I just got this pic from Manufacturer’s Rep Jeff Lucas, of J.N. Lucas & Associates, Hammond, Ind. Jeff got called in by the brick’s manufacturer to see if he could figure out a way to fix the damage.
The building is new masonry construction — a civic center in Indiana. That red brick is made of concrete, not clay. The problems occurred when the mason contractor tried to clean off the job dirt and excess mortar. That’s standard procedure, but the contractor missed the boat on several points, according to Jeff, who’s been in the biz nearly 30 years.
The contractor’s main error was that he didn’t realize concrete brick is more sensitive than clay brick. He had the right kind of masonry cleaner, Jeff said, but ran into trouble with the pressure rinse.
Once the cleaner has “dwelled” for the prescribed time — usually a few minutes — and dissolved the excess mortar and job dirt, you rinse it off with a pressure washer. That’s where the problems happened. The contractor, or his workers, hit the masonry with a solid stream, zero-degree fan tip, at about 2,400 psi. That’s a virtual laser beam of water.
You can see where it cut through the surface of the brick, exposing a darker subsurface. That’s why the scars are less apparent where the bricks are darker. You may have also noticed the white residue covering most of the wall. That’s where the cleaner dissolved excess mortar, like it’s supposed to. But the contractor didn’t use enough water to fully flush the spent cleaner and dissolved mortar from the wall.
When the wall dried, it revealed the chalky white mess you see in the photo. Jeff said the pressure washer used was a home model, equipped for only about 2.5 gallons a minute. A job like this takes closer to 6-8 gallons a minute. When it comes to flushing spent cleaner and the dissolved contaminants it carries, success is more about gallons per minute (gpm) than pressure per square inch (psi).
It’s more about how much water you put on the wall, and less about how hard you hit it. You get all the pressure you need at 400 -1,000 psi, with a 15-degree fan tip, minimum, and are much less likely to leave your initials in the masonry.
Particularly when working with concrete masonry, which is more sensitive than clay, reduced pressure is important. But I’ve seen clay masonry scarred just as badly by youngsters getting right up on the brick. In those cases, there’s not much that can be done, outside of replacement.
Fortunately for this contractor, Jeff says the damage is repairable. He tested some samples and found that by scrubbing the brick with another dose of cleaner, and thoroughly rinsing, he could remove the thin surface layer that had been scarred. That will once again reveal the dark brick color created by the manufacturer.
It’ll be a lot of work, but the contractor should count himself lucky. He could’ve been liable for replacing the whole thing.
You can learn more about the fascinating subject of cleaning modern masonry by downloading my white paper on the subject – New Rules for new-construction clean-down of contemporary masonry buildings. It’s free. You don’t have to give us any information or anything. Just hope you find it helpful or at least interesting.
Might have saved that contractor some grief.
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