What to ask/look for in soil test for new foundation 1

[greg9504]

Hello,

This coming spring I plan to build a new garage/barn, 26'x50', with 10' high 16" deep stone walls (not a stone veneer). I am currently going through a minor variance request to allow the barn to be built to the proposed height. After I receive the variance, I can submit my building plans for the building permit. In preparing for the building permits I am going to have the foundation designed by a structural engineer. Because of the weight of the stone walls I am a little paranoid about settling, so I would like to have a soil test done to find out the load bearing capacity and drainage characteristics. The foundation will be below the frost line (about 4'-5' feet here I believe).

What should a geotech firm do for a test?
Bore/dig to below frost line take sample there or deeper?
What should I look for in the way of tests performed?
What are acceptable methods?
Does time of year matter? it is currently early winter here (Ottawa ON Canada). Ground is not frozen yet, but may be by the time the test is done.

I've searched posts on here but was left confused as to what I should ask for. I don't want to get a $75 hand probe test done thinking that's all I need, but I also don't want to spend thousands on tests which wont be of much help.

Thanks.
Greg.

 

[BigH]

Greg: As a geotechnical engineer, I would suggest that you find one and let him propose to you what he intends to do. Normally, we will lay out the program that is necessary and provide the estimated costs (usually a function of on site drilling time), prepare a report. Most of all, with the good firms, you have senior people overseeing the juniors (so as a junior will likely write the report - he's cheaper to the company - good firms have, in place, their own in-house review system. And, they have professional liability insurance if something goes wrong which is in their purview. Now, for $75 probe - what will you get - certainly no help if their is a problem. (Don't hire a drill firm to bore a hole and then give you a log - and walk away). I say this because Ottawa has, in places, some pretty bad soil - Leda clay (also Champlain Lake clay) and your rock walls will be a bit heavy. I wouldn't mess about.

 

[ctmtwilliams]

Much like BigH said, if you let the Geotech know the scope of work, they can develop a work plan that will properly fit the needs of your project. Additionally, after you have the geotechnical work done, then the structural engineer properly design a foundation to fit the site conditions described by the Geotech. I personally would have at least two (preferably three) Geotechnical firms bid on the project and evaluate what they propose.

 

[BigH]

A lot of people love to have three or so geofirms (and sometimes even as many as 5 or 6) bid on small projects (and, sorry Greg9504 - your project is a small project although potentially a tricky one). But, in general, in competitive markets, the savings of one firm over another is relatively small and, at least, now, relatively inexpensive (I've discussed 1960 prices with 1995 ones in a previous thread). Just think of the wasted money by 3 or 4 or 5 firms who put together their proposal and lose. Sure, individually, they might not lose that much, but the drain collectively is outlandish. Greg - I would discuss with some local civils you might know - or a developer in the area - then pick two medium firms (not the biggies) and request they put together a proposal. As a background, you can dig out the surficial soils maps of Ottawa area to determine the most likely soil stratigraphy to be encountered - then you might be able to ask some reasonable questions to your alternative firms as a check to their responses. If both firms give a similar programme, you should be fine. Let us know - and your structural engineer can help too so long as you have him retained prior to the geo work.

 

[fndn]

If this site currently has other buildings on it, then you may try to dig up info and see if they ran into soil problems. Also if you have neighbours, find out about their foundation construction experiences. If everything is ok, then you can hire a smaller firm, and call your excavator and do test pits say 5 meters deep at two diagonal corners.

If all is well with the test pits, and you have clayey soils, you may ask your structural engineer to design a "trench footing" It is more suitable and costs less.

If the test pits reveal poor soils, despite the previous structures history, then call for two soil borings and a geotechnical report.