Plywood Over Shiplap Roof

If you have roofers that don t know the difference between shiplap skip sheathing find a roofer that does.

Plywood over shiplap roof.

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. Thanks for the heads up. But since the rafters will be open this plywood will be visible from the patio. Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle.

At one point in time it was standard to use shiplap tongue and groove one inch boards or other boards for your roofing 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. Shiplap is now considered an enemy of asphalt shingles. As roofing contractors in seattle we are often asked why do we need plywood over our old solid sheathing.

Today a shiplap roof is usually 60 years old. If the roofing underlayment is applied directly on top of the shiplap it will sag into the spaces and eventually leak. There is another issue whether the shiplap is aiding your household air infiltration. After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood.

Plywood will eliminate the buckling problem completely but still needs to be properly vented. Whenever your roof was first installed the nails were put into the solid wood. Shiplap does work but requires good intake exhaust. I am sure i am not the only one that has been deceived by what looked like venting but wasn t.

Being ideal for asphalt shingles in the early days of its creation shiplap sits beneath the roof of many homes about thirty years old. In most cases if it is a cold roof shiplap will be fine. However that isn t the case. Remember the keyword is solid.

Shiplap roof decking was widely used in the 50 through 80 s era when plywood hadn t yet made its way into new construction. Open spaces form between the once tightly fitted shiplap boards. As for slope i haven t actually measured it. These 8 to 12 inch wide boards were nailed together tight.

I was low balling it to see if indeed as the roofer said low slopes necessitate adding plywood over shiplap. 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. 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.