Foam Board Roof Decking

1 4 dens deck roof board.

Foam board roof decking.

Foam on the underside of the roof deck would provide a more reliable air seal but has long term issues related to roof rot since the unvented roof deck would get a lot of. R values 28 tested in accordance with astm c518 spannings. Given that it seems that the ideal roof deck build up would consist of. Frothpaks or 5 for 1 part foam cans.

For new construction use rigid boards to insulate slabs and the outside of foundation walls. 1 2 rigid foam board 3. Rigid roof insulation board. Attach to deck board.

Johns manville r panel rigid roof insulation board offers r values of up to r 23 6 providing high thermal efficiency. The snugness of the foam itself should be sufficient to hold the strips. Note that table r806 4 indicates the amount of insulation above the roof deck or air impermeable insulation below the roof deck required for condensation control assuming minimum required total insulation as indicated in section n1102 building thermal envelope. For a basement remodeling project consider insulating basement walls with foam board.

At 600 board feet you can get the spray foam cost down to about 1 20 board foot compared to 3 35 bf ft in the 12 b f. I am curious as to whether the first layer of osb could be omitted if the foam board did not react to. After the roof deck is prepared the rigid foam boards need to be cut to size to fit snugly together on your roof. Composed of a closed cell polyisocyanurate foam core bonded in the foaming process to retroplus roof board on one side and a glass reinforced facer on the other.

The panels need to fit together tightly to help prevent warm air from leaving the top of the building. Use a premade kit for this type of project. 1 4 spans flute widths up to 2 5 8 flexural strengths parallel lbs. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls.

R panel is manufactured with a closed cell polyisocyanurate foam core bonded to fiberglass reinforced facers and designed for use over metal nailable and non nailable roof decks with a variety of membrane systems. Attach the tongue and groove insulation boards to the concrete wall with adhesive. Position the foam board between the rafters and push it upward until it fits snugly against the underside of the roof deck. Rigid foam is produced in various size panels 4 ft x 8 ft 4ft x 4ft etc.

This section outlines the conditions for unvented attic roof assemblies.