Hi there!
Novice DIY here. I just finished my pole building style projects, and now have run out of time for a storage shed – deck style 16′ x 20′ with 20 short posts of PS 4×4 in a 4×5 grid pattern to support the floor frame. I originally planned to bury the posts in concrete for lateral support, and to lower hardware costs – it is very dry in Eastern Washington, and my ground is rocky and sandy. But starting Wednesday it is going to be (way) below freezing at night.
So:
1. Would it be ok to still bury short 4×4 into about 16″ deep of 10″ diameter fast-set? After 16-18 inches there is a foot layer of rock, then rock and sand.
2. Could I use just non-uniform gravelly soil, mostly rock? I have 10″ plastic footing plates.
Or just wait for summer!
Thank you!!!
Replies
What are the dimension of this shed?
The shed is planned to be 16' x 20'.
You can pour the concrete even if it's going to be below freezing. Just insulate the wet 'crete with hay or foam.
I agree with Andy. Especialy if you are using fast set and day time temps are above freezing. You will be okay.
Use warm water if you are worried but even that shouldnt be necessary.
Setting PT into concrete should be avoided whenever possible. It may not be as big a problem in a dry region like yours, but otherwise it will rot faster than other methods. No matter what you do, the other comments are right, even though air temps will go below freezing, the ground is still warm.
Great, thanks to all!!
Happy to be on the site.
By no means disputing direct setting, here's an interesting, quantitative tidbit to that, to put things in perspective of location and time scale.
I had an RV shed at the previous home put by previous owners over 30 years prior. It was 6x6 PS of some sort, set i concrete to the ground level, and covered with dirt over the decades. When I started converting it to a workshop and excavated around, only 2, or 3 of the posts had visible rot, and some dry rot signs to them, in varying degrees. It was still a very solid structure.
At the same time, the same treatment to 4x4 fence posts in Seattle left them rotten through and fallen at my friend's place in 5-7 years.
My posts will not be directly exposed to precip, eventually!
Thanks again.
There are many grades of PT, and not all are rated for ground contact (they have to say so on the label). There are also different chemicals used by different brands and at different concentrations. Until 2004 or 2005 CCA was used, but not anymore (except for a couple of specific industrial uses). There are many reasons beyond how rainy it is in an area that can determine how long PT lasts in the ground, the ones mentioned above, was the post treated on the cut end, was the post a peeler core (containing the pith in the center, not good)?