I have a sub grade vertical stack of perforated brick (foundation) which I need to coat in a thick layer of mortar or concrete in order to fill gaps, creating a flat surface for subsequent painting/hydro isolation.

Besides cleaning the brick, what else should I do to prepare them as a substrate?

  • The brick should be plenty rough for the new mortar to get a good grip on it.
    – FreeMan
    Jul 6, 2020 at 13:07

1 Answer 1


Make sure that they are neither bone-dry nor dripping wet, either of which interferes with getting a proper bond. Damp is good. Recall (or learn) that mortar and concrete do not, as commonly misnomered, "dry" to set, they hydrate to cure, in a chemical reaction where crystals grow throughout the mass, and that needs water to work. A common problem with casual brickwork is excessively dry bricks that suck the water out of the mortar and prevent it from curing properly.

There is also a matter of technique to get mortar to stick to a vertical surface - it wants to be thrown or slapped on and spread out, not applied in a tentative manner.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.