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-   -   Membrane Over Top Of Joist (PTW) (http://www.diychatroom.com/f14/membrane-over-top-joist-ptw-19846/)

rjordan392 04-13-2008 07:23 AM

Membrane Over Top Of Joist (PTW)
 
Hello,
About 6 years ago, I replaced the deck planks on my deck. I noticed in a few spots that the top of the joist's had checks in them and ignored them. Well that was a mistake. I found out yesterday when I use a belt sander to sand down the exposed sides of the joist because the solid stain was now starting to peel on about 70% of the joists. I could feel dampness on the wood which explains the peeling from water seeping through the checks.

Now I am looking for ideas that are the least labor intensive to fix this. What I came up with is to place a tarp over the deck to allow the joist's to dry out when rain threatens. Then to apply solid stain back on the joist's and then working on top of the deck, apply either rope caulk, container caulk or water repellant between each deck plank. It appears using water repellant would be the least labor intensive. I have used Thompson's water seal in the past and do not like this product. I believe I read that someone recommended some type of membrane to slip over the joist's before installing the decking. I recently saw a deck being built of PTW and they did not use a membrane.
Does anyone have an idea to improve on what I am about to undertake?

Ron6519 04-13-2008 01:29 PM

Sorry, but there is nothing that will fix this short of removing or sistering the offending joists. No fillers or stains or caulking will be the least bit successful. If the joists are rotting, they will not stop with these methods and it will compromise the safety of those people who are standing on the deck.
Ron

rjordan392 04-13-2008 06:31 PM

Ron,
Thanks. None of the joist's are rotting yet. So I will keep an eye on it. They are over 18 years old and at present, do not have the funds to re-build the support structure. Hopefully in the future, differant materials will become available to replace PTW for support structures. The old stain job lasted 6 years maybe I can get the same again and after that I should be a candidate for a complete replacement, including the best decking available. If I have to use PTW for supports, I'll make sure the contractor applies a membrane over the top of the joists. Even a piece of aluminum bent to two 90 degree angles should do it.

Termite 04-13-2008 11:48 PM

There is always going to be moisture in wood that is used in an exterior application. Even if they don't get rained on, humidity alone will drive the moisture content of the wood above 20%.

The repair you described will not help the condition, and will likely worsen it. The best thing you can do is let the wood breathe. When it gets wet, it will dry out. Caulking, painting, staining, or capping the joists will only prohibit the moisture from getting out of the affected area.

rjordan392 04-14-2008 06:37 AM

How would capping the top part of a joist affect moisture? With a cap on, water will run off from between the deck boards and rest on it or runoff the capping. The rest of the joist would be exposed to breathe. Are you saying that the underside of the deck materials and 6" by 6" supports including the deck planks should not be sealed? How does one get his PTW support structure to blend in with the color of the new materials for deck planks and railing? My deck structure is 18 years old but the deck planks and the railing were replaced 6 years ago and no part of the original railing (2"by 6") had checks in them as big as the ones that I seen on the top part of the joists. The pictures I see on the net show that exposed outside beams and joists appear to be stained or have some type of veneer applied to them. 6 years ago, I still think it was a mistake not to cover the checks with capping to prevent water from getting down into them.

Maintenance 6 04-17-2008 07:58 AM

It sounds like your finish is more of a problem than the wood. Pressure Treated wood will get wet and dry out over and over. If the moisture is lifting and peeling the finish, then the coating is not breathing to allow the moisture to pass through it. I would look for a penetrating stain. Sealants can attempt to trap moisture in just as well as keeping it out. And yes, Thompsons has a good marketing campaign and little else.

rjordan392 04-17-2008 10:24 AM

It looks like I will have to learn more about stains and ptw. My deck is elevated. So the underside structure is viewable and creates a problem when I use a stain on just the deck surface and railings. If I have to let the support structure breathe, then I have mismatch colors. I am not to fond of penetrating stains as my experience with them is that they darken up too soon and require maintenance every two years.
This is how I ended up using a solid stain on all surfaces.

So now I am trying to make the best of it and will probally have the whole deck replaced in another six years with one of the newer type deckboards and railing products. So I will need some good advice on what to do with the support structures that do not match the deck and railing.

shimp 06-01-2008 09:09 AM

i use wolmans on my pressuer deck

http://www.wolman.com/product_detail...ID=10&path=fpp


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