No Gap Between Roof Sheathing Panels

It doesn t mean that panel edge clips h clips are required although there are types of clips that will help with properly spacing the panels.

No gap between roof sheathing panels.

Plywood and oriented strand board osb like all wood products will expand or shrink slightly with changes in moisture content. 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. If the wood structural panels are tightly butted there is no room for expansion and buckling can occur. When you sandwich the layers so there is no air gap you only get the insulation value of the closed foam in the prodex material.

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. Some older h clips do not provide a built in gap. Avoid butting osb panels tightly leave a 3 mm 1 8 inch gap between the osb panels to allow for expansion. Lay sheets in rows with the long edge horizontal to the roof bottom.

The recommended maximum gap between roof sheathing boards for low quality 3 tab shingles is 1 4 inch. Stagger the panels over the roof with 2 supports between panel ends. Not always required but a good idea. Sometimes plywood or osb was installed right on top of the boards.

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. By no means am i an expert on insulation but from what i ve read you need to have an air gap between the foil facing and the exterior material like the shingles or sheathing under it. The minimum osb panel size is 24 inches in any direction and each sheet end must rest on a rafter. Provide a 1 8 inch gap.

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. If asphalt shingles are installed over sheathing with gaps exceeding 1 4 inch over time these gaps may telegraph through and become visible. That can mean costly time consuming callbacks.