Crack in Slab - InspectionNews

Reggie Russell · #1 (**permalink**) 06-08-2009, 06:18 PM

Hey Guys,

I did a HI today on a small 10 year old home sitting on a slab. Since I am still a newbie, I would appreciate you guys' opinions on the severity or lack thereof on this crack.

Jerry Peck · #2 (**permalink**) 06-08-2009, 06:36 PM

I wonder why that slab edge was ground down???

If you take a photo of things with your tape measure there, we could see the relationship to size on the tape measure.

I, for one, do not like to see slab cracks like that, regardless of size.

Ted Menelly · #3 (**permalink**) 06-08-2009, 07:32 PM

That all depends on what else is going on in the home like cracks in the wall, dips or a rise in the floor, doors out of square. How about the grading around the home. It looks by the close up picture that it is pretty flat around the home. All kinds of suggestions to make.

If nothing else is going on, I am sure there is with grading, no gutters etc etc, at least advise them that the crack should have an epoxy injection repair to close up that crack because monster termites can get into the home thru a crack that size.

I would suggest a foundation repair company at the least. Most of them do grading and drainage as well. An engineer won't help if there is nothing else apparent that a foundation company won't pick up on.

Reggie Russell · #4 (**permalink**) 06-08-2009, 08:40 PM

Thanks for the replies! This is the side of the attached garage. Although there were a few small cracks, this one was the biggest I saw. I did not notice any unusual movement while looking around the home, no doors out of square or anything like that.

Jerry McCarthy · #5 (**permalink**) 06-10-2009, 01:39 PM

The question that begs asking is why was the concrete slab edge saw-cut?

Jerry Peck · #6 (**permalink**) 06-10-2009, 06:38 PM

Quote:

Originally Posted by Jerry Peck

I wonder why that slab edge was ground down???

Quote:

Originally Posted by Jerry McCarthy

The question that begs asking is why was the concrete slab edge saw-cut?

Another question I keep wondering about: Why is that slab that color? Why ... why would someone tint the concrete in a slab? The aggregate is exposed and the concrete between the aggregate is still that color. Why?

Jerry McCarthy · #7 (**permalink**) 06-10-2009, 07:55 PM

Maybe, just maybe..... somebody retrieved an old precast concrete panel from a shopping center tilt-up building and employed it as a slab foundation for their home? Naw, but I guess I'll have that 4th glass of Napa Valley Chardonnay now...........

John Kogel · #8 (**permalink**) 06-11-2009, 09:37 PM

Quote:

Originally Posted by Jerry Peck

Another question I keep wondering about: Why is that slab that color? Why ... why would someone tint the concrete in a slab? The aggregate is exposed and the concrete between the aggregate is still that color. Why?

Ever been to Sedona, AZ? Red sand makes red concrete that looks like that. They trucked that slab a long way!

Jerry Peck · #9 (**permalink**) 06-11-2009, 10:20 PM

Quote:

Originally Posted by John Kogel

Ever been to Sedona, AZ? Red sand makes red concrete that looks like that.

Actually makes sense because when I was in Gainesville, Florida, near Ocala, a few builder used concrete block from Ocala instead of the block made in Gainesville.

This was because Ocala had yellow sand and the concrete block was yellow, and called "Ocala Block".

I owned a new house made of Ocala Block, laid up by real masons who knew what they were doing.

The advantage of using Ocala Block was that it was yellow through and through, and as long as you did not paint it, you never needed to paint it - VERY LOW exterior maintenance.

Those mason knew how to lay block so it did not leak, even without paint on the exterior of the block. And the block was laid straight and true, leaving the mortar joints exposed was part of the look.

In South Florida, they had leakers even with 1/2" of stucco plastered on over the block to hide all of the block laying defects ... which was of course why they were leakers - all those defects.

Joao Vieira · #10 (**permalink**) 06-12-2009, 05:21 AM

or maybe someone just added color pigment to their mix..it's ok if not in huge amounts that would weaken the mix strenght.

Concrete is a very flexible material now I am thinking about it. I am making those concrete counter-tops and I can tell you that the learning process has been and it is a great experience.

About the photo itself: it seems also that there is a regular gray concrete on the middle just under the crack....I would recomend to investigate further on the interior of the house and would note on my report. Cracks on concrete slabs are very common. some can be serious while others just sit there for more reasons than I have time to explain. More often than not builders of small houses don't compact the soils properly. If there is rebar or wire mesh in the slab then it's normally an easy fix. saw cut along the crack or use a small power tool, or even chisel and hammer (making sure to not cut reinforcing steel) and apply concrete crack filler material. there is a gazillion of choices.

edited: My post relates to the fact that the house has been there for 10 years so the crack it is what it is unless there are recent changes on the subgrade.

Rick Cantrell · #11 (**permalink**) 06-12-2009, 05:39 AM

JV
Nice looking top.
Is the 2nd top concrete, made to look like wood? If so, why?

Joao Vieira · #12 (**permalink**) 06-12-2009, 06:05 AM

thanks!
well the first with the exposed aggregate was the test..my wife didn't like it much and on the end me neither..but women win all the time anyway ;0

the smooth brown was poured on a flat surface that's why it has the smoth look..the difference is that I didn't sand down the second unitil I exposed the aggregate like I did on the brown one.. bothe have pigment mixed in the concrete mix and that's why my comment about the concrete color

Bruce Ramsey · #13 (**permalink**) 06-12-2009, 06:31 AM

The original poster is located in Alabama. Red clay is the common soil there. When it rains, the red clay splashes against the house and dies everything red.

Remember the scene in My Cousin Vinny where he spins the wheels of the caddy in the field in the red clay and then slips in falls in the red clay? Alabama.

Even so, it still looks like pigment was added to the pour.

gary gramling · #14 (**permalink**) 06-12-2009, 09:25 AM

The question as to the saw cut is very interesting. It suggests that there was slop that needed to be squared.
As to the crack, there does not appear to be any significant displacement, horizontally or vertically. The crack edges are matched up pretty well and the visible bottom of the slab seems to be in line on both sides of the crack. I agree, a tape measure next to the crack would be helpful.
Unless the garage floor is covered with an epoxy surface, you should be able to observe the top of the crack. How wide is it there? Is there vertical displacement?
Hopefully, there is rebar in the slab. Mesh would probably be corroded through after 10 years. It would be in my area.
At the very least, I would call attention to the crack in my report, recommend the sealing to prevent insect and moisture intrusion; and, recommend that it be reviewed frequently for signs of displacement. And, would tell them that, at the first sign of displacement, to get a qualified concrete contractor on the site.
Gary

Jerry Peck · #15 (**permalink**) 06-12-2009, 10:28 AM

It looks more like the marks from grinding down than from a saw cut.

Ed Garrett · #16 (**permalink**) 06-12-2009, 11:37 AM

Hi Reggie,

I've seen a lot of strange things in rural parts of the country including building out over a patio slab.

With the color, I wonder if this was a patio slab off the house that was "converted" to a garage floor. Could have been any shape previously but needed to be squared off for the wall.

If there is a footing underneath or the rest of the house has the same color foundation, then it was probably part of the original construction (all assumptions based on the available information provided). On the other hand, if the rest of the concrete is not colored, I would suspect you are looking at a patio slab that has been conveniently converted into a garage.

If you don't find a thickened edge for the slab, then you are probably also lacking adequate reinforcement for vehicle parking. May be enough to handle wall loads for a garage but not driving in and out.

As far as the crack size, it is similar to what we see in the Sacramento Valley of California on our expansive Clay soils. If there is rebar properly embedded (which you really can't tell by looking) you could see this size of a crack in a slab and it not be a problem ... However, you get quite a bit more rain in the summers than we do here in CA ... so ... combined w/ the colored concrete, the saw cut and the cracking ... I would be concerned.

What to do with that concern is the question ... for me, the first question is if this is a patio slab. It is relatively simple to check the edge to see if it is thickened (dig out next to some part of the slab). If it does not conform as a "footing" then I would expect you have a cut back patio and it would be up to a structural engineer to advise on support or use.

--
I'm wondering if this is in an area where permits are required (I know of some places where building inspection and permitting is only within city limits)? If so, a check w/ the building department could show if the house was originally built w/ a garage ... Tax assessor might also show original size of house and any garage or change.

My thoughts,

Ed