I am going to make a little landing "porch", about 4 X 4, but trapezoidal-shaped, outside the back door that walks out on to the open carport. The carport floor now is concrete. The new porch floor will be about 15" high. It will be braced underneath with a 4X4 landscape timber or treated posts sawed into 13.5" pieces which will stand vertical and rest on the concrete floor. The carport gets washed often, so there will often be water under the new porch.

In addition to treated wood, what can I use as "@#$%&" to clad the bottom of the posts? There will be maybe 16 to 20 of them, so they need to be cheap, preferably something I use and throw away.

There are galvanized post brackets designed to be bolted into the top of a concrete deck pier, and then the end of the post is set into the bracket and nailed in, so there is no direct contact between the post and the concrete pier. Every home center should have them. Someone will be along in a minute with a picture.

Edited to add: here you go -[www.amazon.com]



Edited 1 time(s). Last edit at 02/19/2012 01:48PM by John B..

Coat the base of each post with roof tar up to about 3-4 inches above the line where it's set into the ground/concrete.

These should work.

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And, just get posts that are treated for ground contact - that's all you need. Then, use the brackets mentioned here.

Those were the first thing I thought of, but they're not watertight and in fact would hold moisture around the bottom that otherwise would evaporate quickly.

What about going the opposite direction and holding the 4x4s a couple of centimeters off the concrete with something like four chair-leg nylon washers or the metal chair-leg extenders?

Just reread your post. No way do you need 16-20 legs for a 4x4 platform. I think I had fewer legs on my last home deck, which was about 20 x 50.

16 to 20 posts for a 4x4 deck ? Way overkill.

Before you buy any material, I suggest you buy the follow book:

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It's not a conventional deck. The structure is nothing like a deck. It will be a piece of plywood screwed to the posts and surrounded on 3 sides by the house itself (brick) and the jut-out of the fireplace. 16-20 is overkill, but I thought I would make it substantial. I want to to be solid, so 12 might do it.

Those things on the Amazon link are way too expensive. Also, I am not going to screw anything into the concrete because it will be removed one day.



Edited 1 time(s). Last edit at 02/19/2012 02:40PM by Dennis S.

Agree with MrD that anything with substantial contact to the wood surface might trap moisture and hurt more than help.
Based on the additional information I would just set the "treated" posts right on the concrete, but maybe consider some sort of treatment of the concrete to decrease its absorbant/wicking properties, like this?

[www.vanhearron.com]

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Dennis, if you're going to remove it anyway, just use ground contact pressure treated posts - they will be there way after all of us on the forum are gone...

Ground contact treated posts...

Thanks for that link Black!

OK, thanks everyone. Unless someone says don't do it, I am going to take a ground contact treated post and dip it in Thompson's Water Seal, which I have a can of, and put it right on the concrete.

Although, to complicate things a little, I have a big piece of flat rubber about the thickness of an inner tube from a Firestone factory. Would it help or hurt to glue a patch of that to the bottom of the posts?

Don't do it - put water seal on the treated wood - the pressure treated wood does better with nothing like that on it. Just put the wood right on concrete - it will be there from now on...

What LaserKun said. DON'T put water seal on the bottom of the post. It'll just keep the moisture that gets into the post from draining out. You need a seal on the concrete to stop water wicking up, not a seal on the wood to stop water draining down. I like these [www.decksdirect.com] but you seem to want to get away with a no cost option. I don't have a specific recommendation there, but I think Black is headed in the right direction...seal the concrete and use ground contact wood.

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And if you do insist on water seal-- it's recommended to apply it after the wood has been exposed to the elements for a while (IIRC.)

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I'm not going to seal it after what Davester and LaserKun said. I have never seen this miraculous ground contact pressure treated wood, but I take it it works as is.

I do need a recommendation for a general concrete cleaner before I seal it, though. The whole carport is fairly stained and spotted with oil, steering fluid, rust and who knows what. This would be a good time to clean it all up as best as possible.

Oh, one question, though. Does the ground contact treated wood still work where it is cut through and a new raw end is exposed?