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3 signs your contractor is doing more harm than good to your masonry building

We learn early on in the preservation field about the dangers of abrasive “cleaning” on old masonry. Heck, it’s even immortalized in the Secretary’s standards, saying, “Chemical or physical treatments, if appropriate, will be undertaken using the GENTLEST means possible (my emphasis). Treatments that cause damage to historic materials will not be used.” (What’s that? You’d like a refresher on the other 9 standards? OK, you can check ’em out here.)
I like to refer to this as the sandblasting standard; in other words, don’t do it! When it comes to masonry, don’t blast it. Don’t blast with sand, water, walnut shells, ice pellets,  or anything else that comes out of a heavy rubber hose at high pressure. Just don’t.
Sometimes I forget that not everyone who owns an old, historic masonry building has learned this important lesson, so I’m asking you today, dear reader, to help us get the message out. Let design review boards, preservation groups, owners of brick buildings, and anyone else who could benefit from the knowledge, know that blasting historic masonry is just plain bad.
Meanwhile, I’ll share with you my unfortunate experience I had the other day, and some signs that the masonry contractor is doing more harm than good to your building.

These guys may be setting a speed record on paint removal. That's not a good thing.

These guys may be setting a speed record on paint removal. That’s not a good thing.


1. Fast paint removal
I’ve always thought of any construction project as having three pillars of output: time, price, and quality. Of course, every owner wishes to have the project done quickly, cheaply, and of high quality. But in this case, two out of three is perfection. You can’t have all three, so you have to decide which two you’re going to focus on (might I suggest high quality as one of the two).
This means that if you want something done quickly and to high quality, you’ll pay the price. If you want something done cheaply and to high quality, you can bet it will take a long time to get the project finished (if you can even pair up price and quality to begin with). And if you want something done quickly and cheaply, you’ll likely pay for it with a low quality job.
In this case, beware the contractor who offers “fast” paint removal from brick. The only way you’ll get fast paint removal from brick is at the cost of compromising the very integrity of your masonry. This is where blasting brick to remove paint comes in. Blasting brick is a great way to remove paint “fast.” What it does to the brick? Not so great.

2. Brick valleys
Masonry, even the old “soft” brick is a pretty smooth building material. It doesn’t have ridges and valleys, like what we see here, once the damage has been done.

They had the blaster set to "destroy" for this job. Notice how the horizontal lines extend along the same level, from one brick to another? This was caused by the blasting material (in this case, water), the proximity of the tool to the surface (too close), and the pressure of the blasting.

They had the blaster set to “destroy” for this job. Notice how the horizontal lines extend along the same level, from one brick to another? This was caused by the blasting material (in this case, water), the proximity of the tool to the surface (too close), and the pressure of the blasting.


When the hard outer shell of the brick has been removed, you’re left with a much softer interior. Soft interiors+freeze/thaw cycles=bad news. But, while the structural integrity of the brick has been compromised, at least the paint’s gone!
Bye bye paint, bye bye brick crust, bye bye brick integrity.

Bye bye paint, bye bye brick crust, bye bye brick integrity.


3. Nozzles and brick: up close and personal
Now, it’s not that we frown upon anything harsher than cotton balls dipped in warm water, delicately rubbed back in forth in a gentle, circular motion, to cure what ills your brick. It’s just that there’s this wide gulf of possibility between too gentle and too harsh. Yes, you can loosen flaking paint with water jets. But, you have to be careful that the pressure setting won’t harm your brick. You also have to be mindful that water, as the sworn enemy of historic buildings, will do bad things if it gets into the building. And, even a low setting too close to the wall can be bad for your brick. A high setting too close to the wall is more like fatal for your brick.

As preservationists, we should all savor the opportunities to educate people about the wonderful assets they have, and that the care and maintenance of elderly buildings is best left to restoration professionals.