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Thread: Know anything about concrete?

  1. #1
    Flashaholic* pedalinbob's Avatar
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    Default Know anything about concrete?

    i have a concrete step at the side door that i want to modify. i thought it wa a "pre-formed" step, until i looked more closely--it was formed directly upon the driveway concrete. in other words, it is part of the dirveway! removing it may be very difficult.

    so i would like to make it a little larger. the current step is 5" high, and only protrudes 13" from the house.
    people have stumbled because the step is both too low and does not protrude out far enough.

    i would like it to be about 7" high and extend about 15" from the house.

    can i prep the concrete, create a form, and pour some concrete on top of/around the old step?

    will it hold up? any problems? i am currently looking into concrete info, but cannot seem to find info on this specific application.

    Bob

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    Default Re: Know anything about concrete?

    Ummm... It was invented by the Romans of the Roman Empire. Rebar was far more recent. [img]/ubbthreads/images/graemlins/grin.gif[/img] Other than that, it is oout of my knowledge.

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    Default Re: Know anything about concrete?

    If it we're me, I would drill some holes to accomodate some rebar. In other words, tie the new pour into the existing concrete steps. This will give the new pour some extra strength and help to keep it from pulling away from the existing steps, then frame up a form. Any Homedepot/Lowes will cut rebar to length, or at least show you where the cutter is and let you at it. It's really easy to cut with the rebar cutters. Basically they are huge bolt cutter mounted to a 2x12 (usually).

    There could be problems depending on how exposed it all is to the elements. Looks like your in Michigan ..... feezes there. So, if you get water between the old concrete and the new stuff and it freezes ..... it could "pop" it apart if not done properly.

    However, since your not adding too much ...... you might think about using brick and mortar. They make bricks different thicknesses .... or maybe even tiles. You could extend the steps up and out with these materials as well.

    Mike

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    *Flashaholic* James S's Avatar
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    Default Re: Know anything about concrete?

    IANAM (I am not a mason [img]/ubbthreads/images/graemlins/smile.gif[/img] ) short answer is yes, but like so many things there is a BUT...

    If the new stair surface is not high enough over the old step then the new surface will be weak and will end up cracking and pitting much faster than usual or even just separate completely from the old step. If it's possible to remove the old one thats best. If it's not possible then you'll want to drill a bunch of holes into it and put some rebar or bolts or something to link the 2 pieces together. Obviously these can't stick through the top surface. If the top surface is really thin and there isn't enough room to do this properly then you might look into some other methods of re--enforcing it, there are some fabric like things and such now, but I don't know where to go to get more info on that.

    I THINK that you'll want to make the original step as wet as possible before the pour so that it won't pull the moisture too quickly out of the new concrete and cause it to cure poorly on the bottom. I don't know for sure about that, but it's definitely something to look up or ask somebody about.

    Apart from that just make sure to clean up the old step before you pour over it.

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    Flashaholic* pedalinbob's Avatar
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    Default Re: Know anything about concrete?

    ok, this is the info i needed.

    sounds strange, but i am also considering creating a wood step that would nicely fit over the concrete one. i dont believe it would be difficult to do, and could be made to be very durable and nice looking.

    thanks,
    Bob

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    Default Re: Know anything about concrete?

    Go for the wood! [img]/ubbthreads/images/graemlins/wink.gif[/img]

    Great advice here. One thing I noticed in your original post though... you never "prep the concrete and THEN build the form" You build the form, check it about ten times, and THEN prep the concrete to pour. Once you've mixed the concrete, you don't screw around. You dump, scree and finish. Leave the form on for at least 24 hours, and then very carefully remove it. If it is hot and dry when you do this, water the concrete regularly. You don't want it to dry too fast. Your concrete will reach maximum strength in 50 years. Seriously. [img]/ubbthreads/images/graemlins/smile.gif[/img]

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    Flashaholic* turbodog's Avatar
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    Default Re: Know anything about concrete?

    Supposed minimum thickness for concrete is 1" or is that 2"? Still, I would go with the drill, rebar, pour method. The brick method would be nice also.

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    Flashaholic BF Hammer's Avatar
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    Default Re: Know anything about concrete?

    Would it be possible to just construct a wooden step or deck around the concrete? You should be able to tie it to the concrete with a few masonry or concrete screws.

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    Default Re: Know anything about concrete?

    If your considering wood, you might take a look at a product called Trex ..... Trex link.

    Supposed to be very good stuff, won't rot either.


    Mike

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    Default Re: Know anything about concrete?

    I suggest you consider the wood or brick solutions above, just because they'll look so much better. More expensive but very elegant is to get some 2" granite slab and mortar that in place. I just did five granite steps to my front porch because I see so many 200 to 300 yr. old ones around here that still look great.

  11. #11
    *Flashaholic* bwaites's Avatar
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    Default Re: Know anything about concrete?

    My preferred solutions in order--

    1) Granite or tile slab, (whichever you like better, or Brick if you prefer!)Just remember to prep the old concrete with an etcher or other chemical to get to the raw surface so new mortar or will bind well.
    2) Trex step. Really incredible stuff, lasts forever it seems, doesn't hardly weather, minimal prep, just use a few concrete lag bolts to join it to the old step.
    3) Wood step. Weathers poorly, but looks great initally, just have to do lots of maintenance to keep it looking like that.
    4) Rip out and repour the whole thing. Lots of work, but lasts almost forever. You can make the step look however you like.
    5) Pour over old step. Lots of risks, unless you are familiar with the proper ways to prep and work old concrete into new. People think this is easy, concrete will stick to concrete, right? But concrete isn't really formulated to join two things like mortar is, (see #1 above), so it seldom works as well in practice as it does in real life.
    Good concrete guys can make this work, but even they don't usually like it as their first option.

    Good Luck and let us know what you decide on.

    Bill

  12. #12

    Default Re: Know anything about concrete?

    Just drill holes and put some rebar 2 inches on center. You should be fine...

    Cryptoguru, Major, USAF ret.
    Registered Civil & Mechanical Engineer.

  13. #13
    Flashaholic* pedalinbob's Avatar
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    Default Re: Know anything about concrete?

    "Cryptoguru, Major, USAF ret.
    Registered Civil & Mechanical Engineer"

    this place always blows me away as to the incredible diversity of minds!

    we have our own "think tank" for just about anything you could imagine.

    i am looking into the "rebar" method, the "granite/brick/tile slab" method,
    the "rip out the old one" method and
    the "Trex step" method. i think the wood method might work as well, but i really want it to last--the Trex stuff looks very nice.

    i will have to weigh cost, time, durability and difficulty.

    many, many thanks to all,
    Bob

    Ps how deep should the drilled holes be, and should the rebar only be sticking up vertically, or will i need it to be somehow horizontal as well?

  14. #14
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    Default Re: Know anything about concrete?

    I would say the 2" on center for the rebar (like another poster indicated). Depth, maybe go 4" on that. I would also say both vertical and horizontal would give you the most strength. This would be because the new pour would be "locked" in and not really able to go anywhere.

    The problem will be as stated from another poster, the problem of separation of the new pour from the existing concrete. Proper prep is very important, if not done correctly you could have a mess on your hands in a short amount of time.

    Mike

  15. #15
    Flashaholic* MoonRise's Avatar
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    Default Re: Know anything about concrete?

    Rebar 2" OC??? You making a runway for heavy cargo mil aircraft? [img]/ubbthreads/images/graemlins/smile.gif[/img]

    There are a couple of different points here Bob. Number one is the step size. Figure that out first and -then- consider construction methods.

    Most locations have building codes and those codes typically call out allowed step sizes, proportions, variation between steps, etc. If you have one 'area' from ground to the door sill, then you are looking more into a landing as opposed to a step. I digress (again)...

    Standard step height is usually around 7" with a tread width of around 10". The sum of rise plus tread should be between 17"-18" and the product of rise times tread should be between 70-80. Max rise can usually be no more than 8" (per UBC), and minimum can be between 5"-7" depending on the jurisdiction/locale. If you only have one 'step', then you don't have to worry about the typical allowed max variation between steps and of the whole staircase of 3/8".

    You sound like you want to make more of a landing than a single step. No general problem there. Building codes usually call out required sizes for landings as well. Your desired 7" rise shouldn't be a problem for either stair or landing codes. Your thought of a 15" deep tread might not make it though (too deep for a stair step and too small for a landing). For a step, ballpark tread depth is 10", and for a landing it is 3 ft.

    Once you decide on the allowed and desired size for your remodelled step/landing, then you can wrestle with construction details. But -if- you were to try to form and pour a 2" thick 'cap' onto your existing concrete, it would be iffy as to getting it to bond and stay together with the existing concrete. Possible but iffy. You probably need to at a minimum agressively clean and etch the existing concrete and maybe also use a modified concrete product for a thin layer application (think latex bond additive ala a mortar additive).

    A mortar and brick/stone approach might be a better way to go. Clean and etch the existing concrete, extend landing to desired size, then add brick/stone surface mortared in place.

    If you want it to look like one single concrete landing, the 'best' way to do your concrete IMHO, would be to cut the old stuff out and remove it. Then do a new pour of fiber-reinforced concrete for the new landing. Put proper expansion/contraction joint between all old and new work and caulk afterwards.

  16. #16
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    Default Re: Know anything about concrete?

    [ QUOTE ]
    MoonRise said:
    Rebar 2" OC??? You making a runway for heavy cargo mil aircraft? [img]/ubbthreads/images/graemlins/smile.gif[/img]

    [/ QUOTE ]

    Well, we don't know how large a lad Bob is now do we? [img]/ubbthreads/images/graemlins/wink.gif[/img]

    Mike

  17. #17
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    Default Re: Know anything about concrete?

    If you do decide to rip out the old one, see if you can get a piece of granite the size you want for the new step and drop it in place. Don't drop it on your finger or your toe [img]/ubbthreads/images/graemlins/smile.gif[/img]

    I needed a single step for the back door into my garage from a stone patio. I put a precut granite step there 7" high by 32" wide by 10" deep (I'm guessing, I'm not going out in the rain to measure it) A hand truck and a big friend are a necessity. It's about as durable as there is and goes in fast, plus you can move it if you ever repave the driveway, then just put it back later. The hard part will be ripping out the old one - you could just rent an electric jackhammer or chipping hammer.

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