Retaining wall base

Discussion in 'Hardscaping' started by ozd12005, Jan 25, 2007.

  1. ozd12005

    ozd12005 LawnSite Senior Member
    Messages: 342

    I just got back from a luncheon given from one of the dealers I use. After meeting some LCO's we started talking about other services we provide and got on the subject of retaining walls. Funny thing is the big discussion was about what we use for the base, I have alway's used grade 8 but others were saying they use sand :confused: IMO grade 8 compacted is the best base, am I wrong ?
  2. LB1234

    LB1234 LawnSite Gold Member
    Messages: 3,208

    I was at a meeting about a week ago with a similar discussion. Guy said he used stone dust as his screening material. I asked if he finds himself going back to the job a year or two later.

    He admitingly said yes but he'd rather spend a few hours fixing a section or two then hearing his employees complain about having to use sand cause they didn't like sand.

    BTW, he claims he has been in this business for over 25 years...;) :dizzy:
  3. cgland

    cgland LawnSite Bronze Member
    Messages: 1,929

    Some suppliers recommend installing your base as normal, then screeding an inch of sand on it to help w/ leveling. I personally will NEVER use this method.

  4. GroundScapesIncorporated

    GroundScapesIncorporated LawnSite Senior Member
    from VA
    Messages: 386

    We use a very thin amount (.25 inch) of concrete sand and have never had anything close to a problem.
    Some manufactures recomend one inch or less, I personally think anything over half an inch is accessive.
    But I also think that a small amount is almost necessary to productively install a base course.
  5. PatriotLandscape

    PatriotLandscape LawnSite Bronze Member
    from MA
    Messages: 1,209

    the manufacturer of the stone we use recomends a base of 6x24 of dense grade and no more than 1/2 inch of sand only to fine tune. we usually get the base just right were we lay the wall directly in the dense grade.
  6. paponte

    paponte LawnSite Silver Member
    Messages: 2,366

    I couldn't agree more with this. Pavers are a floating system... in other words sand is OK. A SRW on the other hand eeehhhh, I just don't feel comfortable about putting sand under one. Too many issues that I can think of. I'll just stick to spending the little extra time to get my base perfect.
  7. tthomass

    tthomass LawnSite Gold Member
    from N. VA
    Messages: 3,498

    4" 21A.........CR16 (or is it (CR6)..........compacted sub base. You can use a "leveling agent" but less than 1".

    Walls 30' tall are even built on a 4" base.........straight from NCMA
  8. Bobcat s250 NY

    Bobcat s250 NY Banned
    from texas
    Messages: 98

    I usually set my block on the compacted rca , but sometimes it just is a PITA. I used to use like a half inch of sand , but after asking on here a while ago i was told not to. Why are the manufactures telling people to use 1 inch of sand.. It just doesnt make any sense. The sand is eventually going to move, thus the wall. Yes leveling on the compacted base takes longer, but i suppose over time it will hold up better. The reason i am writing in is to find out your thoughts on what one of my new guys said they did at his old company[SIZE="3[B][B]"].(one of the big guys here on the Island & Yes i know that doesnt mean anything for workmanship). [/SIZE] [/B][/B]He said that they used to put in like 6-8 inches of rca and instead of sand they would set the base course on a inch or 2 of concrete. Sort of like doing a rowlock on a driveway. I was scared to let him do it , but i did let him show me what he had on a 18inch by 25 foot decorative wall. I have to say he had it up quick and perfect. I just dont know how it will be in long the term. Any comments?:confused:
  9. orionkf

    orionkf LawnSite Member
    Messages: 122

    I used to use an inch or 2 of sand with no grade 8 under decorative walls, which have held up pretty good. However, I don't do this anymore, and have always used grade 8 under anything structural.

    On a related note, is anyone from the St. Louis area familiar with "minus". Across the river in IL everyone uses limestone 3/4" minus, grade 8, CA6, all the same thing, different names.

    We did a job last summer in the STL area, and all I could find was what they called minus, which was like a 1/4" minus, and it was a sparkly white color, as opposed to the dull gray which I was used to. This was sold by a landscape supplier who sold blocks and pavers. Can anyone confirm or deny that this is a legitimate base material?
  10. mrusk

    mrusk LawnSite Gold Member
    Messages: 3,260

    It takes some effort to be able to get the road base perfectly level. After doing a couple walls and patios your basicly able to do things with a rake that you never imagined before!

    There are many little tricks and tips that really make things easier. You just need to do a couple and pick up the skills from experience.


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