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Questions about concrete sub-base for Pavers

Discussion in 'Hardscaping' started by Juan if by land, May 12, 2010.

  1. Juan if by land

    Juan if by land LawnSite Member
    Messages: 41

    I'm a builder in NY.Many moons ago I receive a degree in Horticulture in Landscape Development at SUNY.Landscape is not my full time gig,but I try to get involved with it on most jobs because my clients trust me and because of the level of incompetence I see in the landscape industry.

    About 20 years ago I started to see pavers installed on concrete sub-base slabs in these parts. Maybe an inch of sand or rock dust as a leveling base for the paver.Mortared down edging with open joints.

    I recommended against this type of installation at the time.I was certain it would fail,because of frost heaving.Well,I've revisited these installations from time to time and they have held up and stayed true.Other installations,even with excellent edge containment have had settling issues.

    So,I'm going to have to say that this type of installation seems superior.But I have some questions regarding the installation details.I will ask about top of the line installation methods,as these are the only one I would get involved in,anything below that I just won't get involved in.

    So here are some questions.

    In large installations,500 SF plus,are you using expansion joints on the concrete sub-base?

    Are you using any type of drains in the slab itself to relieve water beneath the pavers?

    If the slab is pitched and then terminates to a mortared down edge detail,where is the water going?

    I was told of someone installing the edge pieces to the concrete with PL...huh?
  2. tturbonegro

    tturbonegro LawnSite Member
    from nj
    Messages: 97

    the water is going where you tell it to go...just as if it were a white concrete pad
    PL works great
    drains & expansion when and where needed
  3. Juan if by land

    Juan if by land LawnSite Member
    Messages: 41

    That's the thing...the installations I have seen haven't taken any of that into account.Maybe pitch,that's it.I haven't seen any special sub-base drainage precautions done or any type of expansion joint.Our soils tend to be very sandy with excellent drainage,some of it like a sandbox.But how does that help,if the subbase can't drain in the first place,since it pitches toward an edge that has a wet-set border?

    And believe me, the installations that I have seen were not done by outfits that put any type of engineering into it.They violated a number of common sense building rules in other areas of general construction knowledge for me to figure that out.
  4. Stone Creations

    Stone Creations LawnSite Member
    Messages: 37

    Consider that only about 1% of rain water actually gets thru the pavers to the subbase. If properly maintained and joints are sanded and patio is pitched right there should be no water reaching that subbase!
  5. Juan if by land

    Juan if by land LawnSite Member
    Messages: 41

    Yeah,the percentage is probably pretty low,most times,but say a 24" slow snow melt,or standing water after snow/then heavy rain makes me wonder.
  6. Rex Mann

    Rex Mann LawnSite Senior Member
    Messages: 621

    When mortar or PL is used to secure the border weep holes must be left to allow water to exit. You can also drill 2-inch holes in the concrete, fill with pea gravel and cover with geo textile



  7. Stone Creations

    Stone Creations LawnSite Member
    Messages: 37

    it should still not get thru properly maintained joints..it will runoff on top of the pavers...
  8. Bru75

    Bru75 LawnSite Senior Member
    Messages: 582

    Properly maintained or not, some moisture is going to get through.
  9. Stone Creations

    Stone Creations LawnSite Member
    Messages: 37

    Not enough to cause any damage!!
  10. Bru75

    Bru75 LawnSite Senior Member
    Messages: 582

    Suit yourself. As for me, I allow for drainage.
    Why not drill some holes? It's cheap insurance.

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