Wood Piling to Continuous Footing Connection

[rpeng]

I am building a two story coastal home on timber 8x8 pilings. The blow count was inconsistent, between 6 and 20. A local engineer recommended using an extended concrete footing (width of 12", depth of 16" between the pilings with (4) x #5 rebar passing through the pilings. I have read on this site and others that the concrete should be isolated from the pilings, or that mecnahnical connectors should be used to transfer the load.

 

[msquared48]

Normally, a concrete pilcap is used over the piling and the grade beam rests on top of the pilecap. The pilecap is large enough to cover the top 6" or so to keep the alignment, and the pile is either treated wood, steel, or concrete. There is also vertical rebar from the pilecap into the grade beam.

Just having a grade beam of the size you describe will not be sufficient in my estimation.

Mike McCann
MMC Engineering

 

[Splitrings]

Your concern is decay of the timbers do to moisture at the concrete interface? You will get several opinions on this forum. Your piles are likely treated to a UCS level of 5A-C which will likely be 1.5 pcf of CCA. This is twice the level of treatment that was once available to the general consumer. A lot of folks try and compare the longevity of a PT 4x4 mailbox post they bought at a home supply store that rotted and fell over in two years to products such as your piles. They aren’t anywhere near the same. The 5A-C treatment assumes continuous exposure to moisture. Your best bet would be to speak with a pile supplier in your area. It may help ease your concerns.

 

[msquared48]

The reason for the strip footing is to spread the load between the pile should any settlement occur. He was concerned with the blow count difference as related to the individual capacity of each pile and the load seen by each pile. The grade beam should have continuous top and bottom steel too.

Mike McCann
MMC Engineering