Blog Archives

Block the Biggest Offenders

Posted by on 15/ 11/ 15

Block the Biggest OffendersПодпись: Ceiling joistПодпись: Two pieces of 1-in.-thick rigid-foam insulation glued to V2-in. plywoodПодпись: Foam weather-stripping acts as a gasket seal.Подпись: OSB deck acts as rimBlock the Biggest OffendersПодпись:Подпись: DrywallПодпись: SoffitBlock the Biggest OffendersПодпись:The attic access is a big leak that can be fixed quickly: Build or buy an insulated cover for the access bulk­head. The key is to provide a rim to connect to the sealing cover. The rim can be made from strips of sheathing, framing lumber, or rigid foam; then the cover sits on top or fits around the rim. On this job, I added a deck of leftover 1/2-in. plywood and OSB after the insu­lation was added.

Interior soffits that are framed before the drywall is hung can leak huge quantities of air. Fill in the openings between the ceiling joists above the soffits with solid materials like rigid-foam panels, drywall pieces, or sheathing scraps, then seal the edges with expanding foam or caulk.

Joist bays should be sealed with rigid blocks to keep insulation where it belongs...

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SLOPING AND PLACING GUTTERS

Posted by on 15/ 11/ 15

Ideally, gutters should slope down toward down­spouts 1 in. per 16 ft., but this is not always pos­sible. For starters, this may not look good: Next to a level fascia board, the steeper the slope of the gutter, the more it looks out of whack. As long as there is a slight pitch—say, І2 in. in 20 ft.—with no low spots en route to the downspout, a gutter will drain. If a house settles so that its roof edge or trim slopes away from downspouts, either install new gutters with downspouts properly located or raise or lower the gutters so they slope toward existing downspouts.

Place the front lip of the gutters below the roof plane, low enough so the sliding snow won’t tear them off yet high enough so the rain runoff won’t overshoot them...

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BRIDGE DECK MATERIALS AND SYSTEMS

Posted by on 15/ 11/ 15

Bridge decks can be constructed of timber, concrete, or steel.

Timber Decks. For bridges on unpaved roads or low-volume roads in rural environ­ments, timber decks of modern construction, such as Glulam (glued laminated) decks, can be serviceable and durable. For high-traffic-volume highways, timber is at a great disadvantage because of high cost, difficulty of fitting to a variable support profile, lack of skid resistance if a separate wearing surface is not provided, and difficulty in maintaining adhesion of an asphalt wearing surface. The choice then is usually between concrete and steel, or a combination of both.

Cast-in-Place Concrete Decks...

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Other Materials

Posted by on 15/ 11/ 15

Aluminum. A few bridges, including highway plate girder bridges and arch-type pedestrian bridges, have been constructed of aluminum. These bridges have generally performed well and have not required much maintenance. The plate girder bridges do not seem to have experienced problems that one might anticipate due to the difference in thermal coefficient between the alu­minum girders and the concrete deck. The main reason aluminum bridges have not captured a larger share of the market is high cost. Design specifications for aluminum bridges may be found in Guide Specifications for Aluminum Highway Bridges, AASHTO, 1991.

Aluminum railings, while not having the strength or ductility of steel, do not require maintenance painting...

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Micro Scale Simulation of Combined Mechanical-Water Induced Damage

Posted by on 15/ 11/ 15

The motivation for the following micro-scale finite element simulation, is the on­going discussion about cohesive versus adhesive failure mechanisms in asphaltic mixtures. It is the authors’ belief that, depending on the ability of the individual components and the bond between them, either one of these failure mechanisms may be dominant. It is, therefore, of paramount importance to establish the fun­damental relations between environmental weathering and material strength and stiffness. These relations can be used to assist the designer to optimize the water damage resistance characteristics of the mixture at purchase time on the basis of the response of the individual components.

In Fig. 5...

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Brace the walls

Posted by on 15/ 11/ 15

The sudden, intense pressure exerted on a wall by a hurricane, tornado, or earthquake can be devastating. To withstand these forces, the walls must be well braced. As a novice carpen­ter, I used to cut 2.x stock with a handsaw and let it into the studs, running it diagonally from plate to plate. It was a good brace, but it took about an hour to make each one. These days, braces are much easier to install. You can attach L-shaped metal angle braces or nail ply­wood or OS В sheathing to the frame. Code requirements vary, so be sure to check with your building department to find out how the walls should be braced. In some areas, bracing is also required on certain interior walls.

USING METAL ANGLE BRACES. Metal angle braces are easy to install (see the photos on the facing page)...

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Replace, Seal, or Enclose Recessed Lights

Posted by on 15/ 11/ 15

Recessed lights are one of the most overlooked sources of air leaks into attics. The best choice is to change old can bodies (1) for airtight insulation-contact-rated (IC-rated) models (see the photo at right) and then seal the rim to the drywall with foam or caulk. IC-rated lights that aren’t airtight can be sealed by covering the fixture with an airtight box made from rigid-foam insulation (2 and 3), metal, or drywall, or by sealing holes in the can body with spray-foam insulation (4).

Remember that non-IC-rated cans need an airspace around them and can’t come in contact with the insulation. Some sources recommend installing a sealed box over non-IC-rated cans, but recessed-light manufacturers frown on this practice.

Replace, Seal, or Enclose Recessed Lights

The best practice is to replace non-IC-rated cans with air-s...

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Nail on the double top plate

Posted by on 15/ 11/ 15

In some parts of the country, carpenters raise the walls before cutting and nailing on the double top plate. In my opinion, the time to nail on the double top plate is now—while the wall is still flat on the floor. Otherwise, vou will have to use a ladder. The top plate is an important structural member. It ties the entire frame together. Without it, severe lateral stress from an earthquake or high winds could easily rip apart a building. If you frame with a single top plate, secure them together with metal plate straps.

On a 2×4 butt wall, the double top plate extends beyond I be top plate a bit less than 3k in. (cut it / in. short—about 3k in.—to make sure it doesn’t protrude beyond the
through wall), so that it can tie into the notch in the double top plate of a through wall.

On ...

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Gutter Hangers

Posted by on 15/ 11/ 15

Gutter sections need to be supported by hang ers at least every 32 in.; closer if there’s a heavy snow or ice load. The many variations can be grouped into two general types: roof mounted, which employ a strap nailed to roof sheathing, and fascia mounted, which screw or nail directly to fascia boards or rafter tails. Whatever type hanger you use, gutters are less likely to pull free if you nail or screw the attachers to framing behind the fascia or roof sheathing. Here are profiles of four common hanger types:

► Spike-and-ferrule hangers nail directly into rafter ends or through fascia boards. Although this is a simple system, its detractors point out that 7-in. spikes leave large holes, encourage rot, and—in the end—don’t hold well.

► Roof-mounted strap nailers support gutters well an...

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Some Typical Loads, in Pounds per Square Foot (PSF)

Posted by on 15/ 11/ 15

Подпись: Attic, where finished rooms are not a possibility = Bedrooms = Living areas = Snow load — variable — ask local building inspector = Fully saturated earth (10 PSF per inch of thickness, thus 8 inches = 80 PSF) = Crushed stone: Same as saturated earth (10 PSF) = Conventional roof framing with roofing and insulation = Heavy timber framework, roofing and insulation for an earth roof =

Note: this is the dead load. With conventional (non­earth) roofing, the dead load is included in the rafter span tables. Thus, if you are looking at a table for rafters for a zone of 70-pound snow load, the

20 PSF 30 PSF 40 PSF 10 to 100 PSF 10 PSF per inch 10 PSF per inch 7-10 PSF* About 15 PSF*

dead load is also factored into the table. With heavy frames, such as for earth roof construction, it is better to add the dead load to everything else.

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