Drywall Compound with MDF ?

[Ray]

I have been building a bathroom in the basement, with the usual problems with

sewer pipes etc. I have used 1/2" Mdf to build boxes and built in cupboards around the main stack and pipes. The question is Can I use ordinary drywall compound and techniques to blend these boxes into the standard drywall walls ?

It looks like I could, because I have slopped a bit of drywall compound in a few spots on the MDF,

and it seems to sand and blend ok

Thanks for any opinions

Ray

[Duesenberg]

I just did it recently in my basement with closets. I didn't notice any moisture issues with the MDF. I used store bought pre-mixed compound and thinly applied the compound in two stages.

[hrhofmann]

You could blend in a little white/Elmers glue in the first coat of mud if you are worried about adherence. But then you ned to put it on very evenly so that the second coat of mud will completely cover it. Otherwise, you will go thru a lot of sandpaper removing the white glue mud.

[Ray]

You could blend in a little white/Elmers glue in the first coat of mud if you are worried about adherence. But then you ned to put it on very evenly so that the second coat of mud will completely cover it. Otherwise, you will go thru a lot of sandpaper removing the white glue mud.

I guess I am thinking more about uneven expansion, and cracking more than adherence

Ray

[Duesenberg]

I'll find out soon enuf. For adhesion I screwed the mdf into exsisting studwork/drywall where possible. I wasn't using the mud as adhesion, but to smooth out things.

I used drywall tape along the seams where mdf met drywall and in corners I used paper faced metal corner beading. Hopefully it'll keep for the next 20 years.

I think thinner application of mud prevents worse cracking. Instead of glopping it all on, spend the time to do multiple thin coats. Also thinner coats mean the MDF can't swell as much with the moisture.

Also I wonder if paintable silicon to fill in the cracks would prevent noticeable small cracking. I didn't do it but might be an idea.

[Steve Barker]

I would probably suggest the self adhesive mesh tape for the transition. I don't think you'll get the regular tape to adhere to the mdf, and without tape you'll always have a crack there.