Gap Between Roof Sheathing And Insulation

The moisture is held in place by the insulation which allows for damage to the framing and other building components.

Gap between roof sheathing and insulation.

Use baffles between each rafter space to prevent it from being blocked see figure 5 11. For best performance the airspace in the vent chute should be a minimum of 2 in. T he problem with the insulation against the sheathing expands. If there is a roof leak the insulation will be damaged by the water leaving you with less insulating value.

Batts should cover the top plate of the exterior wall but not block the venting. Spacer type panel edge clips are available from some manufacturers. Unless you re bulk filling rafter bays between 2 10 or 2 8 rafters with closed cell spray foam this approach. 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.

The gap between the roof sheathing and the insulation over a ceiling is varied between 1 and 3 inches. Of airspace between the top of the insulation and the back of the roof sheathing. 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. The problem arises with moisture.

An air space between the insulation and the bottom of the roof sheathing is desirable. The code calls for a minimum of 1 in. Several local and international building codes recommend a minimum of 1 inch gap between the sheathing and insulation. 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.

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. 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. 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.