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Cantilevered Concrete Slab


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  • Cantilevered Concrete Slab

    Hi All,
    I am in the process of designing a waterfall which will hang out over a swimming pool. I plan to pour a concrete slab that will be veneered with natural stone. The reason I wish to pour a slab is strictly for strength and safety reasons. As much as I don't wish it to happen, I am sure someone will eventually use the waterfall as a platform to dive into the pool and I want to insure it will be strong enough to support a person.

    My question is this, if I cantilever a 5" slab out 4 feet from the edge of the support, how far back on the support should I extend the slab, and also what recommendations for rebar spacing would you suggest. I was planning to use fiberglass reinforced concrete, but if you have any suggestions I am open to that as well.



  • #2

    I suggest you contact an Engineer in your area to calculate the streses with the dimensions you wish to make it to see if it can be done the way you invision. All areas have differant building coads as well.


    • #3
      nice project , sounds quite a challenge. I would suggest for every 1 ' out you go 3 ' back 2'out 6 back. You are going to have allsorts of extra weight on there, water, tile, mortar, kids... The one problem will be supprting all that concrete in liquid form 80# for every 1.25 foot square. I have seen concrete roofs collapse if supprt removed too 4 weeks min. As far as the rebar every 6 inches. Also fibreglass is good idea, very effective. probably want the back end ancored down. Now a further problem you are going to have is you are going to have a very large amount of weight bearing down vertically on the pool wall and out side ground. Depending on your soil type you could have a collapse of the pool wall. soil structure is important to be aware of here. also if the soil the concrete will be resting on will ever get saturated as water can turn soil to a soup. I would suggest a foundation for the slab .that ties into the rebar to prevent any movement,..Im not sure if your soil ever freezes..if so need to go down a 3 feet. like I said quite a project. You could also be very creative with treated lumbar, tile board, depending on the type of lines you want...but since you are using tile it would be squarish so this might be a option you could ancour down with galv, ties etc. and forego all the heavy concrete. you are not going to have need for heavy wieght or durablity tile surface is what you will see.

      Best of luck.


      • #4
        just a suggestion - cellular floors, like what they build hotels with, is concrete with 1/4 inch rebar and hollow cells running the length of the slab. its allowed to flex a little without getting structurally unsound. weight is less too! next thing, how would you build a form for it? again my thoughts -- find a flat area, put down some poly and pour a slab with 1/2 inch screen embedded in it, then use 2" galvanized sheet metal "pipes" the long ways. pour concrete over this, add another layer or 1/2" screen and your finish coat. screed and finish this floor and let cure.