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ca 1900 crumbling brick


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The subject is a 1900 Baltimore City rowhome. The damage is seen from the cellar between where the main floor joists sit in their pockets. There is no damage below the joists, just between them. This damage is on the dividing side wall between units.

What could have caused this and what should be done about it?

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I believe Bill K will probably have the most understanding of what is really going on, but my guess is they're simply very poorly fired bricks, more baked dry clay than a truly fired ceramic material, that are slowly deteriorating over time. They were never much of a brick from the beginning and were probably installed where they are because they aren't exposed to the elements and don't do much more than act as a filler.

Bricks, back in the day, were not consistently fired. It was the downside of old rather primitive kilns. So, the units were culled and installed according to their structural integrity and anticipated work load.

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Hey, don't you guys remember that I asked Bill about this very thing at the Tri-State seminar? He said it's caused by moisture. Since your damage is at a party wall between units, it might have a different cause, such as what Michael said.

I see this very often in older solid brick structures. There's often no real clear indication of where the moisture is/was coming from, plus I'm often beyond my comfort zone when trying to decide just how severe the damage is and what course of action to recommend.

I'm looking forward to Bill weighing in.

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Without knowing more than I do, I played it safe by putting the following comment in the report. I'll send it this way unless someone has a better suggestion.

Portions of the brick foundation wall are deteriorating. The location is the dividing wall between this and the adjacent rowhome. The deteriorating bricks can be seen from the cellar in between the floor joists pockets. This inspection cannot determine any negative affects that might happen because of this condition. You should have a qualified masonry contractor examine these deteriorating bricks and provide you with whatever solution may be needed.

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Hey, don't you guys remember that I asked Bill about this very thing at the Tri-State seminar? He said it's caused by moisture. Since your damage is at a party wall between units, it might have a different cause, such as what Michael said.

I'm looking forward to Bill weighing in.

Often, that is correct, but sometimes, the brick are so poorly fired that you can literally scratch them apart with your finger nail or pen, etc. In such cases, a degree of moisture within the bricks actually helped hold them together, and as they dry out, their integrity becomes actually worse. The material is slowly becoming merely clay with no real molecular bond whatsoever. So, it simply disintegrates with vibration from walking on the joists, slamming doors, etc.

Usually the big factor with moisture and brick is freeze/thaw expansion/contraction, which probably isn't a factor here.

I think they're just crappy (pretty useless) bricks from the very start. That's my story and I'm stickin' to it, till Bill enlightens us. ;-)

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Michael is mostly correct. The bricks were likely farthest away from the core of the kiln, resulting in very little surface glaze. That's why they were used on the interior. Since the early eighties, there's been a trend among young urban professionals to remove perfectly good plaster from the interior of brick walls. Now they're all bitchin' about the constant red dust all over their imported contemporary furniture. There are even some bricks that were used on the interior of low-end buildings that were nothing more than sun-dried.

In cities along the east coast, unwashed or inadequately washed local sand, that contains salt, was often mixed with the clay. Salty sand in the mortar can also easily be absorbed into unglazed bricks. There can be sulfates of sodium, magnesium or potassium. Even minimal moisture/vapor can recrystallize the salts and disintegrate the bricks while expanding.

Moisture is most likely a factor here. There can be air currents, constantly moving damp air from the basement through the space at the edge of the floor. There can also be capillary action, moving moisture from the ground up the wall. Adding the "water-proofing" paint probably accelerated the deterioration. See how it's worse where the paint stops at the top of the wall? It's best to allow brick walls in a basement to "breathe", just like they need to on the exterior, above ground. If there is a desire to treat the interior, it should be a lime-wash or lime-plaster.

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Michael is mostly correct. The bricks were likely farthest away from the core of the kiln, resulting in very little surface glaze. That's why they were used on the interior. Since the early eighties, there's been a trend among young urban professionals to remove perfectly good plaster from the interior of brick walls. Now they're all bitchin' about the constant red dust all over their imported contemporary furniture. There are even some bricks that were used on the interior of low-end buildings that were nothing more than sun-dried.

In cities along the east coast, unwashed or inadequately washed local sand, that contains salt, was often mixed with the clay. Salty sand in the mortar can also easily be absorbed into unglazed bricks. There can be sulfates of sodium, magnesium or potassium. Even minimal moisture/vapor can recrystallize the salts and disintegrate the bricks while expanding.

Moisture is most likely a factor here. There can be air currents, constantly moving damp air from the basement through the space at the edge of the floor. There can also be capillary action (we called it rising damp in the UK), moving moisture from the ground up the wall. Adding the "water-proofing" paint probably accelerated the deterioration. See how it's worse where the paint stops at the top of the wall? It's best to allow brick walls in a basement to "breathe", just like they need to on the exterior, above ground. If there is a desire to treat the interior, it should be a lime-wash or lime-plaster.

This might be a silly question but does the surface glaze have something to do with blocking the entry of moisture into the brick?

Marc

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