# filling seams



## ortho1121 (Mar 29, 2016)

Using plywood backing on the walls prior to putting up some wood moulding boxes. what's the best way to fill in the seams between the plywood sheets? Surfaces will all be painted. Caulk? Spackle? Joint compound? Wood putty?
Thanks for your input.


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## Alchymist (Jan 2, 2011)

Pretty hard to completely hide seams in plywood using the above methods. Some methods will eventually crack, others will swell/shrink with time. How much the seam will show depends on several factors. Were it me, I'd cover all seams with a thin molding. Mount your boxes then install molding over seams and butt to the boxes. Not a lot more work than trying to fill seams.


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## ortho1121 (Mar 29, 2016)

Hiding the seams with moulding would break up the aesthetics of the design. Is there a better material to use for the backing? Would 1/2 inch MDF be a better choice?


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## danrush (Oct 16, 2017)

We had a job that called for mdf and sounds a bit like your situation. Biscuits at the seams (although now I think I would use dominos) with lots of yellow glue, more than usual. The joints did swell up a bit when dry, but MDF sands beautifully. A quick skiff with bondo and we handed it off to the painters. 

We were worried about the seams raising or otherwise telegraphing thru, but I was there a couple of years later and the joints held well. Note that the home was fully acclimatized and I'm sure was very steady through the seasons. 

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