Need advice how to fix this mess: soil under the footings is soft

[rustyshakelford]

I gave my opinion because soils vary greatly from area to area, state to state and country to country. What would work here in Texas might've completely wrong for you in Canada with frost heave or whatever else you cold weather guys have to deal with!

Brett

 

[Oldoak]

You are certainly on the right track. Digging deeper and adding a foot of compacted#2 or even "pea" gravel. I would also add a loop of drain tile with an outlet leading to daylight. Definitely wouldn't hurt and much easier, at relatively little additional cost, to incorporate now rather than later.

This is basically what is done in preparation for setting prefabbed concrete walls for residential homes in my area.

 

[Loaderman22]

I'm in the residential building trade, & I'm glad you are having an engineer view it. Look at it this way, it may cost you a few hundred now, but if you do what they say & it fails, you can go after their insurance. Litigation is not the ideal scenario, but this is what they are trained for.

 

[boggen]

tossing rock under it all and going thicker and yada yada.

but how are you going to deal with "french drain" setup and the sump for the sump pump? do you have an area were you can run water further down hill than bottom of basement?

are you just going to deal with french drain setup on the outside? or also put something just on the inside of the footers to help pull any extra water out?

checkout basement "de watering systems" for already built homes. along with french drain setups.

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also checkout different types of "water proofing" for the exterior of the basement sides that are below ground. from tars, to roofing liners / pond liner.

i am edgy about poured concrete walls with water proofer agent added to the concrete. there will still be some stuff sticking through wall most likely to hold the forms in place and set the thickness of the walls. the patch job after words may still be an issue of water coming into the basement.

i am edgy about "paint on water proofers" each type is different in how you PREP the concrete wall / concrete block wall. if you mess up the PREP the paint blisters and peels. read the directions and verify with manufacture. dust, to how long stuff has cured, to possibly mutric acid washing, to possibly some sort of primer may be needed. again water proofing paints all differ.

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general rule of thumb. only dig down as far as you need to never more. or have more issues of compaction/settling issues.

wet clay soil = slip n slide. if to wet it just gushes and does not really compact.

 

[RickB]

Really appreciate if we can stick to the topic of this thread.
Thank you for understanding.

p.s.: Personally, I respect and appreciate any suggestion and advice from this community and not treat them as "amateur unverified and semi-anonymous advise" otherwise I'll not be here.

My response is directed exactly at the topic of this thread. You solicited opinions. You have mine, like it or not.

 

[Streetcar]

Old oak made great suggestion with h daylighting pipe to drain current and future water

 

[Cord]

You can pour under water, but not on mud. If you over excavate, perhaps you could try pouring a mud slab? This is low strength concrete that doesn't have a structural strength, but is intended to provide a solid base for the structural concrete. Being concrete, it won't shift and settle like gravel which would be my concern it being under a footing. All you need is 2,000 psf (vs 4,000 psi for structural concrete) to provide residential bearing capacity. The mud slab doesn't need a particular thickness but it should be 2-3x the width of the footing. The big advantage is that once the concrete sets, you'll have a nice surface to set footing forms on top of. Often lean concrete is used for this purpose (600 psi), but I'd suggest using 3,500 psi concrete because the excess water will weaken it.

I will say that your photos don't show much for mud. The excavator would only need to scrape off a few inches to get to final grade. If this can be done the morning they start setting forms and can stay off the footing footprint you might be ok.

I agree, you are probably dealing with a perched water table. Because you have a walk-out basement, I'd suggest directing the drain tile to daylight so it can work continuously.

 

[quicksandfarmer]

A soil expert should be able to look at the soil and tell you if it is below the water table, seasonally inundated, or soil that is normally dry that happened to get wet. They have distinctive looks. Here, a septic field has to be in dry soil, a soils guy comes in for every installation and makes an assessment. They do it all the time and it's not expensive. I would think you're asking for trouble building a house in anything other than dry soil.

 

[Tractor Seabee]

These type problems are encountered here in the Puget Sound area often. The State and Counties are now getting gun shy of lawsuits when they approve a permit application and things go south. All new houses now have to have an engineered foundation sealed and signed by an engineer of record. Part of that is backed up with a geological data report and also addresses storm water runoff solutions and/or remediations. You are on the right track getting your architect in the act. I know architects who have decided you go back to school for engineering courses so they are more aware of site issues. Their license doesn't cover site engineering issues.

LOL, Ron

 

[Redlands Okie]

Several good idea presented so far. But your comment on a engineer showing up with the architect is your best bet. You need to pour on compacted or virgin soil in general. Gravel and drainage are good factors in general. No information if your pouring footings only or a concrete slab which if poured correctly can help spread the load. Footings on interior load bearing walls are a factor to keep in mind. Lots of rebar helps in general. As pointed out you can build almost anywhere. Heck homes are built on WATER that float on a concrete base. It's not a matter of IF it can be done, it's a matter of how to do it correctly and what is the cost. So hopefully the engineer knows his stuff. This may not be the web site to gamble your life savings on but it can be a great site for ideas and that seems to be what your after