Hydraulic cement for repointing block basement

cmcguigan

Member
Mar 9, 2017
11
Charlotte nc
My basement seeps around the bottom of the wall. I did some prep work for painting and noticed spots of mortar that had softened significantly. So I cut out the bad spots with a mason grinding wheel and repointed with hydraulic cement.
Now I've read that might have been a bad decision. I'm curious what to expect and if others have made the same mistakes. Is this a fingers crossed nothing happens or an oh chit your f'd?
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
3,984
NE PA
Too many variables to determine how well it will work. When you read about patches falling off it is usually due to a deep crack that the quick drying cement can’t be forced very deep into the crack. If you only penetrate a crack 1/4 inch, the expansion can crack away the surface of the cement or block resulting in a larger missing piece on the surface. Grinding a wider groove, you probably got the new cement to the bottom of the groove and the force is not just on the surface. It depends on the softness of the material as well. It can expand into older soft block without damaging the face of the block.
Mortar in cracks and repointing supports weight unlike polyurethane caulk. A moving crack requires caulk. So treat repointing and cracks differently when there is a chance of movement.
For an older wall that has cracked, but shows no new movement, like from original settling, I use regular mortar even though it shrinks slightly. Then work extreme dry lock into hairline crack before coating entire wall.

I’m not a professional mason, but a stone mason friend of mine taught me the tricks of repointing and repair of homes I recondition as rentals, and every one of them has needed this type of repair to basement walls. Only one had water coming through for years that adding gutter and proper grading outside helped tremendously, then I sealed mortar joints and dry locked. Clean and dry ever since.