# Tie Existing Stone Foundation to New Concrete



## shazapple (Jun 30, 2011)

Bump!


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## jomama45 (Nov 13, 2008)

shazapple said:


> Hello all, My house is 100+ years old and has a stone and mortar basement foundation. It is about 7 feet from floor to joist because at some point in the past concrete footings and floor were added (the floor is lower than the footings by about 8", so I assume the footing does not extend all the way underneath the original stone foundation).
> 
> We are putting a 15x25 addition on the back. A contractor will be hired for the foundation work and I am looking to educate myself on where the old and new meet.
> 
> ...


I can't speak for how the 100 year old walls were constructed in your area, but I can tell you what they all look like here. The inside is rough & wavy, but it looks like a laser-straight line compared to what the exterior looks like. Typically, they dug the hole to the exact dimension of the house & used the dirt bank as the back form for the wall. They had no intentions of anyone ever exposing the backside, because they certainly aren't pretty. You'd need copius amounts of mortar to get the wall flush enough to damproof, and even more to get any kind of foam insulation to sit against it.

To be perfectly honest, 100 years ago when the basement was new it wasn't meant for anything other than shelter from serious storms, a house for a cistern sometimes, and a cool dark place to store your veggies from the garden. Try as you might, it's near impossible to make a wet old stone foundation much more than that, unless you're willing to spend some serious money, at which point you'll likely be better off with an underpin.


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## shazapple (Jun 30, 2011)

Thank you very much! The original stone foundation is more of a mechanical room than livable space, and I agree that it's not something that can ever be converted into a living area. Even the addition foundation area will be storage/work space, so a shelf/step where new meets old would be fine. Should we consider some sort of interior drain or drain tile under the slab where it meets the original foundation? 

There is mortar on the exterior exposed portion of the stone foundation, but I wasn't sure if it went down all the way. I guess the best plan of action is to assume it doesn't and have mortar on hand for the areas we are exposing and where the waterproof membrane will tie in with the old. Good grading and down spouts will have to do the rest.


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## mchard (Mar 21, 2008)

*field stone addition*

Hello
I came across your post from a few years ago on your field stone basement addition. I would like to put an addition onto my 100 year old farm house, but I'm not sure how to build onto my old field stone foundation. 

How did the contractor complete your addition? Did they pout new concrete against the outside of you stone wall? Did you remove the stone wall? I've thought about building a complete new poured wall about 24" from the old stone wall and leaving dirt in between them. If you could give me any advice I would appreciate it. My stone walls are very good and straight, but I'm just not sure the best way to do this.

Thanks
Marty


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## stadry (Jun 20, 2009)

you can't add ON to a stone wall unless you tear part of it out & weave the new wall into it,,, we've always placed new conc right up against the existing wall & completed the exterior wtrproofing w/rqd toe drain using pond liner over hlm5000 [ no $ interest ] why leave any dirt in 'tween them ?


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