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.

Unless you re bulk filling rafter bays between 2 10 or 2 8 rafters with closed cell spray foam this approach. For best performance the airspace in the vent chute should be a minimum of 2 in. There are no irc requirements for spacing wood sheathing that i am aware of. Roof sheathing panel spacing hints.

Use baffles between each rafter space to prevent it from being blocked see figure 5 11. 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. The code calls for a minimum of 1 in. The problem arises with moisture.

T he problem with the insulation against the sheathing expands. Spacer type panel edge clips are available from some manufacturers. 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.

Batts should cover the top plate of the exterior wall but not block the venting. 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. 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. The gap between the roof sheathing and the insulation over a ceiling is varied between 1 and 3 inches.

The moisture is held in place by the insulation which allows for damage to the framing and other building components. If there is a roof leak the insulation will be damaged by the water leaving you with less insulating value. Several local and international building codes recommend a minimum of 1 inch gap between the sheathing and insulation.