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-   -   Painting exterior brick with latex? (http://www.diychatroom.com/f4/painting-exterior-brick-latex-26393/)

hellothere123 09-06-2008 08:41 PM

Painting exterior brick with latex?
 
I have exterior brick for a fireplace and want to chenge the color. Can I get a good primer used for brick and then just go over the primer with an exterior latex paint?

I'm hoping it can work that way?

slickshift 09-06-2008 09:07 PM

Yes
Just make sure the primer is rated for brick or masonry

Nestor_Kelebay 09-07-2008 10:41 PM

Hellothere123:

I'm presuming you're wanting to paint the exterior of your brick chimney on the outside of your house, and not the brickwork on the inside of your house.

I'd use something called a "masonary paint" instead, which will also be a latex paint. Also, so long as the brick mortar on this chimney is more than a few years old, you really don't need a primer unless you're looking for something like a block filler to smooth the rough surface of the brick and mortar. Brick and mortar are plenty rough enough that you don't really need to prime them to get the paint to stick well to either.

Masonary paints are latex paints designed specifically for masonary walls. They have acrylic resins in them that will allow H2O molecules to pass through the paint, but not liquid water. That way, any water that collects in the masonary can more readily evaporate out through the paint rather than be hindered from doing so by the latex paint. That is important if you live where water freezes in the winter because of potential damage to the masonary from the accumulation of water in it and subsequent freezing.

The way masonary paints allow H2O molecules through them, but not water is easily understood if you imagine a latex paint resin as being a long wire scrunched up into a ball. There will be spaces between the parts of the wire in that ball. Masonary paints will use resins where those spaces are much larger than a single H2O molecule, but smaller than the minimum distance between H2O molecules in liquid water. So, individual H2O molecules can pass through the paint easily, but not liquid water. The forces of molecular attraction that give rise to surface tension in water keeps all the H2O molecules in liquid water together so they stick together in a group rather than dispersing into the scrunched up wiring around them.

FRESH mortar or concrete, say less than 2 years old will still be highly alkaline. In that case, you'd be better off to wait a few years for the alkalinity of the mortar to subside before painting. There are special acrylic primers you can use for fresh concrete or brick mortar, but those would not have the special charactaristic of masonary paints to allow easy movement of water vapour through them but no movement of liquid water, and would just defeat the purpose of using a masonary paint.

hellothere123 09-08-2008 04:15 PM

Thanks for the info.

The brick is on the outside and if I don't have to prime it then I won't. The house is about 30 yrs old and hasn't been painted for 20 years.

They have the brick as a orange - red color and I am going to make it a brown tone.

I have some ext latex paint that I was just going to roll onto the brick.

Nestor_Kelebay 09-08-2008 07:45 PM

I wish I could convince you not to paint that brick. As long as brick is natural, there is very little maintenance. Once you paint it, then you open up the possibility of that paint peeling, in which you have one more thing to maintain around your house. And, there's always the possibility of you or someone else growing tired of that colour, and that prompting you to repaint it a different colour.

If it were me, I wouldn't paint it.

hellothere123 09-08-2008 09:25 PM

1 Attachment(s)
You make a good point...I guess what I'll do is I'll paint the house and then see if I can live with the color of the brick.

The house will be a darker brown with white trim...maybe the red-orange brick might be ok and then like you said, I won't have to worry about it



If I did happen to paint the brick with latex, am I looking at trouble with it (chipping, paint peeling off) in like 10 - 15 yrs, or would it happen within 2 - 5 yrs kinda thing?


Thanks!

Nestor_Kelebay 09-08-2008 10:47 PM

If you had a problem with paint adhesion, I expect it would manifest itself by the paint peeling off fairly soon, within a year or two. However, if there was no problem with the paint adhering, then peeling of the paint would likely be due to rain water getting into the brickwork and causing the bricks to get wet. The evaporation of water from those bricks would push the paint right off the brick's surface, causing the paint to crack and peel.

The other thing that occurs to me is that it's a BAD idea to paint a chimney. The reason why is that it is perfectly normal for the top portions of chimneys to need to be rebuilt periodically. It's not often, say about every 60 years or so, but it is routine maintenance for a chimney. The reason why is that flue gas contains CO2 and H2O vapour, and some of that H2O vapour will condense inside the cold chimney before the chimney warms up from the flue gas.

When liquid water forms in a CO2 atmosphere, there will be a lot of CO2 dissolved in the water. Some of the dissolved CO2 molecules will actually react with the H2O molecules in the water to form something called "carbonic acid", CH2O3, which makes the condensate that forms from the flue gas quite corrosive. It's also why carbonated soft drinks like Coke and Orange Crush have an acidic "bite" to them that dissappears when the carbon bubbles out and the soft drink goes flat.
http://en.wikipedia.org/wiki/Carbonic_acid

That corrosive condensate forms on the entire inside of the cold chimney but as the chimney warms up, the condensate re-evaporates and the lower portion of the chimney remains dry. It's the top part of the chimney, the part that sticks up above the roof that is cooled by the wind that remains cool even while the furnace is operating. Condensate that forms in the upper portion of the chimney doesn't re-evaporate, but is absorbed into the masonary. It eats away at the inside of the chimney and deteriorates the bricks and mortar joints from the inside.

Chimney inspectors will remove the "clean out" immediately below where the flue duct from your furnace or boiler enters the chimney. This is where you will find sand, which is what's left of the brick mortar after the corrosive condensate attacks the brick mortar. The more sand you find, and the more pieces of mortar, the worse the condition of the interior of the chimney. Most of that sand and mortar will be from the portion of the chimney above the roof line.

Generally it's only the mortar that deteriorates. The bricks themselves don't contain any lime or limestone, so they stand up well to the corrosive condensate. Eventually, though, a bricklayer needs to take apart the chimney above the roof line and relay the bricks in new mortar.

If you paint your chimney, then you're going to make it harder to assess the condtion of your chimney. They can still tell by the amount of sand and mortar in the clean out what to expect, but it's still advantageous to a brick layer to inspect the condition of the bricks and mortar from the outside.

So, in my view, it's better not to touch that chimney with paint at all.

skolfoppa 09-10-2008 12:16 PM

That chimney looks pretty nice. I'd work the brick color into your house color scheme scheme. I agree with nestor, painting masonry brings a new set of potential problems to the table, imho.

Matthewt1970 09-17-2008 09:33 AM

Uggg, please don't paint that beautiful brick chimney. If you paint it, it will look great or a couple/few years and then, like any paint, it will start to collect dirt, start to fade and could start to peal. If you don't paint it, it will look great for 50 years.

Matthewt1970 09-17-2008 02:21 PM

Quote:

A fact like this doesn't seem right when the large paint companies have us believing that repainting every seven years is "just the way it is". But this is equivalent to the 100 mpg carburetor - an oil company bought the patent and shelved the invention.


That's amazing. I didn't know that 75% of the gas in a combustion engine went out the tailpipe. I am open minded but I am also skeptical of a company that would use that as well as a product I can't seem to find one review on.

Matthewt1970 09-19-2008 08:50 AM

Quote:

Originally Posted by perfectcolor (Post 159346)
good point.. some things will just become more attractive when they get older

I wish my girlfriend did... :laughing: :wheelchair:


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