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Parging or motar?

Ken Wigboldus | Posted in General Questions on

I will be excavating my 85+ yr old poured rubble foundation this spring in order to get the proper drainage and to repair areas where the motar has disintegrated to the point where I can fit the length of my fingers into some joints. It is happening predominantly on one side of the house where the brick is also starting to crumble. What is the best material to be using for this repair…repointing with brick mortar or using parging with bonding agents. Alternatively is there a sand/lime/portland mix that I can prepare myself. The mortar decay has also been happening on the interior side in some areas only. The mortar has simply turned to grey sand and I am able to remove full stones from the wall. Can I use the same mix on the interior as on the exterior?

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Replies

  1. Bob Coleman | | #1

    note, i'm not an expert

    i have a similar foundation, although not in as bad of shape and have read up a lot on the best way to work with it

    before i bought the place my exterior above grade was once'd over with some parging that has held up wel, but not great

    the 'true' professional would take some of your original mortar and have it tested to get the right mixture. if it is before they introduced portland cement into mixes (varies with area and who constructed it) they'll use a lime/sand only mix. you can't add just a little bit of portland. also not as easy to aquire this stuff and use it - hence why portland ws introduced.

    many contractors will come in and just refil with common materails used now - it cost a lot more and takes where more time to do it the old way, and many are not familiar with it.
    they may also reparge over the wall with a sand like portland mixture which leaves a plaster look, as the new mortar won't match the old mortar and/or replaced blocks if you leave it exposed on the exterior or interior

    i've also seen where there is so much work that they just pour new outside and sometimes inside think foundation walls to shore things up. Using foam on the outside and the original wall as the inner frame, runing rebar in between and connecting it to the foundation by drilling and runningsome rebar horizontally through it and then filling the gap. you can then tie proper drainage into this

    it really is a job for a pro, one that has been around a while so you can call them back to take care of any problems. if you put portland in your mix it will expand as it cures and bust the old stones and mortar. there are so many different ways to go with this. best bet is to do your research and then bounce ideas off local contractors and go from there.

    this really isn't the best site for this type of question
    also, if you can get the house lifted off the rubble foundation, getting a sill seal between the two and a barrier membrane(s) around each part would go a long way as well

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