Structural problems...

[Chuck Leeper]

The floor in my house is sagging to the point that the walls are cracking, and the bedroom door won't close.
I've purchased 6 ceiling jacks, [16,000# cap], some 2x10's for added beams, to address the problems.
[The idiot that built the place set a stone FP on the floor, and added no additional supports.]
The house showed no outwardly signs of problems until I moved my entertain center in. The "balance" was tipped, and things headed to the crawl space..
The ??'s
1. Once the jack locations are determined, what should I use for a base? Ideally, it's a poured foundation, but that's pretty much impossible, due to the limited crawl area. NE contractor folks have idea?? [The ground is VERY hard, dry, red clay.]
2. I have some 1/4" steel plates, about 12x12..Would that work, or should I use 4" cap blocks, laid on their sides? Or??

I'm going to temp in some jacks today, to try to stabilize the walls, and make permanent changes ASAP...

 

[Junior Samples]

Sorry man I have no clue but I did google a couple of links


House Jack, jacking and leveling a house, support sagging floor

Raising A Floor With A Hydraulic Jack

 

[John Larkin]

After watching home improvement shows repeatedly, one of the neatest things I've seen is a spinning 360* laser level. Those guys use it to establish a baseline for level and then work off that. If you can get your hands on one, you can mark your foundation walls for a true level as a reference.

As for what would support the base of the post jacks, I've used pieces of 2x8s temporarily. If you're not jacking too high, you'd never punch through plus you can nail the post plate in a fixed position. You could always drill some 3/4" holes in the corners and drive a short piece of rebar through them to stabilize it, remembering to have a way of extracting the rebar or just driving it on through into the soil. Then you can work on your permanent solution. I tried paving stones and they frikking broke right through. I'd stack some 16" concrete blocks under the main beam also as a safety.

How high do you have to jack the floor?

 

[John Larkin]

Also remember to not raise or lower more than about 1/4" per week. The wood needs to expand and contract gently.

 

[Chuck Leeper]

yep..

"After watching home improvement shows repeatedly, one of the neatest things I've seen is a spinning 360* laser level. Those guys use it to establish a baseline for level and then work off that. If you can get your hands on one, you can mark your foundation walls for a true level as a reference."
John,
I tried 1 of those. The problem is, I had to keep ducking, so it wouldn't cut my head off!!

I'm working w/ string lines, and a digital level. I'm finding the floor stringers are actually caved in, right under the FP.
I think I'll try the steel plate base for a temp repair. I have some 12 x 12 plates, 1/4" thick.
The jack instructions confirm what you said about the 1/4" lift.. They say to take up the load, then 1/2 turn. Then wait a week and continue w/ 1/2 turn per week, til it's back up in place..
And, all along, I thot the cracking/popping at nite, was the metal roof cooling off, and contracting. NOT!!
Thanks for the input...
[This is ALMOST as much fun as head gaskets on a GN...]
MERRY CHRISTMAS!!!

 

[jwillettgn]

Also remember to not raise or lower more than about 1/4" per week. The wood needs to expand and contract gently.

This is very true.

I will ask my son (Zack's 85GN) when I get home to see what he says. He is a foundation inspector.

Jim

 

[John Larkin]

It's scary stuff. I had to "lower" my kitchen floor since one of the piers under the main beam tipped at some point in the last 30 years. It kicked the end up and I had a 1/2 crown". Had to cut a block on an angle, fill with concrete, and knock out the old one. Then when replaced, it sits pretty darn flat; no more than 1/8" out now. But when I lowered it, it was like Rice Krispies. I could get some more out of a joist that's a hair high but I figure leave well enough alone.

 

[ijames]

From an old textbook of my Dad's, a safe compressive stress for timber perpendicular to the grain is a few hundred psi, so use 100 psi to have some safety margin. If the jack holds 16,000 lbs then you need a wood base of 16000 lbs / 100 psi = 160 sq in or about 13x13" square to support the whole load. Unless the plate on the bottom of the jack is that big, I don't think wood will work since the jack will just drive through the wood. More important is the soil load. I found one note on a footing design where they set a pressure load limit of 1 ton/sq foot of soil. That's 2000 lb/144 sq in = 13.9 or say 14 lb/sq in. For 16000 lb, that's 16000 lb/14 lb/sq in = 1143 sq in or 34x34". I don't know what kind of soil they assumed, and your dry hard clay may be a good bit better than that, but I bet by not more than 50%. That means you need a footing between 2'x2' and 3'x3' under each jack to distribute the load onto the soil. Concrete has a compressive strength of about 2500 psi, so if you use a factor of 3 for safety that's a working limit of 2500/3=833 psi and 16000 lb/833 psi = 19 sq in or about 4.5"x4.5" or a 5" disc. So long as the plate on the bottom of your jack is bigger than that you could put it directly on the concrete footing, or if it is smaller just put one of those 12"x12"x1/4" plates on the concrete under the jack. Either way, you are stuck with that big footing under each jack. Hmm, wonder if concrete paving stones would work - I'm sure you can get those in 2' square and you shouldn't load any single jack up to 16000 lbs anyway.

 

[jwillettgn]

My son said you are doing the right thing, just go slow and take your time.

Jim