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Posted by saka on October 11, 2009, 9:52 pm
saka had written this in response to
http://www.thestuccocompany.com/construction/Re-Redoing-garage-concrete-floor-18079-.htm
:
jloomis wrote:
> Hi,
> Is the existing subgrade acceptable?
Not yet. We are at this stage now, dig up the soil, lay the vapour sheet,
tamper the sand and gravel.
> Are you preparing that so that the "same" does not occur?
That is the plan, how deep should the sand/gravel be? 1 inch ?
> 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)
Yes there is a large roller door/side door that can be accessed from the
front.
> You can use overhead screed boards on the left and right sides so that
> there
> will be no stakes in the concrete pour.
How exactly do these overhead screed boards work? since there is no
formwork on the right and left hand sides.
> 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 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?
> 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
Thanks for your post, it is very much appreciated don't feel so lost now
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> 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
> -------------------------------------
>