No Gap Between Roof Sheathing Panels

Sometimes plywood or osb was installed right on top of the boards.

No gap between roof sheathing panels.

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. Lay sheets in rows with the long edge horizontal to the roof bottom. 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 asphalt shingles are installed over sheathing with gaps exceeding 1 4 inch over time these gaps may telegraph through and become visible.

What h clips do h clips provide additional stiffness between bearing points for the unsupported edges of wood panel plywood or osb roof sheathing along with the necessary 1 8 gap for expansion as shown below illustrated on a bag of simpson h clips. The recommended maximum gap between roof sheathing boards for low quality 3 tab shingles is 1 4 inch. Not always required but a good idea. Roof trusses must be dry when sheathing a roof with osb to prevent mold growth in the roof and coverage gaps as the trusses dry and shrink.

Some older h clips do not provide a built in gap. Apa recommends a 1 8 inch space between panel edge and end joints. 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. 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.

If the wood structural panels are tightly butted there is no room for expansion and buckling can occur. Stagger the panels over the roof with 2 supports between panel ends. 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. 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.

Provide a 1 8 inch gap. That can mean costly time consuming callbacks. Avoid butting osb panels tightly leave a 3 mm 1 8 inch gap between the osb panels to allow for expansion.