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Porches & Decks

Porch Moisture Concerns

14 years ago

Looking for a little guidance before I make decking choices.

I'm in the process of developing screened porch/deck plans for my home. The enclosed screened area will be rougly 20'x 15' (20' along the house). I would like to use some type of T&G plank (Ipe, TT Floorizon, PT, etc.) but am concerned about the moisture buildup beneath the deck resulting in mold and cupping. At the base of the house the deck planks would be ~12-14" above the ground and sloping away from the house to ~36" at the front of the deck. Only two sides (front and one side) would be exposed to air, as the other remaining side is part of a retaining wall. This porch would be built in Northern Virginia.

Is this type of environment suitable for a T&G application as is, or do additional steps need to be taken to avoid potential moisture buildup? Is one type of material going to reduce the issue of mold buildup vs another (I assume using a PVC product can reduce the cupping issue)? Or do you say don't go the T&G route?

Would a better alternative be to use conventional decking planks with the manufacturer recommended spacing and screen the underside? I assume this would give me the neccessary ventilation between the planks.

Any thoughts and previous experience would be greatly appreciated.

Thanks!

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Comments (5)

john_hyatt
14 years ago
Mold build up/cupping/moisture is going to be the same with face fastened material or T&G.They both drain the same way thru the gap. J.
rumrunner9
Original Author
14 years ago
John...

So am I correct to assume that face fastened material will not allow more ventilation? My main concern is about the build-up of mold under the deck, not neccessarily the accumulation of water on top of the planks.

Thanks.
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john_hyatt
14 years ago
Installed coretley T&G decking is the same in every way as face fastened material but uses fewer fasteners.

Ventalation should be suplied under the deck,cross ventalation,air in air out. Vents in the decking,like floor vents in your house surface mounted, will help provide cross ventalaton for a decking project. The gaps in the decking will not provide cross ventalation. J.
jimwoods49
14 years ago
Hello RumRunner, You are wise to consider moisture before constructing your deck.
Standard decking and T&G will react the same to moisture.
T&G is a beautiful option in a covered porch. Your slope and ventilation will be fine. Be sure soil under deck is packed smooth without large ruts. Cover with plastic with large rocks on top to secure it. I read this on a BWDepot.com blog, used it several times and have only happy customers. Congratulations on your new deck.
john_hyatt
14 years ago
Not a good idea to lay plastic under any deck. J.

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