I am going to do something about the dampness getting into my basement this summer. The house was built in 1910 with a limestone rubble foundation wall. I live in Owen Sound, Ontario, Canada (on the southern shore of Georgian Bay. The prevailing soil around the house is heavy clay.
The area of town I am in is part of a slope (the Niagara Escarpment). Fortunately I am on the downhill side of the street so I don’t have to deal with hydrostatic pressure from a 50′ hill. From the front of the house to the street is sloped slightly towards the street (perhaps 1′ over 25′). At the front of the house the slope changes to a fairly aggressive slope in the other direction (towards the back)along side the house (2′ – 3′ down over a 55′ run, the house is 40′ from front to back). In the back yard about 16′ from the house there is a sharp drop off (5′ down over a 4′ run).
The dampness (no running liquid at all) is worse along the north side of the house. “Coincidentally” this side has the neighbours with no eavestrough… There is about 5 1/2′ of space between the two houses (it is MUCH closer on the other side!). That side of the house is always a little bit damp. After several days of rain it gets really damp.
My original plan was to dig a trench down the center of the space between the two houses about 24″ deep. I would put down weeping tile run straight out to the back yard and onto the surface at the bottom of the little hill. I had thought to grade the ground between the houses so that I am down about 6″ at the wall of each house (i figure that going to both houses will ensure that I don’t make things worse for the neighbour who I get along with). Then I would put down however much gravel I need to cover the tile adquately (and whatever other membranes would be helpful to stop the pipe from clogging) and then put back as much of the old soil as would fit. Voila! the surface water is controlled.
Upon thinking about it I thought “why not dig down 2′ right beside my house and put down the tile bed and membranes just there…” Then I can put an inch or 2 of insulation in the top half of the below grade part of my wall.
Can I get away with a drain pipe which is only 2′ underground in my cold climate? (Canada). Does having the drain pipe right next to my foundation that situation better? (I am thinking about freezing here of course).
Then I started thinking about digging all the way down (4′ – 5′). Thats when I started to call excavation and foundation contractors since I do not believe in my ability to dig a trench 50′ long and 5′ deep. (Remember, only 5 1/2′ of clearance between the houses…)
Whether I go all the way down or not, how much gravel do I need on the weeping tile? I have heard everything from 1′ to right to the top.
If I do go straight down to the bottom is there any reason why I can’t do the job myself if I hire the appropriate number of labourers with shovels or just get an excavation contractor to do that part of it and backfill.
Any comments?
Replies
Hi DgH
With regards to going 2 feet deep for your drainage tile, I have an alternate (or maybe supplemental) solution based on experience and then seeing an article in a Taunton book on basements.
My brother put an addition on his house that included a basement. Even though he is in an area that only gets 14" of precipitation (the east side of Tucson), the basement walls leaked like a sieve during rains. I suggested that he attach a rubber membrane to the top of his foundation wall just below the top of grade, running out to about 5 or 6 feet at a 10 degree slope. My brother, believing that rubber was just too wimpy, put in a more expensive no slope subgrade concrete slab that extended out 4 feet from the foundation wall. He caulked the cold joint between the foundation wall and the slab and has had no leakage problem since. Subsequent to his fix I saw the article in the Taunton book (which I think was an old article from FineHomebuilding). It dealt with the same situation, and said the solution was to use a sloping subgrade rubber roofing membrane attached to the foundation wall with an aluminum termination bar (brownie points for my original suggestion).
I would guess that running out 6 feet from the foundation with an impervious membrane would give you greater protection than a french drain at 2 foot depth. I'm no soil expert, but I do know that the horizontal movement of moisture varies with soil type. If your drainage tile is not at the bottom of your foundation, you will likely get moisture penetration at a lower level if there is not some other sort of barrier.
Obviously, you will have to consider your existing/ future landscaping root system into this solution.
Enough babbling
HLR
I had a discussion with my neighbour yesterday. He has some worries about how strong/puncture resistant the membrane would be. I will have to get my hands on a sample to convince him I think. I will also need to look up that FHB article...He sggested that we at least compare the price of covering over the area with asphalt... He says he spoke with a previous owner of our house about this but that the other guy got a divorce and sold out before anything got done.Any Comments?Last year I didn't know what any of this stuff meant.
I'm from Georgetown, On. A suggestion I have for you would be to use the delta ms as suggested. Dig down to your footing level instal Delta. Lay 3or 4 inches of gravel, lay down pipe RIP OFF SOCK!! Socks usually clog with sediment eliminating the effectiveness of your drainage pipe all together Istead lay tyvek (buiding wrap over top to allow the water to pass though and nothing else. In Canada, Let alone owen sound you cant afford to be above the frost line with anything water realated frost line is 4 feet. A plastic pipe 2 feet down chances are might be good enough. If you ever had a water build up and If froze you'd be right back where you started. IF you don't want to use Delta, You could just paint it with tar. Before anything else try to raise the height of you soil on the side of the house up to the same height or higher than your neighbors grade it towards the center of the two houses making a little valley for water to follow. This might be the cheapest route to go. If it works you'll save alot of time an money.
Hi DgH
The book I cited is "Foundations and Concrete Work", and is $17.95 U.S. It is part of Taunton's Fine Homebuilding "For Pros by Pros" series, which are basically compilations of articles from the magazine. The article (which begins on p 105 of the book) is "Details for a Dry Foundation" by William B. Rose. The last section of the article (pp 112-113) deals with using the rubber membrane. I couln't find it in the website index, but there are a lot of articles that aren't listed there. You should be able to find it in one of the year end idexes (in the Jan/ Feb issue, I think).
EPDM roofing membrane is pretty tenacious. If your soil is rocky you could shade the membrane with several inches of sand and/or screen the backfill. (My brother, like your neighbor, is suspicious of something that thin, which is why he went to concrete. To my way of thinking, that is tantamount to killing a fly with a hand grenade. The concrete was many times the cost, and it still leaked at the cold joint until he dug it up again and caulked and flashed it, and is susceptible to future cracking. And if for some reason he ever needs to dig below that level...well, you know what creek he's up.)
With asphalt you will likely have to frequently reseal the cold joint at the foundation and the cracks that are bound to open up in the surface.
HLR
I put some stuff like this product around the basement of my house after I had moisture problems:
http://www.deltams.com/deltams/index.html
It keeps the soil from touching the foundation, so moisture can't wick through.
.
What you're proposing will help get the groundwater away. But the soil will still be damp, so I suspect your basement will be too.