Old Roof Decking

Until the 1940s exterior grade plywood was not available.

Old roof decking. Old houses with asphalt shingles usually had either tongue and groove boards or straight sided boards abutting. Strip away the old you re permitted to have two layers of asphalt shingles on your roof so if there s only one in place now you can have a new layer installed right on top. If you remove it all then reinstall you can have cracking and popping of the drywall ceiling. Since the boards used for shiplap were manufactured here in the pacific northwest it was still cheaper than plywood up through the 1960s.

It is important for us to point this out because here in maine many historic homes are maintained for both residential and business uses. These decks rarely had roof insulation installed on them since energy was relatively cheap so typical construction might have called for a layer of rosin treated paper followed by two layers of bitumen impregnated roofing felt nailed followed by three more layers of 15 asphalt or pitch impregnated organic roofing felt mopped together. Roof decks on homes built before 1970 are often 1 8 fir pre plywood shiplap. To prevent future mold growth remove the source of moisture causing it.

As long as the new plywood itself can span the distance and carry the roof wind seismic and snow loads for your region adding new ply over old is just fine. It s important to know what kind of a substrate is underneath the wood shakes before removing. Older homes may very well have a different type of roof decking than newer structures. In the 1950s plywood sheathing and particleboard became common and today most standard construction roofs use either half inch plywood or particleboard s big brother oriented strand board osb.

Plank sheathing usually 1 6 or 1 8 was used as a roof deck before plywood. The new plywood thickness should be. Plywooding over old roof deck one thing to consider when stripping off the old plywood is to remove and replace as you go. That will save you as much as 1 000 and a fair bit of mess but it means the roofer can t inspect and repair the decking and flashing underneath.

Prevent future mold growth. In older houses decking is typically made of lumber place perpendicular to rafters trusses.