filling voids in fieldstone / rubble foundation?
Old house on a fieldstone / rubble foundation. The exposed portions of the foundation are pointed with mortar. The NON-exposed portion (i.e., exterior and below-grade) of the foundation is a loose jumble of random-shaped fieldstones that flares outwards to a width of several feet as you approach its base. The stones throughout have substantial voids between them. Unclear whether this has always been the case, or whether 200 years of water has washed the fines into the cellar.
As I work to improve grading around the perimeter and install underground gutters beneath the eaves, I have easy access to the very top of this void network. Should I do anything to fill them?
The voids are substantial enough that either pea-gravel and a watery concrete or mortar would somewhat flow into them. The local vole and chipmunk populations would be very unhappy with me.
Thanks!
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Replies
Karl-
I'll be tackling my old fieldstone/brick foundation once I get past a few other projects. I'm also in zone 6A. I'm not a pro so take my feedback accordingly...
I have done some testing around the perimeter of my house to determine the impact that in-ground gutters might have on the water entering our basement after soaking rains and on humidity levels. Basically, I laid some scrap EPDM pieces (6-8ft wide) over some graded stone along the perimeter of our foundation. I weighted the EPDM down with rocks. I wanted to do this test before I took the time to dig up everything to install them in-ground. I estimate that it improved our basement by 90%+ by getting the water away from the foundation.
Once I do dig down a bit to install the in-ground gutters I expect to find many voids in the stone foundation. I think I'll use some 1/4" crushed stone to fill the voids. Depending on what I find I may install some stainless critter mesh. Really, I would just be looking to critter proof things. I want our local voles and chipmunks to be very sad.
I'd be curious to know what you end up doing.
Karl, on one occasion we fully excavated the exterior of a mid-1800s house and found what you describe--the interior stonework was so pretty that the owner didn't want to cover it up, but water sprayed in several feel during rainstorms. On the exterior, the stone wall got wider and rougher the lower we excavated. We parged the exterior below grade with concrete mix and placed a dimple membrane over the stones before backfilling. We installed both a perimeter drain and drains for gutters rather than using a ground gutter system. The combination stopped the water infiltration problem.
I like Michael's plan for a full foundation excavation. In my case, I'll likely stick to a partial excavation as I'd have concerns about stability for a full excavation. Plus my interior stone is not pretty at all. I've looked into shot-creting the interior, but haven't chosen a path yet.... bit of a tangent.
Hi Steve and Michael, thanks for your thoughts and replies. I'm not sure that the voids are ACTUALLY a problem, but I don't like them. Before we re-pointed the cellar walls, it was clear that the voids allowed for surface runoff (and in one spot, cold winter wind) easy access into the cellar. That's *mostly* under control, but the resident vole population still seems to use the voids (and our cellar) as a shortcut to get from one side of the yard to the other.
Steve, like you, we also experimented with a bit of scrap EPDM. It helped. Unfortunately, our water table is also seasonally high. At present, it keeps our sump pump occupied for a couple weeks each year. We're on enough of a slope that perimeter drains along 2 sides would be the gold-standard solution (and a corresponding cost).
I've been warned against excavating too aggressively, so I'm hoping that a combination of re-grading, a "distant" perimeter drain on the uphill side, and a near-to-surface underground gutter will do the trick. I figure that while I'm digging to re-grade and install that underground gutter, I might as well install some wing-insulation beneath the EPDM. Unclear whether I'll use reclaimed foam or try foamed glass gravel, instead. A factory for the foamed glass stuff just opened up here in Vermont.
Voles. Not a fan. It seems 1000 of them spontaneously decided that they wanted to live on my lot. Prior to this year I had never seen one. I did find some nibbling on the EPDM I put down....which makes me wonder whether they will tunnel right through an underground gutter membrane.
It's interesting that you mention Glavel. I picked mine up at the VT factory- I'm using it for a base for my concrete-free slab. I can tell you that voles love the stuff. I know this is counter to what is stated by Glavel (From Glavel: "Inert - Prevents rodents, termites, bacteria, and rot"), but it is my experience. Voles made many nests in my bagged glavel (uncompacted). In fairness- I'm guessing that compacted Glavel will be much less appealing to critters and that the issue will cease once compacted. Even given this "potential" concern, I still feel that it is a much better choice than foam where it's suitable.
For my new addition I placed a ~2ft wide perimeter of 3/4" crushed stone down to the bedrock. No critters are really interested in tunneling through it. I plan to use a compacted stone product adjacent to my underground gutters....primarily for critter control. Maybe some stainless mesh in there too.
Steve-- thanks for sharing your experience with rodents and Glavel. That is not what I had been hoping to hear. I too hope that the compaction (and whatever overburden exists) will deter them.
I priced stainless steel mesh a couple years ago, and it quickly gets expensive. From what I read, stainless can also sometimes be incompatible with certain soil types, though that seems to only happen when there's zero access to oxygen.
Let us know how you eventually proceed!