Paint on CMU Block wall

[Lee Goldman]

Hello List,

We would like to fur-out our walls in our house. The walls are painted CMU Block. Originally, I wanted to apply type of 'mud' that smoothes out the block wall without sacrificing space (If we fur the walls with metal stud and drywall, we lose sqaure footage space for the room - it's very small as it stands right now, even a few inches would make a large difference).

I was told that there is no type of material that applies to painted CMU block. Is this correct?

Thanks

Lee

[Rich]

I've never heard of anything that would do that. Short of sandblasting the wall to remove the paint and then filling with Sakrete. If sandblasting is determined to be a method you would employ make sure to use black sand... there is less silica in black sand. Silica dust is very bad for your lungs...etc. Sorry I couldn't be of more help. I'll keep looking for some other resources.

[Shanley]

You could scratch the wall with a wire brush and prime the wall with a bonding agent prior to applying stucco

[Rich]

Probably less mess with that method too. :D
Welcome to the forum Shanley (finally someone who knows about masonry - whew)

[grumpydasmurf]

The extent of my masonry knowledge is limited to coping tile, parapet walls and chimneys. All masons I have met with always tell me painting brick, block and mortar is a bad idea. It prevents the material from "breathing" and will lead to breakdown.

Having said that, would it really be a good idea to prime the wall?

Again I am not an expert in masonry.

[Shanley]

Ive been in the masonry trade for 25+ years...By breath I assume they mean move due to thermal variation...Interior CMU walls have minimal if any movement because the interior of bldgs do not normally experience significant thermal fluctuation...so I don't believe breathing is an issue in this application

[Rich]

I guess my question to Grumpy would be what about foundation walls (masonry) that are waterproofed? Not really expecting an answer Grumpy. But that kind of throws their theory out doesn't it because that's done all the time?

[grumpydasmurf]

I dont know what you mean by move. I am talking about crumbling mortar. It seems every painted stone, brick, masonry wall I have seen has crumbling mortar joints. Yes mortar joints will crumble on their own but it seems that the painting speeds this up.

Aren't most foundation walls solid? I havent seen many that are block construction. The ones I have seen usually leak. My obeservation around here is most foundations are poured solid concrete with no mortar joints.

Again I must state I am no expert. I am passing along information told to me by my mason buddies and sharing my own uneducated observations.

[Rich]

I personally would only do poured in place concrete for a foundation wall.. but it is a much accepted method of constructing foundations. Any feedback Shanley?

[Shanley]

Although uncommon in the northeast cmu foundations can stand the test of time provided it is properly reinforced, grouted, and waterproofed. Typically Type M mortar is specified for below grade applications