Crawl Space and House Jacking

[Nostraquedeo]

I don't have a lot of detail, but my brother told me he has about 1" of sag in his floor, so he needs some help pouring some pads and putting in some new piers/supports down in the crawl space. Just looking for any input you all might have. Anybody done this? Footing size? Depth? Crush rock under pads? What did you use for piers/supports? How much did you jack it up, and how fast? Safety concerns?

Like I said, I haven't even looked at it. I helped him do some plumbing under there when he bought it ten years ago, so I do kind remember what it looks like. I am just fishing for ideas at this point.

It's a small two bedrooom bungalow. Probably about 1,100 square feet. I think I remember a center wood support running down the middle. This is the one sagging.

Obviously, we are not gonna get a structural engineer involved, so overkill is what I am seeking here.

 

[joelowrider]

we did this to our house as for footing size you really need to call your local code inspector

But for the jacking part the slower you go the less likely to crack drywall

we went up 1/2 a day on the main beam for 2 1/2 inch's of sag we got no cracks

however I helped a friend with his and his drywall was already cracked we did 5ins in one day with no issues.

The more screw jacks the easier it is we used 4 of them on a 20ft span

 

[Stuart in MN]

You need to mention where the house is located - if it's in warm climate or a place where the ground freezes will affect what kind of footing is required.

 

[theoldwizard1]

With footings bigger is better. I would guess a minimum of 12"x12", but 24"x24" would be better. At least 6" deep, 8-10" better. Use some rebar in the cement.

 

[Nostraquedeo]

Kansas City, MO.

 

[BillK]

nq,
I am certainly not a structual engineer but if it was my house and I was doing it, I would probably be thinking 2' x 2' by at least 2' deep pads. At least to the depth of the rest of the house foundation ? Also is going to depend on how many you are going to do. The more supports you put in, the less weight each will be supporting.

Maybe you could dig a hole or two outside of the house to see how far you have to go down to find solid ground ?

I remember seeing them do this on one of the home improvement shows and I am pretty sure the holes they dug for the pads were pretty deep.

 

[rockchucker]

Larger and thicker the Footing is the easier job you will have. Use at least 2x6 Form Boards. Go slow. I would scrape away the surface dirt until you hit undisturbed Soil. Set your Form and pour. Let it set up for at least 3-4 days before applying load.

A Tile Grout Mixing Tub can be really helpful for getting mixed Concrete to the Form. They are very low profile but hold quite a bit. 5 Gallon Buckets can be a real PITA to try and drag in a crawl space but a Tile Tub can be slid around like a sled. You can even attach a rope then just crawl in with it attached to you.

I have done this too many times to count with Pops while he was remodeling old homes.

 

[SteveCh]

Last summer I bought, at Lowe's, a largish low-sided tub, rectangular, for a puppy to play in [with water in it]. $14. It is meant for mixing anything, really, potting soil, concrete, mortar, whatever. That might do the trick, you can drag it or push it ahead of you.

Just how high is this crawl space, anyway?

 

[Automatic Slim]

Define "crawlspace"

Might be easier to cut hole in the floor to do work, imo - esp. if the crawlspace is so low you have to belly craw' like a baby..........

 

[BFBOB]

Sorry if this is a stupid question, but digging and pouring in a restricted space doesn't appeal to me. How about jacking beams on either side of the existing piers and shimming the tops? They might continue to sink - but if it took 40 years to sag the two inches, will I live long enough to see any more sag??

 

[Professur]

Sorry if this is a stupid question, but digging and pouring in a restricted space doesn't appeal to me. How about jacking beams on either side of the existing piers and shimming the tops? They might continue to sink - but if it took 40 years to sag the two inches, will I live long enough to see any more sag??

This is valid only if you know why it's sinking now? If it's because water started moving somewhere ... it's gonna sink faster and faster.

 

[kbs2244]

I used cardboard boxes as forms.
About 24W x 24D x 12H
You don’t have to get carried away on site preparation.
The pads are pretty well protected from moisture and temp by the house around them.
Scrape the dirt down so it is flat enough that the concrete won’t leak out around the bottom.

I used 5 gal buckets to get the concrete to them and used a square of mesh at the half way point.
After they are about 2/3 full you can level the top by lifting the low side.
A little concrete will leak out the bottom edge to keep the new height.
I ended up with the top about 4 inches above the surrounding dirt.
I just left the boxes there. Nobody is going to see them.

I used separate screw jacks to do the lifting and then adjusted the permanent screw type posts up tight to take the load after lifting.
You could use hydraulic jacks doing it this way, but I had the screw jacks.
One man per jack and lifting until you heard the first “snap” from something rearranging itself.
Then wait 24 hours.
You are not going to undo 70 years of dropping in a few hours without something breaking.
Take you time on the lifting part.
It two days of after work time to pour the pads and about a week of an hour per night to do the lift.

Four pads under a two story Victorian with a sag that varied from 2 to 6 inches.
30 years ago.
Floors are still level.

 

[Falcon67]

No freezes down here, so our old pier and beam house used cinder block pads, blocks, treated boards and cedar shims. Teh company that did it included a life time guarantee. This kind of blocking is SOP around here, but may not be where you are.

PS - If it gets cold enough under that house to freeze the ground, might want to look into skirting the thing or plugging some holes and insulating the perimeter.

 

[Nostraquedeo]

Thanks for all the help! The crawl space is about 30" tall. Forming is the easy part. Digging the holes and getting concrete down there is going to be the PITA! I like the tub idea, as I was concerned about getting a bucket down there.

 

[Highbeam]

You don't have to dig a hole. Just scrape a level spot. A footing does not get any strength from being below grade. You want a length and width to provide enough square feet of bearing area since the purpose of the footing is to spread the load. The thickness of the cookie is only to prevent it from breaking when you apply the point load from the jack.

Honestly, go to home depot and buy the regular concrete pyramid type pier pads. The ones with a hole in the top. Stick in an adjustable height saddle, this will be your "jack". Set the pier pad in place on solid and level dirt. Then cut a 4x4 or 4x6 chunk that extends from the saddle up to the beam you're jacking. At the top of the chunk of 4x6 you can install a simpson fitting that keeps the 4x6 from moving. Then just jack up the beam.

You'll do a few of these and it won't take a lot of torque on the jacks to lift the floor. I've lifted roofs accidentally doing this. Pulled the rafters apart at the top.

 

[rlitman]

You don't have to dig a hole. Just scrape a level spot. A footing does not get any strength from being below grade.

It needs to rest on undisturbed earth, BELOW the frost line.

 

[Scott r c]

Sorry if this is a stupid question, but digging and pouring in a restricted space doesn't appeal to me. How about jacking beams on either side of the existing piers and shimming the tops? They might continue to sink - but if it took 40 years to sag the two inches, will I live long enough to see any more sag??

This is what I typically see in Oklahoma. I would try this first as it is so much easier.

 

[BFBOB]

Funny you should mention OK. That's where the house I'm writing about is. Sitting on solid clay on frying-pan-flat ground. I haven't been under yet (less than 3' headroom) so I don't know for sure whether the piers are sinking or the beams deteriorating. I do know there's not a river flowing under the house. But, spring rain soaking far enough in to soften that hardpan? Could be.

 

[RVDan]

the crawl space might already be below the frost line, and would there be any frost heaving under the house anyway?

 

[rlitman]

the crawl space might already be below the frost line, and would there be any frost heaving under the house anyway?

That depends on whether the insulation runs along the perimeter or the floor, and what the local climate is.

 

[Bib Overalls]

There is a possibility the existing pads have fully settled. I would certainly consider jacking and adding shims at the tops of the posts. Run a string line the full length of the center beam and use that as a reference.