Simple retaining wall question

Discussion in 'Hardscaping' started by Marinucci_Landscaping, May 4, 2011.

  1. Marinucci_Landscaping

    Marinucci_Landscaping LawnSite Member
    Messages: 53

    Hey all,

    I have a painfully simple retaining wall question. I'm a young landscaper, not a hardscaper... but I do have some customers that have me put in very basic walls (I highly doubt you would call them that). We are talking Home Depot brick simple. I live in NY and the ground freezing and shifting is an issue. My question is, what do you sink underneath a wall to compensate for it being above the frost line? I know weight matters here, but we are talking one or two levels of 20lb brick, max.

    I've been told a few different things, and I'd really love some clarification from the professionals, as it has been eating away at me whenever I build one of these simple little walls. Firstly, go down 3-4 inches, pour in crusher run, tamp, top with a paver base and tamp again until flush with the ground. Second, dig down 3-4 inches and pour in two different sizes of paver base, and tamp and adjust at each level. Third and final would be all of one paver base or all crusher run.

    I'm pretty "disinclined" when it comes to hardscaping, so any simple advice or suggestions here would be great. One good natured user here recommended for me to check out a site, Allanblock, but it was still a little difficult for me to wrap my head around, so here I stand. Thank you in advance.

    - Marinucci
  2. JDiepstra

    JDiepstra LawnSite Bronze Member
    Messages: 1,511

    One or two levels of brick? At my house I have a 2 level wall that I dug out the grass, made the dirt level, and threw the bricks on top of it. After 7 years it is still perfectly level. Around 3 trees in my yard I have 2 levels of bricks. I put the bricks down on top of the grass and to this day they are also as level as the naked eye will ever know. That's in Michigan... plenty of freeze and thaw cycles.
  3. Marinucci_Landscaping

    Marinucci_Landscaping LawnSite Member
    Messages: 53

    For whatever reason, I've seen blocks that have shifted and sank over time throughout my area, which have not had anything placed beneath them. I'd like to be able to at the very least assure my customers that I've done my part to prevent this.

    - Marinucci
  4. Marinucci_Landscaping

    Marinucci_Landscaping LawnSite Member
    Messages: 53

    Anybody? Would really appreciate some clarification here.

    - Marinucci
  5. Dr.NewEarth

    Dr.NewEarth LawnSite Bronze Member
    Messages: 1,476

    O.K. Since no-one else is giving an answer, I'm the one that's going to get flamed if I get some-thing wrong. Mostly I'm a Journeyman Horticulturist and Arborist, but I am versatile in my services and abilities.
    I am AllanBlock Certified, but don't build walls that often.

    The main thing is any-time there is a slope, you need an Engineer... if the wall is on a hill, or has a hill above or below it, or it will be built on fill soil
    or if there is a potential water problem, or any wall higher than 4 feet, or if there is a third terraced need an engineer to look at the site and draw up a plan. He will determine global stability, the slip arch etc.
    They'll tell you if you have to excavate or what you can put behind the wall.

    If your wall is very short, say two courses I wouldn't fret. The settling and frost heave will be minimal. These type of retaining wall blocks have been used for decades with no real problems if installed correctly.

    Just be sure to excavate the trench, put down a good aggregate compacted and leveled
    get your first course set level and perfect and the other courses go up quickly.

    If you need drainage, put it in behind the first course. Daylight the drain at least every 50 feet.

    For the base excavation, let's say you go down six inches, plus one inch for every foot of height. Level, and then add the depth of half of a brick if you want more stability.
    (some-one else will add to this I'm sure)

    The bricks are filled with gravel and they are self draining. You put aggregate behind the wall which also adds to the drainage. In my opinion, if the wall and the area around it are draining properly there should not be a problem with frost heaving.

    Fill the gravel in two inch courses and compact it until you get to the level you want

    If you follow the videos on the AllanBlock website, do your due dilligence and have an Engineer check it out when required (as noted above), put down a deep enough gravel base and level all of the first course, the rest is easy.

    If built properly and to manufacturers specifications, you should be able to give a lifetime warranty and sleep well at night.
  6. Marinucci_Landscaping

    Marinucci_Landscaping LawnSite Member
    Messages: 53

    Thank you New Earth. I really appreciate the descriptive post, I'm going to have to save this one for future reference.

    - Marinucci
  7. DVS Hardscaper

    DVS Hardscaper LawnSite Fanatic
    Messages: 6,569

    Lifetime warranty???? Lord, I hope not. When I'm
    85 years old I'll start doing a lifetim warranty. My lifetime!!!!!!!!

    One things bout walls. If it was a perfect world.... A wall
    Would NOT be needed. So in terms of an engineer if the wall is a true retaining wall and not a planter, it's almost always going to need to be engineered. Keyword: almost.

    Posted via Mobile Device

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