drainage from around a retaining wall

Discussion in 'Landscape Architecture and Design' started by jayman99, Oct 13, 2006.

  1. jayman99

    jayman99 LawnSite Member
    Messages: 13

    Here's a drawing to explain my idea for the drain. Maybe only 6 inches of dirt is not enough?? How much does grass need to grow?
  2. jayman99

    jayman99 LawnSite Member
    Messages: 13

    Here is a drawing so you can better understand what I'm thinking about doing.
    Maybe only 6 inches of dirt is not enough to keep the grass happy?

    Do you think it'll work?

    Attached Files:

  3. huh

    huh LawnSite Senior Member
    from Lubbock
    Messages: 251

    well now that I know where you live I will offer more

    first while I do know a bit about soil I am not an engineer...have taken a few courses though :rolleyes:

    first it is hard to tell if you have gutters, but it looks as though your neighbors don't which makes me believe you do not as well...they would be a good idea at least for that side of the house

    it has been a LONG while since i plied the shores of lake Conroe but I believe by "clay" you have more the black gumbo clay than the redish correct?

    how old is the house?.....the houses look 7-9 years old but the dock looks about 12 years old....i ask just to get an idea of how long that wall has been in place

    do you know how deep the foundation is poured for the house? that would be the FIRST thing I would find out

    how long do you plan to own the home....i ask to get an idea of what type of work you are prepared to do to the wall

    as for how long it takes water to get through clay...in your area forever/fast......by this i mean that ground is probably ALWAYS damp a few feet down....and if it is not it is probably bone dry and cracked....then when wet again the clay is wet, but water probably never "flows down" very far.....the soil just gets wetter and expands.....which im sure you already know is what happened down at the end of the wall...and the water probably never weeps from the holes because the soil just holds it

    again I AM NOT AN ENGINEER, but I did grow up in Houston and know all about shifting slabs, black gumbo soil, and a bit about Lake Conroe too

    I hate to say this, but if it was me that wall would be DOWN and a new properly build CONCRETE or otherwise STRUCTURALLY sound wall would be build in its place with whatever facade covering it for looks that you like

    I say this based on what I see at the end.....that wall has NO structural support of any kind...if it is over 5 years old I am surprised it held this long....there is NOTHING behind it to actually contain the movements of the soil that i can see

    the sketch you drew might work in some areas, but in my LAYMANS head it will not work where you are at....the forces at work on the area of ground between your house and the wall are spread over the entire area....in other words while your idea may prevent the area right in front of the wall from becoming soaked in a heavy rain/run off event it will do little to stop the forces behind that area....and not to sound super negative, but I would even have concerns of the area under the drain drying out in between small rains and then with a LARGE rain event it becomes rehydrated from water soaking in up closer to the house and flowing towards the wall and it actually adds to the heaving that is working on the wall

    really in my NON-EXPERT opinion what you are up against is not water soaking down and eroding and pushing the wall or undermining it....you are up against soils that expand and contract a great deal

    and in my opinion the only way to handle that long term is to have something that can resist that movement....like a concrete wall or a well build wall of railroad ties or a concrete reinforced cinder block wall....something that will not be pushed around by the movements of the soil

    there are a lot of options...the least expensive I would consider would to be dig down on the lake side of the wall 3-4 feet and then maybe auger down another 3-4 feet deeper every 5-6 feet of length and pour a new concrete wall about 1 foot thick all the way up to slightly above the rock wall that is there now.....with form boards on the lake side and the existing rock wall as the back side of the pour....you could extend the existing (not doing much drains) that are in the rock wall on out to the other side of the new concrete wall......then again put on what ever facade you want to the new concrete

    the other option is to do the same except on the house side of the rock wall.....with the ground as one form and the rock wall as the other....but I bet this would blow out the rock wall if not careful pouring the concrete...and really would be a LOT more work than the first idea....and you would need to dig down BELOW the bottom of the existing rock wall to get into soild ground....otherwise it is just a concrete wall being pushed over behind a rock wall that is being pushed over

    the last option is to RAPIDLY tear it ALL out during a dry time and pour a new proper concrete wall or rail ties ect.

    the key to me is to get something structural down ANCHORED into the ground below the lake side grade....otherwise that large mass of soil will just start to push on whatever is build new in front of it

    again let me stress these are the opinions of someone that lived in the area growing up and knows about how the soil acts down there....not an engineer....i am all for saving money too, but BOY that is not much room between the house and that NON-STRUCTURAL wall...and I doubt that the soil between the house and the wall was "undisturbed" before the wall was built so the soil is less stable than normal

    and again in my opinion you are fighting the ENTIRE area of soil between the house and the wall...not just the area near it....and concreting over it or otherwise preventing more moisture entering that soild area could be just as bad because the soil will move when dried...and if it ever was to get wet again it would MOVE AGAIN A LOT....and it would dry around your foundation as well

    with the SMALL area between a NICE house slab and a wall that has no support holding back a lot of ground.....the height of the wall....and the type of soil I would strongly consider getting a true soils engineer out there

    yes they cost money, but you would be surprised how much they can SAVE as well from doing it wrong....and if you are a good handy person I see no reason YOU could not follow the specs laid out by said engineer and do it yourself and still save some money

    hate to rain on the parade, but that is how I see it.....if an engineer is out and too expensive then I would dig the trench on the lake side......auger down further for deeper "piers" and pour a 1' thick reinforced wall up to the top of the rocks and slap on a new facade....and I might look into the fibre reinforced concrete was well to prevent having to use so much or possibly any rebar....and before I poured I would put a thin vapor barrier on the lake side face of the rock to keep moisture from coming through the new concrete and poping any mastic off holding on the new facade

    Conroe is a great area, but I never liked the lake much...when I was young i did not like to fish and Conroe had too much hydrilla to ski on the open spots...but great fishing... and then when I learned to like fishing they had killed the hydrilla and a lot of the bass with the stupid grass carp :hammerhead:

    and damn lake Conroe was crowded in 1980s can't imagine what it is like now....but still a great area and when you are living on the lake you go out on the "off times" and leave the weekends to the amatures :laugh:

    as new as the houses look I can't believe they allowed that tall of a non structural wall to hold back that voulme of MOVING soil with such a small distance to the house slab.....unless the slab has 4'+ deep pours 1'+ wide on the slab edge and deeper piers every so many feet

    im sure my answer was not what you are looking for, but a few years back I went to a friends wedding in Houston (im from West Houston) and ran into some old friends who had finally decided to LEVEL their existing house in Walnut Bend and build new because they loved the area, but got tired of practically having the foundation guy move in with them over 10-15 years....if something is not build right do deal with the soils down there it is near impossible to "rig it up" so that it works right

    good luck hope this helps....some
  4. huh

    huh LawnSite Senior Member
    from Lubbock
    Messages: 251

    also just one other thing....looking at the part of the wall that has already failed.....it slants out at the top...if it was poor drainage undermining the base it would possibly slant out at the base more or crumble in sections.....slanting out at the top tells me that you are fighting a mass of soil all trying to flow "down hill" like a soil glacier.....not a localized issue right at the wall digging behind the wall then filling back in only puts less stable soil against the wall and that would allow more of the "mass" behind it to want to move

    and Walnut Bend/Lakeside where I grew up is by Westhimer/Beltway Eight very flat and NO lake near by.....I put the example of my friends house in to say that even in a FLAT part of Houston the soil MOVES and if not handled properly....IT WILL JUST MOVE MORE....around Houston you don't worry about drainage so much as worrying about how to deal with the moving soils....so yes a drain at the base of that wall would help....(a little as you see with th weep holes that don't weep much)....but the real need i see is to contain that mass of moving soil

    just to throw up more alarm an engineer is a good idea again because that foundation is so close that if you contain the soil at the wall with a solid structure I may well have concerns of the soil heaving in other directions....IE around the house....because one thing i WILL GUARANTEE is that soil will move....you just need to know how it will move and if all of your structures are properly build for the movement
  5. DVS Hardscaper

    DVS Hardscaper LawnSite Fanatic
    Messages: 6,623

    What is the distance between the wall and the dwelling?

    If there is at least 15-feet, you may be able to simply just cut a swale between the wall and dwelling. A swale when properly done, will make the water flow to where you direct it. And you will not be relying on drains, etc. When it comes to drainage, I always try to make the water flow via gravity. And if thats not possible, we then resort to drains, etc.
  6. Dirty Water

    Dirty Water LawnSite Fanatic
    Messages: 6,794

    Huh, a properly designed and geo-gridded wall would be fine in that situation, you don't always need a mass retaining wall.
  7. RockSet N' Grade

    RockSet N' Grade LawnSite Silver Member
    Messages: 2,454

    I have looked at your pic's and read the posts. We do this kinda magic on a daily basis and build rock retaining walls and yada-yada-yada. I have been doing some type of construction ( from apartment building, tilt-ups, remodels, tracts, machinery, etc.) since the early to mid '70's till now.
    The point I am going to address, that rasises a huge red flag for me, is..."I was thinking of getting day laborers to dig down behind the wall", etc. From what I have seen/done through the years, you are asking/begging to get someone buried and killed by having them dig to the bottom of a failing 7' wall. These things may look easy and safe on paper, but the reality of a bunch of guys who don't know each other or the potential hazards digging in a 3'wide hole 7' deep is asking for a good maiming or early pine box. After doin' this kinda stuff for over 35 years.....going home safe at the end of the day has become pretty important....
    Enough of the soap box......The fixes are fairly straight forward after you gather a bit more info. I would open a hole in the middle of the wall area somewhere and see what kind of footing is supporting that wall. Next, I would consult a local soils/geo engineer and have him give a written recommendation. Then, I would sort through your options......
  8. huh

    huh LawnSite Senior Member
    from Lubbock
    Messages: 251

    i disagree completely

    I don't think geogrid would work well at all with that soil type....the soil will just heave with the grid in it

    also with the short distance between the house and the wall i would want to dig as little as possible in the soil on the house side of the wall.....if you get that soil moving then you run the risk of dealing with the house foundation in the future

    a heavy gumbo soil with a high shrink swell and a shallow water table (next to a lake) needs more than some blocks and geo-grid....again just my opinion

    and lastly he said the wall was 7' and on most paver sites it says over 6'-7' get an engineer

    who ever the mason for the origional wall was a great mason because that wall is really holding up.....unfortunately it looks to have no foundation or a very shallow one

    his situation is like a mini-california mud slide.....the whole chunk of soil between the house and wall is moving and needs to be contained...i don't see pavers and geogrid doing that i see pavers and geogrid sliding around
  9. AGLA

    AGLA LawnSite Bronze Member
    Messages: 1,778

    I don't think that it is a coincidence that the failure happenned outside the area between the house foundation anf the wall. Assuming that the house has some crawl space or basement, the surcharge on the wall from the soil between would be less than if it were continous soil.

    I agree with the number of people who suggest that it makes more sense to talk to a structural engineer rather than unknown sources with unknown experience on the internet. You at least need to shift the liability of this to someone else. The proper someone is a structural engineer.
  10. Mike33

    Mike33 LawnSite Bronze Member
    Messages: 1,649

    Its woth a try hand dig down somr and see what you find. You will find a lot of good in put on this site and most are very prof. How ever we are not at your site so you will have to make good judgement on your own at some point. The trouble with clay is most of the time it will never dry out in a area like this becoming much heavier making a surcharge on the wall. But you might luck out and it might be dry. Any way you will have to divert the water you mostly cant stop it being there just deal with it . keep us posted and good luck to you.

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