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In planning our cabin project we need to use a post foundation. Is it ok
to use treated posts sunk into the ground? If we do how long can we expect
them to last? We’ve heard of, read of and seen other cabins in the area
built this way with good results. We’ve been told by our builder that they
will rot and he strongly advises against it. The soil is sandy and well
drained.
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We do post foundations for some of our addtions..
normally a 4x6 SYP, treated to .060 retention,
the guy who says they rot, must have been using "landscape" timbers..
pressure treated foundations and posts are code approved.. and sometimes are actually the MOST APPROPRIATE ...
IMHO
*I've been using PT posts for years. Only times I have ever had a problem is when either the post hasn't had the opportunity to dry out or it was placed in unstable soil and moved. Just be sure it is rated for continuous contact and if you saw the end recoated or sealed.
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Ted,
I agree with Mike about the .60 retention. { 6/10 of a pound of chromated copper arrsenate per cubic foot of wood. There will be a tag stapled on the end of
the column indicating the treater's name, warranty, and cca rention in the wood. Make sure you don't buy any .40 ret. material for in the ground foundation or pole barn construction use. The landscape timbers Mike was refering to are actually the cores left over from peeling veeneers at plywood mills. They are normally only treated to .25 cca ret. and really shouldnt even be used for fence post, although many lumberyards sell them for that use. By the way, you aren't by chance
Col. Ted Buck of Air Force One fame about 25 years ago?
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Ideally a factory treated end of a .60 post goes into the ground. Any cuts are unlikely to be job site treated adequately. Anything other than .60 retention would not meet code to the best of my knowledge.
joe d
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Thanks for your input. I'm not that Ted, but I was a Capt Ted Buck
of C-141 fame in the Air Force 5 years ago.
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We've been doing some work on some beach cabin/homes lately, and all of the foundations are 12" x 12" piers, .40 CCA treated. They are buried 12' in the ground (as well as the base being in concrete) and seem to work fine. The foundation company that has done most of the pier work has been in business since 1890, and gives a 50 year warranty on all of their pier work. They tell me .60 around here is used for marine applications, or for direct, continous contact with water.
Here, .40 is within code, and lasts a LONG time.
As for the landscape timbers being the leftover core from peeling plywood veneers, at least here they are not. They are made at the same time, and at the same facility as the 4 x 4 and 4 x 6 treated posts. The leftover cores from peeling plywood veneers are sent to a chipper, and made into small chips for the paper mill (or for shipment to Japan).
By the way, we have 7 major lumber mills around here. About a week ago, the Louisiana-Pacific particle board plant had a major fire, and shut it down. They are debating whether to rebuild and reopen, or just leave it shut down. The other end of the mill still makes OSB, and it will continue operation. This is just in case some of you run into a delay in getting particle board, you will know why.
My question has always been - when cutting the end of a treated piece of lumber, whether it's a post or 2 x 4, what is the purpose of retreating the end? According to the manufacturers, the treatment is applied under about 600 psi, and penetrates to the core. If it didn't penetrate to the core, then it did not get fully treated, and should be discarded, or returned for a good one. It will not protect against insect infestation if not fully treated. I have found a few bad ones, and returned them. You can usually tell by the color of the wood toward the center of the board (after it's been cut). It will still be a light color, like the original wood before treatment, while the rest of the wood will be dark (greenish). Will the effort of retreating the end of the board actually do any good? Since treatment does not deter water penetration, only bug infestation, what is the purpose of retreating after cutting?
Just a thought...
James DuHamel
*when you get into 12x12 i think the code recognizes a different retention. because of the mass..(this is just a guess) most of the .060 as evolved from setting standards for pole barns, and treated wood foundationsas far as retreating the cut ends... i think it is right up there with green cuprinol... great eyewash but not much protection..we just make sure that the factory end goes in the hole and the cut end is up..if we are concerned about further protection.. we get a pest control company in and treat with Bora-care.
*Maybe recoating is just something we do "just because" and really doesn't have any benefit. It may be a hangover from creosote days when we would be sure there was a good cover over everything.In any case there doesn't seem to be any useful difference in longevity as long as the treatment is CCA. Something that is also common is wrapping the piling in 6mil plastic to prevent earth movement from moving the piling. I've seen this used both in permafrost country and in some unstable soils like in the Rocky's.It all seems to work as long as the site is drained well and the wood doesn't have to stay moist continously. Some of the foundations that were put in 30 years ago are still there I guess, at least the buildings on top of them don't look like they've moved.
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James,
Have you been able to tour any of the mills there? A year ago, before I started building houses, I was a retail lumberyard manager. Every year we would take our contractors on some sort of mill tour. We bought alot from International Paper and Curt Bean Lumber near your neck of the woods in southwest Arkansas in the Glenwood, Warren, Arkadelphia and Texarkana areas. IP takes an 18" to 20" diameter log, soaks it in hot water to make the veneer peel easier and reduces that 18-20" to 3-1/2" in 15 seconds. I can remember years ago some mills would resaw the larger peeler cores into 4x4x8's but most customers didnt like them because of the 4 radius edges left from the round peeler core. You have some drywall plants near you there too don't you? Make sure to check your treater's warranty concerning the use of .40 vs .60.....
AWPA standards allow for .40 for ground contact/freshwater use and require 2.5lbs for saltwater (.80 for piles in freshwater). Most of the treaters require you to keep all of the little tags on the end of the CCA material, retain your original sales receipt and will then replace the defective board or timber, less labor, naturally. You may see some dowelled in holes on treated material where the treater has taken a core sample to make sure proper retention was achieved in that particular batch. By the way, I thought TEXAS had to be spelled with all uppercase letters ? :~)
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In planning our cabin project we need to use a post foundation. Is it ok
to use treated posts sunk into the ground? If we do how long can we expect
them to last? We've heard of, read of and seen other cabins in the area
built this way with good results. We've been told by our builder that they
will rot and he strongly advises against it. The soil is sandy and well
drained.