Gap Between Roof Sheathing And Insulation

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.

Gap between roof sheathing and insulation.

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

Use baffles between each rafter space to prevent it from being blocked see figure 5 11. An air space between the insulation and the bottom of the roof sheathing is desirable. The code calls for a minimum of 1 in. Batts should cover the top plate of the exterior wall but not block the venting.

The moisture is held in place by the insulation which allows for damage to the framing and other building components. Spacer type panel edge clips are available from some manufacturers. Of airspace between the top of the insulation and the back of the roof sheathing. For best performance the airspace in the vent chute should be a minimum of 2 in.

Several local and international building codes recommend a minimum of 1 inch gap between the sheathing and insulation. If there is a roof leak the insulation will be damaged by the water leaving you with less insulating value. Roof sheathing panel spacing hints. 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.

There are no irc requirements for spacing wood sheathing that i am aware of. T he problem with the insulation against the sheathing expands. Unless you re bulk filling rafter bays between 2 10 or 2 8 rafters with closed cell spray foam this approach.