I have a concrete block retaining wall about 40 ft long and 3 ft high at the front of my lot. I would like to apply a stucco coating to the font of it to improve the appearance. The wall is drained pretty well at its base, but there is some moisture that seems to migrate through the wall after heavy rains.
Most articles I’ve seen suggest a cement/lime/sand mixture applied directly to the wall after thorough cleaning or to a metal mesh mechanically attached to the wall. Any suggestions as to the best approach or any potential issues to be aware of?
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No answers here, but I've wondered the same myself. If its raw concrete, I would think a standard color coat would suffice. If its been painted, then maybe a bonder first. I can't see any need for metal mesh, unless there was just a nasty, heavy paint on there that was failing.
Waiting to hear from the pundits!
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The water leaching through the block will cause a problem which ever method you use. This is particularly so if you live in a area with freez/thaw cycles.
What you call stucco, we refer to as a parge coat. No metal lath needed, Jsut apply a bonding agent to the cleaned block and thentrowel on a layer of "stucco." Work in small enough areas to ensure the bonding agent does not dry completely and you can work to a wet edge of the parge. Keep a spray bottle of water or a wahite wash brush in a bucket of water handy. You can use either to wet the coating as needed to blend it together.
Most parge coating are applied at about a 1/4" thickness.
I use to use a complete system made by Thoroseal. It had a bonding/mixing liquid with a 5 gallon bucket of stucco. I'm not sure they are even around anymore, but there are other products similar to them out there.
I liked the Thorseal products because they were a complete package systems and I didn't have to fuzz with keeping track of the correct amount of sand/cement/lime etc.. and I didn't need a large mixer for small jobs. A little pricey for large jobs but great for small repair work and jobs like yours.
Portland Cement Association I believe is the name. Directions and mix ratios for any kind of stucco or plaster your little heart desires. 2 coats with no lathe is their reccomendation for block.
This is in no way an answer to your problem, but just something I have observed. After a period time, I have seen cmu walls where the joints have started showing thru the finish. I don't know what the finish was, but what ever it was it was not enough. Just a thought.
That is the standard way they build houses here. It is prevalent enough to have a name "CBS", Concrete Block and Stucco.
They usually paint link (bonding agent) on the wall and do a 2 coat application. This is a fairly water tight surface so if there is hydrostatic pressure from the other side you should have some weep holes.