Plywood Over Shiplap Roof

Shiplap doesn t have any gaps in the boards and can be roofed over as is usually.

Plywood over shiplap roof.

Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle. 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. After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood.

Being ideal for asphalt shingles in the early days of its creation shiplap sits beneath the roof of many homes about thirty years old. I am sure i am not the only one that has been deceived by what looked like venting but wasn t. As roofing contractors in seattle we are often asked why do we need plywood over our old solid sheathing. There is another issue whether the shiplap is aiding your household air infiltration.

These wider boards were all nailed tightly together. At one point in time it was standard to use shiplap tongue and groove one inch boards or other boards for your roofing deck. Thanks for the heads up. The keyword here is solid it used to be standard to use shiplap 1 boards tongue groove or other boards for the roof deck.

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. However that isn t the case. 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. If the roofing underlayment is applied directly on top of the shiplap it will sag into the spaces and eventually leak.

Remember the keyword is solid. As for slope i haven t actually measured it. But since the rafters will be open this plywood will be visible from the patio. Shiplap is now considered an enemy of asphalt shingles.

Shiplap roof decking was widely used in the 50 through 80 s era when plywood hadn t yet made its way into new construction. 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. Open spaces form between the once tightly fitted shiplap boards. If you have roofers that don t know the difference between shiplap skip sheathing find a roofer that does.

Shiplap does work but requires good intake exhaust. In most cases if it is a cold roof shiplap will be fine. Today a shiplap roof is usually 60 years old.