Raising a foundation corner stone (Log cabin)

Sodo · Apr 20, 2015

As you can see I have raised this corner once, but not enough. It seems to have settled out, seems to be not moving anymore. (?) I want to jack it up *** and it's rock too *** and pour some thinset under it without disturbing it (much). You can see how much I jacked it once (3/8), that was not enough, it needs to go about twice that much 3/4". I'll remove those shims. What I'm using as a "gage" is the front door - when it's straight in its jamb I will call that good enough.

I want to preserve the "rustic nature", won't do anything that changes the appearance. Certainly not pouring a concrete footing which is the obvious solution but it wrecks the aesthetics. If it doesn't look 100 years old I aint doin' it!

Ideas to lift that rock so I can pour thinset under it?

oosik · Apr 20, 2015

Honestly, unless you get something under that rock that goes below the seasonal frost line and stabilizes the rock - this will be an on-going, never ending battle.

I would lift the logs enough to pull out the rock - dig a hole to below the frost line - fill with concrete - let it harden - replace the rock - shim if necessary. This entire process is possible without changing the appearance.

Sysop · Apr 20, 2015

What we've done in some places to preserve our pre-civil war barn (also a log structure) is raise it up a bit more than it needs to go, dig the area out a bit (make sure you find a hard bottom), pour concrete in the hole to provide a base for the stone, let that set up. Set the stone in/on the concrete at the level it needs to go, continue filling (while keeping it below the natural grade of the land), and let everything set up. Once the concrete sets, lower the building onto the stone and cover the concrete with dirt around the rock as always. It isn't the way to stay totally original, but it is a way to appear original and it seems to last a long time (I first remember seeing this done nearly 40 years ago and it is still holding fine... One of our issues was groundhogs tunneling and then the tunnels would collapse, lowering parts of the barn with it. Everyplace this has been done that issue has stopped...

If you have issues finding a hard bottom you can hammer a few pieces of rebar into the ground at various angle with the tops sticking up into your hole to be covered with the concrete. With some planning and proper rebar placement you could have the rebar support the rock in the position it is supposed to be while filling with concrete. I haven't done that or seen it done, but it was recommended once that I'd overheard.

oosik and I must have had the same idea and been typing at the same time and his post reminds me

You can generally tell the frost line by the texture and how compacted the soil is. Generally the freeze/thaw cycle breaks up the earth and it is softer than the earth below that doesn't go through the freeze/thaw cycles.

Sodo · Apr 20, 2015

Thanks for that tip how to find the soil line where it hasn't cycled. I've done the rebar thing you describe, to anchor a small building on a steep slope. Its only been 3 years but all is well.

What you (both) describe is how I want it done but honestly its only been this one corner so I devoted an afternoon to it (a 6 hour afternoon) and I am beat. Working in a 14" crawlspace man thats hard but I think I got it. If it becomes time to do it with regard to the frost line I want all the rocks to bear out below the frost line. For now it seems prudent that they all should float ontop. Luckily no evidence of burrowing animals!

I used ratchet straps to tie the rock up to the cabin tight, then jacked it 1/4" higher than ideal. So there was a 1" space below the rock. I filled that with thinset. Its curing now and I'm sitting on the porch!

Thaks for your attention!