Length of grade beams on piers
Length of grade beams on piers
(OP)
I am designing a grade beam on helical pier foundations to carry a 2 storey residential building on a site with 15' +/- of fill. I have designed concrete beams for lintels & suspended floors before and am looking at a similar design for strength to carry my loads but 2 pier contractors I have talked to say my spacing is longer than they usually see. I am 14'-16' in different areas but one guy says average 8' & the other says 10'-12'. I want to keep the grade beam only about 3' deep & I also want to minimize the number of piers. Do you see any problems?





RE: Length of grade beams on piers
I know that sounds a little harsh but...Part of their mindset may be stuck in selling piers and you have proposed a significant reduction in their product.
For example, I have been involved in a number of residential underpinning jobs (expansive soils) which the existing stemwall/gradebeam was adequate to span 14 to 20 feet and I generally placed the piers from 10' to 16'. The contractor tried to talk me into shorter spans. That is what their books say. I looked at their books and the assumed construction was for grade beams which could only span 8' to 12' and sometimes a little less. I am also afraid the contractor had hoped for a higher product volume job.
RE: Length of grade beams on piers
Most helical piling are spaced 6 to 10 feet due to either limitations in the pile capacity or concern over the spanning capability of existing structure.
RE: Length of grade beams on piers
I did a helical pile foundation for a PEMB about 10 years ago that had a structural slab, and found that I needed the pile grid at 10 feet each way with the slab loads seen. Otherwise the slab thickness got too great, overloading the pile.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Length of grade beams on piers
RE: Length of grade beams on piers