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Sheathing Exterior Walls

Plywood sheathing is often the material of choice because of its strength and ease of handling.

Most new walls need sheathing to strengthen them, to act as a nailing base for siding, and/or to boost insulation. Existing walls usually do not require sheathing unless you are stripping off the old siding and applying a different type that calls for sheathing. Be sure to check the siding manufacturer’s directions and local codes to determine whether sheathing is required. For help with sheathing siding, you may want to get quotes from local siding contractors.[GARD align=”left”]

There are two types of sheathing: structural and nonstructural.

Structural Sheathing

This type is integral to the house’s framing. It ties together wall studs, contributing shear strength and rigidity and forming a solid nailing base for siding materials. Most structural sheathings do not add much insulation value.

Common structural sheathings include plywood, oriented strand board (OSB), wafer board, and exterior gypsum board.

When choosing plywood, OSB, or wafer-board panels, be sure they are rated as wall sheathing and choose an appropriate thickness. Although you can use panels as thin as 5/16 inch for some applications, it is usually a good idea to spend a little bit more for sturdier 1/2-inch panels. The most common panel size is 4 by 8 feet, but you can also get some products in 4-by-9- and 4-by-10-foot sheets.

Using 6d (2-inch) galvanized nails, fasten panels (usually horizontally) to wall studs, spacing nails 6 inches apart along the panels’ edges and 12 inches apart mid-panel (or as specified by your local building codes). Allow an expansion gap of 1/16 inch between panel ends and 1/8 inch between panel edges.

Nonstructural Sheathing

This type of sheathing does not add significantly to a wall’s strength but can greatly increase its insulation value. Rigid foam and cellulose-fiber panels may be attached directly to wall studs or masonry walls, under or over structural sheathing (depending upon nailing requirements), or, in some cases, over existing siding before re-siding.

The two most common types of foam-board sheathing materials are extruded polystyrene or polyisocyanurate. Polyisocyanurate has higher per-inch insulation (R) values-up to R-8.7 per inch-than polystyrene.

Foam-board thicknesses range from 3/8 inch to 4 1/4 inches. For covering existing siding, 1/2-inch and 3/4-inch thicknesses are commonly used. Standard panels are 2 by 8, 4 by 8, and 4 by 9 feet, although some can be purchased in fan-folded panels that run up to 50 feet long.

This exterior gypsum board sheathing is faced with fiberglass mats instead of paper to help resist mold and mildew.

Which type of panels to choose, and which side to face outward, depends on the makeup of your walls and the siding you are applying. Use panels with either reflective aluminum or matte facings beneath brick, stucco, and certain wood sidings. Non-foil-faced panels are generally recommended beneath aluminum, vinyl, and wood-based sidings.[GARD align=”right”]

Most foam and cellulose panels are extremely lightweight and capable of being cut with a utility knife. Nail the panels to wall studs with large-headed galvanized nails long enough to penetrate studs by at least 1 inch. Space nails according to the manufacturer’s instructions. (Because these panels are not structural, 12-inch spacing is usually sufficient.) Drive nails flush, being careful not to crush the panels with your final hammer blow.

Fire codes and safety considerations may affect how nonstructural panels are applied because of combustibility. Be sure to follow manufacturer’s instructions in this regard.

 

How to Prevent Ice Dams

Ice dams cause water to back up the roof and leak underneath the shingles.Suzanne Tucker / Shutterstock.com

When water freezes along the eaves, ice dams can form, causing water to back up under the shingles.

Heavy snowfall can create ice dams that cause a roof to leak along the eaves. An ice dam forms when snow melts over a house’s heated spaces and runs down the roof, only to freeze again over the cold eaves. This ice builds up along the eaves and traps snow-melt water, which eventually flows under the shingles into the attic.

When putting on a new roof in a region with cold winters, it’s smart to install a special membrane called an “ice shield” beneath the shingles along eaves to prevent ice-dam water penetration (talk to a roofer about what installing one of these on an existing roof entails).

Here’s how to prevent ice dam problems:

1Check and, if necessary, improve the attic ventilation to minimize the thaw/freeze cycle. Cold air should be able to circulate from eave vents to ridge or gable vents, minimizing temperature variations on the roof. Be sure the soffit vents are not blocked by insulation. If the underside of the roof is insulated, be sure the insulation is held back from the surface by at least 1 inch for air circulation.

2Improve the ceiling insulation to help keep heat from leaving the rooms below during winter.[GARD align=”right”]

3As a last resort, install electric heating cables made for this purpose along the section of roof above the overhangs. These melt enough of the ice to provide an escape route for runoff.

If damage has already occurred, take photographs and check with your insurance company regarding coverage. Then, immediately remove as much snow from the eaves as possible, or call a roofer to handle the job.

Featured Resource: Find a Pre-Screened Local Roofing Contractor

Call for free estimates from roofing pros now:
[telnumlink] 1-866-342-3263[/telnumlink]

Common Roofing Terms

Roof framing involves a lexicon all its own. As you can see in the illustration at left, roofs have hip rafters, ridge boards, jack rafters, and more. When working on a roof, it pays to be familiar with these terms.

Here is a closer look at common roofing terms:

Roof Framing Diagram          ©Don Vandervort, HomeTips

Butt
The larger, exposed end of a shingle.

Collar Tie (also Collar Beam)
In profile, the framing of a conventional pitched roof forms a triangle: Mirrored pairs of rafters meet at a ridge and are connected across the base by a ceiling joist. The inherent strength and integrity of the triangular form makes the roof a sound structure. The bottom “chord” of the triangle—the system of ceiling joists—keeps the house’s walls from spreading apart under the significant roof loads pushing down and outward. A collar tie—sometimes called a collar beam—runs parallel to the ceiling joists but higher. Each collar tie connects a matching pair of rafters at mid-span, stiffening the rafters and strengthening the overall structure. Above rooms with vaulted or raised ceilings, collar ties sometimes double as the ceiling joists, providing the essential lower chord of the triangle, and may also provide a backing for attaching a flat portion of the ceiling.

Deck
Plywood or oriented-strand-board (OSB) sheathing used as a base for securing roofing materials.

Drip Edge
An L-shaped metal strip positioned along a roof’s edges to allow water to run off the roof without running down the eaves or siding.

Eaves
On a sloped roof, the horizontal underside that projects out from the house wall.

Exposure
The part of a shingle that is exposed to the weather, usually less than half its length.

Felt or Underlayment
Asphalt-impregnated roofing paper that creates a secondary, watertight barrier between many roofing products and the roof deck.

Flashing
Metal pieces that keep water from seeping into intersections, such as valleys or joints at vertical walls, or around roof penetrations such as chimneys or vent pipes.

How to calculate a roof’s pitch

Pitch
Roof pitch is the measure of a roof’s slope or angle of incline. Is there a difference between pitch and slope? Yes…and no. To understand how to properly use these terms, a brief lesson in roof geometry helps.

Pitch is expressed as a fraction, such as 1/4, each number representing the coordinates of an angle. That angle is based on a roof’s rise (height) and span (width). Pitch is the rise over the span. Say your house is 38 feet wide and the gable roof has a 1-foot overhang on each side; that makes the roof’s span 40 feet. From the eaves to the peak, it’s 10 feet high—that’s the rise. Figure 10/40 and reduce that to 1/4. It has a 1/4 pitch. Roof slope is expressed as the ratio of a roof’s rise (vertical distance) to each foot of run (horizontal distance). A “4-in-12 pitch” means the roof rises 4 inches for every 12 inches of horizontal distance. The word “pitch” was first used in the early 17th century to denote “the highest point.” This referred to everything from musical sound to the height that a falcon reaches before swooping down to attack its prey.

Rafters
The framework that supports the roof deck and roofing. On a sloped roof, these are the angled timbers on the underside.

Rake
The sloped edge of a roof over a wall.[GARD align=”left”]

Ridge
The peak where two sloped roof sections meet. Part of a roof’s frame, a ridge board runs horizontally along the peak of a sloped roof. Essentially the spine of a conventional stick-framed roof, the ridge board is sandwiched between the meeting ends of the roof rafters. Spelled “hryge” in Old English, the word was first used in reference to house roofs in the 16th century. In the 17th and 18th centuries, “ridge-piece” and “ridge-pole” were used respectively to designate a horizontal timber or a pole at the ridge of a roof. What was once a pole or timber is now a milled board—typically a 1 by 6 or larger for houses—hence, today’s use of the term to “ridge board.”

Square
A measurement of roof area that equals 100 square feet (an area 10 feet by 10 feet).

Slope
A roof’s slope is the number of inches it rises for every 12 inches of horizontal “run.” A roof with a “4-in-12 slope” rises 4 inches for every 12 inches of horizontal run. The same roof has a 4/12—or 1/3—pitch. The terms “pitch” and “slope” are simply two different ways of expressing the same measurement.

Soffit
A soffit is the horizontal underside of a roof overhang, an archway, a staircase, a ceiling, or a similar architectural component. From the Italian “soffitta” for under and “figgere,” to fix, the word “soffit” dates back to the days of early Palladian architecture. Typical soffits on today’s houses include the flat area under the eaves where vents provide attic ventilation, the lower perimeter of a drop ceiling, and the ceiling that is mounted to the underside of a staircase.

Valley
The angle formed where two sloping roof surfaces intersect.

Featured Resource: Find a Pre-Screened Local Roofing Contractor

Call for free estimates from roofing pros now:
[telnumlink] 1-866-342-3263[/telnumlink]

Roof Types & Shapes

In This Article:

Roof Framing

Drive through nearly any neighborhood and you can see that roofs have many different shapes. Houses have gable, hipped, mansard, gambrel, flat, and shed roofs. Many homes combine roof types on one roof. It’s quite common, for example, to see a hipped roof with gable dormers.

Roofs are built in a variety of shapes.

Roof shape is one of the key factors in setting the architectural style of a house. Roof shape also dictates how difficult and costly a roof will be to build and how it will serve the house. For example, flat, shed, and, in some cases, gable roofs tend to be relatively affordable to build.

Gambrel and mansard roofs offer more head height for attic rooms. Shed roofs are usually the easiest type to connect to an existing roof when adding on.

Roof framing can be simple or complex, depending on the roof. Overhangs, hips, and dormers add greatly to the complexity of the framing.[GARD align=”right”]

Roof Framing

Nearly all roofs are framed using one of two methods: standard “stick” framing or newer “truss” framing.

Stick-framed roof is built one member at a time.

Stick-framed roofs utilize individual rafters that span from the top of exterior walls to the ridge.

Roof trusses are manufactured ready-to-install.

 

 

Truss-framed roofs are built from triangular-shaped, pre-made truss units.

Gable and hip roofs may be built primarily of trusses; other roof shapes, particularly those with dormers or on houses with cathedral ceilings, attic rooms, or attic storage areas, are stick built. Stick framing creates a triangle between the rafters and ceiling joists. A collar beam adds strength at the middle.

Roof Framing Diagram

Like wall studs and floor joists, rafters and trusses are spaced every 16 or 24 inches from center to center. Most roofs utilize 16-inch spacings for strength and rigidity. The rafters are usually positioned directly above the wall studs.

A truss is one contiguous double rafter/ceiling joist unit. Truss construction is just as strong but is lighter weight and uses smaller sizes of lumber than stick framing.

Because trusses are carefully engineered units that shouldn’t be cut, they are not a good choice for roofs that may be modified at a later date. And because they have several intermediate support members, they don’t allow for use of the attic space.

 

Featured Resource: Find a Pre-Screened Local Roofing Contractor

Call for free estimates from roofing pros now:
[telnumlink] 1-866-342-3263[/telnumlink]

Roof Types & Shapes

In This Article:

Roof Framing

Drive through nearly any neighborhood and you can see that roofs have many different shapes. Houses have gable, hipped, mansard, gambrel, flat, and shed roofs. Many homes combine roof types on one roof. It’s quite common, for example, to see a hipped roof with gable dormers.

Roofs are built in a variety of shapes.

Roof shape is one of the key factors in setting the architectural style of a house. Roof shape also dictates how difficult and costly a roof will be to build and how it will serve the house. For example, flat, shed, and, in some cases, gable roofs tend to be relatively affordable to build.

Gambrel and mansard roofs offer more head height for attic rooms. Shed roofs are usually the easiest type to connect to an existing roof when adding on.

Roof framing can be simple or complex, depending on the roof. Overhangs, hips, and dormers add greatly to the complexity of the framing.[GARD align=”right”]

Roof Framing

Nearly all roofs are framed using one of two methods: standard “stick” framing or newer “truss” framing.

Stick-framed roof is built one member at a time.

Stick-framed roofs utilize individual rafters that span from the top of exterior walls to the ridge.

Roof trusses are manufactured ready-to-install.

 

 

Truss-framed roofs are built from triangular-shaped, pre-made truss units.

Gable and hip roofs may be built primarily of trusses; other roof shapes, particularly those with dormers or on houses with cathedral ceilings, attic rooms, or attic storage areas, are stick built. Stick framing creates a triangle between the rafters and ceiling joists. A collar beam adds strength at the middle.

Roof Framing Diagram

Like wall studs and floor joists, rafters and trusses are spaced every 16 or 24 inches from center to center. Most roofs utilize 16-inch spacings for strength and rigidity. The rafters are usually positioned directly above the wall studs.

A truss is one contiguous double rafter/ceiling joist unit. Truss construction is just as strong but is lighter weight and uses smaller sizes of lumber than stick framing.

Because trusses are carefully engineered units that shouldn’t be cut, they are not a good choice for roofs that may be modified at a later date. And because they have several intermediate support members, they don’t allow for use of the attic space.

 

Featured Resource: Find a Pre-Screened Local Roofing Contractor

Call for free estimates from roofing pros now:
[telnumlink] 1-866-342-3263[/telnumlink]

Ladder Safety

A ladder should rest on a firm base.

The easiest and safest way to position a tall ladder against a wall is to push the base against the wall, walk the top of the ladder up until it’s vertical, and then pull out the base.

The angle at which the ladder is placed is critical to safety. If its base is too close to the wall, the ladder will be unstable and likely fall backward when you climb it. If it’s too far away, the ladder may bend or slide out from under you. The distance from the base to the wall should be equal to about one quarter of the ladder’s length.

Be sure that the ladder rests on a firm surface. As you climb or reach up, keep your weight centered. Do not lean out to either side, keep your hips between the rails, and never stand on the top two rungs.

When using an extension ladder to reach the roof, extend at least two rungs above the eaves. This way, you can hold onto the ladder as you step onto the roof.

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