Knotty alder has natural imperfections such as knots and voids that are part of its aesthetic appeal.  These features inherently make it difficult for a protective top-coat to adequately seal the lumber against moisture gain/loss.

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To prevent moisture intrusion and validate the B.C. Door Limited Warranty for Wood Doors, all exterior doors are required to have voids filled on exterior faces.  All interior faces may be filled or left open depending on the desired look.

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While both looks are similar, key differences between Open Voids and Filled Voids are:

 

• Open Without Fill will show a dark-shadowy area that penetrates into the lumber.

• With Fill will show a dark area that is flush with the face of the lumber.