCiA ON PLUMB-CUT RAFTERS TO ACCOMMODATE STANDARD GUTTERS. BOXED-IN EAVE Alternative Detail ROOFiNG   ROOFiNG iNSULATiON SHEATHiNG & FiNiSH SEE 197A   SHEATHiNG & FiNiSH   ^ ABBREVIATED EAVE   NOTE DUMMY RAFTERS ARE RELATiVELY SHORT, SO A HiGH GRADE OF MATERiAL MAY BE USED. CONSiDER uSiNG Them iF THE ExpOSED pART OF THE RAFTER iS TO Be A DiFFERENT SizE THAN THE uNExpOSED pART OF THE RAFTER OR TRuSS; OR iF ExpOSED RAFTERS ARE DESiRED wHEN pLYwOOD i-RAFTERS ARE uSED FOR THE ROOF Structure, SEE 151­153, FOR ABBREViATED EAVES, THE ENTiRE EAVE assembly may be shop- BuiLT iN LENGTHS up TO ABOuT 16 FT.   ROOFiNG   RAFTER   gutter SEE 193-196 1x SOFFiT wiTH cONTiNuOuS screened VENT 1×6 OR 1×8 BOARD screwed to dummy TAiLS & TOp pLATE Abbreviated Eave   Exposed Eave   DUMMY RAFTER TAIL   When an overhang is required at the rake, the over­hang is made with barge rafters, which stand away from the building and need support. There are several ways to support barge rafters. The roof sheathing alone may be strong enough to support the barge rafters (see 144B), or the ridge board or beam can be designed to support the barge rafters at their upper ends (see 144C), and the fascia may be extended to support the barge rafters at their lower ends (see below). Lookouts or brackets may be also used to support an overhanging rake (see 145A & B). NOTE VERGE RAFTER NOT SHOWN; FOR Details SEE 146. OVERHANGiNG RAKE Supported by Sheathing stud wall under end common rafter If the ridge, the fascia, and the sheathing together do not provide sufficient support for the barge, look­outs may be added. Lookouts extend from the barge rafter to the first common rafter (or truss) inside the wall. The lookouts are notched through the end rafter at the top of the wall or, alternatively, bear directly on the wall. The size and spacing of lookouts depend on rafter spacing and live loading. FiRST COMMON RAFTER END OR VERGE RAFTER Brackets attached to the face of the wall framing can support the barge rafter by means of triangulation. nails Typical Bracket Attaching the bracket to the inside of the barge rafter avoids problems of weathering. The alternative bracket connection to the barge rafter shown below is common on Craftsman-style buildings. With this detail, moisture collects on top of the bracket, and this contributes to the decay of the bracket and the barge rafter. NOTES EXPOSED ROOF SHEATHiNG MUST BE EXTERiOR-RATED PANEL OR SOLiD (T&G) MATERiAL. FOR ALTERNATiVE DETAiL WiTH TRiM BOARD, SEE 147A & B. EXPOSED RAKE WITH VERGE RAFTER Framing What type of Posted by admin on 21/ 11/ 15 construction system? Roofs are constructed either with rafters (stick-framed roofs) or with trusses. Stick-framed roofs are usually made with dimension lumber but may also use com­posite materials such as I-joist rafters (see 151-154). Stick framing originated before the development of balloon-frame construction in the 19th century. Antecedents of the modern stick-framed roof can be seen on ancient roofs around the world, and modern stick-frame roofing remains popular because it is the most flexible roof-framing system and the materials are least expensive. Trusses are made of a number of small members (usually 2x4s) joined in a factory or shop to make one long structural assembly. Only in very simple buildings does the labor savings of a truss system compete with stick framing. « Previous 1 2 3 4 5 … 7 Next » Tweet Copyright © 2025 Library builder - Articles about the repair, construction, interior design and landscaping, plumbing, electrical, waterproof wire, wire gas, building materials, construction machinery and equipment ...