I am going to be using a piece of 3/4″ mdf to patch a rectangle approx 10″ x 32″. Long story but this is the best material for this application. My question is once I have placed the mdf in place would it be wise to primer before I tape and mud the joint.
Thanks a lot,
Vancouver, Canada
Replies
Yes, prime the MDF. Mud could cause it to swell.
I agree that priming will reduce the chance of the MDF swelling when it gets wet from the compound. Oil-based primer will lessen that chance much more than latex primer.
However, I would suggest that you reconsider using MDF because dissimilar materials will expand and contract at different rates with varying humidity levels. Even plywood would be a better choice, but my first choice would be 2 layers of 3/8" drywall.
We run into situations where we butt to mdf with drywall and tape it in a lot lately. The mdf has to be primed and usaully has a recess cut in to accept the tape. I have not seen failure at thes joints except in cases where it is used for trimless doors that get heavy traffic. ( I work for a drywall co.)
Mike
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