garage floor sinking
 

A large section of my garage floor (8x10) has been sinking over the last couple of years and I need to contact someone local to repair it. The garage is attached to the house and am worried about a wall that could cave in. I painted the walls and floors about 7 years ago and noticed that the paint line is now 1-1 1/2" lower than when I did. Need some idea's of who to contact to repair. Most likely need to break up and re-do the section that has dropped. The lot the house was built on was wooded, so I think the builder just buried tree stumps and they rotted which maybe the cause.

There is a process like mud jacking where they pump something under it to raise it without all the expense of removing and replacing. Several companies around my area best bet is to go to local concrete supplier and ask for a concrete correction company

I would not mud jack, you should have a new floor poured. They should pin it to the foundation.

Thanks you both for the advice. Looking for all the idea's I can get and I'll try the most mentioned one to correct.

Is the wall sinking as well as the floor? If so, you have a different kind of problem. If the wall is going down too, then the footing (or pier) is compromised. That means you need to get to undisturbed earth to correct it.

Many times foundations are not drained properly around the perimeter. This means that water flows under the footings in streams. When this happens, the earth underneath is eroded and the footing breaks. Couple this with the use of the lowest PSI concrete in the average footing and you have this type of issue.

If it is only the slab that is settling, then you have a somewhat easier problem that might be fixed with the mud jacking or taking up the slab and pouring another one.

The main thing is to make sure that your foundation and roof are adequately draining away from the structure and not under it or you could repeat in the future.

Think it might depend on how hard the area will be to work on whether or not mud jacking will be viable. My folk's place had a driveway sinking toward the house which was routing rainwater into the basement. They removed it and repoured the concrete with a slope out. Think it was much less expensive than the estimate of mudjacking.

It's only the slab on the side of the floor to the house. I went down in the basement and the wall looks ok, but I don't think it would be a good idea to not correct it. I didn't mention it, but it's a two car garage. I only want to dig up the the 8x10 area if I can.

You aren't storing really heavy items on it are you? Multiple engines can make them sink.

Just my tool box,maybe a couple hundred pounds. And my wife's car, but it's back a ways from were it's dropping.

Typically the garage foundation slab is not tied directly to the house foundation (floating). Most likely cause was improper compaction prior to the pour. If this is the case, "mudjacking" or "pressure grouting" may only be a temporary solution.

Sounds like when they backfilled the inside of the garage they didn't compact the fill up against the deeper house foundation (frost walls on the garage). Over time the in & out of the vehicles would cause it to settle. Mudjacking or Pressure grouting could cause the foundation of the house to crack rather than lift the existing slab. As you have already found out - concrete is great under pressure but lousy under tension - Mudjacking against the foundation would put the foundation under tension.

I wouldn't consider it a structural defect, more of a nuisance. If it doesn't bother you that much and isn't a hazard, leave it.

Phil, it sounds like a new floor will be required. Do you know if the original floor was reinforced with wire screen or rerod?

Here's an idea to save some money.... Rent an electric jackhammer to bust up the area you're going to replace. If it's wire reinforced all you'll need is a good set of wire cutters. Actually the broken up concrete could be compressed into the sand and used as a reinforcement too. Less cost for new cement. BTW, use 5000lb rated cement this time around.

Sounds like what you have is called stem wall. The footer is poured well below grade, supporting the walls. The garage floor is poured after using the walls as a form sort of speak. What you need to do is remove the garage floor, check the type of dirt you have under it making sure you don't have some sort of muck or organic material(creating a sink hole). You need to bring in a good base, like road rock. It needs to be compacted properly. If you have termite issues where you live then you need to have it treated for such. Lay down a moisture barrier(visqueen). Then repour your concrete using minimum 3000 lb concrete with 6x6 road mesh (or fibre)poured to 6in thick. 4 inch is minimum but 6in is nice. As Deadhead says make sure water is directed away from your house.

How old is the garage? Has the floor also cracked,any recent(7 years) additions near the area? As mentioned before probably poor base. The garage would be a easy place for a contractor to skimp on. You could call Allied Concrete over in Dresher and ask if they recommend a contractor.

My neighbors shop was sinking in the back corner. he had a company that does similar work to the link below do the repair. It took a 1" wide gap in and 2" raise in the concrete floor and made it look like a hairline. The shop had dropped almost 2 inches in the back corner. Once all shop was level again, they drilled a couple of holes in the concrete and filled the space with something to fill the void.

http://www.floridaramjack.com/

One thing to do is to get multiple estimates. his ranged from $7K-22K due to the size of the shop.

Good Luck.

Just want to thank all that have commented. I think am going to keep a lookout to see if it drops too much in the next couple of months and most likely have it dug up and repaired.