Portland Cement Over Brick -- Now What?
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Neal Yonover



Joined: 04 May 2010
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PostPosted: Wed Aug 18, 2010 10:25 pm    Post subject: Portland Cement Over Brick -- Now What? Reply with quote

My aunt has a circa 1856 brownstone. Someone told her that tuckpointing the outside of the building near the ground was unnecessary and that portland cement (?) over the bricks, covering an area 3' high and 25' wide would be okay.

Now there is water trying to get out through the interior walls. And there are bubbles and other weak spots on the outside where the portland cement is flaking off too. That's in addition to efflorescence and other water signs. (see attachments)

So far, the game plan is to remove the wet interior wall and scrape off the flaking areas of the portland cement and let it all dry.

Does the portland cement need to be removed? What's the best way to do that?

All suggestions, tips and recommendations will be most gratefully appreciated.

Thanks.

Neal



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Sean



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Location: Salem, MA

PostPosted: Thu Aug 19, 2010 10:33 am    Post subject: Reply with quote

Is tuckpointing the same thing basically as parging?

Sean
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johnleeke
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Location: Portland, Maine, USA

PostPosted: Thu Aug 19, 2010 6:10 pm    Post subject: Reply with quote

Traditional brick masonry walls like this are designed to give up their moisture mostly to the outside and in some walls a little to the inside, with the moisture migrating out mainly through the mortar joints which are made of relatively soft lime-rich mortar that allows the passage of moisture.

In this case it appears that the parge coating of cement is trapping moisture in the wall so it cannot leave the wall to the exterior. The moisture is driven to the interior where it is causing the plaster damage; and, more critically, further up into the wall, as evidenced by the white efflorescence on the bricks above he cement coating.

The white efflorescence on the surface of the bricks above the coating suggests the unknowledgeable (stupid) workers who did this might also have put high-strength highly moisture impermeable cement mortar in the joints above the coating. This forces the water to migrate directly through the bricks, damaging them, instead of going out through the mortar joints.

It is true that excessive moisture passing out through the mortar joints may damage the mortar, but it is far less costly to repoint the joints that to replace damaged bricks.

When the cement parge coating is removed, it may also pull off the outer face of the bricks, in which case the bricks will need to be replaced.

Is that a new parge coating of cement on the interior wall? If so, that is trapping moisture and forcing the moisture futher up into the wall too.

Track down the source of the water. Is it coming from above (poor roofing and gutter details above, etc.)? Or, from below (ground water, broken underground drainage line, etc.)? Then mitigate the moisture if you can.

Whoever did the last round of work here may have caused a lot of expensive problems.

This may be extensive enough that it would be worth having a traditional masonry specialist investigate, analyzed and make specific recommendations.

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johnleeke
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PostPosted: Thu Aug 19, 2010 6:29 pm    Post subject: Reply with quote

Sean writes:
>>Is tuckpointing the same thing basically as parging? <<

No, tuckpointing is done just to the mortar joints. Parging is a coating over the surface covering the joints and the face of the bricks.

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Neal Yonover



Joined: 04 May 2010
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PostPosted: Sun Aug 22, 2010 10:29 am    Post subject: Reply with quote

Thank you for the very welcome information. I will search out the source of the water.

In the interim, I've removed the wet plaster on the interior. The keys crumbled into dust and were easily vacuumed away. Whatever didn't come off easily got left in place.

I'm not sure what John means about a parge coating of cement on the interior wall. It looks like a standard plaster wall to my untrained eye.

The baseboard was unusual. It looked like red terra cotta, only sort of pliable. Can anyone tell me what this stuff is and how to best preserve or replace it? (see attached photo)

Also, I noticed that there are still some wet spots on the wall above the plaster that remained. Should I remove them, or leave them alone and give them a chance to dry out now that the base of the wall is open?

Since it appears that the parging covers the length of the building exterior (it was just painted to blend in on the back half of the building) and there are some crumbling bricks above the parging, a traditional masonry specialist is especially a priority. However, since the person who convinced my aunt that this work was a good thing to do was "a tuckpointing guy," the challenge will be finding a reputable, qualified mason. Can you make any referrals or suggest where to look?

I look forward to your thoughts and suggestions.



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johnleeke
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PostPosted: Sun Aug 22, 2010 11:02 am    Post subject: Reply with quote

OK, looks like that is the traditional lime & sand plaster on wood lath on the interior.

Consider John Speweik:

http://speweikpreservation.com/

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Neal Yonover



Joined: 04 May 2010
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PostPosted: Sun Aug 22, 2010 1:22 pm    Post subject: Reply with quote

That's reassuring.

I will contact him directly. Though, unless traffic is cooperating, Elgin, to the west of Chicago, is only marginally closer than Maine.

Also, any thoughts about the baseboard? What is that stuff?

Thanks.

Neal
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johnleeke
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PostPosted: Sun Aug 22, 2010 1:27 pm    Post subject: Reply with quote

I don't have a clue on the baseboard material. If you want to send me a chunk I'll look at it.
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Neal Yonover



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PostPosted: Sun Aug 22, 2010 1:32 pm    Post subject: Reply with quote

How convenient. I just happen to have a chunk.

Consider it enroute.

Thanks.
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Neal Yonover



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PostPosted: Tue Aug 31, 2010 12:19 pm    Post subject: Reply with quote

Here's an update on the situation and the latest challenge.

I've spoken to John Speweik and sent some photos of the situation. He seems to have a very good grasp of what's going on. The challenge is that he represents WAY more horsepower than my aunt has budget.

What if you can only afford to stabilize and repair the problem instead of restoring the building to its original splendor?

I will go back to John and see if there's a more affordable version of his help or maybe using the project as an opportunity for his students, but there is a risk of offending him or losing his interest altogether. And then what? The bricks are still dissolving and there is still water in the walls looking for an egress. As John observed yesterday, “Water always wins.”

Thanks again for all thoughts and suggestions.

Neal
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johnleeke
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PostPosted: Tue Aug 31, 2010 4:06 pm    Post subject: Reply with quote

I think your assessment of John is about right. Start by buying and studying his publications, like you have with mine, and you'll at least learn how to ask the right questions:

http://speweikpreservation.com/books/

I notice he has low-cost digital downloads.

The Traditional Building Conference is coming right up in October in Chicago. Usually John gives his bricks & mortar workshop at this conference (not sure if he is this time).

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