Help! Painted Knotty Pine Paneling Has Huge Gaps In Winter

dcfixerupperJanuary 4, 2010

We painted the knotty pine paneling in the family room - unfortunately, this was done before we knew about shellac-based primer. We should have read up on how to do it - our painters primed it two or three times and then painted w/ latex-based paint.

It's looked great through the summer (room has central AC). This winter, we waited a bit, but finally turned on the heat in the room, which is via radiant floors. Now, there's been so much expansion that there are a number of 1/3 - 1/4 or more inch gaps between the planks and in the grooves. Even the double crown molding in the ceiling has gaps between the 2 rows (they used the pine paneling for the molding).

It looks awful! Is it too late to do much? Do we need to pull it out/drywall or can we save it? I really like the character of the painted look. Also, the knots are starting to show through slightly - I assume we can't apply the shellac-based primer now?

Should we caulk it while it's expanded in the winter, reprime, repaint? What will work - I've been searching on the internet and it doesn't seem that others have reported this problem.

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The wood is not stabilized because the back side is not primed or painted. It would probably be too mush to ask to take it all down, paint the back, and install it tight.
Short of putting in a humidifier to keep the moisture level up, your options are limited, because come humid DC summer, it will swell up again. If the spaces are occupied with caulk, it may buckle, or at best squeeze the caulk into ridges. A soft-drying caulk would be better if you go that route. Probably one that says elastomeric on the label.

    Bookmark   January 4, 2010 at 11:33AM
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Thanks - I searched a ton on the internet early this morning and couldn't find anything - which was surprising. There was a ton of info on how to paint it, but I've seen no one complain about the seasonal gaps. That being said, there is horrible insulation on the other side and the house is fairly dry right now. I'm getting pretty close to tearing it out, putting up drywall, and maybe adding some MDF wainscotting for interest later. We'll that's a $2k paint job down the drain.

    Bookmark   January 4, 2010 at 12:44PM
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Wood expands and contracts as it absorbs and looses moisture.

During heating season the relative humidity tends to go down (the warmed air can hold more moisture, and without a source of moisture the RH goes down).

During the cooling season the humidity tends to be higher.
The air from an A/C coil is at its dew point (that is why it gave up water as condensate) and even after mixing with the warmer air in the house the RH is still higher than in the heating season.

No finish can completely stop moisture movement in and out of wood. It can be slowed down, but not stopped.

The movement is a percentage of the width of the board based on the change in its moisture level.
Wider boards move more.

You can minimize the movement by how the wood is cut from the log also.
Quarter sawn wood moves less in width than flat sawn wood, but it still moves.

You could try and apply more paint to the now exposed wood, but depending on how tight the tongues are in the grooves it may be scraped off when the wood expands during the summer.

If you manage to get paint into the joint, it can also lock the tongue in position in the groove.
When the wood then shrinks further splitting can occur (and the tongue having the smaller cross section is a common place for a split to occur.

    Bookmark   January 4, 2010 at 5:17PM
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Still no good news :(

    Bookmark   January 6, 2010 at 7:12PM
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