Installing Wood Siding Over Rigid Insulation

Plus rigid foam insulation applied over the outside walls.

Installing wood siding over rigid insulation.

Wood siding applied directly to foam has a history of failures. What are the risks of installing cedar siding directly over foil faced rigid foam insulation should tar paper or housewrap be used as well. When installing wood siding over rigid foam sheathing you must protect the siding from moisture and heat buildup and use proper nailing. Wood siding including cedar siding should be installed over an air space regardless of the type of sheathing used.

And other non nailable substrates e g. The vsi installation manual notes when the fastener must penetrate through a non nailable material such as foam sheathing the thickness of that material. In fact the two products combined make your home super insulated from outside wind and weather. Julie the installation instructions of the vinyl siding institute and most if not all vinyl siding manufacturers allow vinyl siding to be installed over rigid foam sheathing.

Nailing wood siding directly to foam doesn t work because nails have to be extra long to reach through the siding and foam to a solid nail base. A homeowner in southwest virginia wants to install engineered wood siding over exterior foam insulation but finds that the manufacturer s installation instructions raises concerns he hadn t thought of. Moisture protection and heat buildup. Cladding attachment over thick exterior rigid insulation peter baker p eng.

How should wood siding be installed over rigid foam insulation. With foam sheathing an air space is essential both to reduce the siding s water uptake and to provide a. Installing house wrap with rigid foam insulation. Method 1 james hardie siding installed directly over continuous insulation c i and other non nailable substrates e g.

The answer happily is yes. Installation details are key. One of the biggest questions homeowners have about house wrap is whether it can be installed together with foam insulation. I don t think builders should install wood siding directly over plastic foam insulation.

Since foil faced foam is a moisture barrier it should be used with a continuous film vapor retarder on the inside wall. It adds up to a robust system. The illustration below comes from the vinyl siding institute. Cover the house walls with 4 by 8 foot sheets of rigid foam insulation typically 1 2 to 1 inch thick nailed to wood sheathing with 1 1 2 inch broad headed galvanized nails every 16 to 18 inches.

A vented drainable air space keeps wood siding dry and stable.