Rigid Top Roof Sheathing

Installing rigid foam insulation on top of roof sheathing is a great option for commercial buildings and homes with limited space.

Rigid top roof sheathing.

Apply continuous air control membrane to existing roof sheathing or implement continuous air control at roof sheathing. Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers. With three layers of 11 2 in. Installing the rigid foam and top layer of roof sheathing.

The glue i was using didn t set fast enough to hold the rigid foam panels in place so i ended up installing the foam and osb sheathing at the same time. Then a second layer of plywood sheathing and asphalt shingles following the steps explained in this article. Tiles were designed so that lugs or short protrusions on the top backside of each tile would hook over the step sheathing. My original plan was to install the layer of rigid foam first and then do the sheathing on top.

Remove existing roofing and non adhered underlayment to expose roof sheathing. Installed on the roof exterior foam makes the living space below more comfortable and reduces the likelihood of ice dams. Polyisocyanurate insulation above the sheathing and approximately 91 4 in. More recently however most roofers recommend solid sheathing on the roof to give the house additional resistance to movement or shear strength.

Benefits of rigid foam on top of sheathing. Deck for a thick roof rigid foam insulation installed above the roof assembly can create an energy smart roof. A lower layer conventionally nailed to the rafters and an upper layer installed as a nailing surface for the roofing material on top of the rigid foam. The illustration shows two layers of osb or plywood roof sheathing.

Of cellulose insulation in the rafter cavities the roof shown here has an r value of approximately 63. 4 of polyiso under 4 of eps all above the original roof sheathing.