Why a vinyl siding nail is left loose — the 1/32″ float, and what happens when you drive it tight

Vinyl must float. Center the nail in its slot and leave ~1/32″ (a dime) under the head so the panel can move — driving it tight is what causes the buckled, wavy look.

An edge-on section at a vinyl panel's nail hem, comparing two ways to fasten it. On the left (correct), the nail is centered in the elongated slot and stopped about 1/32 inch — a dime's thickness — short of the hem, so the panel hangs loose and can slide as it expands and contracts. On the right (wrong), the same nail is driven tight, pinning the panel to the wall; on the next hot day the trapped panel has nowhere to move and buckles into visible waves (oil-canning). The rule: center the nail in the slot, leave about 1/32 inch under the head, and never drive it tight. — Source: VSI Installation Manual (Basic Installation Rules) · ASTM D3679

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An edge-on section at a vinyl panel's nail hem, comparing two ways to fasten it. On the left (correct), the nail is centered in the elongated slot and stopped about 1/32 inch — a dime's thickness — short of the hem, so the panel hangs loose and can slide as it expands and contracts. On the right (wrong), the same nail is driven tight, pinning the panel to the wall; on the next hot day the trapped panel has nowhere to move and buckles into visible waves (oil-canning). The rule: center the nail in the slot, leave about 1/32 inch under the head, and never drive it tight.

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