Suggested Subflooring over pressure treated decking

112690 · 10-17-2010, 10:28 AM

I have a small (500 sq ft) A-frame near a local lake. A few years back I constructed a new 14x16 deck on the front of the cabin. Now I want to add on to the A-frame by converting the deck into a room. I'm in discussions with a local Amish carpender and crew to frame and roof the addition.

The deck is constructed with 2x10 joists, on 16" centers, spanning 14' perpendicular to the front of the building. The decking boards are 16' in length and run parallel to the front of the building. The decking boards are in excellent condition, firmly attached to the joints with ring shank nails and are not warped.

The question is around the subflooring installation. Can the 4x8 subfloor be installed directly over the existing decking? If so, any special technique? Would 1/2" be sufficient?

The anticipated finish flooring will be 3/4 hardwood.

II Weeks · 10-19-2010, 08:11 PM

I would use 3/4" CDX with paper resin between with screws and nails.

**Gary in WA** · 10-19-2010, 08:54 PM

I'd get a permit to be safe. You need a solid foundation and stem wall under the walls to carry the roof load and windows. The spaces between the decking will create convective loop areas for heat loss with the insulation. I would remove the decking and go with sub-flooring 3/4" T&G with glue for no squeaks. I doubt you could get any shear flow in the floor with the decking in place.

Gary