Settling under garage floor


  #1  
Old 09-06-07, 11:25 AM
J
Member
Thread Starter
Join Date: Sep 2007
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
Settling under garage floor

Where my asphalt driveway meets the concrete garage floor(front) there is a gap and its looks like the soil under the concrete has settled quite a bit. There is no support for the slab for about 6 inches. I am concerned that the slab will eventually crack and deteriorate. What would be the best way to fill this void?
 
  #2  
Old 09-09-07, 06:46 PM
Q
Member
Join Date: Apr 2007
Location: Canada
Posts: 410
Received 5 Upvotes on 5 Posts
If the garage concrete floor is settling more than your asphalt driveway you have exactly the opposite of the usual scenario, in which the asphalt settles more than the garage leaving a step at the entrance to the garage.

Either settlement is caused by inadequate soil density. Poor soil density can result from poor soils, inadequate compaction during construction, or a subsurface water problem. Any one of these causes would not normally lead to greater settlement of the concrete slab than the asphalt surface though!

I wonder if the garage floor was built directly on clay without any granular material beneath it, and then granular material was used and compacted underneath the asphalt! Very shoddy work indeed if that's what you have, but that would explain your situation. Do you have any way of looking at the soil underneath the garage slab by digging a pit at the side?
 
  #3  
Old 09-10-07, 07:04 AM
J
Member
Thread Starter
Join Date: Sep 2007
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
The slab is not settling, there is a void under the front edge of the slab. I would guess that it will eventually fall apart because it has no support. It looks like it may be a water problem. There is a downspout that drains into a pipe that goes underneath the floor. I can correct that problem by redirecting the water.
I have cut away 4 inches of asphalt that butts up against the concrete slab. Now I can see the void. The slab has no support for about 6 inches from the edge because the soil and corners of the concrete blocks have disintegrated. My question is what is the best way to fill the void?
 
  #4  
Old 09-10-07, 06:36 PM
M
Member
Join Date: Feb 2007
Posts: 15
Upvotes: 0
Received 0 Upvotes on 0 Posts
Repair

Two ways either cut back the garage floor or cut the blacktop. After looking at it and making sure there is not more erosion than what you saw, buy some crusher run and pack it under the floor and out to the area that you cut away. You can either blacktop the area or you can mix up concrete and extend your floor. If you put concrete in you should dowel the floor into the new concrete. If you edge the concrete where the odl meets the new and at the blacktop area when it cures you shoul run a bead of Urehtane caulk at both of these locations with primer This caulk is sold at masonry stores.
 
  #5  
Old 09-11-07, 12:35 PM
Q
Member
Join Date: Apr 2007
Location: Canada
Posts: 410
Received 5 Upvotes on 5 Posts
I would take some concrete mix, mix it with enough water to make it runny, then pour the concrete slurry in to fill the void. Poke it with a rod if necessary to force in. Runny concrete is not strong but you don't need strength there, just something that'll fill the void without having to cut up any more of what's left on the surface. Then, patch the asphalt hole you cut out. Make sure the water is diverted away from the area.

I am still puzzled at what happened to the granular material that used to be in the void, if there is no settlement!!! If it' going into a black hole, you have another bigger problem altogether.
 
  #6  
Old 09-11-07, 04:55 PM
J
Member
Thread Starter
Join Date: Sep 2007
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
Repairs Underway

I decided to cut the blacktop back 6 inches. The slab is built on concrete blocks. It looks like water/salt(wintertime in NY) eroded away the leading edge of the blocks. The slab is still well supported so I am going to fill the void with concrete and bring the concrete up to the level of the asphalt. I believe the problem is caused by a downspout that is on the side of the garage, right near the front of the slab. Thanks for all the help.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: