Plywood Over Shiplap Roof

After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood.

Plywood over shiplap roof.

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. Plywood will eliminate the buckling problem completely but still needs to be properly vented. There is another issue whether the shiplap is aiding your household air infiltration. In most cases if it is a cold roof shiplap will be fine.

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. Whenever your roof was first installed the nails were put into the solid wood. But since the rafters will be open this plywood will be visible from the patio. Being ideal for asphalt shingles in the early days of its creation shiplap sits beneath the roof of many homes about thirty years old.

However that isn t the case. Shiplap doesn t have any gaps in the boards and can be roofed over as is usually. I am sure i am not the only one that has been deceived by what looked like venting but wasn t. Shiplap roof decking was widely used in the 50 through 80 s era when plywood hadn t yet made its way into new construction.

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. Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle. Remember the keyword is solid. 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.

Shiplap does work but requires good intake exhaust. The keyword here is solid it used to be standard to use shiplap 1 boards tongue groove or other boards for the roof deck. I was low balling it to see if indeed as the roofer said low slopes necessitate adding plywood over shiplap. These 8 to 12 inch wide boards were nailed together tight.

As roofing contractors in seattle we are often asked why do we need plywood over our old solid sheathing. If you have roofers that don t know the difference between shiplap skip sheathing find a roofer that does. Today a shiplap roof is usually 60 years old. 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. Open spaces form between the once tightly fitted shiplap boards. These wider boards were all nailed tightly together.