10-24-2004, 08:15 PM
Hal
Cheesesteak GURU! Wiz with Join Date: May 2003
Posts: 2,660



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Quote:
Originally Posted by chrissayer
Old bricks should never, ever, ever, ever, ever be powerwashed.
Nor shold they ever be sandblasted, etc.

Those 2 treatments are the fastest way to maim a brick house.
The sandblasting will be evident immediately-

The abrasives cut right through the brick surface and expose the soft core of the brick.

Basically, a brick has the same structure as a loaf of bread.
There's a thick outer skin that's baked hard,
and there's an soft inner core that's softer and somewhat flexible
(at least soft and flexible compared to the outside of the brick)

Sandblasting cuts the hard surface off.
Powerwashing may cut the hard surface off, but it also forces water deep into the brick. That moisture can cause the brick to crumble, something known as spalling- The water is absorbed into the brick, it dissolves some salts from the brick, then as the mildly salty water dries out, salt crystals form and that disrupts the brick - it's basically the same crystalization process as freezer burn - and similar to freezing bread - it gets crumbly.

The way you clean brick is simple - start with the gentlest method to clean it, then move to harsher treatments only if necessary.

So, basically, you start by brushing off the dry brick.
Then you move up to washing with plain tap water
- it's amazing how much stuff comes off with that simple combination.

Then you move to mild detergents to get oils and such off.

Normally, that's all you'll need-

__________________
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I have legalised robbery. Called it a belief
I have run with the money. And hid like a theif
I have re-written history. With my armies and my crooks
Invented memories. I did burn all the books
And I can still hear his laughter. And I can still hear his song
The mans too big. The mans too strong

When we had work done, the Historical Commission spoke with the contractor to make sure the "power washing" involved nothing stronger than a garden hose.

Yes! Thank you for the information! I am the homeowner of a 115 year old Victorian twin in the University City section of West Philly. The facade of the house is not ordinary brick, but a kind of 'burnt orange speckled' glazed brick. Not a shiny or glossy glaze, but glazed nonetheless. This summer I may wash it with a pressure hose, but nothing more.

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"Do I contradict myself? Very well then, I contradict myself. I am large, I contain multitudes." -- Walt Whitman, Leaves Of Grass

that's a really good brick. it has a much more durable surface than the usual red clinkers that probably go down the sides of the house. i've heard it called a number of things, 'iron-fleck' is one i can remember.

We always call that fire brick. It is harder than standard red.

As for cleaning and everyone going nuts on pressure washers, it's all in the tip. A commercial pressure washer with a narrow tip could punch a hole in the side of your car. Put a misting tip and you have a different story. Power washers are tools, and like any other tool, if used incorrectly it will do more damage than good.

We always start with a mild organic degreaser/detergent. Moving up to a water acid mix if needed. Some homes the carbon build up from 120 years is not coming off with Simple Green. Also, if there are 7 layers of paint on it, we start off with paint strippers, no other way around it. Yes they are harsh, but I've not heard of any other way to get paint off.

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Chris
Sustainable Building
From Foundation to Finish
www.thestockgroup.net

Government's view of the economy could be summed up in a few short phrases: If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it.
Reagan

Great stuff! I was thinking of having the front of my house re-done and there are some great points here. I hadn't even thought of sandblasting - that's pretty extreme and I could see that damaging the brick (and making a big mess). I do agree with the last comment about power washing - it's all in the tip. I used to paint houses as a summer job and the wrong tip would score the wood like a knife through butter. I can see it doing the same thing with brick. I'll probably have it scrubbed and washed (or do it myself). As for the repointing, that's interesting about the amount of mortar used. My house does have a very thin layer of mortar between the bricks. It does need to be redone, but I'll have to find a good contractor who doesn't just gunk a ton of mortar in there.

Our facade has the "bread and butter" joints/mortar. The people who renovated our house before we moved in decided against power-washing or re-pointing, as they liked the patina and did not feel it needed to be re-pointed. I am glad they did not power-wash, as I enjoy the darker patina as well.

But I do have a question: How do I know when it is time to re-point?? As far as I can tell, the mortar is designed to sit back in the joint, i.e. not be totally flush with the facade. Is this correct? Or at least that's how it appears on our house. If this is correct, how do you know when to re-do it?

Another interesting phenomenon: I gather the mortar was mixed with sand and lime. On occasion (i.e. after sustained rainy periods), some of the lime will leak out of the mortar on our house and many others on our block, and you get large white spots/streaks on the facade. Interesting. First time it happened I thought something was wrong, until I noticed it on all the other houses on our block. After a few weeks and a couple more rains, it washed away.

Butter jointed homes usually have the mortar very close to, if not even with the front brick. They are so tight that there is really no way it could be slicked back. Slicked back it the term used to recess the mortar as the tool is called a "slicker".

__________________
Chris
Sustainable Building
From Foundation to Finish
www.thestockgroup.net

Government's view of the economy could be summed up in a few short phrases: If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it.
Reagan