Redoing garage concrete floor

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How does one redo a concrete floor in an existing garage?

My old floor was shifting and cracking all over the place due to the soil.
The floor was divided into 6 segments and at the joints gaps of 1 inch had
formed. Not only had gaps formed but some slabs were 1/2" different in
height/level - so I removed all the concrete in the garage.

Now I am unsure as to how the concrete should be laid since it is not as
simple as laying concrete slab in an open area.

If someone could give me some insight as to how concrete is poured into an
existing structure that would be great!

Advice is much appreciated.

Garage Specifications:
Length: 8.5 metres
Width: 5.5 metres

Desired concrete thickness: 100mm
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Re: Redoing garage concrete floor


Hi,
Is the existing subgrade acceptable?
Are you preparing that so that the "same" does not occur?

In any case, pouring concrete in a confined area presents problems.....
The same story as painting yourself into a corner.
There must be some doors....and or windows? (access)

You can use overhead screed boards on the left and right sides so that there
will be no stakes in the concrete pour.
Down the center a person can use a metal buried screed form, that represents
top of concrete and rod off of that.  It remains in the concrete and acts as
a "cold" joint, or expansion / contraction line.....

I would make sure to use a "grid" of re-bar in the slab to keep the concrete
together.  I have had more luck with re-bar and cracking than any concrete
wire or 6-6  10-10 mesh used.....
Also keeping the rebar at the right height is important so that it does not
get imbedded in the sub-grade.

Are you using a vapor barrier?
If so, I always make sure it is deep enough to cover with a layer of sand to
facilitate concrete pouring.....I never pour on plastic alone....
It can create problems with water and finishing.......

With concrete tools, I always jitter bug the top layer of
concrete......always.
It helps bring up the fines for the top finish, and set some of the larger
rocks below top.

Using a float on a long pole is helpful in a confined area....
I have several mag floats for preliminary surface prep. and then steel
trowels on poles for finsih work.

In the past 4 years I have purchased a power float.....that goes on poles
also.
It is a lifesaver......works wonderful.....can bull float the concrete as
well as finish it all from outside the slab..........
It weighs 24# and has a small gas engine......works great.

Knee skids are also beneficial for finishing concrete in confined areas....
I use metal, knee skids, and like "snow" skis.....you can move out over
concrete without leaving board marks......of course there is a time when
they are most successful as when the concrete is hard enough to use them.

some of my inside pours I have pre-set boards high enough on the walls that
a plank can span the area being poured......
You can "walk" a plank out and finsih an area without even getting in the
concrete......an aluminum "rental plank works well......or a 2x12.....or
scaffold plank.

I do this a lot for colored or stenciled concrete where the surface cannot
be walked on......

have fun.
I am sure I have missed something......
jloomisconstruction and concrete

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Re: Redoing garage concrete floor


saka had written this in response to
http://www.homeownershub.com/construction/re-redoing-garage-concrete-floor-18079-.htm
 :

jloomis wrote:

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Not yet. We are at this stage now, dig up the soil, lay the vapour sheet,
tamper the sand and gravel.
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That is the plan, how deep should the sand/gravel be? 1 inch ?

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Yes there is a large roller door/side door that can be accessed from the
front.

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How exactly do these overhead screed boards work? since there is no
formwork on the right and left hand sides.

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I found a site metalscreed.com so I now have an idea of what these are.
Are these expensive? and could they be used on the left and right sides as
well instead of using the overhead screeed?

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Thanks for your post, it is very much appreciated don't feel so lost now




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Re: Redoing garage concrete floor


On Oct 11, 6:52=A0pm, sakatumi21_at_gmail_dot_...@foo.com (saka) wrote:
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saka-

You got a lot of good information from jlloomis but I would advise
against doing a confined flat work job of 500 sq ft (50 sq m)  as your
first DIY attempt.

cheers
Bob


Re: Redoing garage concrete floor


A person would need help.
I assume saka has some building sense?
On Oct 11, 6:52 pm, sakatumi21_at_gmail_dot_...@foo.com (saka) wrote:
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saka-

You got a lot of good information from jlloomis but I would advise
against doing a confined flat work job of 500 sq ft (50 sq m)  as your
first DIY attempt.

cheers
Bob



Re: Redoing garage concrete floor


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I was getting total "rookie" vibes base on the OP & his
reply ..........   but flat work scares me, so maybe its just my fear.

I've done a little flat work & I've seen experts do it......I prefer
to watch it done.  :)
The results are much better.

Plus his original post, noting 1" gaps & 1/2" differentials has me a
bit concerned.
I'd hate for him to do all this work & have the new floor not work out
any better than the one he's replacing.

cheers
Bob




cheers
Bob

Re: Redoing garage concrete floor


saka had written this in response to
http://www.homeownershub.com/construction/re-redoing-garage-concrete-floor-18086-.htm
 :

fftt wrote:

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Thanks for the replies guys.

Pretty much am a total rookie, but didn't plan on doing this all myself
unless it was fairly straight forward, which it doesn't sound like it is.
Was hoping to get some info on how it is done (which I did so thank you)
so when I get quotes I can access if their method is good. I also have a
friend that does concreting but he is fairly new to it.

Yeah, it would not be good if the concrete turned as bad as before. But
most likely will be paying someone to do a proper job :)

Thanks again for the info
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Re: Redoing garage concrete floor


On Mon, 12 Oct 2009 17:14:35 +0000,
sakatumi21_at_gmail_dot_com@foo.com (saka) wrote:
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Good. I'm relatively experienced at construction (not a pro, but I can
build) and I'd not try that slab myself. (I did a 10m x 20m
building/slab a couple of years ago, the only think I contracted out
was... The slab!)

Re: Redoing garage concrete floor


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Okay, I gotta ask - is the slab the best or worst thing?  ;)

R

Re: Redoing garage concrete floor


On Tue, 13 Oct 2009 05:55:42 -0700 (PDT), RicodJour

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Actually both turned out very well. I'd use the contractor again in a
minute, he did a credible job on the slab. The building turned out
very well too, better than I'd expected.

I've had to tell several friends that they can't move into my
garage... <bg>

Re: Redoing garage concrete floor


I would bury a pressure treated 2x4 on the left and right side to act as a
screed and the form since you do not have any forms....
I cannot see exactly the situation so, I have to guess...
The metal buried screeds would work, yet ordering and getting them is
another thing.

Subgrade depends on what it is and what its compaction is all about.
A person could put sand and or gravel on a lousy subgrade and end up with no
changes....
So, if the ground under the "to be poured concrete pad" is good, then a
layer of sand and or gravel is fine....I use sand since it retains concrete
moisture and facilitates in pouring....
gravel lets the moisture drain down quick.....anyway, either will work.
You are in a cover area so the sun factor will not be present.
john
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