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  1. #1
    Join Date
    Mar 2008
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    40

    Lightbulb To paint or not to paint exterior brick, that is the question

    The discussion on painting exterior brick varies, and I am from the persuasion that "historic masonry" is old, past its prime, and cost prohibitive to ever attempt a re-point with lime mortar. I counted four buildings just today while walking down the sidewalk for two blocks that had lime mortar, 1900's era brick, crumbling gaps between bricks, faded, dirty, discolored bricks . . . they all needed pointing. If the stuff were so great, and self-repairing, why all the crummy results over time? When deterioration of the mortar has already happened, and things are a mess, and the bricks are worn, ugly, and dirty, plain unsightly, why not paint? One can surely re-point with the proper soft, matched mortar, and then paint. If, and I stress "if", moisture flows through paint into the mortar, then can it not get back out the same way? Paints are not one way barriers. But, if the paint is "not breathable" as masons state, then what is the trouble in the first place? No breathe, then no moisture enters to begin with.

    So, this idea that paint destroys the mortar makes sense if water is trapped inside the wall from INSIDE?

    Any painters or owners who have painted their exterior brick homes that have as original mortar the lime/mortar style?

    C

  2. #2
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,776

    Default Re: To paint or not to paint exterior brick, that is the question

    Are there people inside this building you are thinking of painting? People perspire. People need toilets which evaporate moisture into the building air. People wash their hands and get moisture in the air. People make coffee and tea and get moisture in the air. If people live there, then they cook, bath and do other things that put moisture in the air.

    Warm moist air hits the walls and some of the moisture condenses. Some of the moisture is absorbed and permeates through the walls and into the bricks. The bricks become laden with this moisture. If it has a coat of paint on the outside, the brick can't breath, so it gets wetter over time, and the brick and mortar soften and eventually flake off.

    Some people think old brick looks good. It has character.

  3. #3
    Join Date
    Aug 2007
    Location
    Portland, Oregon, formerly of Chicago
    Posts
    1,808

    Default Re: To paint or not to paint exterior brick, that is the question

    Were oil paint to be used on the exterior brick, I would buy Keith's argument. However, modern acrylic paints do breathe. They have the ability to repell flowing water, yet allow vapor to pass on through. This is why acrylics are a major step forward as exterior house paints in general over oils and the preferred product for masonry. Acrylics are also far more elastic than oil paints, which are initially brittle and get more so with age. This is more an attribute when paointing over stucco, which is known for hairline type cracking.

    Of course, it is always a good idea to control excess moisture in a home with good exhaust fans in moisture producing areas such as kitchens, laundries and baths with showers. Whether there should be an absolute vapor barrier on the inside exterior walls is debated widely among the building science people. Most would agree that a vapor inhibited paint should be used on those walls at a minimum and that those walls should be sealed against air infiltration from the house.

  4. #4
    Join Date
    Mar 2008
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    40

    Arrow Re: To paint or not to paint exterior brick, that is the question

    Thanks Ordjen, confirms my thoughts as well. Most people have modern improvements such as A/C, exhaust fans, etc. If humans breathing causes so much vapor that it penetrates walls and decays fragile mortar, then we are all in trouble!

    I like historic masonry quite well when it isn't ruined and past restoration and cost factors. Most examples I see have been pointed with OPC mortar in places already.

    Acrylic paints are the key. Sounds like it is fairly safe to use on exterior brick. I agree, MVB materials are debated and when I think about them, they scare me, the idea of trapping moisture in a wall. Would common fiber insulation batts with Kraft faced barriers be as potentially trap prone as a plastic barrier? Some people put plastic over lathe before installing drywall in restoration situations where the plaster failed and was removed.

  5. #5
    Join Date
    Jan 2008
    Posts
    2,203

    Default Re: To paint or not to paint exterior brick, that is the question

    My objection to painting any masonry surfaces (including concrete) is that you're going down a one-way street that's going to the wrong place. Once painted it will have to be constantly re-painted but left alone is will rarely need maintenance. Once painted it can't be un-painted to restore to original it without doing damage to the masonry underneath. Repair or re-point the mortar as needed every few years- it will take far less time, effort, and money than painting it will.

    If the masonry is weak or crumbling, paint isn't going to save it- and even if painted over it will require proper repairs to endure anyway, so with that done there's no need to paint. And you avoid any possible problems painting might or might not cause. It's your call, but to me painting masonry is almost never a good idea.

    Phil

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