I have begun making cosmetic repairs to the interior of my home which was built in the 50s. I've got brick veneer on the outside, cinder block inside and then a layer of either chicken wire plaster or just plaster applied directly to the block. After removing the top layer of plaster of a cracked area under a window sill corner, I discovered a settlement crack about an inch wide. The home is no longer settling so I know the crack isn't enlarging. My uncle who is a contractor instructed me to fill the gap with hydraulic cement, dry, apply a few layers of durabond and then top with a coat of mud to finish up the top layer.

Would this be an adequate repair to make sure it's done "right" and not just a quick patch job? Not trying to screw over the next owners.

UPDATE: just needs finishing sanding and primer/paint

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    ...so, edit this, take the last sentence, post it as an answer, perhaps take a few pictures as you do the job. Your uncle is not wrong, IMHO.
    – Ecnerwal
    Commented Dec 19, 2019 at 15:33
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    I would use hydraulic cement or mortar both will work just fine, hydraulic cement would be stronger I believe.
    – Ed Beal
    Commented Dec 19, 2019 at 16:55
  • Hydraulic cement seems a little overkill to me, especially if you're not trying to stop a current water issue, but it will do the job - no doubt there. I am curious however as to the stability of that whole section, from inside the house to the exterior. If it's just a crack that has opened up on the inside from settling, tuck pointing regular mortar and covering with plaster/durabond may be all that is needed. Hard to tell from the image - but nothing looks water damaged, just looks loose from movement. Movement that may also need investigating and stabilized.
    – tahwos
    Commented Dec 22, 2019 at 23:27

1 Answer 1


I disagree with your uncle on the hydraulic cement part. Hydraulic cement when used properly has the viscosity more like water and is used to flow into cracks and crevices and harden which makes it hard to do on the side of a wall as it will just run down the block. In addition it is very hard when dried so eventually other cracks will appear on both sides of the crack you tried to fix in the future, because the block is weaker than the hydraulic cement.

The best approach is to place a backer rod which is like a mini pool noodle in the crack and then use elastomeric concrete crack filler, its like chaulking for concrete. The benefits are that it will bind to the concrete and if there is any movement in the future it will not crack and yes there will be movement however minor. After you seal the joint then follow Uncles advice.

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    Fully disagree hydraulic cement can be mixed to many different slumps and is commonly used for sealing concrete that has been cut I have never mixed it to the consistency of water.
    – Ed Beal
    Commented Dec 19, 2019 at 16:58
  • Respectfully disagree with you Ed but thanks for the down vote anyway. I worked for one of the largest concrete suppliers in the world so I do know a little bit about the subject. If you look at the images and follow my recommendation you will not have to come back in a few years and fix it again. Or follow your advice and be back for round 2 - then again if I were a contractor I could turn this into repeat business, blame it all on settling. Commented Dec 19, 2019 at 19:18
  • Would the backer rod still be recommended whether I use the hydraulic cement or concrete crack filler? Commented Dec 20, 2019 at 22:39
  • Yes the backer rod is essentially a stop for the material you will be adding to keep it in place, otherwise material will be wasted running down the back of the block. Commented Dec 23, 2019 at 1:35

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