Australia Storm Book

After The Storm - 22

Roof Repairs: Sheathing Application

General

The sheathing layer of the roof is nailed to the rafter or trusses of the roof system.

After the Storm Fact Sheet 21 discussed minimum standards for materials. If you need that information or other leaflets on roof repairs, call your county Cooperative Extension center. This leaflet deals only with installing the sheathing selected following guidelines in fact sheet 21.

Best results come with replacing damaged sheathing with the same material as the undamaged section of the roof. In no case may a different thickness be used. Thickness may not satisfactorily be built up with felt, shingles, or furring on rafters or trusses. Roof strength usually depends upon the same thickness.

Under the multiple pressures of shortages of time, skilled or reputable workers, materials, etc., it may be tempting to take shortcuts or make do on repairs, but remember that a depreciated house and future expensive trouble can come with such a decision. You may receive insurance or other assistance now; later when problems reappear you may bear those costs alone.

Tips

First, a word of general advice on applying sheathing to rafters. The most frequent problem with roofs is buckling and warping, caused mainly by improper spacing of solid sheathing materials.

Roofs more than any other area of a house are exposed to extremely hot and cold temperatures. Roofing materials expand when hot and contract when cold, actually "breathing" much the same as the human body. This means that adequate cracks, about 1/1 6 to 1/8 inch, must be left at joints between solid sheathing. Plenty of cracks are present with 1 x 6 sheathing, thus spacing is not as critical. Manufactured spacing clips are available to use in spacing sheets of material and serve only that purpose. If clips are not used, be careful to provide adequately wide cracks on all sides of each sheet of material used. Next summer your roof will look like a calm lake surface rather than a hurricane wave!

Following are some minimum procedures required for:

  • 1 x 6 T&G (Tongue and Groove) Boards -- Fasten to rafters with corrosion-resistant, HD (hot-dipped) nails or staples at the rate of two 8d nails or two 1-3/4 inch staples per board on each rafter or truss.

  • Plywood Sheathing -- Joints must be placed over rafters. Space sheets as described earlier. Sheathing must continue over two or more spans. The face grain of the plywood must run perpendicular to the roof rafters.

  • Particle Board Sheathing -- This may be applied either parallel or perpendicular to rafters. Care must be taken to stagger applications so that four panel corners do not meet at one point. A minimum 1/1 6-inch gap between boards is required. Do not nail within 3/8-inch from the panel edge. Provide 1/2-inch gap from masonry (i.e. walls, chimneys). Take care to over cut holes for fitting around vents, plumbing, etc. Do not force fit. Fastenings should be with three 8d nails or four 1 3/4-inch staples per rafter crossed.

  • Installed "breathing" sheathing will form a good base for the roofing felt and asphalt shingles, which will be discussed in After the Storm Fact Sheet 23.

 

 

 

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