Walking around the neighborhood I have been impressed by the number of homes that have been "cleaned" through sandblasting and subsequently repointed. These usually present as orangish in color with fat new pointing.

Brick is baked at high temperature. The exterior forms a hard but thin glaze. The interior of the brick remains softer and more crumbly. Sand blasting removes the hard glaze and exposes the soft interior. These bricks will deteriorate. Notice the thin cracks in the brickwork now exposed. Does not bode well.

Personally I like the patina of 100 years plus. But if you must clean, stick to a high pressure hose and soapy water.

The guy who will sell you a cleaning job will also try to sell you a repoint. Victorian and turn of the century brickwork is set in "bread and butter" style, The bricks are laid close together. Little cement is used. This kind of brickwork hardly ever needs to be repointed. The guy doing the job will make the joints look fatter than the mason intended thus ruining the effect he was trying to achieve.

I have never ever heard of sandblasting a facade. I think the homes you are talking about have been power washed after repointing. Some of the brick facade homes in the area are over 120 years old. Brick doesn't last forever, hence the surface cracking.

All brick joints need to be tuckpointed after wear and tear creates voids in the joints. The new "fat" joints are created by poor workmanship of the repointer.

And of course the type of mortar used is very important.
Modern mortar is too hard for older bricks and actually destroys them (the bricks are softer so they give as opposed to the mortar).

Definitely make sure the guy doing your re pointing has a clue.

__________________
Czar of the 26th Ward.

An if you're in the Spring Garden district the Historical Commission will stop the work if it's not done right...

I know little about these things, but attended a Preservation Alliance workshop last Fall about masonry. They also said never to sandblast brick, and even to be careful about powerwashing. I have old (prolly non-masonry) paint covering my house I'd love to remove and thought I'd eventually sandblast off, but I'll have to find another way it seems.

And yes, they said it's super-important to know which kind of mortar your house needs.

The workshops are all excellent.

I haveThe ones that have been blasted have a rough somewhat uneven surface. The power washed ones retain their smooth hard glaze. Brick can last centuries.

I have witnessed one house on Parrish being blasted last fall.

I dont doubt you. Just seems very foolish, not only in it will ruin the bricks, but sandblasting makes an awful mess. Power washing will do the job just as well without all the cleanup.

Even a brick that's never been sandblasted will take up an amazing amount of water, and water is enemy #1 of any building--wet building materials invite fungus, mold, bugs, decay, corrosion, you name it. If you get the bricks in your masonry wall wet from powerwashing, the wet bricks can have enough water in them to dissolve out important parts of your mortar, damage the bricks by carrying dissolved salts into tiny cracks and pores, and because water expands when it freezes, your wet bricks can break themselves apart. If you can't take good enough care of your building to prevent the need for cleaning, try a very brief low pressure wash, or even climbing a ladder and brushing the crud off with a dry natural fiber brush (no wire!).

Not all cracks in brick are a bad thing. Most older bricks were made by hand by pushing as much clay as possible into a mold. Those cracks at the surface are one of the results of that process. Handmade bricks have been around for centuries, little cracks and all, so it's not a sign of inherent weakness in the brick.

And never ever coat your building in cement stucco, vinyl siding, permastone, or even paint. They'll destroy your brick and only serve to cover up a problem.

A great little guide to the basics is the Philadelphia Rowhouse Manual http://www.philaplanning.org/pubinfo/rowhousemanual.pdf

__________________
___________________
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

#20 (permalink) 10-24-2004, 01:32 PM
chrissayer
Cheesesteak GURU! Wiz with Join Date: Mar 2004
Location: Overbrook Farms
Posts: 8,542



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Old bricks should never, ever, ever, ever, ever be powerwashed. Nor shold they ever be sandblasted, etc.

Even the chemical treatments are iffy.

Old brick builds up a protective coating through aging. Blast that away, strip it away, whatever, and the end is near.

I believe it is safe to wash them with soap and water . . . or even a mild acidic solution. Basically, they should be carefully cleaned and then repointed.

Hal should jump in here since he is our resident expert on this sort of stuff. But, please . . . no powerwashing.

__________________
___________________
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