Sump pit too close to footings?
Most of the information I see about sump installation shows the pit being dug against a wall, or even in a corner. My concern is about affecting the stability of the soil that close to the footings, as the pit is most likely deeper than the the footings themselves.
Any cause for this concern? I *hope* not, as a corner is the exact location where I’d like to place a sump in the basement of my 100-year-old Victorian. But I don’t want to invite problems by compromising the foundation.
Thanks for any advice! This is my first post to Breaktime after lurking for some time; you folks are an awesome source of expertise. I’ve turned to this forum often in the past year, while building a 17’x27′ addition on my house. By myself. With three kids under age 5. And a day job. <yawn!>
– Becubed
Kitchener, Ontario, Canada
Replies
I am a Foundation and ICF contractor south of Ottawa.
Normally, sump pits are located near exterior walls to facilitate water exit.It is best, in rural locations not to direct the sump water towards the septic bed, as the septic can already be waterlogged come spring.
I have only seen soils erosion by sump water pumpage once or twice in 25 yrs.
The underlying condition for failure was running sand. Running sand is sand with no loam or binder and is easily carried away, floated with fast running water.
The structure involved had a perimeter tile at footing level, but was not encased with filter cloth.ie sand tile. This allowed the sand to travel into the tile, and be pumped away from the sump pit. It took about five years for this particular foundation to show the effects and fail.
Other types of sand, fine flour types, used to backfill, do not flow like running sand, but can plug an unprotected tile, causing basement flooding. I have dug up weeper tiles that were entirely full of sand, with no ability to carry water.
Clayey,hard pan soils, and bedrock pose no problems for erosion, but imported backfill might, so we ALWAYS install sand tile on the perimeter of the foundation.
Reading you post once more, I realize that from the age of your home, you probably have no footings under your home. It was commonplace for these homes to have 3 ft thick stone walls, laid on hard pan.
If your home has no perimeter drainage system, then your whole basement is essentially a sump, with your pump located at the lowest elevation.
A layer of clear stone 3/4 in would be a good medium to allow water to travel, and is good material to bed your new black plastic sump box. Happy diggings.
> It was commonplace for these homes to have 3 ft thick stone walls, laid on hard pan.Good call! I started the project today and discovered that this is, in fact, the case. Stone walls with no footings.> A layer of clear stone 3/4 in would be a good medium to allow water to travel, and
> is good material to bed your new black plastic sump box. Happy diggings.Thanks! This pretty much confirms what I've planned to do. Given the lack of footings, I'll keep my trenches along the perimeter walls to a shallower depth, to avoid compromising the stability of the soil next to the foundation. I'll go with a "burrito" approach of stone wrapped in filter fabric, directing water to the sump pit. I'll double-check, but I think I can squeeze a 3" drainage tile into that burrito, as well.I had a moment of fear earlier today, just as I finished digging the pit. The bottom 2 inches must have passed the current level of the water table, as water started to appear at an alarming rate. The soil here is pretty sandy; I could actually see the sides of the hole start to erode. <!> It seems to have stabilized now, especially since I threw a few shovels of soil back in. I don't get the stone till tomorrow, so this has to sit overnight. (Hope I'm not tormented by dreams of massive erosion.)Thanks again for your replies.
Sounds like you are in for a tough time getting your pit down to the proper level, that is if the ground water is coming in fast. You may have to pump water, as you dig down so you will need an extra body to assist. Sometimes it is impossible to get them down, because of this. If you find yourself in this predicament, abandon the pit until the "dry" season.
If your stone walls are leaky, most of them are, lining the interior with "Platon" and bedding the plastic into your basement stone will keep the moisture level down.
I assume there is no concrete floor, so you should cover the whole area with clear stone, at least 3in thick. OBC calls for 6 in.
I know you will be giving up valuable head room, but, better a dry basement, than one that drips , leaks, and sweats.
In the last year or so, Insurance guys have been picking up on this. They don't like seeing furnaces, water heaters and such on stilts.
Cheers.
> Sounds like you are in for a tough time getting your pit down to the proper
> level, that is if the ground water is coming in fast. I managed to get the pit in the ground today. Not too much trouble; just meant bailing the water out first, then acting fast to dig it out a bit more before placing the filter fabric and setting the plastic basin in 3/4 stone. It's been in for most of the day, and the water level seems to have settled at around 6". That's OK with me!> If your stone walls are leaky, most of them are, lining the interior with "Platon"
> and bedding the plastic into your basement stone will keep the moisture level down.Sorry, not familiar with the term "Platon". Is that the dimpled plastic? I've been intending to place that at the floor/wall intersection before patching the concrete, to direct water seeping through the walls down into the stone.> I assume there is no concrete floor, so you should cover the whole area with clear
> stone, at least 3in thick. OBC calls for 6 in.Actually, there is a concrete floor -- barely. It seems only about 1.5" thick in most places, so it was pretty easy to break up. And it was poured directly on the soil; no sign of stone underneath. I've filled my drainage trenches with between 4"-7" of stone.Thanks again for your tips! It's great to hear this stuff directly from someone with experience.
Hello again : Davo, below did exactly as I would for your situation.
A uniform layer of stone throughout allows water to flow under the basement floor, from any direction.
Tile under the basement floor to the sump box, always.
With your "Burrito" approach, water will have travel thru different materials, sand and then stone. The drainage will be slower.
6 mil plastic over is excellent and "platon" or "cosella dorkin" dimple against the wall is excellent also.
I'd say you've got the picture ! Cheers.
eric,
what brand(s) of icfs are the best that you have used?
This should be a different thread. But since you asked........
I use Nudura mostly, but I would rate ALL 3rd generation ICF blocks highly.
In the Ottawa Valley, professional tech support is available from Nudura, Logix, Amvic and Integra. All are high quality products with lots of Canadian development behind them.
Depending on job dimensions and requirements, some blocks suit certain types of jobs, better than others. eg if you want a full 8 ft basement, and 9 ft 1st floor walls,Nudura would be my choice, As it lays 9 ft high with 6 18in courses.
The other systems are 16 in course height, which relates better, in other types of setups.
Cheers.
thanks, will check out nudura.
Becubed,
I dug up my basement this past November and installed a sump pump. My house foundation was cinder block laid on hardpan...no foundation footer. I dug just deep enough to lay down a bed of gravel approx 3 inches thick, installed a 3 inch dia perforated drain pipe, and another layer of 3 to 4 inches gravel on top. All gravel was 3/4 inch river gravel. I covered the top of the gravel with 10 mil plastic and poured a new concrete floor.
My sump basin is located near the corner, but not in the corner.( approx 4 ft from corner and center of basin is located approx 2 ft away from inside wall) The drain lines all were pitched so the water would flow toward the basin.
System has worked great for me so far...100% dry basement to date.
Good luck to you.
Davo
P.S. I actually removed entire concrete basement floor. My concrete floor, like yours, was placed dircetly on ground...no gravel. And, my floor originally was only 1/2 to 1 inch thick...no thicker. I dug out entire basement and poured a new 5 inch thick floor.
worked on a number of stone walled basements including the one I live in
on a number of these we dug the basement deeper to give more head room
provided the water table wasent too high we dug down parallel to the walls inside and using blocks or concrete made a extension to the exterior walls then used 3/4 clear stone under new 3000 psi concrete floor
we pour the walls and floor at the same time in some cases
been doing this method for 20 + years in Ottawa & south of it & never had a call back