Wood Pilings vs concrete pilings for coastal residential construction 1

[coastaldoug]

Curious which option is recommended for the construction of a 3 story home located on a salt marsh in South Carolina. The home would be elevated 10 feet with a completed height of 44 feet. I have talked with several "builders" and tend to get a mixture of opinions. Both methods are utilized in my area but have not found an overwhelming winner.

 

[SlideRuleEra]

coastaldoug - I am a South Carolinian; in the past, treated timber piling (for residential applications) have been used almost exclusively in the areas that you are describing. More recently, "heavy" structures such as waterfront condominiums and and hotels are using concrete. This may be the builders you are hearing from.

Timber piling work well in the soil (they don't need to be unusually long), they are cost effective, easy to cutoff, pile useful life is often many decades, and you don't have concerns about internal corrosion of steel strands/rebar. Timber pile capacity should easily meet residential loading requirements (including coastal wind & seismic).

http://www.SlideRuleEra.net

 

[coastaldoug]

Thanks SlideRuleEra.
The home that we are building will be about 8,200 sq ft under roof so support and ability to resist wind is crucial. We live behind pawleys island so debris is also an issue if a hurricane came through here again. You mentioned that the life of the pilings would be for "decades", what do you do when their life is coming to an end?

 

[SlideRuleEra]

Pawleys Island - have been going there since I was born, including last month. Guess the home will be just off the south causeway, down the road from the Food Lion. Hurricanes Hazel (1954) and Hugo (1989) did make a mess there but most houses on the mainland (your area) survived. As you have noted, substantial debris from the island could come across the marsh - but that would be a direct hit from at Category 4 or 5 storm.

As for timber piling lifetime - CCA treatment has been restricted for residential use, but should still be available for piling. Treatment with 0.6 lb/ft^3 is normally considered "permanent" - permanent being, say 50+ years (and probably a lot longer). If your have longevity concerns, consider going to CCA treatment of 2.5 lb/ft^3, differential cost would most likely be one or two thousand dollars for piling need for that size house. That level of treatment (2.5) is usually specified for continuous salt water exposure. For your application, pile useful lifetime should be several family generations.

For general information on pile lifetime and other issues, go to my website (link below) and download documents from my
"American Wood Preservers Institute" page. These old articles address creosoted pile, but in my opinion, CCA is just as good, or better - it has just not been in use long enough to have a century of experience behind it.

If you have specific questions, you can contact me thru the email at my website.

http://www.SlideRuleEra.net

 

[SlideRuleEra]

Forgot to mention that impact from debris is addressed by "breakaway" construction under the house. I have not checked, but your location is almost certainly in the Coastal "V" zone where these features are required.

http://www.SlideRuleEra.net

 

[BigH]

Well, SRE knows the South Carolina better than I, but they also use timber piling in New Jersy coast and in the Vancouver areas. Also, as you will see from his site, lots of wood piling in New Orleans. Sadly, some of the houses may be damaged, but the piling wouldn't be.

ps - by the way - nice size of a house!!