Installing Rigid Foam Over Roof Sheathing

To install measure the foam insulation panels to the roof s dimensions.

Installing rigid foam over roof sheathing.

To lessen heat buildup in the summer we installed dupont tyvec attic wrap on the top of the rafters and then nailed 1 furring strips on top of the rafters then installed the. Box beam gable framing new gable overhang is framed in the form of a box beam hanging off of a new layer of roof plywood roof sheathing cantilevered over the top of the 3 layers of rigid insulation. There are three key issues with foam sheathing. You may need to buy longer roofing nails to reach the plywood through the.

Rigid foam over roof sheathing we are in the process of building a home with all the ceilings in the house paralell to the roof and used 2 x 10 rafters throughout. Measure the depth of the rigid foam. Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers. If you are building a new home there are two basic ways to install rigid foam on the exterior of a wall.

Interior moisture can enter the wall from air leaks or diffusion through the wall finish. Install nailbase for cladding. Foam sheathing can help protect walls from moisture problems but only if it is thick enough and installed properly. Rigid foam offers tremendous boost to a home or office s r value.

The plywood was fastened through the rigid foam to the rafters with long screws. You can install rigid foam on the inside of a wall as well but adding exterior foam increases the r value of a wall or roof without eating up interior living space. 1 use a thick enough layer of foam to minimize condensation on its interior face. This type of insulated roof assembly limits thermal bridging through rafters.

Use a straight edge knife or utility knife to cut the panels to size. Exterior foam sheathing is often installed on existing homes as an energy saving retrofit when new roofing or siding is needed. The exposed edges of the 3 layers of rigid insulation are no longer exposed. Rigid insulation layers exterior to existing roof sheathing must provide sufficient thermal insulation r value to control condensation risk see climate specific guidance.

The foam can either be attached directly to the studs or the walls can be conventionally sheathed with osb or plywood before the foam is installed. When rigid foam insulating sheathing is installed on the exterior walls of a home the foam can serve as a drainage plane taking the place of house wrap for time and cost savings. For extra protection dab a small amount of caulk over each nail used to secure the rigid foam insulation to the plywood.