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Sealing outside of fieldstone foundation (excavated) with complex water issues

Sealing outside of fieldstone foundation (excavated) with complex water issues


Old 02-18-12, 01:50 PM
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Question Sealing outside of fieldstone foundation (excavated) with complex water issues

Apologies for the long story:

Our carriage house was built in 1874 and has a very very rough field stone foundation made of soft stone. Some of it is roxbury pudding stone which is an aggregate that is easily broken. The stones are various sizes from very large to small and I would say it was not well made. It was originally mortared with the “soft” mortar and like all old foundations is flaking and crumbling. It has never been painted. It has been repaired (read badly pointed) a few times over the years most recently with modern cement (that is hard). The other issues with the house is it sits in a bowl surrounded by huge roxbury pudding stone rocks and the foundation is partially built on top of the “bedrock” rather than dirt.

5 years ago we totally restored the carriage house (70% new construction), which was falling down and rotted through. We had to lift the entire building and replace the bottom of many studs all sills and pour a new top to the foundation. We also in places dug down and poured new cement next to the old stone to reinforce the outside of the original fieldstone where it had collapsed. Lastly we dug the floor down 24” poured sills around the base of the old foundation and a new floor. All of this was over 1” gravel (where there was not bedrock) with a plastic layer and insulation.

One thing we did right was to install a central collecting point drain with a sump and an internal drain so that water in the basement would drain/be pumped out to the yard. The basement is built into 3 sides of stone but is open to the yard which is only slightly above the floor level. We installed a swale of 2” rocks in the yard (under grass) that the basement catchment drains/pumps into.

The issue is water and two different kinds.

First the carriage house is in a bowl so when it rains the groundwater rushes down to the foundation and seeps in 5 or so different places. We have managed the roof water and have recently done some retaining walls to manage the flow but because of the landscape this will always be an issue and because of the rocks around the carriage house we cannot gravity drain all of the water into the yard (some collects next to the foundation in the bowl)

The second kind of water is a spring that flows through the bedrock and comes in below the foundation level. This flows constantly (though sometimes as slow as a drip drip trickle and sometimes as fast as a refrigerator water supply. This comes in at the base of the foundation in the back.

We have lived with this for 5 years and managed it by making sure the floor is clear (it floods in rain) and directing the water where possible directly to the drain. This is not great – it is damp and we cant really use our nice new storage space for anything we care about and secondly we are worried about mold long term and the two floors above are finished.

Recently my family has had a wonderful Amish family staying with us while they care for their child who is in the hospital for several months. The father (and his frequently visiting family) have been asking for work and when I showed them the problem they said they would be happy to dig out the foundation by hand from the outside to see what can be done. So now the foundation has been mostly excavated (they are really wonderful amazing hard workers). They had to haul rock filled dirt up 10 more feet out of the bowl by hand.

So now the questions:

What do I do?
  1. Do we pour a new cement base on the outside that “seals” the bottom of the foundation to the bedrock and try to seal the outside of the foundation wall (forcing the water to find other ways out of the bowl rather than through my basement?
  2. Do we point the outside really well (with which mortar?) and seal with tar etc and then fill the trench with gravel after we dig as deep as we can so the water tries to go under the basement (through cracks in the stone and the small amount of dirt that is at the base?
  3. Do I drill through the mortar at the base of the back of the basement and put a pipe to my internal basement drain to the swale through the back wall (this is possible) and slope the outside so that it collects in a cistern (rain barrel) next to the foundation and then drains through the pipe and out to the swale?
  4. Lastly as an option on 2 and 3 above do I install a cistern (rain barrel) and drain tile with a pump and pump the water up and out of the bowl the house sits in?
What I do not know is if there is any real path for the water other than through the basement. Did I make a mistake and poured a cement floor and sills on the bedrock and now there is no path out so I have to plumb it to the swale through the basement or is the bedrock cracked and open enough that there are other paths out if I seal the foundation? Either way I think I have one shot to get this right and I would really love to get the basement dry.

Please share any and all ideas....

For reference:
A website with carriage house photos:
Video of outside of foundation:
Video of inside of foundation:
Still Photos of the foundation (in and out)


Last edited by JamieH; 02-18-12 at 04:19 PM.
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Old 02-18-12, 06:41 PM
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Please take no offense by what I am stating here, but I started working construction 42 years ago and have never seen a more complicated set of drainage problems than the ones you are dealing with, and have taken pics of .....

It is ironic, but few builders/contractors are experts on drainage systems. For the most part they understand the fundamentals, but are not true drainage professionals. ...

What you probaly need to do is, stop throwing everyones opinions and "solutions" at your water entry problems and start looking for a 100% professional grade, reputable structural drainage/ foundation specialist. You need someone to take a thorough investigation of the site, document the problems both with photographs and written text.....

Then, they need to present you with a written proposal of the solution and let you determine if it is a rock solid(no pun intended) plan of resolution. And, you may also have to face the fact there is no total cure for the water entry problems with the house sitting in a bowl, with a spring under it... . ..

Yes, it will be expensive, but you have spent a ton of $$$ already and may have made the issues worse. You must love the old house, but you are putting yourself, your family and anyone else that stays at the property health at risk with mold and other fungus health related issues. ....

Some people can eat mold and not bother them, I can get within a foot of it and have a respiratory infection within days. Sorry for the -not so helpful- reply and good luck on your project. Greg
Old 02-18-12, 09:53 PM
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Good thing it's only a carriage house, and not the big house.

I'm no drainage expert, but I have learned over the last 60 years of construction work that water likes to run downhill. I think it's important that you try to divert any/all water away from the foundation, before it has a chance to work its way inside the living area. If that involves reconstructing the landscaping immediately adjacent to the foundation walls, so be it. A few 90-lb. chipping hammers hooked up to a 600 CFM compressor can do wonders on soft rock. Possible remedies to consider while doing so are to install a layer of either thick bentonite beneath the topsoil/plantings/new fake rock, or some other impervious barrier, such as heavy plastic. Constructing additional drainage swales in proper orientation would also help, moving water towards the French drain you already built. Pouring a reinforced concrete "skin" around the exposed foundation walls would do some good, but will not come close to being water-proof unless a heavy layer of rubberized asphalt is first applied to the exposed (and cleaned) wall faces.

Regarding the spring--a new house that was built in our subdivision in Colorado a few years ago had a similar situation. Water poured out of the layered limestone at the far back corner of the footing excavation, but the contractor was able to address it by installing a concrete culvert pipe sump pit (solid bottom, oriented vertically), with gravity-flow, solid 4" PVC pipe running from it all the way around the house and pitched to daylight close to the street's drainage ditch. In your case, I suspect some of the overlying rock outcroppings would have to be removed first.
Old 02-19-12, 08:40 AM
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Thanks for the advice – and I appreciate the validation of the difficulty. I have tried to find someone both when we were doing the original work and later when we found the water problem who would give the right advice and I have had trouble. The guy who did the floor and curb thought he had it solved but as you noted he was not a drainage expert and it was not clear there was a problem as bad as there is. The spring was not obvious until we did the floor (the original was dirt and not that wet and we thought handling the roof water would keep it dry around the base (naively).

I have had 4 other experts in and either they were basement people (who said inside would not work (which was an honest reply) or drainage people who really did not want the job (ie I think they thought it would not work). Either way without exposing bedrock and foundation I don’t think anyone could have given a real estimate.

I don’t think I have found the person with the expertise you describe and would love some suggestions for finding them or even recommendations for individuals.


It has only taken me a few years to observe the water likes to run downhill (smiling) but what I can’t figure out is why the spring comes out at the top of the hill. My neighbor is 20 feet higher (highest house on the block) and the spring runs through their basement as well. Go figure…

I agree on the landscaping changes and I am doing those (where possible). I think I can handle 80% the surface water with your suggestions but I don’t think I can handle the spring. Its 4’ of solid rock that’s integral to the foundation on both corners and the spring comes in below. No way (in a reasonable world) to remove that without compromising the foundation.

I am starting to think that hedging my bets in a two layer solution might be best. Build a cistern with drain tile to take care of the spring and any surface water that seeps through. Pour a base and point the foundation on the outside and tar to “mostly” seal it. I think I may put a pump (to handle overflow) and also direct plumb it to my in basement drain and swale to handle the trickle. I will fill the trench with say 2’ of 1” rock. I can make the cistern large enough that I can clean it as needed. (55 gallon barrel)

I think I will then do a second drainage solution around the foundation above this that gravity drains out to daylight (hard but possible over the rock) with the layers you suggest. I may not get fully dry but I can get dry enough that a de-humidifier will keep the inside reasonable.

As a last note – I have to admit that building is a little bit of a journey for me. I like the end product but I really love the process and learning about new trades and issues. I am aware that it means I make a lot of mistakes (ask me about my radiant floor lessons) but it’s a challenging distraction I really enjoy. Both the main house and the carriage house would have been much easier to tear down and build from scratch (both design and financially) but what’s the fun in that!

Old 02-19-12, 05:23 PM
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I wish I could refer someone for your location but I cannot. We have a company here in my vicinity that would be good on your project but, they are not a national franchise....

I feel your passion for the- fix it up- homes. My wife and I have bought four homes the last 22 years and made silk purses out of those sow's ears. They all sold within two weeks of going on the market and the new owners always gleened over the small and large "nice" features, that we put in them. Now we are both old and tired and have downsized to a smaller sow..

I dont think any facet of home maintenance is any more frustrating than roof leaks and foundation problems. They are hard to pin down and sometimes very costly to repair....

Add to that, all that money and labor could have been spent on something one could enjoy daily, like a 4 car garage or heated pool ! Best wishes on your journey of cures ! Greg
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