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outside water issues, hydrostatic pressure of basement stairs wall, trench size

outside water issues, hydrostatic pressure of basement stairs wall, trench size

outside water issues, hydrostatic pressure of basement stairs wall, trench size

(OP)
My tiny backyard slopes down towards the back of my house. I have a basement stair case with a cinder block wall. There is an aluminum awning over the basement stairs. I put a gutter on the awning to redirect water to my driveway because the side of my house slopes away from the foundation. This has helped but there has been damage to my sidewalk and the cinder block wall.

When it rains, the water runs down to the sidewalk and seeps into the earth and starts leaking about half way down the wall. I need to redirect this water to the side of my house so it will flow away from the house.

I need to tear out the side walk because it tilts towards the house/wall after 60 years of run off from the awning. I was thinking about digging a 2 x 2 foot trench and putting in a level pvc pipe with holes in the bottom the runs 18 feet(width of my house) and redirect it to a solid pipe on the side of house and slope it away from the house.

Does this sound like it will work properly? Is a 2x2 foot trench big enough? I can't dig 10 feet down unless I want to tear up most of my driveway and I can't afford it.

If so, should I use 4 or 6 inch pvc? I plan on filling the trench with concrete sand and then a could of inches of small stones and 2x2 foot pavers(instead of pouring a concrete sidewalk).

I have slotted ADS pipe That I'd like to use but I was told it will get crushed when after continued walking on the pavers.


Thanks for any info/ideas/comments.


John

RE: outside water issues, hydrostatic pressure of basement stairs wall, trench size

Looks like a tough situation. Not much room to work. It is somewhat like the situation at my house, but mine was easier. The drain you are thinking of may well work. Remember that with open graded backfill rock there is potential for those voids to fill with mud over the years and plug up. Instead, I would use a filter for the backfill, such as ASTM C-33 fine aggregate (concrete sand). In time a form of seal may happen at the inlet zone, but you can clean that off and renew its usefulness. I'd guess a trench only 6 or 8 inches deep to be enough.
Sand will accept water more slowly than open graded rock, but it is permanent.

If it is possible to re-grade the surface area also, or at least level it up, I'd "waterproof" the full backfill surface away from the trench top, including the apparent gardens there. I did this to the entire perimeter area of the house backfill (that's at least 10 feet out). In my case I removed all sod re-graded as necessary, used a rototiller for the mixing and re-placed the sod. Several of my clients have done this also. You may want to do some crude permeability studies, such as treated soil in a tin can with holes punched in the bottom to find a suitable mix. Too much bentonite and you can have a real mess. I loves water and expands to fill voids. I used a mix of one part powdered bentonite (drillers mud powder) to 5 parts of a sandy soil here. I treated about 4 inches of depth below sod and around sidewalk areas. Do not use granulated bentonite as sometimes is used for driller's mud, since a thorough mix is needed. In that can with about 2 inches of treated soil in it, the can full of water should show no noticeable water level drop once things are stabilized. Watch it for at least a day. Bentonite can be obtained at most larger plumbing material supply firms.

Bentonite is a natural clay so grass and plants grow nicely in it. Remember digging into that zone in time with new plants, gardens, etc. can destroy its integrity. Use that mix all around joints of slabs also.

RE: outside water issues, hydrostatic pressure of basement stairs wall, trench size

use a grated inlet(s) at the surface. You can buy them at home depot and they will also allow you to flush out the drain if you need. no need to put in a perf pipe which will be somewhat less effective at capturing water but will likely introduce more water below grade, near your basement stairs.

RE: outside water issues, hydrostatic pressure of basement stairs wall, trench size

Per cvg a trench with sealed side and base and grate also is possible, but always be aware of long term issues. There may be pre-cast sections that will work.

I forgot a detail with sand backfill. The sand must not get into the pipe. Use a pipe with sock of a slotted pipe (like 1/6" width slots).

RE: outside water issues, hydrostatic pressure of basement stairs wall, trench size

your problem comes from surface water, soaking into the ground. solution is to drain the surface water away from the house. grading with a slope away from the house is the obvious solution. capture in a channel or pipe to divert around is another. the least effective option is to let it soak into the ground and then try and capture it below the surface in a perf pipe. Once water gets below the surface, it has a chance of migrating downward or laterally towards your basement walls.

RE: outside water issues, hydrostatic pressure of basement stairs wall, trench size

(OP)
Thanks for the replies.

I'm going to have to take out the sidewalk since it slants towards the house.
I'll pull the entire garden out next month if you think it will help.

cvg, are you saying I should get something like this?
http://www.homedepot.com/p/Pro-Series-5-in-x-40-in...

I like this grate kit solution better since I can't dig to the bottom of the wall and it would be much easier to install this kit than digging a trench.

My new idea to to first install this channel grate kit parallel to my sidewalk and redirect the water to a pipe that I'll trench in after cutting out part of my driveway.
I will later jack hammer up the sidewalk and fill will some soil the OG mentions above. This sounds like the simplest solution and it wouldn't be that difficult to implement and test.

Any thoughts?

Thanks again.

jb

RE: outside water issues, hydrostatic pressure of basement stairs wall, trench size

I re-read your post and see you DO have the right idea for filters and pipe (slots). Lining the trench with PVC would help. As to crushing the pipe, that is unlikely unless it has practically. no cover. Be aware if that pipe sits out in the sun (as at the store), it will get brittle. So check that it is fresh made stuff and easily can be rolled out. The rigid PVC with bottom holes won't crush under foot traffic, even if no cover. Confining the drain trench to the walkway and using stones as the "pavement" will work, but that surface can plug in time. I'd say use what you are planning with a lined trench, sand and stone sounds good, but plan to replace or clean the stone every few years (when noting the drain is not working well). Then treating all adjacent areas with a "waterproofing" should pretty much do the job. Note the last cvg comment. The backfill to the house likely is in layers, sloping toward the house. Once below the surface, the water follows those slopes. Withut caring for that infiltration you may still see problems. However,sometimes ding these jobs one step at a time will resolve the issue.

RE: outside water issues, hydrostatic pressure of basement stairs wall, trench size

(OP)
OG, I am going to lay down 2 foot by 2 foot pavers as a walkway after I rip out out the concrete walkway.
http://www.homedepot.com/p/Pavestone-24-in-x-24-in...

If I dig a trench, I will use concrete sand. I have ADS slotted pipe and a sock for the pipe if I dig a trench. PVC with holes at the bottom was another option. Not sure how the ADS pipe will hold up with concrete sand and pavers on top.

jb

RE: outside water issues, hydrostatic pressure of basement stairs wall, trench size

(OP)
ovg,

My only concern with that 9x9 drain is that it might not collect as much water as a longer thinner drain. My entire back (about 20 feet) slope towards the house.
I feel like I should have a 20 foot 6 inch channel grate kit installed.

If I installed the 9x9, should I need to slope all the landscaping towards the drain?

Thanks for your help.

jb

RE: outside water issues, hydrostatic pressure of basement stairs wall, trench size

Those Home depot inlets seem to look fine for the job, only you probably have to install many, say 6 or more. However, with pavers for the walk, these had better be just off to the side. If you have a concrete saw, chances are you could fit them into the walk, with some careful sawing, maybe at a corner of each.

RE: outside water issues, hydrostatic pressure of basement stairs wall, trench size

the problem with the trench drain is that it needs to be installed on a slope. it may catch all the water but can it flow out fast enough? suggest you make an estimate of the runoff and inlet capacity to see if it will work. and since they are so shallow, they really need to be anchored down. pipe on the larger inlet will have much more cover

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