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Are all garage floors this bad?

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  • #91

    Re: Are all garage floors this bad?

    Gravel settling, sand settling, water retention in each, compaction of each:: a lot of theories seem to be getting expressed.

    The underlying soil and the water table probably have more effect than any of the above. Settlement or heaving in clay soils all depends on the water content. Other soils may have a grain make up that allows water to travell upward. This can be bad for frost heave. This type of soil should be replaced to below the frost table. End result for stability the soil moisture content should be maintained at what is determined to be optimum which may vary on different locations. Maintaining this optimum is another matter and there are methods.

    All ll broken rock(gravel, sand) will compact. Even sand. The degree of compaction will depend on the grain size distribution.

    Plastic under the concrete will prevent water from travelling upward. It will also stop the gain or loss of water in freshly poured concrete.

    Just a very little very old information. Times may change and so may information available!
    Egon
    from
    The South Shore, Nova Scotia

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    • #92

      Re: Are all garage floors this bad?

      Originally posted by Greg from K/W View Post
      All I know is that you should call the city and ask them what they would recommend under that new slab your pouring. You are in Thornhill. Here in Kitchener where I am located we are on 300' of sand. I asked the city inspector what they need under a new slab and he said 1/2' CRUSHED STONE. Not gravel or sand. Plus they wanted 10" of it. I asked why with the drain rate the sand has. He said the following.

      1- The crushed stone at 1/2" is self packing and does not hold water at all. At 10" if there is water in it the water will be in the bottom and not effect the slab at all.

      2- Even at minimal percentage of water it can freeze in the sand and heave it. This can cause the slab to crack and maybe heave up.

      Gravel is a mix of sizes with sand and will not be suitable for anything under a slab. I know its used sometimes interchangeably to mean crushed stone but its not the same product and should not be used in this application.
      I've been consistently referring to 13-20mm crushed aggregate, or recycled concrete. 'Gravel' typically contains clay, which is not suitable for a slab base.

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      • #93

        Re: Are all garage floors this bad?

        Originally posted by darius View Post

        Sand is exactly the same material as gravel, except the difference in how large individual grains of sand vs. gravel are. Sand is not defined as having specific chemical composition but as particles of certain size ranges. In this respect, when you top a layer of gravel with a layer if sand you are covering gravel with smaller gravel.
        Oh, and sand compacts to HIGHER densities than gravel by a factor of about 10 to 30% depending on whether it's wet, loose etc.



        So sand shouldn't be used for leveliing since it holds water?


        Yes, he had voids because the soil below the sand settled. The sand filled those voids. That process complete for the purpose of contruction.



        That test means nothing. Try to do the same eperiment with gravel and clay. Clay wins. Would you use clay as a base?
        He won't be installing shovels but an deven layer of concrete over sand that has settled over decades and has nowhere to go due to the garage's perimeter.

        We all have a bunch of work behind our belts. I worked on buildings without ANY foundation. Over 80 year old complex of strip mall type of building built on sand. Not a crack in any of the walls. Location was Long Islan, NY.

        In general I agree - in most cases, especially new sites, gravel and a serious amount of compacting is the way to go. Here we have a very different story and if it were my house I would be confident leaving the sand in place.
        Sand will compact if wet, but it does not stay compacted when dry. Ever walk on a beach?

        You wouldn't use clay for a base because there is no drainage, hence 20mm crush. Same reason you don't use gravel.

        Darius, I'm not sure why you've chosen to make this an argument. I'm quoting industry standards - call any inspector or concrete company and they'll likely say the same as I have.

        I highly doubt, given the amount of work Andrew has already done, that hauling away 2-3 loads of sand in his trailer and bringing back 2-3 loads of suitable base is really going cost him that much more effort in the big picture.

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        • #94

          Re: Are all garage floors this bad?

          Sand compacts quickly and drains well. I think it would make excellent backfill for underneath slab on grade. 3-4 inches of 3/4"clear stone is traditionally used directly under the concrete of slab on grade because it prevents the wicking up of moisture from the ground.

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          • #95

            Re: Are all garage floors this bad?

            No sand will not work for slabs. As stated sand does not compact at all unless it is mixed with another type of soil like loam or clay. So stop with the use sand please.

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            • #96

              Re: Are all garage floors this bad?

              Well, if anybody wants any sand - I've got lots of it https://www.kijiji.ca/v-view-details...dId=1288995115

              If I can't find a taker - I'll get rid of some of it but I don't feel like removing and replacing more than a few cm of material, even that is going to break my back!

              Or maybe as a compromise I could put gravel on the outline and leave sand in the middle. That will keep me happy for the pour, assuming I can find a concrete crew for this season. I can't park on sand.

              Will start calling on monday.
              Andrew Smith

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              • #97

                Re: Are all garage floors this bad?

                Sorry Andrew you have to do it all or nothing. a few cm of sand out of there will not give you any sort of good base. Only going part way at this point will only cause you more trouble with cracking it like the first one. If you don't take out at least 8" of sand you will have exactly that a brand new cracked floor.

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                • #98

                  Re: Are all garage floors this bad?

                  Originally posted by Greg from K/W View Post
                  Sorry Andrew you have to do it all or nothing. a few cm of sand out of there will not give you any sort of good base. Only going part way at this point will only cause you more trouble with cracking it like the first one. If you don't take out at least 8" of sand you will have exactly that a brand new cracked floor.
                  His original floor was 2'' thick and did not crack in 40 years use during which time the ground subsided leaving a void under the floor. That base is not going to sink any further, especially if compacted, until after his new 4'' thick reinforced floor is cured.
                  Rob

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                  • #99

                    Re: Are all garage floors this bad?

                    All I know is what the building code says and what inspectors told me. Anything short of that to me is reason to worry. I would not trust anything else to stand up.

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                    • Re: Are all garage floors this bad?

                      What do you figure is the minimum slope I can get away with so water does drain toward the front?

                      I spoke to one company today and they told me they like to put in at least a 5" drop for a pad this length. Seems excessive to me, not that I should know better. Would a couple of inches be enough?
                      Andrew Smith

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                      • Re: Are all garage floors this bad?

                        I just spoke to our CBO. There is no building code requirements for this as long as there is a slope. He thinks on a 20 foot deep garage even as little as 2 inches would be excessive.
                        In order to understand recursion, one must first understand recursion

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                        • Re: Are all garage floors this bad?

                          For garage slope it is a lot. 1" in 12' would be lots. Its the same for eaves troughs. Its enough for water to run out. 1" in 24' would be plenty.

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                          • Re: Are all garage floors this bad?

                            That's what I thought. I'll then assume that this company doesn't know what they're doing and will keep looking. Gave me a crazy estimate too, like I don't understand what a concrete truck and a crew for a day would cost. I guess most people don't. One of the reasons I hate this "professional" shopping process and would rather do it myself. If only it wasn't so risky for this project...
                            Andrew Smith

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                            • Re: Are all garage floors this bad?

                              It seems that the surface under the floor was not properly prepared and that"s why you have he problem. If that is the case, anything less than removal, correct, replacement is only going to be a short term wast of $. IMO of course.

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                              • Re: Are all garage floors this bad?

                                Originally posted by ofoori View Post
                                It seems that the surface under the floor was not properly prepared and that"s why you have he problem. If that is the case, anything less than removal, correct, replacement is only going to be a short term wast of $. IMO of course.
                                The floor being uneven was not due to the substrate subsiding IMO.
                                Rob

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