Safe to dig beside foundation for drain tile placement
Safe to dig beside foundation for drain tile placement
(OP)
Helping a relative install drain tile beside a leaking basement (and partial crawl). Intention is to dig directly beside the wall, cover in a waterproof membrane then place a French drain beside the footer. I'm a bit concerned (for them) about soil compaction and shifting once we disturb the soil near the footer. Looking for any insight.





RE: Safe to dig beside foundation for drain tile placement
Dik
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
Dik
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
Check with SlideRuleEra's website for a paper I wrote on Historic Brickwork for some background information. Written for brickwork, but a lot of the information is applicable to stonework.
Added: Don't repoint with high strength mortars.
Dik
RE: Safe to dig beside foundation for drain tile placement
Good luck - Dave
Thaidavid
RE: Safe to dig beside foundation for drain tile placement
Just covering the clean gravel with the fabric is not enough. You lay it down, place pipe and gravel and then wrap over it. All possible entry places for water so all possible water routes must be filtered. It can come from all directions.
An alternative is to use a tile with entry holes in the bottom third about 1/4" diam. or so. Slotted corrugated plastic pipe also is fine with 1/16" slots. The backfill that collects the water should be clean coarse sand, such as ASTM C-33 concrete fine aggregate. Probably costs less and is easier. In this alternative no gravel is needed on the job. I usually spec that NONE IS ALLOWED. Most gravel is not a filter and easily plugs.
RE: Safe to dig beside foundation for drain tile placement
Back to the fabric; in addition to reading multiple studies I also had a conversation today with Tim from "Ask a Builder" I know others on this site have spoken about him. Its his recommendation to use no fabric at all in any french drain as that laterally moving water is almost always clear (he gave a cold spring as an example), and that if were relying on fabric to filter sand then what stops the fabric from clogging. Any thoughts on this ? I am quite curious about the cement sand youve mentioned.
RE: Safe to dig beside foundation for drain tile placement
Dik
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
Dik
RE: Safe to dig beside foundation for drain tile placement
I can point to an extreme. A small office building was to go on a site south some miles off lake Michigan that used to have high ground water, but when the basement was dug, no water. Knowing the history the basement floor and backfill to footings was filled with clear stone layer, not a filter. Sump pump was installed also. A year or so later the groundwater came up and now and then the sump pump ran. Our firm was called about 6 years later, because the interior footings had settled and the basement floor was badly cracked and settled. The sump pump discharge was in the open next to the road. A significant delta was present there having been soil carried along with the pumped water. Major failure. Enuff said.
RE: Safe to dig beside foundation for drain tile placement
I haven't seen one plug that soon... my earliest is about 10 years with large amounts of silt...
Dik
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
Engineers investigations at Vicksburg. That pipe had 3/8" diameter holes and they were in the lower third. A small amount of the finer fraction from the concrete sand came in but the larger sand sizes bridged over. Since you have holes all around, then you need some means for keeping sand out. That's where I'd go for plastic drain pipe (hole sizes unknown) inside a sock made of the non woven fabric. Of course you can manually wrap the pipe with the fabric also.
As to clean-outs I used to call for that, but never had an occasion to use them. With a means to keep the sand out this system is very simple and can't be goofed up. You place the pipe, dump in the sand and be done with it. Maybe place clay and topsoil on top to grow plants, etc. For deep trenches you don't even have to enter the trench.
If one wants to he can take the sieve sizes of the stuff naturally there and the gradation of concrete sand and use a few formulas to see what range of soil sizes it will filter out. However, I have noted that real fine clay (doesn't fit this) usually is so fine and cohesive that it doesn't migrate with water, even though theoretically it might get through the sand filter.
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
https://www.certainteed.com/resources/journaloflig...
RE: Safe to dig beside foundation for drain tile placement
While they were 3/8", I would think 1/4" would work fine for a typical footing drain not carrying a lot of water. Then even the finer fractions of sand would likely stay put.
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
Dik
RE: Safe to dig beside foundation for drain tile placement
Dik: I'd like to know how pea gravel can filter out silt when the void spaces there are much large than silt particle sizes? IT AIN'T A FILTER! Go ahead and don't change, it's not for me. Pea gravel, or other materials with no filtering ability are allowed on my jobs because "well meaning workers" see those large voids and figure water flows faster. Fast rate of flow for seepage collection is not needed.
Lawrence: There is no distinction between highway subgrades and house basements when it comes to keeping water out. Hell, I use concrete sand and perforated pipes for stabilizing side hill earth slippage caused by excessive water. Same purpose. I showed the photo to illustrate how you can have holes on the bottom and leaves a smoother path down the center. It is not critical if the bottom also has holes. However, if the collecting water has to flow up into the pipe, it is more difficult for fine particles of sand to migrate in.
No point in making a simple job complicated.
RE: Safe to dig beside foundation for drain tile placement
Dik
RE: Safe to dig beside foundation for drain tile placement
Let's not confuse things. Here is your statement from way above.
use a nonwoven geotextile between existing soil and drainage layer
That's correct. But, without the fabric covering the open graded stuff, you can have plugging of tghe open graded as well as the pipe.
There is one job that I came across that says you need a large area of filter between soil and the collecting place. Using fabric covered slotted pipe and an open graded collecting zone between earth and it. Or, no open graded material at all. With spaced slots in the pipe silt and clay can build up on the fabric just there and plug everything. That's where fabric over the gravel or just concrete sand can do the job.
by the way it's not cement sand.
RE: Safe to dig beside foundation for drain tile placement
Dik
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
I think I'm going to pour a slab after I level it but now I'm concerned with an old stone wall and no footer how close I can get to the bottom of the wall with the french drain without running the risk of drawing water from under it and causing erosion under the wall.
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
Otherwise ,another main problem I have seen is vibrations in the are causing the sand, usually damp, to actually flow out from under. That can be running a vibrating roller nearby or a large industrial compressor operating about 40 feet away.
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
I'm leabing toward keeping french drain about 1 ft out from the wall.
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
It also is easy to implement for new construction IF the builder has the desire to avoid foundation problems and install perforated drain tile.
I had a friend that was a builder and also a member of the state building code committee that made recommendations to the use and implementation to the building officials.
He built over 200 homes per year and vowed to never have wet basement complaint. He had very practical, efficient method that required some special block for the walls, drainage pipe and strict construction methods that were easy to implement when you are big enough control design, construction and sell/guarantee a home. This method was based on keeping the drain tile outside of the 45 degree spreading out from the bottom of the footing toes.
We had a 48" frost depth.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
I'd set the pipe at footing grade. I'd fill the trench up to what might be called "highest water coming in". That fill would be concrete sand, the simplest technique, most rapid, fool proof and cheapest. Following the comments on pea gravel and fabric is labor intensive and easily can be done wrong, takes longer and can invite cave in due to time taken to lay fabric, then pipe, gravel, and fabric. Suppose you are partly done and get cave in or big storm before the gravel is in or covered? A holy mess. Dig out and start over. With concrete sand, you can cover with sand as soon as each section is laid. Cave-in on that sand likely might not hurt, or can be removed later.
Final fill to grade can be what was dug out.
In summary, the interior footing settled examination by geotech might also involve him for these walls, but don't go for something without roper filters. That part of geotgech education usually is missed. The detail I'm going into here is much more than what the operators of this web site like to have us do. About all I'd like to leave is "don't forget filters".
RE: Safe to dig beside foundation for drain tile placement
, or curtain drain proposed will be overkill
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
Our initial thoughts were a retaining wall with a french drain behind, a curtain drain (this is red line on the markup) and then a french drain inside basement-crawl.
We are likely going to put in a large swale right next to the tracks to divert water from that erosion point to a storm runoff area on the property. I'm thinking that the curtain drain may not be needed then as that the drain behind a retaining wall should now catch most of the water coming down the hill.
RE: Safe to dig beside foundation for drain tile placement
Then after sufficient outside grade is changed a cut-off drain can be installed next to the basement. Follow with grading the surface and placing that sloped paving, etc.
This post should have been done about when the original question was asked, but missing important information really has wasted a lot of time here.
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement
But then we wouldn't have a true Back of The Envelope Sketch.
Some great points raised by all!
Jeff
Pipe Stress Analysis
Finite Element Analysis
www.xceed-eng.com
RE: Safe to dig beside foundation for drain tile placement
RE: Safe to dig beside foundation for drain tile placement