Anyone notice this a lot on foundation drawings now?
Anyone notice this a lot on foundation drawings now?
(OP)
Lately, I've seen a lot of foundation drawings that have some kind of note like "Bearing capacity of foundations assumed to be [something low] ksf. Geotechnical investigation should be conducted by licensed professional to assure this assumed bearing capacity is adequate." Or something along those lines.
In other words: we couldn't/didn't get the geotechnical investigation (9 times out of 10 the owner doesn't want to spend the money).....but we need the foundations anyway.
Would this fly if something went wrong? I know the code has presumptive load bearing values, but I've never been sure if running with that or not would be ok.
In other words: we couldn't/didn't get the geotechnical investigation (9 times out of 10 the owner doesn't want to spend the money).....but we need the foundations anyway.
Would this fly if something went wrong? I know the code has presumptive load bearing values, but I've never been sure if running with that or not would be ok.






RE: Anyone notice this a lot on foundation drawings now?
The3 drawings should state the "design" bearing pressure, and state whether or not a Geotechnical report was available and used.
Mike McCann, PE, SE (WA)
RE: Anyone notice this a lot on foundation drawings now?
If your design values are within the generally accepted range for the area (Around here the AHJ has a maximum value that they accept without a geotechnical report) then I believe yes it flies. By that I mean the liability for the failure at that point is shifted to the owner/contractor. Your name will still get dragged through the mud but in the end I can't see it affecting your registration. If you refused to do work on every job without a soils report you would likely go out of business.
Mike, if you don't have a geotechnical report then what do you call the value you choose? It is an assumed value. Call it an educated guess if you would like but I don't think that sounds any better.
RE: Anyone notice this a lot on foundation drawings now?
No it would not fly if the number you used for design was outside the generally accepted value.
RE: Anyone notice this a lot on foundation drawings now?
No. It is a design value based on the IBC.
Mike McCann, PE, SE (WA)
RE: Anyone notice this a lot on foundation drawings now?
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Anyone notice this a lot on foundation drawings now?
RE: Anyone notice this a lot on foundation drawings now?
Me too (especially if a site was landfill at one point).
RE: Anyone notice this a lot on foundation drawings now?
The downside is that you don't know how bad the soil is. It could be fat clay or crap fill.
When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.
-R. Buckminster Fuller
RE: Anyone notice this a lot on foundation drawings now?
No. It is a design value based on the IBC.
Mike McCann, PE, SE (WA)
RE: Anyone notice this a lot on foundation drawings now?
Maine EIT, Civil/Structural.
RE: Anyone notice this a lot on foundation drawings now?
The AHJ does require reports for the majority of new commercial construction however in a retrofit/reno situation they are usually willing to accept assumed values provided they are below a certain range (around here it's 1500 psf for end bearing and 250psf skin friction)
RE: Anyone notice this a lot on foundation drawings now?
Mike McCann, PE, SE (WA)
RE: Anyone notice this a lot on foundation drawings now?
You we get the liability, somebody else gets to pay for that liability.
My 2 cents.
RE: Anyone notice this a lot on foundation drawings now?
State the design bearing pressure and perhaps the allowable differential settlement, reference the geotechnical report if available, and qualify that the engineer is to be contacted if the criteria cannot be achieved. I think that the use of "assumed" or "presumed" gives the impression that the GC or the Owner are also allowed to assume and presume. The responsibility of the Owner/GC to meet the design criteria or notify the EOR should be clear.
RE: Anyone notice this a lot on foundation drawings now?
As a side note...long ago, I worked part time for a company that did trackhoe and dumptruck work. That work included demolition. At some point, they bought some property a couple of miles out of town. This property had a pond on it. So for a couple of years, any concrete or other rubble that got demolished, got recycled as gravel or fill or riprap. But any wood that got demolished went into that pond. Until there wasn't a pond, that is. So somebody sometime is going to be wondering "what's under here" and what's under there will be eight feet of rotten wood.
RE: Anyone notice this a lot on foundation drawings now?
I find the larger the project the more likely there will be a report. Unfortunately I sometimes design small metal buildings (2,0000 square feet to 10,000 square feet) where the client does not want to pay the extra money for the report. So something needs to be done in this instance. On rare occasions I have refused to provide design services if I know the building is in a low area surrounded by wetlands and the owner refuses to get a report done.
RE: Anyone notice this a lot on foundation drawings now?
RE: Anyone notice this a lot on foundation drawings now?
Too many owners just want a finished product, but not pay for anything. I design precast bridges, and get the same thing, "what do you mean you cant put a 42' bridge on 1500 psf soil with 6' of cover over it...thats good soil, I built my garage on it last year"
Cover your ass, and if you need to walk from the job, do it.
RE: Anyone notice this a lot on foundation drawings now?
RE: Anyone notice this a lot on foundation drawings now?
This statement on the plans is like an indemnity clause in a contract....its entire purpose is an attempt to shift liability. In this case it will work, unless their presumptive bearing capacity is outrageous and wrong. Contractor beware.