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Seal/Not Seal Brick Exterior

Posted by Danvirsse (My Page) on
Wed, Jul 13, 11 at 7:27

We have a 1838 Double Brick Home we purchased last fall. It is located in the Mid-Atlantic, so we have months of freezing temperatures. The masons have completed the exterior re-pointing/brick replacement. Now the question seems to be whether or not we should apply a sealer.

Any experiences/thoughts would be appreciated.

The bricks are very soft and porous as they were produced at the local brickyard in had packed molds. Does that change anything?

Thanks for any help you may offer.


Follow-Up Postings:

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RE: Seal/Not Seal Brick Exterior

In a word, NO.

See link.

Unless the repointing was with lime-based mortar, your bricks will start falling apart anyway.

Been there on both counts. I sandblasted, siliconed and repointed. Hey, that's what all the renovators were doing at the time!

Here is a link that might be useful: Clear coating of masonry buildings.


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RE: Seal/Not Seal Brick Exterior

Very interesting reading on the link you provided. Thank you. Fortunately, the re-pointing and repair work was done with lime-based mortar and all the bricks were original to the home. They also "bagged" the joints, rather than striking them so there is minimumal indentation and thus match the originals.

Thank you again


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RE: Seal/Not Seal Brick Exterior

what do the masons say? my thought would be that if you aren't having water issues, don't seal. also, keep electric, etc, surface mounted on the inside as you do work. old brick needs to breathe.


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RE: Seal/Not Seal Brick Exterior

Mason says to seal, but doesn't have a product to recommend. He suggested talking to the local brickyard. They seem un-interested to determining suitability of a product for the old brick etc. We are constructing 2 x 4 walls on the interior, parallel to the brick, but not touching or attached. We expecting to run our electric in those walls and insulate. That (hopefully) will allow the brick to continue to breathe.


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RE: Seal/Not Seal Brick Exterior

And you say the bricks have been done the job of bricks since 1838 and that they are in good enough condition to reuse today?

DO NOT SEAL THE BRICKS. Ignore the mason - he's trying to line you up for his next job repairing bricks that fail:) Thank your lucky stars that sealing products weren't around in 1838.

We reused 1919 bricks on our home and there is no way we would seal them - not 5 years ago when the work was done and not today.


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RE: Seal/Not Seal Brick Exterior

"Mason says to seal, but doesn't have a product to recommend."

Is he going to repair bricks spalled by freezing for free?

If the sealer holds moisture in the brick and it than freezes it will spall the face of the brick.

If the insulation is poor and the brick face never reaches freezing (from heat escaping) nothing might happen.

If moisture gets trapped and freezes though...


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RE: Seal/Not Seal Brick Exterior

Thanks to all that have responded. Yes, most of the bricks on the home are still in great shape 173 years after they were made...amazing. We were fortunate to have bricks available from an internal chimney that had to be removed. Those were used to make the few repairs needed. We'll be following your kind advice and leaving our home unsealed.


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RE: Seal/Not Seal Brick Exterior

okay, hopefully this help - this is from the national park service historic preservation briefs (a great series BTW)

Water-Repellent Coatings and Waterproof Coatings

To begin with, it is important to understand that waterproof coatings and water-repellent coatings are not the same. Although these terms are frequently interchanged and commonly confused with one another, they are completely different materials. Water-repellent coatings--often referred to incorrectly as "sealers", but which do not or should not "seal"--are intended to keep liquid water from penetrating the surface but to allow water vapor to enter and leave, or pass through, the surface of the masonry. Water-repellent coatings are generally transparent, or clear, although once applied some may darken or discolor certain types of masonry while others may give it a glossy or shiny appearance. Waterproof coatings seal the surface from liquid water and from water vapor. They are usually opaque, or pigmented, and include bituminous coatings and some elastomeric paints and coatings.

Here is a link that might be useful: Brick Preservation Brief


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RE: Seal/Not Seal Brick Exterior

Perhaps you already understand that the term "breathe" is a misnomer and should not be taken literally. "Breathing" means that the wall is water vapor permeable so it can dry to the exterior after it gets wet. If porous brick can't dry in areas with frequent and severe freeze-thaw weather cycles, it will cause the brick face to spall. Therefore, a waterproof "sealer" would increase the risk of damage.


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RE: Seal/Not Seal Brick Exterior

The brick has survived just fine since 1838.

Why would you want to mess with it?

New is NOT always better.


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