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Old 03-22-2012, 10:09 PM   #1
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Foundation Drainage: To excavate or not to excavate??


Hi Everyone, I am writing again about my 200+ year old New England farmhouse, and the foundation issues I am currently working on. The stone walls are bowing in, lots of cracks, loose mortar, etc.. The soil around the walls is heavy compacted clay. The clay is so compact it is difficult to dig up with a shovel and force is needed to break it apart. There is no drainage with the house at all. Water leaks off the roof onto the ground right next to the foundation.

So... I understand that when the compacted clay freezes, it exerts pressure on the walls causing them bow in. My original thought was to excavate along the walls, install a drainage pipe and fill with gravel (as described in this post

However, after speaking with several people, some folks have advised against doing this. They say that for the last 200+ years since the house was built, that soil has been settling and compacting and is now probably so tight that it would be better off left undisturbed. A better alternative which would accomplish the same thing, they suggest, is to prevent water from getting into the clay around the foundation in the first place by landscaping-- grading soil away from the house, using landscaping fabric, a buried poly membrane, etc..

Can someone offer any advise, or confirm that the landscaping solution is indeed a "solution" that will work? I am only looking to prevent the foundation walls from bowing in any further, and would much rather do some landscaping instead of a whole excavation project.

I appreciate any ideas anyone can offer, Thank You!

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Old 03-22-2012, 10:49 PM   #2
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Foundation Drainage: To excavate or not to excavate??


Real hard for anyone to tell you if what was suggested is ALL you need to do. All are good, standard ideas. YOU need to decide, it seems to me, if those walls are OK or if they are about to topple in. I would never dig near them w/ a machine, myself. That may be OK, or it may cave them in. Perhaps it is time to call in an engineer who specializes in soils and a reputable house-jacking company. It just may be time to lift the house and put a new foundation under it. ???? Whatever you do, be low and slow. Can you extend the overhang on the eaves and not have it look tacked-on and/or just plain funky?

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Old 03-23-2012, 08:24 AM   #3
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Foundation Drainage: To excavate or not to excavate??


A couple of things stand out in your post. First, are you absolutely certain you have clay soil? Many people, including some experienced people,confuse clay and silt because they appear to be similar visually. They behave completely differently.

Clay soil does not freeze, because the water in clay is chemically bound to the clay particles. Silt soils freeze solid and exert large pressure on foundations, because the water in silt is NOT bound to the silt particles.

I am going to hazard a guess that you have silty soil, not clay soil. Anyway, it generally takes an experienced engineer to tell the difference, or at least someone with training. As for the opinions about not removing the soil because it has densified etc., that makes no sense to me. If you have a foundation problem caused by lateral earth pressure, due to a combination of soil type and high groundwater, then your idea of removing the soil, installing a perimeter drain, and backfilling with proper material (sand and gravel) could work.

The comment by a previous poster about the dangers of excavating next to an existing foundation are spot on. Such a project requires CAREFUL attention to temporary support of the existing foundation, especially since you have indicated that the wall is already bowed, hence compromised. There is very real danger of collapse. This is not a DIY project in my opinion, but one that should only be undertaken by an experienced, competent contractor, after a thorough evaluation by an engineer, and preparation of a detailed plan of action.
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Old 04-17-2012, 02:42 AM   #4
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Foundation Drainage: To excavate or not to excavate??


Thanks for the replies and my apologies for not responding sooner. I've been hard at work preparing the temporary supports for for this project.

Anyways, Daniel-- Thanks for the info about the soil types, I didn't know that about clay v. silty soils and I thought that was interesting. With that in mind, I'm not sure what type of soil I have, but you're probably right about it being silt based on the shape of the wall and the pressure that's been at work. And thanks to jklingel also-- you are right about it being time to jack the house and pour a whole new wall, but unfortunately my budget won't allow that. This house has no heating system, no plumbing, and the well does not work so I just have to do what I can for now to prevent further damage and possible collapse. If I can reinforce the wall enough to hold it in place I will be happy.

So, after much research into this, I've decided to install columns throughout the basement to help ease some of the load from the foundation walls, along with a temporary support wall along the "bad wall" just a few feet back. I'm still at this point in my project. As of now, (my projects constantly change!) I plan to pour a sloped buttress/sister wall against the inside of the bad wall (to help prevent collapse during excavation), excavate, pour another sloped buttress wall on the outside, install drainage, backfill with gravel, and move on to my next project!

Oh and, yes, I did finally decide to contact a structural engineer about this since the other walls have similar problems. We are still working on arranging a date, but it will be done before any concrete is poured. Thanks again to those who replied!
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Old 04-17-2012, 09:39 AM   #5
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Foundation Drainage: To excavate or not to excavate??


One thing that stood out in your first post was water running off the roof. I don't see in subsequent posts what your plan of attack is to resolve that issue. If you keep putting water in the ground, you're going to have a hard time fixing the foundation problems.

Since you have a rubble foundation, I question whether the plan to buttress it with concrete is viable. In addition to the structural engineer, get Someone out who specializes in stone foundations. A masonry company. (Preferably one with at least one employee older than 22 lol).
In a 200 year old house it would be a shame to cover that foundation in haphazard concrete work if it can be SAFELY salvaged. Just my 4 cents.

Last edited by Evstarr; 04-17-2012 at 09:45 AM.
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Old 04-17-2012, 11:29 AM   #6
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Foundation Drainage: To excavate or not to excavate??


And no mention of having any gutters.

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