Garage Concrete Floor Cracking
 

Got a garage put up this summer, builder did concrete and frame work and exterior work. 3 1/2 months later seeing cracks, chips and pitting in the concrete and cracks in and 6" pony wall. Kind of a angry thought going through my mind to see this and I haven't even parked in it yet. Is it or will this get worse if we were to park on it or stay off it.
Builder says its normal only cosmetic, I say no way, any thoughts on what or could be done to prevent this, and is there anything I can do.

Concrete does crack in this province. Do you have any pictures?

Some cracking can be normal but what you say doesn’t sound like it to me. Could be Subgrade soils conditions contributing to issue

Could be finishing issues or concrete itself (the aggregates/powder/admixtures)or both. Contact the concrete supplier and have their rep look at it and then discuss with your contractor.

Next would be to do some non-destructive testing of the concrete for strength. A geotechnical Engineering firm can help with that. Next would be to core the concrete to test. Maybe the supplier will do so themselves

Good luck

How much rebar or wire mesh is in it? Are the cracks wide or is it more the surface spalling / a poor mix of concrete type issue? The pony walls kind of sound like a subgrade prep, movement issue. Are they slab on grade or do those pony walls go down 1.5 meters to a footing?

I put lots of rebar in my bsmt floor and got very little cracking, at some relatives homes there are 1/4" to 5/16" cracks in spots. I was quite surprised that rebar isn't required in basements but mine got it.

A lot of people in the trades think its no problem to add water. Everytime water is added strength is diminished! This fact is especially damaging at power trowel stage. If water is added to early or to much spalling will occur . Alberta building code requires air entrainment to give freeze thaw cycle durability . When you combine air entrainment and extra water at site power troweling will cause spalling.

Cracking is normal . If you can get your finger nail in it or wider can be a sigh of excess water added at site. Hope this helps.

One more thought to share.

Many places in alberta and ne bc have really poor aggregate containing a rock that looks like rust. This rock when water is applied looses its strength swells and can cause spalling .

As far as a solution its too late . Apoxy may slow your spalling issue . But no effect on cracking .

There are a lot of variables involved. Was air added, is it a broom finish, did they power trowel it, hand trowel, was a door left open and it rained, was Super P. used or was it slumped up with water, etc. I suspect what is going to happen is that the contractor will blame the concrete supplier and the concrete supplier will blame the contractor.

how was the base prepared. Some cracking is normal but this early into the life of your garage seems really odd. I would get another contractor to give his/her opinion on it and start documenting everything. Also get the concrete supplier involved to inspect the work and provide you with the details of the mix that was used.

I have some light surface cracks that run parallel to the front support beams in my attached garage. I ended up putting black and white tile down and haven’t noticed any issues where the cracks reside. I used PL 5000 I do believe to fill and blend the crack out before laying down tile.

sound like sub soil prep. issue. where are you?? sub soil type?? compaction? Rebar or mesh? lifted? As other have said what was result of concrete slump testes etc. type of concrete used??

All concrete will crack. Rebar only stops the cracks from getting huge. Sounds like poor installation, might be too thin, poor prep work or subgrade concrete for a garage pad. can you remember how thick the pad was when poured ? I would pour 5 to 6" for a garage pad if I ever did one again. It's worth the extra $$ for a couple more meters of concrete verse 3.5 to 4" thick cracking. I poured a pad at the cottage over 30 years ago, lots of sand base and about 5" thick. only can see a couple hairline cracks to this day.

Thanks for the opinions, I think its gonna get way worse if its this early. I should have went with a 10" base but concrete is so friggn pricey. Rebar was used,1/2", 12"centers, 4" thick. Wasn't thinking it would show cracks this early without even parking on it .You get what you pay for, lesson learned.

how big is the slab? Does it have thickened edges? My slab i poured for my garage is only 4" thick rebar is 12" on center and i only have 2 hairline cracks 4 years later.

I’d be talking to a lawyer pronto.

Its a 24x26 garage, so pad would be 23x 24 with 6" pony wall, the 1 crack is through pony wall, showing on the outside. Got a bad feeling on this, these cracks just started to show in the last week, I just insulated the walls and never noticed them before.

Make him fix it now. You have a large enough problem, early enough, that you know it is only going to get way worse as the ground freezes. Concrete contractors are good and bad but lately there seems to be more bad than good. Take him to small claims if you have to but I would try negotiating first.

Ask the contractor and the cement supplier to meet with you onsite to review the issues and what can be done moving forward. Record/write down date and all that was discussed and have all parties sign. Take detailed pictures as well soon as is possible. They may want to review the work again in the summer, which is reasonable, to see if there is any more excessive cracking. Concrete is a very tough material to work with properly and as you have seen with all the above posts, there are a Great many factors that contribute to its appearance.

Post some pictures with a scale reference and many of us may be able to diagnose what’s going on.

Also if the contractor asked the cement truck driver to add water to the concrete it should be noted on the invoice. Adding water is a big no-no, when I poured my pad I hired a crew of finishers and I did all the rest of the forming etc. The crew was p$$ed that I wouldn’t allow any water to be added. The driver did have some plasticizer on hand, lucky for the crew or they would have just had to work harder. That was over 10years ago and I don’t have any cracking.

Post pictures.

My garage pad is 24x28, thickened edge monolith slab. No issues and I know my thickened edge is over designed. Rebar at either 12 “ OC or 16”-I can’t remember .

As I mentioned before sounds like combination of poor concrete and improper subgrade prep and now possible too small size of footing to bear the load. Maybe your footings are founded on uncontrolled fill soils and not native / undisturbed soils or weak subgrade.

Lots advice provided by others. Get all parties involved and get another opinion from a second contractor and possibly a geotechnical engineer

Built a 38x36 garage in 2012 and not a single crack in my floor, but I also poured the floor 7” thick. I used 3/8 rebar at 2’ apart and drill the rebar into the pony walls. I just built my MIL a garage 2 yrs. ago and poured the floor 10” thick with the same rebar setup and no cracks to date. I also went with 18” x 8” pony walls with pilings every 6’ and went 4’ deep. I built cages to drop in the holes and tied the wall rebar into these. Adding fibreglass helps as well with the strengthening of the concrete.

Yes


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For industrial slabs and maximum strength, it is very common to put a layer of poly down over the sub base. It takes quite a bit longer till you can get at it with a power trowel, but you get a much better product. I see many crews pouring driveway and garage slabs that don't even wet down the subgrade prior to pour. Rarely if ever see them use a sealer or poly on top after the pour. I've done this for every home I've had and the results speak for themselves.

Placers hate poly.

ALL CONCRETE CRACKS. ALL. You might not be able to see it but it does. Worked in quality control for a major concrete supplier for years. There are so many possible issues here. As said above. Make sure you let the contractor know you are not happy with the product he provided. Get the supplier and an independent engineer who is qualified to speak about concrete and geotechnical together and have a look. Allow the contractor to have his say too and go from there.

Placers hate poly and post pour hardeners. That doesn't make for better concrete, just happy placers.

I know that.

I knew you knew that. :)

I poured my 40'x50' garage floor in 2006, did relief cuts on every 10'x10'. My floor is 4"-5" and in 2 corners 7" because I had equipment that weighed 28000 and 31000 lbs on those corners. I have driven my 11000 lb forklift with a 5000 lb lathe on it or lifts of drywall, not a single crack anywhere.
I went heavy on rebar, and have always had the garage heated in winter. I really think that is the key, keep it heated.
I spent a lot of time on prep, tamped the hell out of it for 2 days with a 4 wheel vibrating tamper. I used elimination sand for a base.
I had my basement carpet stripped a couple years ago and there is not a single crack there either, but again I tamped it for 2 days and went heavy on rebar which is cheap if you look at the life of it. I poured the house floor in 2001.
Not all concrete cracks :)

Was a geotechnical report available and followed? Did you have the foundation designed? Was concrete sample/tested at the time of delivery? If answer was no to any of the 3, legal action likely not going to be an option.

If concrete samples were not taken/tested at delivery supplier will point finger at placer, placer will point finger at supplier. Unless negligence is obvious and can be proven, your only chance may be to negotiate a simple cosmetic fix (if that) with the placer in my opinion at I suspect. And your chances are low even for this. As others said, concrete is going to crack in this climate.

99% of residential slabs are poured with a single layer of rebar near the bottom of the slab which is useless regardless of O.C. spacing and or thickness of the rebar as concrete will crack from the top, bottom, left, right, front, back, and so on.

If you want it done right...
- Design of grade beam, curb, slab that may require pilings based off of geotechnical report recommendations.

- A proper sub grade prep, compaction, moisture, frost control prior to placement. Test sub grade to validate it meets design.

- 2 layers of rebar (top and bottom) with appropriate O.C spacing with additional rebar at opposing angles for corners, drains, etc. Validate rebar to ensure it was installed to spec.

- Proper thickness of slab and thickenings if required.

- Use of the proper cement type, strength, slump, and air entrainment. Test concrete to validate it meets design.

- Proper placing, curing and finishing. Validate pouring/curing to ensure it was installed to spec.

Lots can go sideways with concrete and lots can be done to control cracking. Key word is "control".

I'll 110% guarantee you have cracks in your concrete. They may not be ~1/16" / 1/8" thick or the sort but you have cracks even if they are just hairline cracks. Just take a wet sponge over the surface of the slab and you'll see cracks appear as it begins to dry more cracks than you might be able to imagine (unless you covered it with a floor coating). ALL concrete cracks.