Fill knot holes in pine ceiling

Old 06-26-19, 06:14 AM
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Fill knot holes in pine ceiling


As the title says, I'm looking for some advice on filling knot holes in a raw tongue and groove pine ceiling. It is in wood heated, 3 season cottage and, with the expansion and contraction of the wood over the winters, the knots have popped. It looks like mice have found a way into the ceiling and are using at least one of the knots as a route inside. Obviously we have to find and fix the exterior access but we'd also like to patch the knot holes so they won't pop again.

There are about 15 holes from 1 cm to 3 cm in diameter. The boards can't be removed without doing considerable damage. The ceiling is a spray foamed cathedral with the boards nailed directly to the ceiling joists so there is no attic to access from above.

My thought is to use wood filler on the smaller ones and a combo of dowel plugs and wood filler for the larger ones. Not sure how the wood filler will stand up to the swing in temperature though.

Any suggestions would be greatly appreciated.

Thanks in advance,

Last edited by Pennopoly; 06-26-19 at 06:23 AM. Reason: Typos
Old 06-26-19, 06:33 AM
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I would use an epoxy putty like Bondo with a little bit of dark stain or dye mixed in to get closer to the natural knot color. Over fill the knots a little bit and sand them back.
Old 06-27-19, 01:33 AM
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Does the pine have any type of finish on it? If not, a finish will make the wood more stable.
Old 06-27-19, 04:32 AM
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If using a putty in the bigger holes I would try driving a few small brads into the sides of the holes. Make sure the nails are up inside the hole and not protruding below the face of the ceiling. Leave the nail protruding out a bit to provide a mechanical hold on the filler. That way as the wood swells and shrinks with the seasons it's mechanically pinned in place.
Old 06-28-19, 05:18 AM
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Instead of a lot of sanding, a piece of wood and maybe wax paper (something that will peel off easily) could be pressed against the filler to allow it to cure flat.

Old 06-28-19, 02:21 PM
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Wood filler is not good for anything larger than a countersunk finished nail head. Would also recommend Bondo, although the textures will not match and the colors will be off. Boards can be replaced, although it is an involved process. Basically remove the offending board, cut new to length, remove the backside of the groove so you can insert the tongue and then overlay the groove and nail in place.
Old 06-29-19, 08:39 PM
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These are some great recommendations. Looks like we will be going with Bondo. I'm pretty good with faux finishes so the difference in colour and texture shouldn't be too much of an issue.

Thank you all so much!

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