Expansive Clay soil & existing 1953 basement.
Hello all,
My 1953 home is in climate zone 6A
And is in clay soil. We get a lot of snow in the winter and decent rain in the summer. My home has a full gutter system that runs into a underground pipe system leading to a pop up in the back yard. It has a few issues with water getting behind the gutters which will be fixed soon. I have no exterior or interior drain tile & no sump pump.
My basement walls are cracked in many areas and two of them are leaning in at the top. I discovered the sill plate had never been anchored to the walls at all which has amazed the foundation repair men I am getting estimates from. I suspect it may be due to the exterior decorative rock mortard to the visible part of my foundation that I have no water entry issues. My neighbor across the street has a spring that comes up just at her foundation and so runs a sump pump continously! I worry what that means for the future of my basement & shifting underground watert
The basement is very humid as it is a old post war build. There is no exterior insulation, no poly sheet below the floating slab, no gravel below the slab either (this I know because of the basement tub has pipes running into a dirt filled hole) and i suspect the foundation does not contain rebar as my neighbors home proved to be rebarless- the foundation repair men suspect this to be true as well.
All but one foundation company is giving me bids to patch cracks & reinforce my walls alone. One company, is bidding to dig out the exterior of these two walls, straighten & reinforce walls, patch cracks & add waterproof membrane, add exterior draintile & a interior sump pump.
I will choose the company who will be doing the dig out. I also want to add exterior insulation as they’ll be exposed anyway but i need to talk with the contractor about it, likely me doing it myself to save $. I also need to discuss radon mitigation with him as well.
His inital explanation of layers of gravel above and below the pipe and such was less that what i read our municple code requires… Which leaves me assuming not many people here opt into the full go as I want to. (We are not a rich community) and then he said they would backfill it with the same dirt they removed.
I am no expert & only have a little google info but I feel like something better can be done than to refill the trench with the same clay dirt. I need very much to keep expenses down as low as safely possible! But should something more be done? Refill and top off with different type of dirt or something?
Any opinions on waterproof membranes? Dimple mat vs peel & stick vs brush on?
Id love your advice or links to columns. I admit I am tempted to DIY this but I’m 90% positive I’ll leave it to the professionals.
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Replies
Not all clay soil is expansive. Are you sure that you have this type? I've seen details that call for a partial backfill with sand but using clay for the last couple of feet. The clay helps to prevent bulk water from seeping into the soil.
If you plan to have your perimeter dug, take the opportunity to look at how water moves through your property. You may want to regrade some areas.
Yes I am sure it is expansive. And I need to regrade around the home. I am not sure what you mean by how water moves through the property? If you are speaking of surface water that I understand and will be improving with regrading around the house. Refill with sand?
There is no expansive clay near me, so I'm not familiar enough with it, but it has cracked your foundation once, I would not backfill with it.
As for water proofing, unless you have major ground water you are trying to keep out, standard roll on dam proofing+dimple mat is good enough. One option if you are also insulating is to use grooved EPS foam and skip dimple mat. The grooves on the foam similar purpose as the dimple mat.
Thank you so much Akos!