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Garage Floor Cracks

Capo

Registered User
Joined
Jul 28, 2020
Messages
11
Location
USA
Hi All,

My home is built on a concrete slab with a 3 car attached garage. The foundation and garage floor were poured this summer and the home should be fully complete by December. We recently noticed that some cracks are starting to appear in the garage floor and where the edge of the slab meets the garage floor.

I know concrete can and will crack - however, I just wanted to confirm these cracks are cosmetic vs structural.

There are about 3 crack lines that run from the edge of the foundation towards one of the center expansion joints. The longest crack is in the main expansion joint that runs the length of the garage. My builder has claimed they had an engineer check it and said it was cosmetic, but I want to verify on my end as well.

Here are some pictures

 

Mark K

Platinum Member
Joined
May 12, 2010
Messages
1,707
True expansion joints do not have concrete continuous across the joint. I thus assume that you are referring to a crack control joint; If the crack runs along the crack control joint it is doing what it was intended to do. In my experience this is not that common. If it was a true expansion joint this would still not be a problem since expansion joints are intended to open up..

Unless the slab on grade was part of an esoteric structural system it is not considered structural. ACI 318 which is referenced in the IBC makes that clear.
 

Capo

Registered User
Joined
Jul 28, 2020
Messages
11
Location
USA
True expansion joints do not have concrete continuous across the joint. I thus assume that you are referring to a crack control joint; If the crack runs along the crack control joint it is doing what it was intended to do. In my experience this is not that common. If it was a true expansion joint this would still not be a problem since expansion joints are intended to open up..

Unless the slab on grade was part of an esoteric structural system it is not considered structural. ACI 318 which is referenced in the IBC makes that clear.

Thank you for the response. I apologize if my terminology was incorrect. Based on the 4 pictures I shared, those are crack control joints that are on the floor of the garage?

Also, based on what you can see, any concern from those cracks being a bigger issue or purely cosmetic at this point? (You may need to zoom in on some of those pictures)

My thanks again!
 

ADAguy

Sawhorse
Joined
Sep 11, 2013
Messages
5,262
Location
California
1. was slab poured over welded wire, over sand, over membrane?
2. was subgrade scraped prior to #1?
3. was a soils report required/done?
4. depth of water table?
 

Capo

Registered User
Joined
Jul 28, 2020
Messages
11
Location
USA
1. was slab poured over welded wire, over sand, over membrane?
2. was subgrade scraped prior to #1?
3. was a soils report required/done?
4. depth of water table?

I'll try to answer as much as I'm able:

1) I believe membrane. I've uploaded another picture that shows the garage area while they we were prepping it but before they poured.
2) Not 100% sure. Are you able to tell from the picture?
3) Not sure. I know the county we're in is suppose to have fairly stringent building codes (or so others have said), but I'm not sure on this one. I'll see if I can find anything. My builder is a national builder, so I assume they will do what is required by code (hopefully), not not much more.
4) According to https://cida.usgs.gov/ngwmn/index.jsp , I see two locations of data (assuming I'm looking at the right info). One is about 10 miles south of me and appears to range from 4 to 17 feet depending on time of year, I assume. There is another about 10 miles north that ranges from 25 to 48 feet (general elevation increases heading north). Is it safe to assume I'm somewhere in the middle? Also, if it helps, we have clay dirt here and my lot is somewhat of a hill in the community, which the ground going to lower points as you get further past my house.

Thanks for your or anyone's thoughts!
 

Mark K

Platinum Member
Joined
May 12, 2010
Messages
1,707
The cracks shown are consistent with shrinkage cracks not ground movement. A geotechnical report would not help you to eliminate shrinkage cracks.

A geotechnical report would identify if there was expansive soil but the cracking pattern would be different if the cause was due to expansive soils. If you have expansive soil I would expect to see the symptoms within a few years after the site has undergone some wet and dry cycles. I would be surprised if the cracks due to expansive soil showed up this soon after construction.

The practice of placing sand on top of the membrane has been discredited. Current good practice is to place the concrete directly on top of the membrane. In certain dry climates placing concrete directly on top of the membrane could increase the likelihood of curling of the slab. To control this the slab should be well cured . The symptoms shown do not suggest curling of the slab has been a problem.

The map of ground water tables is irrelevant for this particular site since groundwater can vary considerably.

Appreciate the fact that the information that you provided is not sufficient to identify all of the potential problems and to make a definitive diagnosis. If you want more hire a local engineer to advise you.

You are fixated on the cracks and are likely overly sensitive to the cracks. To put this into perspective approach several friends that have houses with garage slabs that are more than 5 years old. Ask them if they have had problems related to the garage slab. Then visit the garage with your magnifying glasses. It is very likely that you will find that they have not had problems while the amount of cracking you find will probably be at least as bad as what you see on your slab.

This is not a problem that can be resolved by the building code. The contractor will not be willing to fix this problem, if it is a problem, thus leaving you with the option of hiring an attorney and suing the contractor. You will likely not win the litigation and you will have to pay the lawyer. There may be other problems with the house but chose your battles.

If you feel compelled to do something you could hire a local engineer who will probably tell you the same thing. Wait a few years and if you still are concerned hire a local engineer to address your concerns and possibly design a fix.
 

Capo

Registered User
Joined
Jul 28, 2020
Messages
11
Location
USA
Thanks, Mark. Appreciate the info.

Good to know these do appear to be shrinkage cracks. Can I then infer these are likely just cosmetic in nature?

Certainly understand that lots of concrete have these, but good to verify with you all here nonetheless. It was mainly the long one that ran the length of the crack control joint I wanted to verify.

Thanks!
 

ADAguy

Sawhorse
Joined
Sep 11, 2013
Messages
5,262
Location
California
Note, never assume that national contractors are any better then locals. What month of the year was slab poured?
How many houses in the tract?
 

classicT

Sawhorse
Joined
Aug 2, 2017
Messages
1,589
Location
Washington State
I agree with Mark, those appear to be shrinkage cracks. Proper layout of control joints can help manage this, or at least make it less noticeable.

But they are mostly cosmetic in nature. I'd recommend sealing them with one of the epoxy crack fillers. Will prevent accumulation of debris or a pathway for ants.
 

Pcinspector1

Platinum Member
Joined
Oct 28, 2009
Messages
3,450
Location
MID WEST
Photo #1 does not show rebar or re-mesh wire, did you indicate that you have one or the other?

Photo's #2 and #4 show a crack going vertical up a small curb wall or short wall. What is above the wall in the garage? Is there an I-beam running across the ceiling to another wall? Could have a concentrated point load being transferred to the foundation curb or short wall?

Agree that the tooled expansion joints are there for cracks, but puzzled why they have appeared so soon? Within a year?

Also some house contracts may have a disclaimer in regards to concrete and cracking, check your contract or with your relator. Any warranty?
 

Mark K

Platinum Member
Joined
May 12, 2010
Messages
1,707
The shrinkage cracks occur early on because that is when most of the excess water leaves the concrete. The less water in the concrete mix results in fewer and smaller shrinkage cracks.

Unless the cracks become large epoxy fillers are overkill and will not solve the problem. If epoxy filler is needed wait a few years until most of the shrinkage has occurred. Otherwise new cracks can occur adjacent to the filled joints.
 
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