Gap Between Roof Sheathing And Batt Insulation

Tape the seams in the poly with sheathing tape.

Gap between roof sheathing and batt insulation.

There are lots of ways to insulate a low slope roof and most of them are wrong. Actually panels marked sized for spacing simply mean that they are slightly smaller to allow for the recommended 1 8 gap see attached apa tt 055. Let s look at stucco cladding over foam sheathing over osb sheathing. Ensure that proper ventilation is maintained below the roof sheathing from the soffit vents to the ridge vent at the peak of the roof.

For best performance the airspace in the vent chute should be a minimum of 2 in. Seal the gap between the bottom plate of the wall and the floor with acoustical sealant or caulk. Use special airtight electrical boxes see photo tip 5 or seal the poly to the electrical box with acoustical sealant. The moisture is held in place by the insulation which allows for damage to the framing and other building components.

In older buildings the usual method is to install fiberglass batts or cellulose on top of the leaky ceiling with a gap of a few inches or sometimes a few feet between the top of the insulation and the roof sheathing. First the easy stuff. Vented roof sheathing. However it is considered good practice to leave a 1 8 gap between sheets and that is also recommended by apa but it is not required.

Synthetic stucco photograph 8. Press the poly into the sealant. This is best accomplishing by installing baffles on the underside of the roof sheathing in between every rafter prior to installing insulation between the rafters. Updated on april 8 2016.

Providing an air gap between the stucco cladding and the exterior face of the foam sheathing prevents the debacle we got with face sealed exterior insulated finish systems a k a. The problem arises with moisture. Of airspace between the top of the insulation and the back of the roof sheathing. Air impermeable and air permeable insulation.

Apply a 2 inch layer of spray foam insulation r 10 to r 12 directly to the interior surface of the roof sheathing. This will keep the surface warm and help minimize condensation. Generally spray foams have to be applied by a professional. You can then apply batt insulation around the foam without worrying too much about the air space.

The code calls for a minimum of 1 in. If there is a roof leak the insulation will be damaged by the water leaving you with less insulating value. T he problem with the insulation against the sheathing expands.