I’m working in the basement of a house built in 1904 with double brick foundation walls. the walls are structurely solid but parts of the interior brick and mortar are crumbling and quite loose. My original thought was to put on a thin coat of mortar to fill in all voids and create a smoother more solid surface. But questions came up about putting new mortar on old bricks and mortar- that it might expand and create a worse problem, ie all the brick faces coming off and creating much more potential for structurel problems. Is there a certain kind of mortar that bonds with old brick or should I use stuco or what?
Any thoughts from masons or others with experience like this would be appreciated.
Thanks,
John
Replies
It's probably a lime based mortar and you don't want to use the harder modern type mortat.
Check around in the Old House Journal website, they'll have a lot of info for you.
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Sojourners: Christians for Justice and Peace
Brick is a miserable material for foundations. Very absorbant. Leads to 'rising damp'. The all lime mortar from that era dissolves over time when it never has a chance to dry, and water washing through the walls makes it worse. Add frost heaving, and things get really bad.
Parging may add some strength, but is not a good substitute for repointing. The parge will not bind very well with the lose stuff left in place.
1904 bricks are likely medium-soft. If my guess is right, I would probably lean towards Type S. Interior wall is not subject to the same freeze-thaw cycles, so you are less likely to get spalling. I would use Type N on the same brick if it were above grade and exposed to prevent spalling.
Thanks for the reply,
The bricks certainly are soft, but I think beyond (softer than) the medium stage. would type S mortar still be appropriate? Also, what is involved in repointing? I have done lots of concrete and drywall work but almost no masonry. Basically how does that differ from simply filling in the voids and putting a thin coat on the brick? We are mostly interested in preventing any further decay if possible before putting furring strips and OSB on for shop walls.
In this case by repointing, I really meant doing the extra step of removing as much of the loose mortar as possible prior to parging. Difficult to judge hardness from here...
Check this out:
http://www.taunton.com/finehomebuilding/pages/h00032.asp