Plywood Over Shiplap Roof

Shiplap roof decking was widely used in the 50 through 80 s era when plywood hadn t yet made its way into new construction.

Plywood over shiplap roof. Remember the keyword is solid. If it is a hot roof and the design assumes airtight sheathing it would be easy at this point to install plywood zip sheathing and tape it. Thanks for the heads up. If you have roofers that don t know the difference between shiplap skip sheathing find a roofer that does.

Plywood will eliminate the buckling problem completely but still needs to be properly vented. I was low balling it to see if indeed as the roofer said low slopes necessitate adding plywood over shiplap. Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle. There is another issue whether the shiplap is aiding your household air infiltration.

At one point in time it was standard to use shiplap tongue and groove one inch boards or other boards for your roofing deck. In most cases if it is a cold roof shiplap will be fine. As for slope i haven t actually measured it. Whenever your roof was first installed the nails were put into the solid wood.

I am sure i am not the only one that has been deceived by what looked like venting but wasn t. If the roofing underlayment is applied directly on top of the shiplap it will sag into the spaces and eventually leak. Shiplap doesn t have any gaps in the boards and can be roofed over as is usually. However that isn t the case.

But since the rafters will be open this plywood will be visible from the patio. Open spaces form between the once tightly fitted shiplap boards. These 8 to 12 inch wide boards were nailed together tight. I m building a solid patio roof and was planning on using 1 2 plywood over the rafters 24 oc for the roof with spruce shiplap over the eaves to match existing house look.

The keyword here is solid it used to be standard to use shiplap 1 boards tongue groove or other boards for the roof deck. Sometimes on older houses they have had so many different roofs that the deck is all shot up splintering in this case a redeck is in order. Shiplap does work but requires good intake exhaust. The shiplap does look like its in good condition however i haven t put nails into it or given it any other test of strength.

After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood. These wider boards were all nailed tightly together. Shiplap is now considered an enemy of asphalt shingles.