Replies

1. 
   Guest_ | Jun 12, 1999 02:10pm | #1

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   What type of timber? Is there drainage behind the wall or will water sit there and encourage fungus and rot? Some pressure treating will penotrate through to the centre, again this depends on the species. Here in Australia we use mostly hardwoods and the preservative will only penotrate the sapwood.

2. 
   Todd_Gamble | Jun 13, 1999 08:51pm | #2

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   When I use pressue treated lumber for retaining walls I offer the customer the option to wrap the embed portion with bituthene. I also use it on the back of the wall. It seems to keep critters and water away nicely.

3. 
   Guest_ | Jun 14, 1999 05:48am | #3

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   I haven't seen too much of it here recently, but there used to be a few landscapers in my area that coated both the buried portion of fence posts and the back sides (front and bottom as well if concealed) of the timbers with tar.

   A five gallon bucket of it and a roller would do the job. A bit messy at times. It could raise questions over petroleum products in contact with the earth if that's a concern to you or the homeowner.

1. 
   Guest_ | Jun 14, 1999 09:35am | #4

   *Twenty years ago I did landscape work and have found that the timbers that I bought and installed that were the most expensive are just now looking a little shabby. There are a lot of really poor quality timbers sold. If the wood has rot in it, even with pressure treatment, it will not last. the decay will continue.I subcontract the tree work from several landscapers and nurseries and they very rarely put in a timber wall anymore. The interlocking concrete systems have pretty much become the standard. Better qualaity control, better material that is longer lasting too.Tom

4. 
   David_McWethy | Jun 17, 1999 07:16pm | #5

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   You asked if a true ground-contact pressure-treated 4x4 is "green" all the way through. Nope. It's only green in color if it's treated with CCA (chromated-copper arsenate) and then the penetration will be significantly more through the end-grain than through the sapwood of the walls. The best is kiln-dried before being pressure-treated, and will be stamped some variation of KDxx. In all cases, however,and particularly where the wood is southern yellow pine, the chemicals will not penetrate the resinous heartwood, so if you have to cut a treated 4x4 to length you will have exposed end-grain that is at least partially untreated. What to do? If you can, stand the cut end in a can of 10% pentachlorophenol wood preservative overnight. The end grain will soak up this liquid and provide just about as good a protection against rot as the original uncut 4x4. Be VERY careful with 10% penta, however: It's nasty stuff and should be handled only with a NIOSH respirator, rubber gloved, goggles, and no rubberneckers or children wandering by....

   Contact me directly if you have any more questions.

5. 
   tgordon | Jun 17, 1999 07:16pm | #6

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   Two questions:

   (1) Has anyone ever used "landscaping" 6X6
   timbers for use in a short (~2.5ft) garden (i.e. non-critical) retaining wall? (Landscaping timbers are the rough cut timbers with a true dimension of 6"X6" as opposed to a ground-contact smooth cut timbers that have a true dimension of 5.5"X5.5".) Since in a short retaining wall, I'm not using it merely as mass not as a structural member, I was wondering if I could use the cheaper timbers. If anyone has ever used them, how long have they lasted?

   (2) Is a true ground-contact pressure- treated 4X4 timber green all the way thru? Or can be green on the outer 1" or so and appear yellow on the inside? (I'm trying to settle a difference in opinion between lumber yards.)