Repointing a Basement Wall

Our 1905 house has a brick foundation.  Brick is a great building material that lasts for centuries, but it does require periodic maintenance.  The mortar holding the bricks together is typically made of sand, cement, and lime.  Old houses, pre 1900, had lime and sand mortars.  Cement based mortars did not become mainstream until around 1930.

Due to water intrusion, some areas of the mortar have disintegrated.  This happens because the water passes through the mortar and dissolves the lime bonding agent.  What is left behind is just the sand and that can be raked out easily with ones finger.IMG_7562Removing the old mortar is not that difficult of a job.  I used a 4 1/2″ angle grinder with a diamond tipped tuck pointing blade ($35 at Menards).  Be sure to wear plenty of protective gear because it will be a dirty and loud job.


After doing a 3’x2′ test section of wall and switching out batteries 8-9 times, I ordered a corded grinder off  You can get good deals on reconditioned tools that are just as good as brand new.


For the replacement mortar, I chose to mix up a type O mortar.  The following table from shows the mortar specifications.

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Type O mortar has less compressive strength than the other more popular mortar mixes (M, S, and N) because it has less portland cement and more lime in it.  Lime fell out of favor with builders around 1930 because it took longer to cure than cement and it had lower compressive strength.  Lime based mortars are more flexible, self healing, and direct water better than cement heavy mortars.

Big box stores do not carry Type O mortar, but you can make your own with three simple ingredients.  Type S hydrated lime, portland cement, and masonry sand are the only ingredients that you need to make up any mortar mix.


I am happy with how this test section of wall turned out.  With any luck, the new mortar will last 50 years before needing replacement.


I did not want to start another section of tuck pointing until the corded grinder arrives.  I was able to cross another masonry job off my list by patching up the gaping hole left by a previous owner / HVAC contractor in the north wall.


Why they didn’t spend half an hour to make this look nice is beyond me.




After being gone for a long weekend we came back and noticed that the basement walls/floor in the north west corner were damp (as usual) except in the area that I repointed the mortar.  That was bone dry!

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