The gap is necessary to allow for expansion of the plywood or OSB (Oriented Strand Board) panels when the humidity and/or temperature rises. A 1/8” space is recommended and it's clearly visible when you look up at your sheathing in the attic. The roof sheathing can buckle at the unsupported edges on hot/humid days if the panels are butted together without the gap. Wood is actually more sensitive to the moisture content changes caused by increased humidity than a temperature rise.

    Small metal H-clips are used at the unsupported edges between trusses to both stiffen the panel edges and ensure the necessary gap is maintained. See our article Are H-clips required by the building code for roof sheathing? to learn more.

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Here’s links to some of our other articles about roof sheathing:

• Why is my roof sheathing sagging between the trusses?  

• What causes a lump or dip in the roof? 

• What is the difference between plywood and OSB sheathing?

• Are H-clips required by the building code for roof sheathing?

• When did Florida start requiring re-nailing of roof deck sheathing for a roof replacement?  

• What are the roof deck/sheathing panels that look like pressed spaghetti?

• When were staples banned for roof sheathing attachment in Florida? 

• When did the Florida code start requiring roof sheathing nails to be ring-shank instead of smooth? 

• What is the average life expectancy of roof sheathing?

• What are the different roof  attachment discount categories for a wind mitigation inspection?