How To Foam Board Roof

To attach the insulation you can use screws with large washers a special adhesive made for adhering foam board insulation or for smaller pieces you can seal them in with caulk or spray foam.

How to foam board roof.

By this video you can learn how to cut foamboard 45 degrees. Remove existing roofing and non adhered underlayment to expose roof sheathing. Some parts of the country necessitate a vapor barrier under the rigid insulation however this wasn t necessary in our case. Most foam sheathed walls include a rain screen gap between the foam and the siding.

The foam panels need to be secured to the roof around every 12 inches for safety. The 4 x8 sheets of rigid foam board insulation were then laid out in a staggered pattern across the entire surface of the flat roof. Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers. There are typically 10 to a pack.

On small porches as long as you use a 2x plate where the rafters meet the foam it should be fine. As my article states you need a minimum of about 1 5 inch of eps 1 inch of xps or 1 inch of polyiso. If you want to install rigid foam above your roof sheathing in climate zone 3 then 1 2 inch of rigid foam board is not ideal this rigid foam layer needs a minimum r value of r 5 and that s impossible with 1 2 inch of foam. Use a straight edge knife or utility knife to cut the panels to size.

After the foam is tacked in place temporarily with a few nails it is secured in place with vertical 1 3 or 1 4 strapping that is screwed through the foam to the underlying studs. Measure the depth of the rigid foam. Measure the roof area and cut your rigid foam boards to fit by scoring it with a razor knife and snapping the board at the incisions. Apply continuous air control membrane to existing roof sheathing or implement continuous air control at roof sheathing.

A helpful hint for installation is to use a straight edge along the cut line to ensure the panels fit best. Repeat along all of the edges across the entire roof. As for the porch roof you could either remove it entirely or cut back the sheathing and framing enough to allow the new foam to slide into place. You may need to buy longer roofing nails to reach the plywood through the.

Foam board insulation is easy to cut with a circular saw with a masonry blade or scored with a utility knife and snapped like you would drywall. This video shows how to make a roof.