Plywood decking and water

Originally Posted By: Thomas Tracy
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My house is in the framing stage in NE PA and the plywood decking has been exposed to the elements for at least a month or so. It has taken on quite a bit of rain and snow, no more than usual really but where is the point at which problems start. What should I look for? It is 3/4 inch T&G Fir plywood and not Advantec.


Originally Posted By: dhadler
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that the plywood has had ample drying time before applying your covering


As far as I'm concerned the only covering for a deck is vinyl Never use that roll on rubber crap that they say will last for 10-15 years. That is the biggest load of horse manure you'll ever see ![icon_evil.gif](upload://1gvq2wV2azLs27xp71nuhZOKiSI.gif) I've see newer homes 3-5 years old, that the deck is in far worse shape than if they would have left it totally uncovered

MY theory is that the plywood expands and contracts causing cracking on the joints... then the moisture gets in there and the coating actually encourages rot by holding the moisture under the areas where the coating actually sticks...ruining the deck faster than nothing at all.

Also, never use pressure treated plywood...it is only designed to be used in a vertical position like a foundation wood wall. They won't guarantee it if it's used laying flat.

I believe good old fir plywood is still the best choice!


--
Darrell Hadler
Five Star Home Inspections
Medicine Hat, Alberta CANADA

Originally Posted By: Thomas Tracy
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Maybe I confused you by using the word “decking”. I guess subfloor would have been a better word- with unfinished hardwood and tile (with wonderboard) over top. Sorry about that.


Originally Posted By: rmoewe
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Thomas,


It should be ok for about a month or maybe longer. You will want to look for the plywood de-laminating. This happens when it has absorbed too much water and the wood expands and weakens the adhesive used to secure the sheets together. This will happen to plywood that is very wet and freezes too. Whether it is ok or not depends, on how much de-lamination that has happened and what type of flooring that you are going to use. Small sections can be screwed back down, while the bigger ones should be replaced. You should also watch out for any mold that starts to grow as well. In your part of the country, this time of year, you should be ok. If there is any make sure that it cleaned properly, before the under lament or carpet is installed.


Hope this helps.


Originally Posted By: dhadler
This post was automatically imported from our archived forum.



Sorry Thomas, I did take it as decking… icon_redface.gif but the first paragraph would still apply.



Darrell Hadler


Five Star Home Inspections


Medicine Hat, Alberta CANADA

Originally Posted By: Thomas Tracy
This post was automatically imported from our archived forum.



Thank you both. So far the only thing I have noticed is some uneven spots at the seams. Nothing really resembling the delamination you’ve described.


Originally Posted By: rcloyd
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Thomas:


You can use a product such as thompson's water seal all over the decking when it is dry. Spray it on with a garden hand pump sprayer and this will prevent the plywood from absorbing water unitl the home is dried-in.

Regards,


--
Russell G. Cloyd
Intra-Spec Home Inspections
& Code Consulting, LLC
859-586-4591
www.intra-spechomeinspections.com