Floor slab & tile crack diagnosis & repair questions & answers:

FAQs about how to diagnose & repair the different types, sizes, shapes, locations, & patterns of cracks found in concrete floors & slabs. Some floor slab cracks are harmless or even just "cosmetic" while others may spell trouble ahead.

This article series describes the types of cracks that occur in poured concrete slabs or floors and explains the risks associated with each, thus assisting in deciding what types of repair may be needed. This series also describes how to recognize and diagnose various types of foundation failure or damage, such as foundation cracks, masonry foundation crack patterns, and moving, leaning, bulging, or bowing building foundation walls.

Page top photo of a supported slab on grade design is provided Carson Dunlop Associates, a Toronto home inspection & education firm.

FAQs on how to Diagnose & Fix Cracks in Concrete Floors

These questions & answers about the cause, diagnosis, cure or prevention of types of cracks in concrete slabs and floors were posted originally at CONCRETE SLAB CRACK EVALUATION - home - be sure to see that article..

[Click to enlarge any image]

Photo: shrinkage cracks in a concrete slab in South Texas, poured / placed in July 2018.

On 2019-04-13 by (mod) - don't assume that a wood floor gap is due to slab cracking unless ...

Jana

I don't assume that a wood floor gap is due to slab cracking unless there is other supporting data; after all the slab is covered -we can't see below the wood; before assuming it's the slab I'd wonder if there is or was movement in the floor itself.

You could do some moisture measurements (use an electronic device not a pin type) - if you see moisture higher at the crack that's indeed suspicious and raises the level of your water entry concern. At that point one might need to make a test opening to look into the floor cavity.

An astute inspector will find other probable causes of water entry outside or perhaps even inside.

On 2019-04-12 by Jana

We are thinking of purchasing a home that has a 1/4 inch space in the hardwood flooring that I can assume is from a cracked slab.

We have seen this particular model of home with the same crack in it before. It doesn't appear to be on the outside wall of the home. It is as you walk inside in the first room on the interior.

My gut tells me this is a bad idea to purchase this home with this known problem. I am wondering though if we could fix it. My main concern would be water intrusion and mold buildup in the home as well as the integrity of the foundation. The house is 4 years old.

On 2019-03-12 by (mod) - How can you tell if there really is fiber in your concrete?

Good question.

Check ck the specifications on the concrete order. It may be difficult to see fibres by naked eye.

We should both do some more research.

Also you may want to be sure you have an accurate diagnosis of the cause of slab cracking.

On 2019-03-11 by Judy

How can you tell if there really is fiber in your concrete? We were told there was by our contractor but when we had the guy out to see what could be done to fix our cracked slab he said he wasn't seeing any fiber at all.

On 2019-03-11 by (mod) - crack runs width of house

I think the slab jacking company is right in that they probably can't get their equipment into a too-tight crawl area.

Sometimes it's possible to inject mud for slab jacking from the edges. You might discuss that option with them.

Helical piers are an alternative suggestion to a Mud Jacking but probably face the same access difficulties unless you can provide adequate support from the edges of the slab.

Alternatively you might have to hire a structural engineer to design a completely independent support system for your home using a combination of beam and piers 4 placement of the peers outside of the existing home perimeter. In my opinion that's a rather ugly solution. It probably is less expensive to temporarily disconnected move the home or to Pump from the edges of the slab.

On 2019-03-09 by Judy

We had a concrete slab poured 15 months ago for a 32x60 double wide. We had to have a large amount of fill brought in about 8 to 10 gravel trucks full to level the property. The contractors we hired used nothing to compact the fill only a small tractor to level it off and only used that after all gravel was on sight.

We now have a 1/4" crack that starts about 16ft the width of the house and runs 46ft the length of the house.

It tapers off to about 1/8th inch wide the last 20ft and basically is the shape of a half circle, This crack also runs across our water lines which are under the concrete.

There is also a 1/2"stair step crack that runs directly off the vertical crack and extends over 3 blocks to the underneath of the house. We have started seeing wall cracks, doors sticking and now are ceiling is starting to crack. Have spoken to a mud jacking company and they said the house would have to be moved to fix the problem. Any suggestions other than that drastic of a measure to fix our problem?

On 2019-02-24 by (mod) - broken pipe, water undermined foundation

It sounds to me as if some of the soil underneath your foundation or slab has been disturbed by water.

A foundation repair contractor might drill some exploratory holes to establish the conditions and might pump grout or use other slab jacking techniques to stabilize the floor. So you want a consult with an experienced Foundation contractor or geotechnical engineer.

On 2019-02-24 by Lucia

An underground pipe break caused a massive amount of water to shoot beneath my home’s foundation.

The house was built 40 years ago and in the 20 years I have lived in it
up until the water episode, my house never had any cracks or signs of movement.

I now have some very sizeable cracks in the foundation beneath my carpet and floor tiles on the slab are separating at grout seams. Both vertical and horizontal cracks are appearing and spreading on both interior and exterior walls. In addition outdoor concrete areas are cracking and in certain areas lifting.

Interior doors no longer align. I was told my house was built on bed rock and I have nothing to worry about . Yet as my house continues to move, I can’t help but be worried since research suggests that when water is forced into an area without an outlet, it will seep downward causing damage .

Could I possibly have a sink hole? What type of expert do I call to find out? It sounds like many of the problems Ash ( jan 16 /19 ) is describing is a lot of what I am also seeing. I would really appreciate your feedback.

On 2019-02-02 by (mod) -

Probably one of the causes listed in the article CONCRETE SLAB CRACK EVALUATION, Jeremy, such as bad mix, freezing, absence of control joints, concrete shrinkage.

From a one line query and not a shred of actual information about the job, site, pour, conditions, mix, etc. that's about all one an say.

On 2019-02-02 by Jeremy

Garage floor concrete slab casted with steel reinforcing 24 hours ago. Today concrete is dry but cracks appear all over. Cause?

On 2019-01-26 by (mod) - had a vehicle drive off my driveway dropping 15 ft. below

Darrell

It should be possible to make a very close inspection of the crack, including using magnification, and photo-document the observations, showing whether or not the crack is new - freshly broken - or old - containing dirt, debris, weathering.

Use the Add Image button to show me the situation and to add some closer images of what you see and I may be able to comment further.

One image per comment.

On 2019-01-26 by Darrell

I recently had a vehicle drive off my driveway dropping 15 ft. below it took two tow trucks one on each end of my stamped driveway and 4 hours to remove it they cracked my driveway down the middle approximately 50ft of it

my insurance company is claiming the 15000 lbs of vehicle weight did not create the crack that it was existing is there a way to prove that there was no pior cracking before the two vehicles parked

there they waited 11 days before an estimator came out and looked at it and we had several days of heavy rain during that time creating flooding in that area so all the cracks were filled with dirt at that point any suggestions out there

On 2019-01-16 by Ash

My house is about 28 years old built on a slab and at one end of the house I noticed the brick outside cracking in a path now it has cracked through the inside through my walls and I can feel the cracks in the slab underneath my carpet.

My walls have cracked around the windows and door facings up to the ceiling, where do I start ??? I'm guessing it has dropped at least 2.5 to 3 inches im guessing.

On 2018-12-21 by (mod) - should I be concerned about a hairline crack?

Larry: do some further investigating: are the cracks only in the waterproof coating?

Add an image so that we can take a look.

On 2018-09-04 by Larry C

I just had my basement water proofed and now in 96 linear ft. of new concrete I have 22 hair line cracks should I be concerned ?

Question: do we need a structural engineer to look at the cracks in our concrete slab?

(Aug 28, 2015) Dejolly said:

We are building a new home. Just beginning Sheetrock. Have noticed several cracks in concrete slab. All are running east to west pattern. Should we be concerned. Should we calls in a structural engineer?

Reply:

DeJolly I can't diagnose your slab cracks from just your e-text. They may be shrinkage cracks and not significant or they may be important. Take a look at the article above for examples of both. If the cracks are regular they may be marking pour joints or concrete form locations;

if you can't figure out what's going on you can both send us photos of the cracks - our email is at the page bottom CONTACT link, and you can and should ask for help from a local, exprienced masonry contractor or engineer.

Watch out: don't hire a "generic" engineer nor contractor who does not have expertise & experience in concrete construction & crack diagnosis & repair.

Question: criss cross cracks in the garage floor, new construction: what happened?

(Sept 21, 2015) Anonymous said:I am purchasing a new construction adult housing.

It is a ranch with attached 2car garage. Last week I noticed that the concrete floor of the garage had a criss crossing crack - all the way from front to rear and crossing in the middler from right to the left. Why would new construction already be cracking?

I initially looked at this property end of March, but did not think to look at the garage floor.

At that time it was just a shell. windows were in but walls were just studded.

I also know that the area is clay. My daughter lives about a mile away, also has clay. Her house is 14 years old and the garage floor has no cracks whatsoever. Why do you suppose this happened?

Reply:

Omission of control joints

Settlement

Concrete shrinkage

Expansive clay soil - heaving or shrinking and settling

Take a look at the

article CONCRETE SLAB CRACK EVALUATION for details

Question: 1955 slab giving way below a laminate floor - can it be repaired?

Oct 16, 2015) Jeana said:My house was built in 1955 on a slab floor. I can feel the floor giving way under my laminate flooring. Its about 10 feet long and the gap is about 4 inches.

Can that area be repaired or does the whole front room have to be done? Why would this happen?

My pipes are in the walls and go out the opposite way of crack.

Reply:

With apology that it sounds more glib than intended, any problem can be repaired, the concerns are 1. making the right repair so as not to have to repeat it and 2. cost.

Various methods including insertion of piers or pumping concrete below a sinking slab (mud jacking) are common repairs, but don't start asking for a repair before knowing the cause.

I'm not sure what 4" gap you mean: if you mean a 4" wide crack or floor that has settled 4" that is a major movement and even though your home is built as slab on grade, the building could be unsafe - for example if a sinkhole is developing.

You need an accurate diagnosis of the cause of the problem before a repair can be properly chosen.

Question: cracks appeared in garage floor after I turned on the radiant heat there

(Nov 3, 2015) Joanne said:Hi there,Last May I moved into my newly built house.

A few weeks ago I turned on the garage floor radiant heat and now I have excessive cracking so much so that my garage floor looks like a jig-saw puzzle. The floor has been in well over a year without any cars parking in the garage.

This is a vacation home. We are thinking of spending money and days to fill in the crqacks than epoxy over.

Should I be concerned about the future of the garage floor and not epoxy just yet?

Reply: Before simply filling cracks with an epoxy I'd want to know what's going on.

oanne something sounds wrong with the slab construction or the radiant heat floor construction as such cracking is not typical;

Before simply filling cracks with an epoxy I'd want to know what's going on. It's possible that insulation was omitted below the slab, that backfill was left soft, or that other snafus are going to mean further trouble.

If you have photos of the cracks and also importantly of the floor during construction, use our page bottom CONTACT link to send them to me for comment.

Question: raised cracks in garage floor, maybe from tree roots?

(Nov 7, 2015) Scott said:We are about to sell our home and have a series of cracks in out garage. This is a concrete slab home. The cracks are raised, at their highest point, 1/4 to 1/8". We know of roots in our yard, but do not have any major trees that close to the house. Are we in big trouble for an inspection?

Reply:

Scott, not to put too fine a point on it, the range of home inspector competence, ethics, and ability to communicate is stunning, so I can't predict what fuss may be made about cracks in a garage slab. I would want to see the crack pattern, location, building history, signs of ongoing vs old movement and other factors before forming an opinion.

Shrinkage cracks and slab cracks that do not extend into the building supporting structures such as a footing or a concrete wall or stem wall are not normally a structural concern so are less scary.

Not just tree roots but settlement and tipping can cause one side of a floor to be higher than the other across a slab crack.

A crack up 1/4" can be a trip hazard regardless of cause, though depending on its location, repair may not be urgent.

If I thought there was ongoing settlement I might think more extensive investigation was justified and that a costly repair could be required.

At the ARTICLE INDEX link given above you'll find detailed articles on evaluating cracks.

Comment: concrete cracking in hot countries

(Jan 10, 2016) Eng.Hasan A AlBahkali said:concrete craching in hot countries this subject is very important

Reply:

Indeed proper mix, curing rate, moisture control are critical in good slab installation in both hot and cold climates. You may see contractors covering a slab to protect it from rain, from too-rapid moisture loss, etc. or using special additives to compensate for temperature.

Question: huge crack in new concrete slab, water leaks into the room

(Jan 13, 2016) Saurabh Heerekar said:

Mine is a newly poured concretre slab just about 2months old,and I have noticed a huge crack on my slab which actullay leaks water drops directly inside the room!

I am seriously concerned about this problem and hoping to get a reply asap!
Note:The water drops aren't leaking from a plumbing pipe defect but from the slab itself!
Help!
Regards.

Reply:

I agree that this sounds like a serious defect and one that merits an onsite expert; there's not enough in your e text to speculate about cause nor effect on the building.

Question: cracked ceramic tile on a concrete slab

(Mar 20, 2016) Sue said:we added an addition on our house which is on a cement slab (no basement).

The addition is in back across the entire back of house which made our kitchen bigger added a bathroom and living room bigger, we put ceramic tile in kitchen and after a few years it had a hair line crack where addition meets the cement the new cement slab we poured is settling,

so we fixed the tile and under rug in living room smoothed it together using epoxy in cement and it is cracked again

how can we fix this problem? I am desperate for answers please help! my email is srenckert@gmail.com

Reply:

Sadly, Sue, fixing tile cracks traced to slab settlement will never work by being repaired from above. You'd need to understand an fix the cause of settlement of the new slab.

It may be that the site was not properly prepared, or a slab is settling on poorly compacted fill, lacks adequate footings, or there could be a problem with handling roof runoff or surface runoff around the home.

You need an onsite expert, perhaps an experienced mason, home inspector, or an engineer who is familiar with residential slab failures. Keep us posted.

Question: My slab foundation has a crack in an outside corner of the house. Can I just carpet over it?

2016/04/22 Danielle said:My slab foundation has a crack in an outside corner of the house. It's path is from one wall to the other wall, about 11 inches long.

I discovered this crack when the carpet was removed. I see no water damage, but there is a huge shrub that was planted way too close to the foundation which means the roots may have caused this problem?

I have not seen any bugs either. Radon gas is probably not a problem since this house is a sieve (not really great construction). Can I leave this crack alone and carpet over it or should it be inspected?

Reply:

Danielle I would not carpet over an open crack; I'd seal it first.

Question: long hairline cracks from one wall to the other in a Texas home

2016/04/26

Hi I live in Texas and planning to buy the attached home (76210), which is under construction. yesterday when I visit this place, I have observed long cracks all the way from one end of the wall to the other end. (attached two photos IMG_0558.JPG shows only one half of the side).

As I understand this is 3000PSI concrete poured about 2 months ago.

I have read some where on your site that as long as the lines are not straight it should be okay, however seems these are straight lines and concern me. can you please help with your evaluation?

I didn't find a place to upload in your site, so attached them through email. Thank you for reading my email. - Anon [by private email to editor]

Reply:

Is the floor dead flat across the cracks?

Was the pour done in sections?

Are there expansive clay problem soils in your area?

Does the floor contain control joints?

Are there pipes or conduit buried in the slab?

Was the soil compacted before the slab was poured?

Looking at the wall-slab abutment, is there sign of slab settlement ?

Reader Follow-up:

The floor is not dead flat, but I see a little curve (like U shape) on the floor all across the crack. (the crack is at the bottom of U). Regarding the pour done in sections, I am not sure, I will get that information tomorrow morning from the builder.

...

The floor was not done in sections, they pour the entire slab in one shot & the seems like floor is not dead flat.

Moderator:

So with the apology that I cannot possibly know what's really going on simply by e-texting, the floor could be settling due to inadequate site compaction prior to the pour, or it could be cracking along lines transmitted from a pipe or conduit or buried form in the slab, or between subsequent pours.

If the slab has settled downwards since pouring (look at the abutment of slab to walls) that would often confirm poor soil compaction in those areas, but that clue is not available in all cases. E.g. if a slab rests on the edge of a footing or is pinned to a wall, it may settle more in the center and not at all at the walls.

The size of your slab cracks are not a huge alarm - the look hairline in width. However depending on what caused them, and considering how early they appear in the life of the slab, more settlement, movement, cracking could be in your slab's future.

Watch out: if you see cracks appearing also in the foundation walls, particularly near the floor slab cracks, I suspect more serious settlement is going on.

...

Continue reading at CONCRETE SLAB CRACK EVALUATION - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see CONCRETE SLAB CRACK FAQs-2 - more-recent Q&A about diagnosing cracks in slabs

Or see these

Recommended Articles

• CONCRETE COLD POUR JOINTS
• CONCRETE FOUNDATION, WALL, SLAB DEFECTS
• CONCRETE SHRINKAGE CRACKS
• CONCRETE STAINS: ID & REMOVAL
• CONCRETE SLAB CRACK EVALUATION
• CONCRETE SLAB CRACK REPAIR
• CONTROL JOINT CRACKS in CONCRETE

Suggested citation for this web page

CONCRETE SLAB CRACK FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING STRUCTURES

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.
Our Comment Box is provided by Countable Web Productions countable.ca

Citations & References

In addition to any citations in the article above, a full list is available on request.

---

ADVERTISEMENT

---