Cracks in new CMU and wide gaps


Old 02-24-18, 07:13 AM
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Question Cracks in new CMU and wide gaps

If a CMU is obviously cracked while a contractor is forming the frost wall foundation, what should I do? Accept the explanation of the skimcoat? will cover it and patch it? There is also a >1" gap between two CMUs that form the column between the garage doors. The current "fix" is a wide bead of caulk? that didn't quite fill the void. Should I be concerned, or again, allow the contractor to fill the voids and cracks with grout and skim coat? or whatever coating goes on the outside? Thanks.
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Last edited by DrEH2012; 02-24-18 at 08:10 AM. Reason: Add photo
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Old 02-24-18, 05:16 PM
Join Date: Dec 2013
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largely depends on where your ' where ' is,,, otherwise not the best of work,,, MORE importantly is the coating applied to stop moisture/water,,, code calls for a 3mil asphalt emulsion,,, whille i'm in favor of code-compliance (our main work is basement wtrproofing), you'll never again have the opportunity to 'WATERPROOF' the exterior as such a low cost as you do now while its open AND easy to apply,,, may cost you a few more $ now BUT its $ WELL SPENT
Old 02-24-18, 08:17 PM
Join Date: Mar 2005
Location: USA
Posts: 6,128
The contractor was very "iffy" and could not even lay the first few courses and maintain the traditional running bond. Somehow, the contractor made or found a lot of cut block, which is costly in the end.

I see a few problems with the construction photo, but the wide joints would not have major effect on the strength of the masonry wall, despite it looking very bad. Concrete masonry is very resilient and can overcome most contractors sloppy workmanship. The architect/engineer did not have a cue on how to design a building to modular dimensions.

You use mortar to fill and finish joints and the grout is used to fill the cores where necessary. Mortar and gout and are somewhat similar, but nothing like "caulk" that is non-structural.

There are probably some other defects in the design and workmanship.

Personally, I like to see a below grade CMU wall laid using a very shallow concave tool and the coated with Thoroseal to provide a good surface for any soft, flexible "waterproofing" material.

Old 02-25-18, 11:48 AM
Join Date: Dec 2013
Location: usa
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why 'thoroseal', dick ? i like the product for above-grade more than below,,, we do use aquafin 2k-m more than thoro, tho
Old 02-25-18, 04:04 PM
Join Date: Mar 2005
Location: USA
Posts: 6,128
staydry -

I have been exposed to Thoroseal for the past 30-40 years. Originally, it was advertised as a "waterproofer", but guaranteeing something to meet those requirements was daunting, so it they then classified it as a cementitious coating seemingly because of the poor reputation of the "waterproofing paints" (DryLock, etc.) as far as performance.

When I worked for a public utility that had numerous (20 to 30) low head, but wide dams with a small abandoned generator. The dams created numerous lakes upstream and the associated shoreline homes, requiring the dams to be maintained. The dams were a system of walls parallel to the flow and slabs on both the upstream and downstream sides that took the weather and physical abuse of "Mother Nature". The housing of the generators was poured concrete walls and roof. Obviously any type of structure like this takes a beating over the years since they were shut down for generation, but the dams built in the early teens of 1900 had to be maintained. - The product of choice was a Thoroseal or a look-alike. The damage and erosion of the dams was severe (erosion freeze-thaw and we patch the damage and coated the surfaces with Thoroseal. The dams are still holding well and home owners are happy water skiing.

Thoroseal is not a paint!! - It is a cementitious coating bond to the old concretethat has to be applied properly - it takes work to apply a pancake batter material with a heavily coated brush. The preparation is critical (Pre-wetting -especially if a second coat is used) is the key.

The reason I like it for below grade is because it can be applied over tooled CMU joints to create a surface that even the bituminous/asphalt and "Dry-Lock" type materials can work.

For above grade masonry, it works well if the joints are cut, or better yet, tooled with a shallow tool that allows a surface for other coatings to also be applied.

It is a great product, but it must be used properly to out-last and out-perform the "quickie" products.

I bought a new unoccupied home home that had what turned out to be a leaky basement. The only solution was to sweat out the job of putting applying Thoroseal to the inside of the basement and good system of interior drain tile because of the landscaping, sidewalks, driveway and a deck precluded anything on the exterior. The interior drain tile had the invert of the plastic pipe 4" below the bottom of the footings. Since I had put Thoroseal on the interior of the block walls, I decided to do some investigation after a week of almost continuous rain and the sump pump kicking in every few minutes. I knocked a hole in the interior of the block basement wall about 2' above the floor and the water shot out about 10' into the basement and down the drain, so the contractor's system of spraying and praying did not keep the water out of the basement, but the Thoroseal did. The exterior of the wall did not have a good product, but interior coating of Thoroseal on the interior did work.

Old 02-26-18, 12:09 PM
Join Date: Mar 2009
Location: Northern Virginia
Posts: 3,708
Should I be concerned, or again, allow the contractor to fill the voids and cracks with grout and skim coat? or whatever coating goes on the outside? Thanks.
After the experience I just had, I would suggest that you seriously consider finding another contractor as this could be a sign of things to come. I held onto mine after many mistakes, and many many more mistakes were made, some of them irreversible.

Is this getting a brick veneer?
Old 02-28-18, 08:46 AM
Join Date: Oct 2015
Posts: 181
I don't know anything about laying block but that is just poor work. kick it over and make them redo it. i worked as a mason laborer for a few years and never saw anything like that.
Old 03-01-18, 04:13 PM
Join Date: Dec 2013
Location: usa
Posts: 1,333
i like xypex below-grade - cmu or conc - but thoro's a good product,,, any mtl will fail placed/installed in the wrong scenario,,,we use the 2k-m on cmu firewalls 'tween condo/townhouse units,,, cementitious polymer-modified coating,,, both work well on tooled jnts

haven't yet discovered any mtl that'll keep wtr out of the exterior surface when applied to the interior

don't like excavating below footing btm elevation,,, we'll go down to it but not below,,, basement systems franchisees use a proprietary' extrusion that sits ON the exposed fnd but there are as-equals of course,,, we use 4" s&d - smooth perforated pipe w/4" cleanouts at ea end of the system,,, no corrugated ads as it easily collects sediment restricting wtr flow,,, little more work but we don't get call-backs
Old 06-09-18, 06:54 PM
Join Date: Jun 2018
Location: USA
Posts: 6
Execrable work. Make him rip it down, hire a qualified mason, and have it done right.

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