Brick breath

[david shapiro]

"Painting not only destroys the look of mellow brick and tile, but can also prevent these natural materials from breathing. . . ."--B&Q's You can do it.

So what? I get that all unglazed masonry is at least a wee bit porous, but my understanding is that brick walls leave periodic mortar gaps for this purpose. Is this another case of a (UK) DIY book saying something that's factual but misleading, or is there a real concern?

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[Jerry Peck]

David, first a question: structural brick wall, or frame wall with brick veneer exterior?

I'm thinking it is a frame wall with brick veneer.

Brick veneer walls have a ... are required to have a ... 1" air space between the back of the brick veneer and the water-resistive barrier (WRB) covering the structural wall behind it that the brick veneer is attached to.

Water penetrates through the brick (some), through the mortar joints (a bit more than the brick), and between the mortar bond to the brick (also some). The moisture/water runs down the back side of the brick veneer to the through-the-wall flashing, then out the flashing through the were holes (which may also be head joints which were mortar and left open for that purpose).

[david shapiro]

Jerry, thanks for picking up on this. Given that they're talking about maintaining the character of older homes in the UK, the design could be anything, and the codes it complied with originally could be any.

Given this framework, . . . further thoughts?

[Jerry Peck]

David, structural brick walls, which are 'solid brick', don't have any 'mortar gaps' (from your first post) as the mortar is what holds the masonry units (brick, stone, etc) together in creating then structural wall.

Those walls are typically at least two wythes thick with masonry units use across the two wythes to make 'one solid wall'. Another masonry wall method is to separate the two wythes from each, creating a space of several inches, and that space is then grouped solid, making for a solid wall.

But I'm sure you've seen stuff on the old masonry construction, with lots of different materials used in different configurations to create a structural wall.

I think you are asking about painting structural masonry walls and how it affects the masonry - as you noted, the masonry breathes in that moisture and water enter the masonry, the masonry stores that water, then dries back out when given the opportunity.

Painting structural masonry walls does, from what I've read in years past, negatively effect those masonry walls and their ability to handle moisture and water, and potentially be damaged by that altered ability to handle moisture and water.

Beyond the above ... I see nothing, I know nothing (Sgt Shultz)

[david shapiro]

Thanks, Jerry.

What i take from this is that with some walls, their warning is valid.

So, "lies told to children"; DIY books tend to offer executive summaries, rather than drilling down to discriminate between different situations.

In this case, probably not dangerous. (Well, okay, maybe if someone read this and said "OMG, I have just bought a painted brick home, I need to sand off that [lead] paint," and didn't take the time to read ahead to the undoubted warnings about checking for lead paint, about paint-stripping safety, etc.)

[Jerry Peck]

David, I suspect that few "brick houses", vs brick veneer houses, have been painted.

And, with brick veneer houses, there is ... should be ... an air space between the brick veneer and the actual 'thermal envelope' of the structure house. Thus (I think) painting a brick veneer house is 'not as bad' as painting a "brick house".

To my recollection, I have only seen and inspected one "brick house" (not brick veneer, but with structural multi-wythe brick walls). That house was up near Gainesville, FL, and I was 'inspecting' it for a niece. As I walked up to the house, I thought 'Not another screwed up brick veneer house with no weep holes.', but as I walked around it I got the feeling that it was indeed a "brick house". When I go into the garage, that was confirmed as the entire wall was two wythe thick with the brick wall showing in the garage and the laundry room. I could see it at the door doors and windows in the garage and laundry room as they were exposed brick, no drywall. And further confirmed when I looked in the attic.

After some investigation, my niece found found out that the house was built by a brick layer masonry contractor for his daughter 'back when' (based on the bathroom mud-set tile, pastel colors and style, I'd guess a 1950's house). He had is best crews lay up the house with solid brick walls. Inside the house, it looked the same as any other house, drywall (except that it was rock-lath with two-coat plaster).

Painting that house would not be something I would recommend. Not that I would recommend painting brick veneer either.

Chicken Little may have said "The Sky is falling! The Sky is falling!", but at least Chicken Little didn't huff and puff and try to blow the house down ... the Three Little Pigs would have been safe in that house.

[Markus Keller]

In addition to what Jerry mentioned I would add a few comments.
I live in the land of brick houses and buildings. 12" multi wythe wall is normal for vintage housing around here.
If you talk to masons about painting brick you'll get both ends of the spectrum. 'You are a moron don't you dare paint the brick' to 'yeah its ok you can paint the brick'.
I do a lot of water intrusion investigation in newer buildings but also a good amount of vintage masonry consulting.
Can you paint brick, Yes. Is it the best idea, No. It's sort of like parging a wall. You can do it but it's not a great idea.
How good or bad painting brick is, at least around here, is more about the variables and environmental conditions.
Whats the orientation of the wall, what's the exposure, how are the parapets, how are the copers, how are the window sills, has water management at the wall been addressed as part of the painting, etc.
The problem with painting the wall isn't that painting the wall will destroy the brick. The problem is unless you are a rockstar you aren't going to keep 100% of water out of the wall. An unpainted wall can let that water out. A painted wall traps that water causing damage and peeling paint. Finding someone to do the work that does all the other stuff needed along with the painting to avoid expensive problems is very hard to come by.
Around here painting brick tends to be about trying to avoid the high cost of legitimate masonry repairs.
I will add there are companies around here that will 'stain' brick walls almost any color you want. Their crews will literally stain each brick one at a time to create that new look and not hit the mortar joints. From my experience the staining last well as long as there are no harsh elements coming at it, i.e. road salt, lots fo hosing, tree puke, shrub contact, etc. Any of those factors will deteriorate the staining and from what I've seen that's not covered under the 'lifetime warranty'

[david shapiro]

Thanks, Markus.

[ROBERT YOUNG]

I do not suggest painting unpainted brick masonry, unless it becomes unavoidable. In
other words, the brick were painted before.

Staining brick.
What Is Brick Staining

According to the Brick Industry Association, if you paint your exterior brick, you should be repaint it every three to five years. The quality of your brick also should determine your choice.

Hope that helps.

[Bob Harper]

The BIA recommends ANY exterior coating be 100% vapor permeable (perm rating '10' or higher). Low perm coatings trap moisture. ALL masonry walls are water storage systems. The cavity wall described is to provide a capillary break to prevent further migration of water into the structure.

The weep holes are actually primarily to equalize the pressure gradient from the wall cavity to outdoors, so water is not drawn into the interstitial space by air pressure. There need to be weeps at the top and bottom of the wall cavity.

Another mechanism for water transport is vapor diffusion. When the sun comes out after a rain it forces the water inwards towards the dryer building interior.

Another mechanism is capillary attraction. Water can be drawn into microchannels.

Wind pressure can actually press water into a structure.

The substrate may be hydrophobic (repel water) or hydrophilic (attract water).

Ordinary Portland Cement (OPC) based mortars are notorious for retarding drying. Lime mortars, on the other hand, are well documented at promoting rapid drying.

Soluble salts are like a water magnet. Where there is efflorescence, you will not only continue to have water penetration, but it will exacerbate.

[ROBERT YOUNG]

The BIA recommends ANY exterior coating be 100% vapor permeable (perm rating '10' or higher). Low perm coatings trap moisture. ALL masonry walls are water storage systems. The cavity wall described is to provide a capillary break to prevent further migration of water into the structure.

The weep holes are actually primarily to equalize the pressure gradient from the wall cavity to outdoors, so water is not drawn into the interstitial space by air pressure. There need to be weeps at the top and bottom of the wall cavity.

Another mechanism for water transport is vapor diffusion. When the sun comes out after a rain it forces the water inwards towards the dryer building interior.

Another mechanism is capillary attraction. Water can be drawn into microchannels.

Wind pressure can actually press water into a structure.

The substrate may be hydrophobic (repel water) or hydrophilic (attract water).

Ordinary Portland Cement (OPC) based mortars are notorious for retarding drying. Lime mortars, on the other hand, are well documented at promoting rapid drying.

Soluble salts are like a water magnet. Where there is efflorescence, you will not only continue to have water penetration, but it will exacerbate.

Great post, Bob.

[PeterBrodbeck]

First of all, it's important to understand that brick is a porous material. This means that it can absorb moisture, which can lead to problems if the brick is not properly sealed. Painting brick can help to seal the surface and prevent moisture damage. However, it's important to use a breathable paint, so that the brick can still "breathe" and release moisture. Another thing to consider is the type of brick you have. Some bricks are more porous than others, and they may be more susceptible to damage if they are painted.
So, what are the pros and cons of painting brick?


Pros:
Can help to seal the surface and prevent moisture damage
Can improve the appearance of the brick
Can make the brick easier to clean


Cons:
Can trap moisture, leading to problems
Can be difficult to remove
May not be suitable for all types of brick