Foundations and weird water table

[eclecticcottage]

Greetings!! Sorry for the long absence. We needed a break after finishing the Bungalow, then I ended up back full time and life happened.

So, we are finally ready to tackle the cottage disaster. It has no basement. Floors are out due to a lot of water infiltration issues. The middle of the floor used to rest on a line of cinder blocks with no foundation below. So, we want to put in piers. Now this causes a few things I need to discuss with y'all.

Dirt isn't super deep, it gets to clay pretty quick.

There is a sump hole (@ 30" deep) with trenches ranging from a few inches to about a foot at the sump hole.

#1: I can't find a guide to how deep the frost line would be inside of a structure. I want to dig the piers deep enough, but I can't figure out how deep, deep enough is!! I don't want them to heave. I can't really say the cinder blocks ever did, but they did sink into the dirt a bit and eventually became kind of wavy.

#2 We started drilling 6" diameter holes (because that's the size auger we had, we are discussing enlarging them but we have a complication). We drilled 12 holes. 4 down the center and 4 on each side about 2 1/2' from the outside wall foundation. The outside 8 holes were just to help keep bounce out of the floors. Here's the part where it gets weird, even for an old house. Like kind of defies what I know of science. Some of the holes have standing water, some do not. Weirder yet, one hole has about 28" of standing water, only about 2' from the sump hole with 1" of standing water. So that hole has about 17" MORE water. The surface is dry, it didn't run in the house and into holes. The water level varies in all the holes. Water seeks it's own level, right?? Except in that house?? How is that possible??

[Gothichome]

Good to see you back posting. Only thing can I think of is density and the make up of the soil is uneven. Your sump hole might have more clay in that particular spot acting as a barrier.

[cgutha]

Not completely sure of your construction, However, the holes inside the house should be the same depth as the perimeter. Because you are on clay, make your holes large. clay compresses forever, unlike gravel which compresses for a few inches then is solid.
As for the water table: clay might have small capillaries which wick the water. This might mean the compression strength varies from hole to hole. That is in general. I do not know your ground.
ceg

[eclecticcottage]

Thanks guys! It's the weirdest thing I've seen-each hole seems to have different water levels. And I thought roof shingles as siding on the Bungalow was odd lol.

As for the actual foundation construction-I'm not 100% positive, but I believe it is 2-3 layers of cinder blocks, that's all. I know it's at least two, but can't tell if there's a third layer. I assume the point of keeping it all the same depth would be even levels of movement in the event there is heave?

Also, secondary question since I've looked into the concept of foundation depth and movement. Since we already dug the holes to about 10-14" deeper than I believe the exterior foundation sits, we probably need to remedy that. Options we see: fill in with dirt (no way to compact, so least preferable), fill in with stone or fill in completely and move to adjacent locations. Thoughts on those?

BTW, I've missed this. Thank you all for being here and talking old house stuff!!

[awomanwithahammer]

EC, so good to have you back. I wondered where you were and how life was going. I don't have any words of wisdom to contribute, just wanted to say hi!

[phil]

at my parents place they have clay soil. we dug a well near the lake and it finds a different level than the lake. its higher and the water is clean and pure but has a lot of minerals and not a lot of life , like the lake water does, which is also safe to drink. we concluded that our well is fed from underground springs near the lake which is ideal. Its very undisturbed there, the mountains above are all crown land used only for ranching. when we dug the well we hired a huge backhoe and he couldn't scoop the water out fast enough to depleat the source and it's never run dry so we lucked out on the location. previously we drank lake water but the well water is more clear and tastes better. Its similar to the bottled mineral water.