Mahogany deck help

jen06850December 3, 2009

We installed a mahogany/cambara deck in august with a pretreated wood and it was already showing strange discoloration - mold or mildew or something - by a couple of months later. Any recommendations on how to clean it and then what to put on it? I've read that TWP 100 series is good. And should we sand it first or try to strip it somehow with a chemical solution of some sort? We're in CT and it's getting cold - wondering if it's better just to wait until spring, or will that cause deeper problems with the wood?

Thanks for any/all advice!

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/Users/jwulff/Pictures/iPhoto Library/Originals/2009/Oct 7, 2009/DSC_0026.JPG

    Bookmark   December 3, 2009 at 1:43PM
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Here's a photo:

Here is a link that might be useful: flickr

    Bookmark   December 3, 2009 at 2:04PM
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was something sitting on the deck (or over it) that could have caused the difference in color?

    Bookmark   December 3, 2009 at 9:40PM
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There was a tarp on for about three days while we had some trees cut down. That's it, though...

    Bookmark   December 4, 2009 at 12:11AM
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It looks like the original product is water-based, and the failure you are experiencing is typical of WB acrylics on tropical hardwoods. The entire deck needs to be chemically stripped down to bare wood.

You say the wood was prefinished. I assume that means all sides of the boards. If so, you would need to strip all sides of the boards, so basically the deck needs to be taken apart. Major labor here.

This is why to NOT prefinish all sides of the boards, especially if you use a WB product. (I do not recommend using ANY water-based product on tropical hardwood) If your deck is outside it will get wet. No matter what finish you put on the wood, the wood will absorb water when it rains. When you finish all sides of the board it becoms a problem that the underneath side of the boards are sealed, and actually hold the water in the board that soaks through the top. As the finish on top wears down more water is absorbed into the wood. The finish on the bottom side of the board does not wear at the same rate, so the bottoms are sealed more than the top. Since water goes down with gravity, you create a situation where the water can enter but not exit at the same rate. If the underside of the wood was bare, the deck could breathe much better.

Wait until spring and I bet you will be having major cupping issues. If you only strip the top of the deck, the problem will come back again.

Sorry for not really having any constructive advice about how to fix your current problem. -Aidan

    Bookmark   December 4, 2009 at 2:00PM
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