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Looking for SRW building help (NOT pricing)

Discussion in 'Hardscaping' started by MDLawn, Apr 13, 2010.

  1. MDLawn

    MDLawn LawnSite Bronze Member
    Messages: 1,284

    Seasoned Hardscapers,

    I have a friend who needs some work done with some involving a small wall (around 2ft.) to be built. This backyard area is roughly 20' x 15' and gradually elevates up 12-14 inches to the neighbors back yard which is higher. This was an old garden from a previous owner that they would like to take back and make more lawn/living space with. I suggested the wall so as to eliminate a highly sloped backyard. I have done the Allan Block Retaining Wall course and will be using their Jumbo Junior stone. Please this is no time to argue about what block is best, it is what is readily available. I want this wall to last for them, so based on the knowledge obtained from the AB course would you advise on using drainage for this short wall? They also would like this wall to hold up a planting area to create a screen from the neighbors. Would a plant such as an arborvitae be a bad or good choice in terms of the wall holding up (roots, etc...). Also I have heard people using what we around here call "Crusher Run" for the base and #57 stone for the drainage stone behind the wall and also even for the base. I have even seen a 6" crusher base with 6" #57 base, which may be overkill for this small project. Any input on what you have found works best is appreciated. I have also seen mixed feelings on using a geotextile under the base and behind the drainage rock to prevent fines from working into the drainage stone. Again any input. I just want this to turn out great, as long as they want to do it. If you can help out with any information great! If you need more site info just let me know.

    Thanks in advance for any help.
  2. PatriotLandscape

    PatriotLandscape LawnSite Bronze Member
    from MA
    Messages: 1,209

    1. NCMA Spec 12 inches of 3/4 clean stone behind all walls. you can use 6 inches if it is a core fill wall but I reccomend you stick with 12.

    2. for the base you can use crusher run or clean 3/4 the clean stone is easier for compaction and minor leveling

    3. use corrugated pipe daylighted every fifty feet out the face of the wall to remove incidental water

    4. plant the arbs 3' from the wall. any closer and it may influence the wall in a way they dont want.

    5. NCMA currently does not spec fabric in srw walls. but a manufacturer might recomend it.
  3. MDLawn

    MDLawn LawnSite Bronze Member
    Messages: 1,284

    Thanks. I may have to rethink this. Their yard is tiny enough and I'm not sure they want to lose the space for the wall and arbs. I may just make a berm to plant the arbs on, edge it, mulch it instead of the wall. But I'll still think about the wall. Thanks for the info
  4. xtreem3d

    xtreem3d LawnSite Senior Member
    Messages: 801

    Are you saying it's o.k. to use 3/4 clean as a base? (item #2)
  5. CertPro

    CertPro LawnSite Member
    Messages: 139

  6. xtreem3d

    xtreem3d LawnSite Senior Member
    Messages: 801

    correct me if i'm wrong but material of the same size doesn't compact well ? thats why you would use 1" clean behind the wall ....because it can't compact and allows for drainage...am i missing something?
  7. MDLawn

    MDLawn LawnSite Bronze Member
    Messages: 1,284

    At the SRW course I attended for Allan Block they are using that kind of stone for base and backfilling. I cannot remember what the instructor said the reason was. But I guess thats the way it is now.
  8. xtreem3d

    xtreem3d LawnSite Senior Member
    Messages: 801

    if that is so....why do road crews use 3/4 minus for compacting base for roads? i am no expert but i wouldn't think of using a "clean" material to compact for a base,
  9. MDLawn

    MDLawn LawnSite Bronze Member
    Messages: 1,284

    I was at the training to start learning about building walls but there were a lot of guys there who already do this sort of stuff. They were also confused about the use of this type of stone. However, the instructor ensured this was the correct way. And the videos from Allan Block show them using this stone and not a road base or crusher run stone. Still trying to figure this out as to what to use with these projects.
  10. DVS Hardscaper

    DVS Hardscaper LawnSite Fanatic
    Messages: 6,576

    yes, you use fabric behind the wall. Even if you are using grid. Your wall engineer (for the walls 4' and taller) will specify how the fabric should be placed.

    yes, 3/4" aggregate can be used for the base. it self compacts because it is angular in composition.

    It (3//4") is used for backfilling because it allows water to pass thru, not necessarly because of compaction. Think of the gum balls in a gum ball machine, and imagine pouring water over the gum balls. Water always follows the path of least resistance, and that is the name of the game when it comes to SRWs. Although, the SRW's drainage chimney is intended as a LAST RESORT drain system, an all else fails system. The mindset is to find other ways to route/get the water away from the SRW.

    A SRW base can be CR8 (crusher run), 3/4" gravel, or flowable fill concrete.

    Also, our drainage chimneys are usually 18-24" wide. Seldom do we do one at 12". The wider - the better.

    yeah, we've built a wall or two........or 3, or 4......

    Last edited: Apr 16, 2010

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