I installed a panel job a month ago. The panels were 4 x 8 x 3/4. They were installed on metal studs. I used construction adhesive and screwed the panels from the back. Each panel was splined together and glued. Now there are 1/4" gaps at every panel joint. The panels were sealed and lacquered and only sealed on the back. They were done with a particleboard core.
(Architectural Woodworking Forum)
From contributor J:
I assume you're asking why it happened. Particleboard is more dimensionally stable than solid wood, but it's not absolutely stable. It does shrink when humidity is low and expand when humidity is high (though 1/4" of movement over 48" is a lot). Splining and gluing is a bad move because it doesn't accommodate that movement.
Since the problem is so severe, I'm guessing the panels were stored somewhere unheated/high humidity before installation, and the building where they're installed is heated and has no humidifier. Any chance of this?
If you pressed these panels, cold pressing will leave a lot of moisture in the panel. Also, any earth friendly core is made with PVA glue and has more moisture in it when manufactured. Finally, FR treated core may have added liquids in it that increase the MC.
Contributor J is correct in pointing out that the MC is the culprit and you need to get a MC meter on panels in these situations. In addition, many buildings are super dry with desert-like air. Things may look good in an unheated (or air conditioned) building but when the place opens things shrink.
Also, as all things in the universe are subject to expansion and contraction, you need to build in a reveal and a float method for installation. Tell us what you plan on doing at this point.