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How thick on concrete?

Discussion in 'Water Features' started by Edgewater, Oct 30, 2008.

  1. Edgewater

    Edgewater LawnSite Senior Member
    Messages: 457

    Hey guys,

    I am going to pour a formal water feature. How thick would you make the walls. They will be 14 inches tall...should they be 6 or 8 inch thick?

  2. dbduensing

    dbduensing LawnSite Member
    Messages: 4

    Couple questions:
    1)What climatic conditions are you going to need to take into account? Are you in a freezing or seismic area?
    2) What are your current plans for concrete reinforcement? Steel rebar, fiber mesh or none?
    3) Are these going to be formed walls or shotcrete?
    4) What are your plans to ensure a water tight basin? Concrete is not inherently water tight so you need to consider additives or sealants to guarentee a water tight vessel.
    5) Will there be aquatic plants and or fish in this feature?
    6) What are the general dimensions and are the corners going to be square or a sharp angle?
  3. Edgewater

    Edgewater LawnSite Senior Member
    Messages: 457


    This will be formed and poured. All corners/Angles are 90deg. We are in a freeze zone, and there will only be a few plants, no fish. I was planning to put steel mesh in the floor, and re-bar in the walls.

    I think I read that there are sealers that can go on after, that was my plan.\

    Thanks for your time,

  4. dbduensing

    dbduensing LawnSite Member
    Messages: 4

    Since the actual cost of concrete is relatively inexpensive I typically pour a thicker wall. You are paying the same cost to assemble the forms and your only increase in cost is the difference between 6" and 8" of wall. Go the more durable route. In addition it gives you a thicker top of wall to assemble a nice cap to.

    As far as reinforcement goes you are more apt to have your steel centered in the walls better in an 8" wall but you may also want to consider adding fiber mesh to the concrete to increase the strength and decrease the chance of cracking and checking of the walls. The fiber is typically applied as one bag (approx. $8 - $12 per bag and 1 bag per yard of concrete) per yard of concrete. It is great stuff and we use it in all our work, even when we use steel. Also even it you use wire mess in the bottom your wall steel should be tied to lateral steel in the floor. I'm not insisting you add a lot of steel to the floor but there should be a substantial connection of the floor to the walls. Steel itself is not that expensive but I am not sure of the scale of the project so I won't push this issue since the labor to install could add up.

    Sealing the concrete can be accomplished with an additive to the concrete provided the concrete is installed and vibrated or settled in. Another good method is applying liquid EPDM to the cleaned and preped concrete surface. The liquid EPDM can be applied by paint roller or sprayed, goes on in two coats and is a black, 60 mil thickness. The black EPDM is actually a benefit on formal ponds if the edge is done in a nice clean manner because the black coloring makes the basin or pool look deeper. It is a trick many botanic gardens use.

    We have not discussed if the walls and floor are to be a monolithic pour but regardless if you can mechanically connect the two together you would probably be better satisfied with the EPDM. One brand name is CIM 1000 but there are others.

    What are the dimension of the basin and do you intend to bond anything to the inside of the basin?
  5. Edgewater

    Edgewater LawnSite Senior Member
    Messages: 457

    Thanks for your advice.

    I will go 8" on the walls. Yes I am going to make it monolithic. It makes the forming a little tougher, but I am more comfortable with that than having to deal with keys, or other mechanical seals between the walls and floor.

    The basin is a 12x14 rectangle with intrusions into two corners, and an "island" planter on the inside. The largest open area will end up being about 8x10.

    That EPDM sealer sounds like exactly what I need.

    I will ask the concrete CO. about the mesh.

    Thanks again, your input will surely save me some costly errors.

  6. XStream Aquatics

    XStream Aquatics LawnSite Member
    Messages: 239

  7. n2h20

    n2h20 LawnSite Senior Member
    Messages: 503

    have you ever used Herrco rubber products? its s liquid epdm type rubber paint...
  8. mcclureandson

    mcclureandson LawnSite Member
    Messages: 242

    I use EPDM liner for my masonry features...the concrete must be completely cured before it is applied - which can take weeks. The fountain division of an irrigation supply-house I do business with lets all their large projects sit one MONTH before painting with EPDM.
  9. dbduensing

    dbduensing LawnSite Member
    Messages: 4

    I have used several types, CIM-1000 being one of them. They tend to work well under specific conditions.

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