New article: Crack Analysis

I’m cracking up

Yes, back to helping Kenton in expanding the reference section on his website…anyone? Please, anyone? He is being sincere and I am goofing around…sorry. :pensive:

Nice and condensed reference Kenton. I also like your 'visual inspection of concrete" :slightly_smiling_face:

Thanks Joseph!
Yep, I’m a big fan of Harry Audell’s book. It keeps things fairly simple and provides a good way for people to understand the forces that cause cracks.

We might need to crack down on you, young man!

You know, I posted this subject in absolute sincerity. Joseph is the only one able to lash a leash on the temptation to spout jokes about cracks. Even I am guilty.

It took me some time to put together that article Analyzing Cracks on my website. I’m expanding the reference section on my website hoping that internet searches related to inspection topics covered in my reference section will bring inspectors to my website who don’t yet know about the InterNACHI Narrative Library. Other than my posts, they don’t have any good way to discover it.

I’m also working with a couple of inspection software manufacturers to produce a new feature especially important to newer inspectors.

Based on my experience the As Built Line (ABL) in that reference book is a nice to know, but rarely known or available. Foundations and slabs routinely are out of level or plumb. So when I have to look at a structural issue your basically putting a puzzle together with pieces missing and in some cased multiple unrelated structural issues can be found in one house. This is like two or more puzzles mixed together with pieces missing. With 35 years as a structural engineer and 25 years doing home inspections identifying the cause of foundation and wall cracks can be difficult. One piece of advice is most basement floor slabs are poured independent of the perimeter foundation. Cracks due to movement in the floor slab can be and often are not related to cracks found due to movement in the exterior foundation walls. One tip I can give is 90% of the time a diagonal drywall crack over a door or window almost always points in the direct where the floor or foundation has move down. But the best tool I have is to do a floor elevation survey of the basement floor slab combined with a floor elevation survey of the first floor of the house. Looking at all the cracks and crack patterns from a 30,000 foot view often tells more than looking at individual cracks. Last point I want to make is when looking for puzzle pieces don’t be too quick to say you know the whole picture. Start with knowing the basics of concrete and soils, then learn as much as you can from more experienced inspectors and engineers that specialize in building inspections.

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My favorite floor/slab/property elevation tool:

zip

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I ran into an inspector in Dallas was year who uses this level system, and I was impressed. He was an engineer too. I think engineers know how to use these systems and have the skills to use them correctly and avoid trouble. I kinda worry that inspectors with lesser skills will get themselves into trouble using this technology, since it’s pretty far past the SOPs.

Especially since I agree with Randy that a number of things can be going on with a structure and maybe inspectors should not be too quick to specify in their reports the causes of problems that they’re not required to identify. I think cracks are good clues as to what forces are acting on a structure, and they might lead an inspector to look somewhere he might not have looked if he hadn’t seen a crack.

If either Randy or Darren were to give a one-day class on any aspect of home inspection, I’d happily pay good money to attend.

I agree Kenton. Just because someone can purchase the equipment, doesn’t mean they know how to interpret the results.
I too would pay to attend a class by Randy or Darren.

This is true. I don’t think I’ve ever used this during a HI. Definitely use it quite often in structural assessments and structural baseline studies. Used an older model pretty steady in the months after Superstorm Sandy. Flat out awesome what coastal overwash can do to a foundation. Saw a bunch of homes that were basically tilted toward the ocean, 3 to 4 inches from one end of the house to the other.

This is great info… just inspected a duplex a week ago, built in 1961…1 story, one corner of the building had both horizontal and vertical movement, looked like about 3ft of the corner was just sinking, I agree that in this case, too much info can be dangerous, but I feel it really helps to understand the science behind the problem, I really appreciate the info about rating and identifying the cracks more thoroughly - will definitely help me write a better report.

We offer foundation level surveys with the Zip Level as an option for our inspections here in Texas. Randy, you mentioned foundations are routinely out of level. Especially true with pier and beam foundations on older homes around here but the new construction slab foundations are poured with lasers used to help level them during pour and are mostly pretty accurate. We have expansive, shifting soils around here and over the years many slab foundations do experience settling past the acceptable variance of no more than 1" variance within 30’.

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Jpseph, is “…no more than 1” variance within 30’" a dimension set by a standards organization?

The National Association of Home Builders set it at 1/2" in 20’, last I knew, Kenton.

I run into radial cracks in slabs constantly.
Great information Kenton and Marcel.
Much thanks from this inspector.

Kenton, To answer your question- After 40 years of construction experience the first thing I would say is that here in my parts it’s an industry standard. But also I believe L/360 is the allowable variance / deflection in the IRC for structural floors which equals 5/8" in 20’ or 1" max in 30’.
Also, years back the Texas branch of the Amer. Society of Engineers established the 1/360 ratio as the standard max variance in foundations along with no more than a 1% tilt. Engineers that design the slab foundations around here are also known to use the IRC L/360 ratio for max acceptable variance (of level) on the concrete pour of a slab foundation in their engineered foundation design requirements. That of course has to do with the quality of the pour- not from settling.
We get called out a lot to review settling issues by homeowners for their foundations / structure on homes less than 10 years old. Builders in Texas are liable for the entire structure for 10 years.

Darren, we use the Zip Level for quite a few things. Even commercial property flat TPO roof slopes. Check out our page on Zip Level uses we do. http://www.jwkhomeinspections.com/zip-level-foundation-elevation-survey.html

Thanks Joseph (and Larry).

I thought the engineer who signed off on the plans would be the one responsible for a foundation that didn’t accommodate soil movement since (unless his in-house engineer was the one to approve them) the general contractor is just building to an approved set of plans.
Isn’t the engineer responsible for signing off on a design that takes the result of soils testing into consideration? Why is the general contractor held responsible? I’m assuming by “builder” you mean general contractor and not a developer.

Here is an example of a color coded contour map of a raised foundation slab. Dark blue is the lowest areas and bright yellow is the highest. The left side is the garage slab. The two dark blue areas were settlement due to poor grading, i.e. soft saturated soil. The right side is the floor slab in the house. The large blue area in the middle is due to settlement of a large brick fireplace. It was constructed on the top of the floor slab without a footing.

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Kenton, Yes the Builder (Homebuilder) is the General Contractor - but on new home construction is referred to as ‘Builder’ here in our parts. Yes, the engineer provides the foundation plans, based on soil test & that they sign off on but it’s the Homebuilders product. - Engineer (not in house) is hired by builder. Of course, builder will go back at engineer if there are foundation problems. The engineer designed it, inspected it and certified it. But it’s the Builders product and they are on the hook liability wise for the structural integrity of the home for 10 years in Texas.