Author Topic: drywall mud over plywood  (Read 3070 times)

Offline realtorbill99

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drywall mud over plywood
« on: December 01, 2012, 03:51:20 AM »
Just bought 100 year old house and the second floor walls and ceilings were finished with plywood that was then painted, that is bad looking. i would like to spread drywall mud on the walls and finish it off like a plaster wall, hiding all the cracks and seams. i read where you need to apply a pva primer first to the plywood but it only talked about bare plywood not painted.  Can i apply the pva primer over the painted plywood and expect it to bind to the plywood? Thus allowing me to put the drywall mud on.

Offline chrisn

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Re: drywall mud over plywood
« Reply #1 on: December 01, 2012, 06:03:46 AM »
You could probably get away with that. Me, I would tear down the plywood and sheet rock it.

Offline mymint87

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Re: drywall mud over plywood
« Reply #2 on: December 01, 2012, 09:06:35 AM »
Just bought 100 year old house and the second floor walls and ceilings were finished with plywood that was then painted, that is bad looking. i would like to spread drywall mud on the walls and finish it off like a plaster wall, hiding all the cracks and seams. i read where you need to apply a pva primer first to the plywood but it only talked about bare plywood not painted.  Can i apply the pva primer over the painted plywood and expect it to bind to the plywood? Thus allowing me to put the drywall mud on.
pva is a penetrating primer, it has very poor characteristics over previously painted surfaces.... instead just look for a primer for previously painted surfaces and if the existing wood is smooth and without areas of flexing or movement...then skim coat away

if not, then please read on.......

you can remove and replace as chrisn suggested

or

you can just overlay the wood with drywall

drywall has fireproofing characteristic, plus acoustic and insulating properties

they make thin drywall sheets 1/4 inch for overlaying, you should look into it

why do we suggest removal and replacement or overlay with drywall?

without seeing the wood, i myself have pictured the substraight (wood) you have now being uncontrolled.  all the countersinking of existing nails and swelling ends of the wood sheets plus splintering or swelling around the nail fasteners them selves...and possible flexing or movement..it would take a very thick layer of mud to skim over the wood to provide a smooth finish and any continued flexing or movement will cause the skim coat to crack and fail

so under those conditions you ultimately have less mess, less sanding and an overall cleaner look with an overlay or replacement with drywall
I don't do this for a hobby and I'm damn sure I don't need the practice

the PAINTSMITH

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Re: drywall mud over plywood
« Reply #3 on: December 01, 2012, 10:23:52 AM »
1/4-inch sheetrock is exhorbitant in price; in some cases 3 X the price of 1/2-inch. I was going to do the same in our master bedroom, over existing 5/8" that had panelling glued to it. Removal caused a LOT of damage, but the price of the 1/4" convinced me to try Guardz and a lot of skim
coating. It turned out ok, but had I to do it over again...

One thing to note if considering mudding over ply is potential flex. If the plywood is 5/8 or better I wouldn't worry too much about it, but an old farmhouse is not likely to have framework at 16" OC, probably 20 or even (like parts of my old farmhouse build) 24". That doesn't make for a sturdy wall regardless of plywood thickness.

If possible, my suggestion would be to fir and rock. Yes, you lose a small amount of sq. footage, but you'd have control over stud spacing and some extra insulating property to the exterior walls.

Offline Jared

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Re: drywall mud over plywood
« Reply #4 on: December 01, 2012, 11:29:26 AM »
Quote
you can just overlay the wood with drywall

This is my vote as well.  Even though PS is absolutely correct about 1/4" drywall pricing, I have used it for this purpose before with great success.

Here in SoCal (and in any seismically active area) we get a lot of shear walls - load bearing walls reinforced by plywood as an inner wall layer.  We NEVER mud directly over the plywood in this case - drywall over the ply is the answer.

Note that door and window frames will probably have to be shimmed to eliminate the gap between the frame edge and the trim.
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Offline sidb

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Re: drywall mud over plywood
« Reply #5 on: December 03, 2012, 08:34:41 AM »
PVA will be useless, it is sealed already with paint. I would not trust
mud at this point. I would vote for either overlay(ok) or rip it out and redo (best).
« Last Edit: December 03, 2012, 08:37:38 AM by sidb »

 



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