Gap Between Roof Sheathing And Insulation

Or if you are perfect with your rainwater control such as when you use a fully adhered membrane think roof membrane standing up applied to a wall.

Gap between roof sheathing and insulation.

Apply adhesive along the connection between the roof sheathing and rafters in a continuous bead much like caulk around a bathtub or apply adhesive to two adjacent sides of 1 by 2 blocks 6 inches. Of airspace between the top of the insulation and the back of the roof sheathing. An air space between the insulation and the bottom of the roof sheathing is desirable. The gap between the roof sheathing and the insulation over a ceiling is varied between 1 and 3 inches.

Roof sheathing panel spacing hints. The problem arises with moisture. T he problem with the insulation against the sheathing expands. Unless you provide a small gap between the exterior face of the osb and the back surface of the foam sheathing to provide for some hygric redistribution.

In the winter humidity from the house s interior will get past the insulation and come in contact with the cold roof sheathing where it will condense into water. For best performance the airspace in the vent chute should be a minimum of 2 in. Batts should cover the top plate of the exterior wall but not block the venting. To maintain airflow leave a space of 38 to 50 mm 1 1 2 to 2 in between the top of the insulation and the underside of the roof sheathing.

Use baffles between each rafter space to prevent it from being blocked see figure 5 11. The code calls for a minimum of 1 in. Use a 10d box 0 128 inch by 3 inch nail as a spacer to gauge 1 8 inch edge and end spacing between panels. Several local and international building codes recommend a minimum of 1 inch gap between the sheathing and insulation.

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. If there is a roof leak the insulation will be damaged by the water leaving you with less insulating value. The moisture is held in place by the insulation which allows for damage to the framing and other building components.