Narrative for explaining control joints doing their job?

Hello All,

I have some out of state clients who are buying sight unseen. The house is a 2017 build and one of the cleanest I’ve inspected so far.

In the garage, on the floating slab there are control joints that have cracked and appear as if they have done there job.

Here in Colorado I find 90% of homes have shifting, raised, cracking issues from likely expansive soil but in this case it doesn’t look like that to me.

So, do you write an “informational note” when control joints do their job to inform the client but not alarm them? And if so would anyone care to share one to help me out. The are nervous and I have a feeling the are the types that want to know everything about the property.

Thanks Much,

Control joints are typically used in concrete masonry to reduce the occurrence of shrinkage-related cracking. A control joint is a continuous vertical joint filled with mortar, but with a bond breaker on one side so that tensile stress cannot develop across the joint .”

The concrete mix and curing process of the slab determine how bad the shrinkage cracks will be. I would seal the cracks with flexible caulking (we don’t want water getting there) and live a happy life. People fret over nothing in 2020

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Agreed, those control joints are working as intended to provide a place for the concrete to relieve itself due to normal shrinkage and prevent wild cracking.
As mentioned above, they should be sealed to prevent air from infiltrating the gap and promoting possible slab curl which occurs when the underside of a slab starts to dryout to fast.
I would recommend a good polyurethane sealant which also prevents water intrusion that could rust out the wire reinforcement if any.

Ryan, what City is the house located?

Do you normally write up and comment on things that work as intended? If you don’t normally comment on it outside of the check box on the report form why would you do that in this case?

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You should not be worried about alarming anyone when speaking the truth. That will only lead to bad calls and a lack of information for the client.

In this case, and any cracking concrete case, I would most certainly notify the client. Here is a possible wording to use, modify, or don’t use.

The concrete contraction joints placed in the garage floor appear to have performed their function to control the location of cracking. The National Ready Mixed Concrete Association CIP 6 will provide an explanation of the purpose of contraction joints (as well as others) and can be found here . I do recommend you consider having these cracks properly sealed to prevent moisture migration into the slab which can cause other issues.

Marcel is spot on that they need to be repaired! I write up any concrete cracking and recommend sealing to prevent moisture migration that can damage encased reinforcement as well as other possible damages. At that point you’ve done your job and it is up to and on the client whether they heed the recommendation.

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You left out slump, weather conditions at time of placement, substrate material… LOL. A self leveling “caulk” would work best in this instance. The integrity of this slab was lost the day it was poured anyway. Cracks can tell a story if you know how to read them…

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SIKA makes a good self leveling joint sealer. Been using it for years.

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I don’t usually, I might mention it if the clients were present, but like I said clients are buying sight unseen

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I’m just up the road from you. Odds are the slab was poured over a layer of pea gravel even though the soils down there aren’t as bad as up here. If the joints don’t pose a trip hazard, then they are okay. If anything, suggest they be sealed with a self leveling joint sealer. Other than that, I wouldn’t even bring it up.

Same here; I was usually the one that had to seal all the brick control joints on the building and exposed shop floor control joints that were exposed on schools I built.
That Sikaflex is a good product. Also used the NP1 quite a bit also.

Yep! They used to sell the Sika products in HD but no longer, at least in my area. Best material I ever found.

Yes, Sikaflex is an excellent product, I use it on occasions you can still get it at the other big box store. :+1:

For me, due to the commercial job specs and colors required, we mostly had to use the Sonnoborn NP1 or the Tremco Dymonic.

IMO then it should be a quick phone call to go over the report and tell them this is a control joint. I would not point it out in a report unless there is a defect. Also IMO if they are nervous, are you going to inform them of how Colorado’s weather adversely effects many aspects of their home. Or how CDOT utilizes magnesium chloride to deice the roads and if they drive on it and onto their garage floor the Mag chloride will start to deteriorate the surface of the concrete floor. What I’m getting at is there are many things we can point out or educate our clients on. Better to include those sort of items in a follow up correspondence. Hope you do well up there I lived in the North Metro for over a decade and observed the construction practices of the builder up there. Cheers!

I respectfully disagree with this statement. Prior to HI, I was a PM with a Geotechnical Engineering firm in the North Denver Metro Area. Broomfield has some of the most potentially expansive soil in the Metro Area.

And would you not report damaged concrete as a defect?

Hence the bed of gravel. Gives the bentonite a place to swell into. The soil at my house moves a lot depending on the weather. My driveway heaves 2" when we get heavy rain or a lot of wet snow. There are so many soil types up here it’s rediculous. BTW you are 100% right about that mag chloride is like cryptonite to a driveway, makes it spall like crazy.