Mdf skirting, expanding after painting?

[theflyingpig]

First time fitting mdf skirting. It's pre-primed. Cut it all in, then painted with two coats of paint. Come to fix it on and it all needs a mil or two trimmed off!

What's with that?

(obv only discovered after adhesive applied)

 

[blup]

You mean it expanded lengthways? It can and does, cut ends should be sealed.

 

[Diver Fred]

Was it the cheapo stuff or the more expensive Moisture Resistant stuff?

If it's the former it should have been undercoated before cutting - on all sides and fixed as soon as cut to size. Thin coat of PVA on the cut ends helps.

 

[theflyingpig]

Thanks for input. It was sold as moisture resistant, but to my eye is just regular mdf. Came primed.
I didn't think to seal the ends.