[marc9889]

Over time, part of my home's floor has sunk about 1-1/2 to 2", leaving me with an unsightly slope. This only pertains to the section of floor under a load bearing wall. For 3-4 feet in every direction (from the load bearing wall), the floor slopes up, and is thereafter flat. I'm inclined to believe that the piers have sunk into the soil, but if there is another explanation, please feel free to throw it at me. What's the best way to address this with as much permanence as possible?

1. Will adding more piers prevent future settling or just slow it down? Is 18x18x8 sufficient for the footings for new piers? How many piers are typically needed for a 30' section directly under a load bearing wall (2 story home)?

2. Would it be out of the realm of possibility that the house was built (1984) without footings under the piers?

3. I'm in the middle of some subfloor replacement, so now is the opportune time to address the issue. (The HVAC return duct makes access to the existing piers nearly impossible from the crawl space opening.) Should I postpone the subfloor work until the slope is resolved or can it be done later without negatively affecting the flooring or subfloor?

 

[Nealtw]

This would be the best time to do it, you place a mud box on the ground on each side of the post and use 2 jacks and bring it up 1/8 to 1/4" a day, that allows the house to change shape back to where it was with out breaking it. Then you you dig out and make the footing bigger. Or you put in two new footings to jack with and support the beam on them with posts.

 

[Bud9051]

The less structure in that area the better. Hold off on the planned work.
You need to confirm what is settling. If it is the piers they probably installed without a proper footing or soil was not compacted. Do you have a dirt floor in that crawl space?

What are the piers, concrete blocks?

Is this a center beam with supports under it? If so, you could install a beam on each side of the ductwork and current beam. It will be very difficult to jack up that area so having two beams and many jack points will help

Pictures will also help.
Bud

 

[marc9889]

The less structure in that area the better. Hold off on the planned work.
You need to confirm what is settling. If it is the piers they probably installed without a proper footing or soil was not compacted. Do you have a dirt floor in that crawl space?

What are the piers, concrete blocks?

Is this a center beam with supports under it? If so, you could install a beam on each side of the ductwork and current beam. It will be very difficult to jack up that area so having two beams and many jack points will help

Pictures will also help.
Bud

Yes, dirt floor in the crawl space, and the piers are concrete blocks, which are all located under the center beam. There are no supports other than the foundation itself and the piers under the center beam.

I'll get some photos the first chance I get, though it will probably be a day or two.

Should I expect continued settling with the two additional beams you described?

 

[marc9889]

This would be the best time to do it, you place a mud box on the ground on each side of the post and use 2 jacks and bring it up 1/8 to 1/4" a day, that allows the house to change shape back to where it was with out breaking it. Then you you dig out and make the footing bigger. Or you put in two new footings to jack with and support the beam on them with posts.

If I went with option 2 (new footings) what size is typical? Do I need them to be 8 inches thick? Seems a little excessive, but I'm no expert.

 

[HDS]

Questions already answered.

 

[marc9889]

Can you describe the floor? Is it a concrete slab, basement floor, etc...

Sorry, yeah, I guess that would be helpful. It's a crawl space with floor joists and a center beam. Center beam is supported by piers, which are concrete block. Not sure if the piers have a footing or not.

 

[HDS]

You could do some exploratory digging to check if there are footings.

 

[Nealtw]

If I went with option 2 (new footings) what size is typical? Do I need them to be 8 inches thick? Seems a little excessive, but I'm no expert.

When we do a foundation, the hole is dug out to undisturbed soil and then an geo tech engineers checks the soil for strength and decides what size footing we need after checking the load it will carry. .

The smallest post footing we do is 24x24 often the get up to 36x36 always 10 and sometimes 12" thick with a grid of 5/8 rebar in it to help spread the load.

Even with all that with new builds we have had to dig around them and make them much bigger before the house was even finished.


So anything you get on the net here would be just a guess by experience but just a guess at best. Well worth having an engineer involved for that part. We can help with how to do it.

 

[Nealtw]

I would up a laser level in the house, do a rough drawing of the house and check and map the floor elevations and make sure you only have one problem. some times things are not like they seem to be.

 

[Bud9051]

Definitely agree with creating a map however you choose to do it. But having a reference is really helpful to judge your progress. Example, jack it up 1" and discover it only moved 1/2". The other half was the new footings going down. Best to know that before you get too far.

Do some digging (as HDS suggested, not too much) to see if they even installed a footing and if so, how big.

Bud

 

[marc9889]

Thanks for all the replies, and there were some great ones. I'll get photos and do some digging to see if I have any footings at all and go from there. I do also have a laser level that mounts to a tripod so I'll break that out and take some measurements too. Now if I can just get the laser going without my wife wanting a cat...

 

[P C D]

It's a crawl space with floor joists and a center beam. Center beam is supported by piers, which are concrete block.

Are there posts between the beam (girder) and the concrete pier blocks? What is the spacing between the pier blocks? If you jack up the girder (1/8" per day) and add new posts on pier blocks between the existing ones, and shim the existing ones tight against the raised girder, that should do the trick. If you have enough pier blocks, they don't need a footing underneath, just sound soil. You can use cheap hydraulic car jacks on wood blocks to raise the girder. Use small steel plates between the jacks and the girder to avoid punching a round hole on the girder. Easy does it.

 

[P C D]

I do also have a laser level that mounts to a tripod...

Unless your exterior walls supporting the joists are perfectly level (unlikely), a level will do you no good. Draw string lines from wall to wall, parallel to the joists, and jack up the girder until you close the gap.

 

[huesmann]

Unless your exterior walls supporting the joists are perfectly level

Perhaps you mean "plumb?"

 

[P C D]

Perhaps you mean "plumb?"

No, I meant "level." As in the tops of the foundation walls all being in the same plane, and that plane being level. Think about it.

 

[stadry]

our min here in atl's 2.0 x 2.0 x 1.0 high w/2 mats of #4 bar ( 3 pcs ea mat ) equidistant vertically,,, 1 mat at the 4" level & the other @ 8" turned 90* to lower mat

 

[huesmann]

No, I meant "level." As in the tops of the foundation walls all being in the same plane, and that plane being level. Think about it.

The top of the wall is a different thing than the wall itself. You really mean the sill plate is out of level.

 

[P C D]

The top of the wall is a different thing than the wall itself. You really mean the sill plate is out of level.

I would not trust a construction guy unfamiliar with the concept of a "straight, level and plumb" wall.

 

[Nealtw]

I would not trust a construction guy unfamiliar with the concept of a "straight, level and plumb" wall.

That is why you use a laser and map the elevations of the floor.

Then you have a location for each and every problem, then you just have to find the cause and best fix.