I recently completed a 2 course CMU wall for the Mrs. to be used as a raised garden. getting ready to back fill it this wekend,a dn she is concearned about water from watering her vegetables is harm teh CMU block.
Does the block need any treatment?
ML
From plumbing failures to environmental near disasters, OHJ staffers dish on our worst and best moments.
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
CMU are really hard sponges. They soak up water and then dry out. Unless she is using some reall highly acidic fertilizer I would not worry about them. I see you are in southern California, so there is little likelyhood you ever have freezing weather. The bloch will just dryout between waterings.
You should coat the inside with some form of vapor barrier. The minerals in the water may cause the block to effloresce, and the formation of crystals in the pores of the block will cause it to crumble.
Right now, it won't be hard to do, and is relatively inexpensive insurance that your block will last for many years.
I think what Jigs might be referring to is some kind of damp proofing - basically a bituminous (tar) coating that comes in a 5 gallon bucket and is just loads of fun to work with. It would be applied to the interior of the block.
As Dave above said freezing shouldn't be a concern, but if you plan to paint or otherwise treat the outside of the block and you have water continually leaching through, the exterior coating may likely not hold.
Also, it may be wise to have some kind of drain in the bottom of this structure. Most plants don't like the swimming pool effect.
Somewhat off topic, but relevant, I personally believe that continuous wetting does degrade concrete block. I once lived in a ~50 year old house that had a decades old water problem in the basement. The basement wall block had become so soft that you could easily poke a screwdriver through it. It was a rental and not only did the house end up being demolished but the lot did too! They put in an underpass. :-)
Thanks Matt, she wants stucco on the exterior of the block to match the house along with stone cap. I've seen raised beds and fountains treated with tar before to make them water tight. I placed weep holes along the bottom course for drainage. ML
I'd recommend that you install the asphalt emulsion, and while it is wet, push some of the weed blocker poly felt into it. Then after it dries, do another coat of emulsion.
Any water that gets in between the block and the stucco will cause the stucco to fail, and come loose.
If you want to be really sure that things work, the vinyl shower liner that is used before tile is installed is the best bet, but kind of spendy.
I was thinking of Kerdi myself, but like you said spendy for a garden!