pointing the wall in the basement
I moove in this brownstone about 3 years ago and i have been collecting a lot of dust for the cement coming of the wall in my basement and the space bt the rock is getting wider and deeper, probably from the humidity ???? I would love to get it fixed this summer and was…
I moove in this brownstone about 3 years ago and i have been collecting a lot of dust for the cement coming of the wall in my basement and the space bt the rock is getting wider and deeper, probably from the humidity ????
I would love to get it fixed this summer and was wondering wich cement i should use for pointing ?// or if anyone got some advise for me.
Thank again
Not all basements are done with stone. Mine is brick. The same soft brick that is used in the rest of the building. I wouldn’t use type S if you have brick in your basement.
I just got done doing two projects that pertain…
The first was a historic brick barn pointing restoration in upstate NY-
Soft brick with even softer lime based mortar. We hired a great mason who had to mix custom mortar to match color and strength as not to damage the face of the brick when the mortar expands and contracts differently than the brick in extreme temperatures.
The second was a basement repointing project in Brooklyn just like the one described above-
While mortar strength is always an issue, below grade where it isn’t exposed to freezing temperature and where it is used with stone (a super hard material) it is far less of an issue. We raked the joints, rinsed them out with the hose and used type S, which contains Portland cement (much harder than lime), as do most ready mixed cements. I had Jahan (who I would highly recommend) do this one because of time, but I wouldn’t be afraid to do this myself.
You should call Cathedral Stone, check out their website for their recommendation on the particular mortar.
http://www.cathedralstone.com/
I am an Architect and used their historic mortar to re-point the brick on the exterior of my brownstone. They offer pre-mixed mortar, along with other products, so you do not have to mix it yourself or determine which type you need, such as type S or type N etc…if you are not a mason don’t do this on your own.
THey can be pricey but the consistency of the mixture was more than worth it. They have been providing products to restore many landmark buildings.
I used them in my home because I have specified them on projects for clients. In any case, they are a good resource. Good luck.
Most of the mortar originally used in these old houses is lime based, not cement based. The danger of pointing with a cement based mortar is that the bricks used back then were not as hard (in fact much softer that a cement based mortar) so might crack if you use cement.
My understanding is you want to match the existing mortar as much as possible for strength and permeability.
Putting in a super strong impermeable mortar could act like a wedge and further break apart the wall over time- but I don’t know how likely this is to happen.
To determine mix ( sand vs cement) you need a cubic inch or so of mortar and have to break it down with muriatic acid and a little pressure (not too much pressure or you will actually break down the sand grain which will mislead the results). I have no idea how you can match sand other than experience eyeballing.
Perhaps there is a flexible generic admix you can use instead of water in an off the shelf cement that will prevent the “wedge effect” from happening.