Need help with a Retaining wall.

Discussion in 'Landscape Architecture and Design' started by cavaselis, Jul 15, 2004.

  1. cavaselis

    cavaselis LawnSite Member
    Messages: 10

    I need to build a retainging wall ~6' tall, problem is im not very experienced and have some questions.

    Since this is my first big wall Im looking for a product that can go 6' tall without geogrid, keystones standard units can go 6' 8" in "ideal condiotions" my questions is how do i know if my soil is 34,30, or 26 sand/gravel or silty sand or clay?

    2nd is how much do you backfill with gravel like if the wall is 6' tall does that mean I have to have 6' of gravel behind it all the way up? Because if it does my wall is like 70' long by 6' high.

    70(long) X 6(HIGH) X 6(DEEP)=2520 / 27= 93 CUBIC YARDS OF GRAVEL IS THIS RIGHT? That sounds crazy thats what 9-10 dump trucks of gravel??

    I will post some pictures this week.

    Thanks for all the help.
  2. NNJLandman

    NNJLandman LawnSite Bronze Member
    Messages: 1,306

    Thats a bit "ballsy" building a wall that high without any support. Just a small ground movement or thrush of water can push the wall over. Maybe teir the wall into 2-3ft sections.

    As for backfill you have to backfill about halfway up to the most top block, not including the cap.

    Don't short on the structural soundness of the wall, don't wanna be paying for a shortcut gone wrong down the road. But if you must, try finding a heavy block, I think anchor block are like 70lbs. You'd have to go down mabye a block n a half to "anchor"(no pun intended) the wall.

  3. sabre

    sabre LawnSite Member
    from indiana
    Messages: 1

    any wall over 4 feet need to be enginered
  4. D Felix

    D Felix LawnSite Bronze Member
    Messages: 1,898

    The only type of wall block that I know of right now that does not require geogrid at that hieght is Redi-rock. The problem with those wall blocks is they weigh a minimum of 1500 pounds each, which will require a big machine to move and set.

    If you do not have much experience, you do NOT want to skimp on ANYTHING when building the wall. You need to do it completely "by the book". After you have built several then you can figure out your shortcuts and timesavers.

    And where do you get that you need 6' of fill behind the wall? If you have a wall that is 70' long, 6' tall, you need about 15.5 yards of clean backfill to fill behind the wall. That's less than a tri-axle load. If you are using Keystones, then you will need that additional tonnage on the tri-axle to fill the block cores. You only need about a foot or so of clean backfill behind the wall. You also need to separate it from the soil using fabric or geotextile laid vertically between the "columns" (gravel and soil, that is).

    And while I can appreciate the fact that you know how to calculate cubic yardage (seems like a lot of people don't understand the concept), 93 cubic yards is around 140 tons, which should be around 7 tri-axles.... Not 9-10.:) Not trying to bust your chops on that one, just pointing out what the right number would be...

    I'm not sure whether you are a homeowner or a landscaper, but your best bet is to find someone experienced in wall building and work with them on the wall. A wall that tall, you are looking at 2-3 layers of geogrid, and that will require a fair amount of excavation. Like I said, DON'T skimp on this wall....

  5. landscapingpoolguy

    landscapingpoolguy LawnSite Senior Member
    Messages: 822

    Unilock Slope Block.....No geogrid no heavy machinery to build

  6. Randy Scott

    Randy Scott LawnSite Bronze Member
    Messages: 1,915

    There should be about a foot of stone backfill the entire height of the wall. Meaning a foot perpendicular to the wall. As you backfill the wall you will keep the gravel about a foot deep to the soil. So you would multiply 70 long x 6 high x 1 deep. Divide that by 27 and you would have about 15.5 yards of stone backfill.

    Personally, a wall of this caliber may be too advanced for you. All depends on how smart and talented you are. That's for you to decide, not me. Good luck with it.
  7. cavaselis

    cavaselis LawnSite Member
    Messages: 10

    Ok, im a do it yourselfer that just hates to pay people to much money to do things half ass, ive seen it to many times.I know if I build the wall it will be done the right way, thats why im on here asking questions. The hardest part Im having is with the back filling. I was told that if you build a wall 6' tall you have to backfill it 6' in depth This is where im getting confused??? Does this mean if you have a 6' wall that you have to have atleast 6' of dirt behind it?

    I will post some pics of the area I want to do.For now I have taken on a smaller wall in my back yard maybe you guys can give me your opinion on how im fairing, this is a warm up for me.These are just the Home Depot brand so I understand that a keystone or equilivent would be a little different.

  8. cavaselis

    cavaselis LawnSite Member
    Messages: 10

    Dont understand why the pic is so small.Maybe to high res I will post lower res pics later.
    Thanks for all the help..

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