Slab crack

I found a crack in a slab today. I am trying to do some research on it before I ask you guys to bail me out with some answers. I found this and I am wondering if you guys agree.

" When does a foundation crack become a concern? The Shallow Foundation Committee of the American Society of Civil Engineers has published some guidelines for evaluating cracks in slab-on-ground foundations based on the width of the crack. Their recommendation is that if a crack is 1/16th inch wide, it should probably be looked at by an engineer. They also state that cracks that are 1/8th inch or less do not typically indicate that the foundation is not capable of performing as intended. Also, the Shallow Foundation Committee points out that the presence of cracks in slab-on-ground foundations "does not indicate a life- threatening, dangerous condition."P

Do you guys agree that any crack in slab larger than 1/16 inch of inch should be looked at by an engineer

If you’re unfamiliar withi cracks, then probably yes.

If you have decades of experience with cracks, then it just depends on where the crack is and what other cracks might be nearby.

Generally speaking, no.

“Slab” cracks and “foundation” cracks should be looked at from different perspectives.

In most cases, slabs are not “load bearing” and are essentially independent of the foundation, whether poured monolithic or separate from the footings. PT slabs, of course, are different. So in the case of non-PT slabs, there can be major cracks and/or offsets, which wouldn’t necessarily warrant a call to a structural engineer.

When speaking of footings/foundations, while there is no “magic number,” most cracks need to be viewed as “warning signs.” While many will be simple “settling” cracks, they are indicators of the external loads/forces being applied to the structural components. Large cracks and/or multiple cracks may indicate that the external loads/forces have exceeded (are exceeding) the load-design of the structural components.

Concrete slabs crack.

Unless there is differential settling or significant cracking I explain to clients that it is typical.

I have yet to see a garage slab that was not cracked up here in freeze thaw country.

Usually it’s just hairline crack.

Great answers. Thanks. I’ll post pics in a couple hours when I get hone

Here are some pics and info. Foundation is slab but I could not verify what kind. The crack was about 10 feet long and tapered off to hair line cracks. The widest part was about 1/4 of an inch. The first floor exterior walls were concrete block. The house was surrounded with clay. How does this narrative sound.

The laundry room floor had a 10 foot long crack that was about 1/4 inch wide at its center and tapered off to hairline cracks. Cracks appear to be due to expansive clay conditions. A structural expert should determine the cause, severity, and best method of repair for the crack.

here in Wisconsin there are two kinds of concrete.
concrete that is cracked and concrete that is going to crack.


The following is a good reference article regarding cracks; take a look.

Here’s another about concrete in general:

Jeff, while I generally agree with your statement, it is oftentimes difficult to distinguish whether or not an interior part of of a monolithic slab is actually load bearing and a footing (thickened slab) without looking at the design documents. Just something for the OP to keep in mind. Most monolithic slabs do have interior thickened, load bearing portions, especially two story homes.

Thanks Joe. That did occur to me while I was trying to decide how to report on it.

Absolutely true, and that’s where field experience can make a difference in evaluating cracks from an HI perspective. Most “thickened” slabs will have other load-bearing components in their proximity, such as a shear wall or support wall. This is often more distinguishable when viewing the attic framing/trusses.

For the most part, non PT slab sections that are in an open space, are not considered load bearing.

what ?