Redwood or pressure treated?

[nvbirdman]

I have to build something on 4"x4" legs that will be sunk three or four feet in the ground. Should I use redwood or pressure treated lumber?

[roadie]

I suppose it might depend on what will sit on the legs, but pressure treated fence posts last a good long time. Might be cheaper than redwood too, but I've not used redwood to know.

I have 4x4 posts that have been in wet ground for well over 15 years, and still solid. If you use pressure treated and cut them for any reason, the cut end will need to be treated if it's in the ground.

[tomme boy]

Black Locust if you can find any. Paint the part that will be in the soil with pine tar and it will last way longer than any treated wood will.

[samari46]

20 some odd years replaced the 4x4's on my fenceline and all PT wood. Tarred the bottoms and they are as far as I know still there. Sold the house years back. Had to use a Hilti gun with concrete bits to make the holes bigger than cross braces to make sure they stay vertical. Frank

[Winger Ed.]

If you don't have much problem with the ground being wet much of the time and causing rot, either one should be fine.

We have an issue with posts rotting here, and cedar seems to be the most resistant to rotting.

[Idaho45guy]

The big thing NOT to do is to set the posts in concrete with the bottoms encased. You can use concrete to stabilize them, but make sure they are set at the correct height BEFORE pouring in the concrete.

The reason is because you want the bottom of the post clear so water can drain out of it.

I built a 6' privacy fence in Arizona and wanted to make it super secure. I dug the holes, then put in the posts and poured concrete in, then lifted the posts slightly to adjust the height. When I lifted them, it allowed the concrete to flow under the post and completely encased the bottom 2' of the post in concrete. When it rained, the water flowed through the top of the post and collected underground in the bottom of the post, rotting them from the inside. Within 2 years, I had to replace several posts.

When I put in a privacy fence here in Washington, which gets much more rain, I didn't even use concrete and instead put a layer of gravel in the bottom to ensure proper drainage, and tamped the dirt down good around the posts. 4 years later, all posts are still rock solid. Used the same pressure treated 4x4s from Home Depot for both projects.

[Lloyd Smale]

green pressure treated posts are the way to go. We set HUNDREDS of power poles treated like that and never had a single one rot. Reason is the treatement is a chemical mixed with water pressured into the wood. I wouldn't tar them or encase them in concrete. Only time we used concrete was when we were in a swamp and the ground wasn't firm enough to hold the pole in place. We have swamps that we have to actually take boats out to work on poles in the wet season and they don't rot. The old cedar and event he old creosote but treated poles were lucky to last 20 years. Only thing we didn't like about them was in the winter they would freeze and be hard to climb. That and if you cut out and slipped down one the slivers would burn so bad theyd about make you cry! Ask me how I know

[RU shooter]

Option #3 plastic wood made from recycled bottles and stuff . Never gonna rot, most all lumber /home improvement stores sell it

[shooterg]

Older pressure treated wood(pre-2003 or so) was really longlasting stuff - but since then most pressure treatment is different(no arsenic compound) . The government saving us again...

[CastingFool]

A tip I picked up from a guy who had a side business building decks for people, was to set the posts in the hole, which would have 3-4 inches of gravel in the bottom, then dump some dry cement mix in the hole. The dry cement would keep the post from shifting, no cross bracing was needed, and you could start building right away. No waiting till the wet concrete set up. The dry cement would suck up moisture from the ground and harden up. If putting up a chain link fence, I would still wait a day before installing the fabric, because you do need to stretch it tightly, which would create some side tension. You wouldn't have to worry about side tension on a deck installation.

[MT Gianni]

for 4 I would go with concrete sonotubes under ground and treated sitting in a stirrup in the concrete.

[higgins]

I had redwood deck posts rot in not that many years. Go with PTdeck.

[rancher1913]

depending on how high the posts need to be out of the ground, maybe some number 1 grade railroad ties, if you need long ones, look into switch ties.

[jsizemore]

Ground contact pressure treated still has that arsenic. Tag on the post will say CCA. My state won't let me build on redwood stuck in the ground.

[Duckiller]

So. Cal. Edison stopped using creasote poles and went to pressure treated of some chemical. After a few years these poles were dropping power lines on freeways. They now have a program of regularly checking poles. If a crew finds a pole seriuosly rotting then an emergency call goes to the yard to bring out a new pole and they stay with the rotten pole untill the new pole arrives and it is placed. Suggest you talk to your local building and safety dept and see what they recommend. They see a lot of installations and know what works best in your area. They won't want you to build something that will have problems in the near future.

[BamaNapper]

Home Depot sells post protectors that look really promising. They encase the wood below ground and keep the bugs and bacteria away from it. I haven't used them but have been eyeballing them for a fence I need to replace. By looking at the literature on them I even wonder if the post could be pulled and replaced years later, leaving the protector in the ground.

I'm betting our fence posts here in AL don't last nearly as long as yours in NV.

[la5676]

Ground contact pressure treated still has that arsenic. Tag on the post will say CCA. My state won't let me build on redwood stuck in the ground.

I don't think there has been any CCA lumber for consumer use for quite a while. EPA restricted it's use pretty severely back in 2003. ACQ is what is marked on almost all lumber now. Alkaline copper quat, whatever the heck that is.

[dbosman]

Look for stapled on tags that detail the Ground Contact warranty.
It isn't what it used to be, but we take arsenic more seriously now then in the 1990s.
Don't paint or coat the bottom of the post. It only seals water in, not out. We put used, pulled, railroad ties for fence posts in the 1970 that are still intact.
As others have said, gravel, or at least one decent size rock at the bottom of the hole for drainage. Tamp the dirt or soil in with something small enough to take forever (in a kids mind) to tamp around and after every shovel full of fill. Plan on moving before you'll need to do it again.
I keep outliving my doctors and fence posts. It's the darn fence posts that irritate me the most.

[Beerd]

"redwood" today ain't what it usedta was.
..

[Gofaaast]

CCA has been gone since the early 2000’s, arsenic you know. ACQ (Alkaline copper quaternary) replaced it. I am assuming your in a dry climate so rot won’t be that big a deal. Redwood is good stuff if solid and affordable. I reused some rw 4x4s from fences that had been in the ground 20 years in a wet climate that outlasted new cca 4x4’s.