Concrete help

[Hunter1602]

So attached are some pictures of our walk up concrete path to the front door. However, the ground under the slabbs have sunken over the year im assuming. We purchased the place this year, but when the snow melted I noticed a void between the ground and the concrete. Im worried that without much support other then the beams the concrete will crack and might even collapse. What should I put under the concret to provide more support. I was thinking gravel, but the problem is getting it all the way to the back. I've also heard about this expanding concrete, but not sure about how well it would work. Any suggesting or advice would be greatly appreciated.
Thanks in Advance,

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[ramonmark]

A friend of mine has just dealt with the same issue. He got a local contractor to "mud jack it'. Look it up online.

[Quinn]

Sorry I am not too useful for advice but to me that looks like a fairly thin pour for a sidewalk.

More on topic, maybe that fence post foam( maybe the same stuff you are talking about) would work to fill the void completely.

Others will chime in with a lot for useful info

(And to see others already replied) mud jacking is commonly used. They'll be doing any uneven surface on public walk ways over a year of two of buying your house.

[CaberTosser]

While mud-jacking will certainly shore that up, I suspect that your ground settling won't stop for another couple of years and you might need a second round of grout sometime down the road ('mud jacking' is the pumping in of a cementitious grout, it can even lift sunken driveways)

[Hunter1602]

Thanks guys,
I'll call tomorrow.

[calgarychef]

Sorry but that's a crappy job, you should have at least 4 inches of crushed and compacted gravel under the walk and the concrete should be 4" thick. I know lots of guys will chime in and suggest that that's way over kill but it's not. If you want the job to last that's how you do it.

The subsiding is a separate problem and leaving things to settle for a couple of years is probably aggravating but would have eliminated the problem, as would have a big compactor to really hammer things down. Dirt is dirt though and when it's disturbed it takes awhile to settle back down.

If it was me I'd be talking to the contractor that did the job, maybe lodging a complaint with someone too.

[Grizzly Adams]

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[Grizzly Adams]

Originally Posted by Quinn

Sorry I am not too useful for advice but to me that looks like a fairly thin pour for a sidewalk.

More on topic, maybe that fence post foam( maybe the same stuff you are talking about) would work to fill the void completely.

Others will chime in with a lot for useful info

(And to see others already replied) mud jacking is commonly used. They'll be doing any uneven surface on public walk ways over a year of two of buying your house.

That and poor back filling underneath, very common with new houses. Betting the driveway against the house is the same.

Grizz

[Hunter1602]

Bang on grizz. The driveway has lowered about an inch

[sewerrat]

Is this a brand new house? I would get after the contractor/ builder.

[Hunter1602]

No. House is not brand new. My neighbour mentioned it's been like that for a couple years now. Previous owners did not fix the issue. When we bought the home, the snow was covering it up. We had no idea about the problem until the snow melted. Now after doing some renovations, it's time for this problem to be dealt with.

[EZM]

Mud jacking is the best option if you need to "re-level" or "raise" a separated section but it can also cause the slab to crack ..... especially a thin one like that that is likely pinned at a few points.

If the slab has not sunk - there are better and cheaper options.

I would get some 3/4" crush as pack it in under the slab with the end of a rake handle to provide the slab some support before I'd go risking (and spending money) on mud jacking.

Cheap and easy - no risk of cracking the slab and getting in a worse situation that you started out with.

[Knot Rite]

As a licensed building contractor the best solution is to take it out and do it right as opposed to putting a bandaid on it only to come back and haunt you. For one thing the concrete should be minimum of 3-1/2" with a bed of 28 mm gravel and the sub grade below the gravel should always be sloping away from the foundation and making sure that its compacted. Its also a good Ideal to drill and dowel into the foundation of the house to prevent separating or heaving.
Do it right.

Bobby

[CheeseBurger]

If you are thinking of going the mud jacking route I would echo Knot Rite that you'd be better of tearing it out and redoing it properly.

If you want to stop gap shove some crush under there like EZM suggested. That concrete is way too thin.

[ToXicXxX]

Originally Posted by Quinn

Sorry I am not too useful for advice but to me that looks like a fairly thin pour for a sidewalk.

More on topic, maybe that fence post foam( maybe the same stuff you are talking about) would work to fill the void completely.

Others will chime in with a lot for useful info

(And to see others already replied) mud jacking is commonly used. They'll be doing any uneven surface on public walk ways over a year of two of buying your house.

Fast 2K foam? It's not load bearing.

[twofifty]

Before pouring $ into the fix, walk the house perimeter and assess where else the ground has settled. Look for where grade is sloping toward the house and funnelling water against your foundation. This can be especially problematic on the uphill side of the house, and worse where the foundation jogs into an L.

No sense in fixing the sidewalk without 1st rectifying a grade problem.
What about the footing drainage...is there any water seeping into the basement when it has rained hard for 3 or 4 days?

edit: if shortcuts were taken here they probably were taken elsewhere.

[Brian Bildson]

Good advice but what's your budget? If you need to buy time buy some 3/4" crush and get yourself a shovel and tamping rod. Feed small amounts of gravel under your slab and try and get as much gravel as possible in towards the house. Be patient and keep packing it in. Work out towards the edge of the sidewalk and keep water away as best as possible.

Money no object? grab a jack hammer, remove existing crap slab, place crush under slab, form up with proper slope and grade, place steel, pour concrete, finish concrete. Done deal 24 hours later

[CheeseBurger]

Originally Posted by twofifty

Before pouring $ into the fix, walk the house perimeter and assess where else the ground has settled. Look for where grade is sloping toward the house and funnelling water against your foundation. This can be especially problematic on the uphill side of the house, and worse where the foundation jogs into an L.

No sense in fixing the sidewalk without 1st rectifying a grade problem.
What about the footing drainage...is there any water seeping into the basement when it has rained hard for 3 or 4 days?

edit: if shortcuts were taken here they probably were taken elsewhere.

Solid point

[CaberTosser]

Originally Posted by Brian Bildson

Good advice but what's your budget? If you need to buy time buy some 3/4" crush and get yourself a shovel and tamping rod. Feed small amounts of gravel under your slab and try and get as much gravel as possible in towards the house. Be patient and keep packing it in. Work out towards the edge of the sidewalk and keep water away as best as possible.

Money no object? grab a jack hammer, remove existing crap slab, place crush under slab, form up with proper slope and grade, place steel, pour concrete, finish concrete. Done deal 24 hours later

As Brian noted, but don't forget to compact (that's what started this whole issue after all!). Rent a jumping jack tamper to really get that area fully settled, then proceed as Brian noted. The jumping jacks however aren't so good for the crushed gravel, that's more of a plate tampers job.

[beltburner]

many times there are steel supports anchored to the foundation that basically hold the sidewalk up and keeps it level. repack underneath it really well. garage pad is a mudjack situation unless you want to spend some serious cash. it will usually run up to about 3000 max to jack it

[Popik]

I had the same thing at my old house a few years ago. Had a company com in with heavyweight foam injection. Lifted the driveway 3" and pinned the walkway. They bore a double 1/2" holes and inject it.

Its been a few years now and we drove by there last week and to my surprise nothing slumped.

[Texican]

I used the expanding foam but our sidewalk and driveway are still sinking a year later. And it wasn't cheap. Should have put the cash towards a proper concrete replacement.

[CheeseBurger]

Originally Posted by beltburner

many times there are steel supports anchored to the foundation that basically hold the sidewalk up and keeps it level. repack underneath it really well. garage pad is a mudjack situation unless you want to spend some serious cash. it will usually run up to about 3000 max to jack it

With the sidewalk being as thin as it is, it is highly doubtful that they used steel brackets.

[twofifty]

Tamping is a good idea, but those small tampers, even the larger diesel plate units, do not have a very deep zone of influence.

If you really really want to be sure the backfill won't keep settling on you, you need to excavate, then fill & tamp in 12" lifts with clean non-clay well draining fill.

Doing this gives you a chance to inspect (and correct problems) the foundation's footing drainage and the foundation/footing sealing.

This business of hanging a walkway off the foundation with steel brackets seems like poor practice to me, and not a substitute for a properly compacted backfill job. When the ground settles the walkway is left hanging from its bracketing, like a Fundy scallop boat hanging from the dock off its too short moorings when the tide goes out.