Garage apron footing?

[bookman51]

My garage apron has buckled. I did not build the house but I was first to live in it, and the apron had already buckled. I assume moisture underneath it. I am thinking of replacing it. Should I put footings on it so it does not float and rise above the garage floor where they meet? I live in the midwest were we get a pretty good freezing and thawing cycle.

 

[bookman51]

Anybody....before my query gets too buried.

 

[SALIV8]

i didnt put footings on mine. granted it is not the prettiest but has held up fine.

 

[Bill Bowman]

Hopefully, we can keep this subject up to the top for a while. My apron was poured about 25 years ago, on top of compacted gravel. Not sure of the depth of the gravel, but was at least 16 inches. No problems as of now.

 

[dfiler2]

What exactly do you mean by "buckled"?

 

[bookman51]

What exactly do you mean by "buckled"?

Cracked in several spots and with one section breaking with part of it "buckling" an inch to inch and half above the other. I assume there is moisture underneath it. Also, whomever did the apron did not make the cuts close enough to allow for stress cracking.

 

[Bondo]

Cracked in several spots and with one section breaking with part of it "buckling" an inch to inch and half above the other. I assume there is moisture underneath it. Also, whomever did the apron did not make the cuts close enough to allow for stress cracking.

Ayuh,.... I've never seen a footer or frost wall on an apron,....

When it's boxed out, 'n the stone installed, then the concrete,...
All of the stages of the build, need to be Drained,....

A hole with stone, 'n concrete in it, ain't what ya want,.....

Is the Highest of yer slab chunks, at proper grade,..??
You could mud-jack a lower slab Up to grade,...

 

[CNGsaves]

You've been on GJ a LONG while . . . . surely you know PIC's are needed.

 

[Kevin54]

You shouldn't have to have any footings for your apron. What it sounds like is that they didn't have enough gravel underneath to absorb the frost. If you only have a few inches of gravel underneath, then down to dirt, the dirt will absorb the frost and heave up what little gravel there is plus the gravel.

When you redo it, make sure it is dug down deep enough to have a foot or more of gravel underneath. Power tamp the stone down to where it is fairly compacted tight. Then I would pin the apron to the garage floor with 1/2" rebar drilled in about every 2' along the width of the apron.

 

[Elginz]

When you do put in a new slab put the foam insulation under it. That will keep in from frost heave and rising. The insulation has to extend out on the sides and it would be good to ramp it down on the edges. Put the rebar and wire in it and when it cracks it won't shift.

 

[ConCretin]

I'm with Elginz and others. Footings aren't required for an apron but you need to protect them from frost. You don't want the apron to move differently from the main structure. The most common result of frost heaving is an apron that drains water back into your garage.

You can do this with a free draining granular base and/or a couple inches of rigid insulation. As was mentioned, extend the insulation out several feet from the apron.

I'd want the apron to be 6 or 8" thick and reinforced with #4's at 12" centers. If you are driving vehicles over them, you want them to stay in one piece.

 

[rburke65]

I am also noticing cracks under my apron s I guess I'm going to have to get my excavator guy back and do some more grading....... Good luck.

 

[bookman51]

Thanks much. I appreciate the advice.

 

[lattimer17]

For a basic slab like this, use free draining gravel, then subbase material, then concrete. Use geotextile between the gravels as well as between gravel and subgrade.

ETA: I wouldn't pin the apron to your foundation. Any settling or heaving that occurs will then be putting a moment on your foundation. No bueno. Keep it free floating and protect it from frost by keeping both surface and subsurface water away, and by using a capillary break to keepground water from coming up (the free draining gravel will do that).

 

[bookman51]

For a basic slab like this, use free draining gravel, then subbase material, then concrete. Use geotextile between the gravels as well as between gravel and subgrade.

ETA: I wouldn't pin the apron to your foundation. Any settling or heaving that occurs will then be putting a moment on your foundation. No bueno. Keep it free floating and protect it from frost by keeping both surface and subsurface water away, and by using a capillary break to keepground water from coming up (the free draining gravel will do that).

Best advice so far. I had someone recommend pinning it to my garage floor, but I know that nothing stops the pressure of moisture freezing. So, I think the main thing is making sure a good base of free draining gravel. A couple of years ago I dug under the side of it where it was buckling, and I did not run into gravel. So, it may have been simply laid on the ground...and maybe enough moisture remained in the ground. Odd thing is that the original builder (who built several houses in the area) had originally intended the house for himself. I suspect he did not watch the concrete contractor close enough...or just did not know enough to do so. I found a few other things wrong with plumbing and wiring that suggested he did not hire the best subcontractors.

Thanks.

 

[brickG-man]

If it is a high moisture area some might specify pea gravel as a base under the concrete to provide adequate drainage.

 

[machsnell]

If you have clay I wouldn't necessarily use clean stone for drainage. If you have a stone with void (i.e. no fines) then water drains into this area. If you have clay then the water will remain in the voids and will be prone to being able t9 freeze and heave. If you use clean stone 57's or the like the the bottom of the excavated area must have an outlet. If me and no signs of spring or purged water under garage when you excavate for apron I would use stone with fines and an appropriate moisture content and compact well in lifts on subgrade that is solid. If all of the above is correct your slab won't move. It will not be able to take in enough moisture. Make it a turned down slab and throw a couple sticks 9f rebar and it definitely won't move. I will bet the backfill wasn't done properly and the dirt is **** and soft and wet causing the cracks and in turn heave. Once there's a Crack water gets in.

 

[lakeroadster]

It's a Regional Thing....

I moved from Ohio to Colorado about 10 years ago. Here in Colorado they level out the soil, throw some road base on it, and then pour the concrete.

Road base is like pea gravel along with other small aggregate.

And, not surprisingly, every apron & driveway here cracks.

The larger aggregate allows the water to drain away from the concrete. Without it the concrete will crack... every time.

 

[bookman51]

Re: It's a Regional Thing....

I moved from Ohio to Colorado about 10 years ago. Here in Colorado they level out the soil, throw some road base on it, and then pour the concrete.

Road base is like pea gravel along with other small aggregate.

And, not surprisingly, every apron & driveway here cracks.

The larger aggregate allows the water to drain away from the concrete. Without it the concrete will crack... every time.

Got it...larger aggregate Thanks.

 

[bookman51]

If you have clay I wouldn't necessarily use clean stone for drainage. If you have a stone with void (i.e. no fines) then water drains into this area. If you have clay then the water will remain in the voids and will be prone to being able t9 freeze and heave. If you use clean stone 57's or the like the the bottom of the excavated area must have an outlet. If me and no signs of spring or purged water under garage when you excavate for apron I would use stone with fines and an appropriate moisture content and compact well in lifts on subgrade that is solid. If all of the above is correct your slab won't move. It will not be able to take in enough moisture. Make it a turned down slab and throw a couple sticks 9f rebar and it definitely won't move. I will bet the backfill wasn't done properly and the dirt is **** and soft and wet causing the cracks and in turn heave. Once there's a Crack water gets in.

I suspect you are right about the backfill not done property...and dirt being **** and soft and wet. Thanks

 

[yeldogt]

I got advise years ago to always overbuild the concrete a bit whenever the soil underneath has been disturbed to any depth. Most times the soil around a new build always drops a bit -- not a problem except when concrete or hardscape is installed.

I normally have the aprons poured a little thicker and rebar them well -- I do the same with a driveway over any place where a big tree came out. It is cheap and I never had another problem.