Expert: Michael Curry - 5/21/2010

Question
QUESTION: Hi,

I am building an art studio and using a/c plywood walls.  Someone put some non paintable sealant caulk at where the pieces of plywood meet when I wasn't around.  It can't be sanded or painted.  My carpenter suggested using drywall tape and compound and then sanding.  He's made some questionable judgements in the past so I decided that I had better check this out with an expert.  Can this method be used and will it be very smooth, like drywall?  Will the tape show or will it crack over time?  Do you have any other suggestions?  Thanks in advance.

ANSWER: Hi Shelley,

That type of plywood is usually used outside and the joints have some type of trim over them. Drywall compound and tape generally do not stick to plywood long term and i wouldn't use it. Unless you want to cover the joint with a piece of trim I would remove the existing caulking and replace it with a latex paintable one.


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QUESTION: Hi,
Thank you for your response. I would like to ask a follow up question.  Do you know anyone that has used this method.  I'm wondering what you are basing the suggestion on, that it won't stick over time?  

Very important:  How do I get the caulking out of the spaces and nail holes?  I've tried prying it out..no luck. I've tried heating it and the fumes are way too toxic.  HELP!

ANSWER: Hey Shelley,

Sounds like quite a mess you've got there. The old caulking is probably silicone based and will need cut out. This will probably damage the plywood surface a little.
We used drywall compound and tape years ago to seal drywall in garages to wood for gas proofing and over time it would detach. If the plywood you're using has a paper surface to make it smooth the compound may stick especially if you sand it lightly first, however, that's not the reason I wouldn't use it. Wood expands and contracts with moisture changes throughout the year. If you've ever had a hardwood floor you will know this. Joint compound has no tolerance for even a slight movement and will crack.

If you used plywood so that you could hang stuff in your studio I would just drywall over it and make sure the plywood and drywall joints don't line up. You could even use 1/4" drywall instead of 1/2".

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QUESTION: Hi,

Thanks again.  I would prefer to try to remove the silicone.  What method would you recommend?  Thanks.

Answer
Hey Shelley,

Unfortunately there is no easy way to remove the caulking. In bathrooms we cut it out and scrape away the excess. I have never had to do this with plywood we needed to reuse and I wish you luck.
The maunfacturer of the caulking my have some reccommended way of removing it. Sorry I can't be of more help.