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french type drain system in Baltimore semi-detached house basement.

french type drain system in Baltimore semi-detached house basement.

(OP)

Lots of good info that I haven't seen anywhere else. I like the oldestguy's postings along with the others.

I watched lots of videos from this guy who specializes in basement drain systems and he never mentions concrete sand. I believe he uses 3/4 inch washed stone/gravel and doesn't recommend filter paper because it can get clogged. https://www.youtube.com/watch?v=tzYHtwOKhgs

I've addressed the grade around my semi-detached 2 story/basement and this has seemed to help but I want to install the drain system before I finish the basement.

The hydroarmor guy in the above video recommends ADS pipe placed at the bottom of the footer on top of 2-3 inches of crush washed stone. Then surround the pipe with stone and then place Miradrain over the stone and 4 inches up the wall before pouring the concrete.

I've cut the slab in my basement that faces the front of the house where a previous owner installed a bucket with a sump pump inside it. I've removed the slab and dug the stone out to the bottom of the footer. The trench is 10 inches wide which is a little bigger than the width of the shovel that I used to dig out the trench. There were no pipes going to the bucket.

I want to cut the slab which goes along the side wall from the front to back of my house and then the slab that faces the back of my house. I am not planning on cutting the slab that is up against the wall where my neighbor lives(picture 2 townhouses stuck together).

My questions are the following:

Should I use the concrete sand instead of the 3/4 inch crushed washed stone?

Is there a better product than the Mira Drain to help draw water into the trench in the case of water coming in from a cracked wall?

The oldestguy did mention that the slab maybe helping support the walls so should I complete the front trench 1st and then cut the slab out that goes from the front of my house to the back 2nd?

Is it safe to have the basement trench dug on 3 sides of the house(my walls are poured not block)?

I'd also like to have a clean out/inspection holes in the 3 corners of the basement. Is this overkill or a bad idea(I would have removable caps on them)?

I've attached some photos of what I've done so far and a picture of the slab running from the front to back of the house. This would be my my next cut. There's actually a sewage drain under my next cut but it's below the footer so my ADS pipe would be almost parallel above the sewage pipe.

I don't need to rush this job and I want it done the best way possible.

Thanks for any help or recommendations?

John

(OP)

(OP)

RE: french type drain system in Baltimore semi-detached house basement.

Here comes OG again. Well, from what you say it sounds like water may be collecting in a gravelly layer under the slab and apparently that's what you exposed and dug out. Not much you can do about that, but use it where it is. However, my preaching on filtering using concrete sand comes from seeing what results if you don't filter out the fines at the pipe. With flow of water and no filter, those fines can move. They may just haws out and go to where ever that water goes. They also may plug things and negate the function of the drain. You must also build so the filter sand doles not get lost into the pipe, etc. Slots in the pipe of 1/16" seem to work as good as anything. If you drill holes in the pipe, they should be only on the bottom 1/3 or 1/4 so water flows up, not carrying any sand. Hole diameter of 3/16 works then. If you use gravel only as backfill and then put a sock on the pipe, you stand a chance for the fines to build up on the sock over any holes or slots. That has been the cause of some failures I have seen.

The idea that clear stone may be great stems from the obvious large size of the voids, figuring that is an easy path for water to follow. It's been used for years, and may be specified, but those systems also fail. If you don't have much water flow and the soil along the way doesn't erode much, probably it will work. However, I'd not do it.

Maybe I have told this one before but here goes. One clinic site I knew of was built where ground water was known to be high occasionally. At time of construction no water encountered. Full basement area had a layer of clear stone placed and some perforated pipes leading to a sump and pump. All went well for a few years until we were called to see why the basement floor had settled and some interior column footings had settled. Big voids were noted under the slab and significant settlements. This was in the country where the sump discharge was out at the country road. At that discharge there was a big delta. The fine sand from under the basement was carried out there by the water collected. Enuff said.

As to problem with your trench allow nearby wall movement, that depends on a lot of things and may or may not be a problem,.

One more point. Ask those promoting the use of backfill that does not filter if their business also includes fixing up failure later.

Commonly plumbers will do the original installation, but it falls on other contractors later to deal with the failures.

RE: french type drain system in Baltimore semi-detached house basement.

OG again:

I looked up Miradrain on Google. It looks like it should work OK for collecting water where backfill is against a wall and other places, with a filter fabric over a dimpled plastic sheet drainage device. However, note the detail on one of the cross sections that comes up in Google. Any where in the trench sides where clear stone is against earth, as from under the slab, there is no filter. My recommendation is that any detail that shows gravel against earth without a filter there is open to plugging. Ya gotta cover all entry areas.

As to needing clean outs at every corner, well if the system is properly filtered you don't need any.

For making the system collect both wall seepage and ground seepage, that drain mentioned seems fine, but I'd not do any more with it than leading wall seepage water down to the trench. The trench should be designed to collect water from the soil below and any system there should filter out any fines from that source. The wall collection system is just a way to get wall seepage to the trench and it hardly needs any filtering up above the slab.

I'd forget the idea of gravel anywhere below the slab.

RE: french type drain system in Baltimore semi-detached house basement.

(OP)
oldestguy,

Thanks for the reply and info.

If I use the concrete sand, should I also use the washed stone or just fill the trench with a few inches of concrete sand and lay the slotted 4 inch ADS pipe on top, then fill the trench with more sand until I get to the top of the footer (the slab actually sits on top of the footer)?

I would then place the MiraDrain on top of the sand, then add plastic on top and pour the concrete to the level of the current slab.

ADS sells a pipe with slots that are very thin(almost like razor slices) that is meant to be used in sand. It comes in 100 foot rolls. I'd probably have about 30 feet left over when all the walls are done.

The regular slotted ADS pipe may need a sock to go over it to eliminate the sand from entering.

Is there any type of concrete sand you'd recommend?
I quick google search showed the attached picture of a 60lb bag.

Is that how you'd recommend finishing the project?

Thanks again.

John

Sounds like you got it right. I'd not use any gravel in trench. Too much chance of it being done wrong if you have any help. Gravel unit cost is same as for the sand. I'd set the pipe elevation where it is the deepest, assuming the outlet is sufficiently low to accommodate. Just don't place pipe on earth there. Most of the times these pipes are not laid sloped because the quantity of water flow won't fill it anyhow. Water will flow in the sand below the pipe, but that's usually OK. I'd check with your local ready-mix plant and see if they can't deliver the sand you need. Bagged sand is going to cost more. The sand should meet ASTM-C33 fine aggregate. The bagged sand may meet that, but the local ready mix guys probably do. Some places will let you go there and they will load your trailer of pickup, or you can. Charge is by the weight. Remember that front end loader will hold a lot more than you can carry. I bought a pick-up partial load full recently and they wanted to weight it. I gave the gal a $20 and saved the grief of weighing. The slotted pipe should be fine for this purpose. The concrete sand will have coarser fractions that won't go into the slots, bridging over them, holding back the rest. A little sand in the pipes might happen, but usually no problem. If you want to economize some but with more care needed and if clean sand (beach sand or similar) is pretty cheap, you can use that as fill, but AROUND, UNDER AND ON TOP a few inches of concrete sand is the filter needed surrounding the pipe. RE: french type drain system in Baltimore semi-detached house basement. (OP) OG, Are you saying the regular ADS slotted pipe is fine? Would the ADS Fine slotted pipe that's designed for sand be better or is it not necessary? I'm assuming the regular slotted perforated ADS pipe would allow some sand to enter the pipe but would eventually stop as the sand packed together near the slots. I've contacted ADS and they are supposed to send me the specs on the regular slotted pipe and the fine slotted pipe. I will post what they tell me when I receive the email. This is the ADS Fine slot item number 0409 - 0100' 4" FINE SLOT PERF. (0409 means 4 inch and 9 mean fine slot, -0100 means 100 foot roll. Page 11 http://www.ads-pipe.com/pdf/en/10524_Prod_Catalog.... Thanks. John RE: french type drain system in Baltimore semi-detached house basement. (OP) OG, I spoke with a couple of people from ADS and they were unable to give me the specs on the hole sizes of the fine slot pipe. They call it the knife slit because that's what it looks like. They also said they never shipped it to the North-East. They said it sold mostly in the mid-west for Agriculture. The ADS rep did tell me the dimensions of the holes on the regular perforated pipe. They are the following: .875 length .12 width I guess I'll buy the regular perfected ADS pipe. I've read in some of your previous postings on this site that the concrete sand will bridge the slot gap over time and that some sand will enter the pipe during this process. Would you recommend that I buy the sock that goes slides over the pipe to eliminate any sand from entering the pipe? Thanks again for all the help. John RE: french type drain system in Baltimore semi-detached house basement. the regular perforated slots are 1/8", which is at the limit that one might use. However, there is a factor that may affect how it works. ASTM C33 fine aggregate has a range of gradations. In the coarser zone for the Number 8 sieve (opening of 0.0937") has an allowable percentage passing of 80 to 100. If the supplier has sand that is on the fine size, 100 percent could enter those openings and very little bridging would be expected. My experience with what is in this area (no maker name Wisconsin) is that the slots are not that wide, more like 1/16" yet we do see some sand get in the pipes. I'd check with your sand supplier and if any question, go with either of two options: Perforated or drilled holes (any size under 3/4") in pipe covered with filter fabric (sock) or the smaller width slotted stuff you mentioned. RE: french type drain system in Baltimore semi-detached house basement. (OP) OG, To be on the safe side, I'll cover the ADS pipe with the sock that is designed to go over the pipe. I've already contacted a few suppliers that have the ASTM C-33 sand. They will load a half ton on my flat bed trailer and I'll start hauling it down to my basement. We had a lot of rain yesterday in Baltimore and my trench now has a few inches of water in it. I'm going to try and pump that out tomorrow. I'd rather not dump concrete sand into a trench with standing water. I'd like to get some pipe in the trench asap along with the sump basin because I know more water will be coming. Here's a video of a DC meto station yesterday. https://www.youtube.com/watch?v=phUmVT7tZcY&ap... It looks like the DC metro needs some help in redirecting rain water. Thanks again. John RE: french type drain system in Baltimore semi-detached house basement. John: Nice going. One story that may be of interest. Some years back I lived in the country, but within the village limits of a small town. It was a very hilly area. We had an ice storm and I had a long drive that was covered with ice. The village had a large pile of sand for winter ice control. I loaded a half yard or so on my trailer, but placed a tarp on it first to help keeping it in place. On my way home I had to go up quite a steep hill. As I arrived home I see the neighbor had a drive also covered with ice and I had plenty. I stopped on the road ad got out to shovel some sand on his drive way. Low and behold my trailer was empty. No sand, no tarp. I go back along the route and see a pile of sand sitting on a tarp in the middle of the road at the top of the hill at the steepest slope. All was together, nicely staying there. No wastage. RE: french type drain system in Baltimore semi-detached house basement. (OP) OG, Good thing nobody ran into it. I'm going to put some side rails on my flat bed and use tie downs to secure it. I few gravel/sand companies near Baltimore will only load dump trucks. One place said I needed a hard hat and safety vest. I'm going to start with 1/2 ton and go back when I need more. I've seen price range from$21-40 for a ton.
I think the place I'm going to is \$32 a half ton. Still cheaper than buy the bag at home depot.

John

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