Timber Pile Installation Criteria

[AndBre44]

Hey all, just looking for some general information/guidance as I look into some information regarding timber piles. I have a client who's building a home near the coast with poor soils from grade to approximately 17 feet below grade, and groundwater present around 10-12ft below grade as well. Typically when I've had sites with poor soils I've always defaulted to using drilled helical piles, however the client came back asking for a recommendation for timber piles as well, and I can't say I have a strong familiarity with them.

I've looked through and read up on the following document from the Timber Piling Council (

https://preservedwood.org/portals/0/documents/TimberPileManual.pdf

), as well as a couple of scattered papers, but just wanted to put a general inquiry out there to if anyone else may have other suggested resources I could take a look at, or even just some good rule of them design recommendations from those that have done it before. Thank you to anyone who has any insight/suggestions to share on the matter.

Warm Regards,
Andrew

 

[SlideRuleEra]

See "FEMA Coastal Construction Manual", starting with Section 10.5 "Pile Foundations". This document covers much of the information you need to consider when using driven timber piling.

 

[JedClampett]

This might help, although it's more oriented toward marine structures.

 

[BigH]

Check:

https://intrans.iastate.edu/app/uploads/2018/08/graha96a.pdf

file:///C:/Users/User/Desktop/Download/TimberPileManual2016FINALPublished.pdf

There was a really good book with a number of "case histories" that I had years ago - if I find time, I will try to find it. One thing that might be an issue with wood piles is if the water table fluctuates. Timber piles do no behave well in a wet-dry-wet scenario. Years ago, an industrial building in Vancouver area which was on wood piles had one exposed to see its condition. After inspection, they backfilled and then a year or so later, reopened and found that the wood pile had deteriorated. In the 1986 Expo in Vancouver, I recommended untreated wood piles as the piles had to be pulled/removed in 1987, They worked well - also replaced steel pipe pile design in Sault Ste Marie Ontario with timber piles. They worked well. Do remember, if my memory serves me right, the Swedish parliament building was put on wood piles back in the 900s - and still behaving well.

 

[DanielSgeo]

Timber piles are pretty common here in the Pacific Northwest. Sometimes we use untreated piles too, but only when they’re permanently below water or buried by more than 6 to 8ft of soil to promote anaerobic conditions, and not a marine environment. These untreated pile are more for ground improvement (rigid inclusions) where we don’t have a structural connection between the pile and foundation.

Typically we design timber piles for an allowable compressive bearing capacity of 20 to 40 tons depending on application, and even in poor soils (SPT N ~ 2) we can get 20 tons with a 40 to 50 ft stick. In a structural foundation application, We almost always are using them as friction piles, but for your low load application end bearing would probably be fine.

You can drive a Douglas fir pile up to about 80 to 100 tons before they start exploding during driving (that’s pretty exciting). If you add steel straps at the butt and tip, you can drive them to 150 tons.