Finish TradesQuestion 221 of 700

Why do finish carpenters and painters often 'back-prime' exterior wood trim and siding before installation?

a.To make the visible face glossier
b.To seal the back and edges so moisture absorption is balanced, reducing cupping and paint failure
c.To eliminate the need for any face primer
d.To add structural strength to the board

Explanation

Priming the concealed back and edges balances moisture movement into and out of the board, which reduces cupping, warping, and premature failure of the finish coat on the face. It does not change face gloss, replace the face primer, or add strength.

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