slab quote

[Kapt]

I got an estimate today to pour my 24x26 slab. The structure is complete except for the floor and the floor has radiant heat tubing running on a 2' grid of #4 rebar over foam. The slab will be 5". So the prep is complete.

The estimator said I don't need contraction joints and I don't need the expansion joint material that runs along the inside of the cinderblock. He said the concrete would go up flush against the cinderblock. Also, he wants to slope the floor a total of 2-3 inches.

Everything I've read said I need contraction joints that run 1/4 the depth of the slab every 10-15 feet. Also, I want very little slope due to a future lift. And what about the expansion joint material?

I have another estimate coming tomorrow. Any thoughts??

Thanks. Oh yeah, total cost including pumper truck 2950.00.

 

[carguy123]

I've never seen the expansion joints in the middle of a slab in a garage. I don't know about around the perimeter. Ya'll sure do build em weird up there.

We build the slab and then put the house/garage on top of them down heah.

 

[gto65goat]

Kapt,
I'm in Maryland also. Anne Arundel County. I'm building a 25' X 28' garage.
There will be no seams in my floor.
Out of (4) quotes from contractors, I settled on the person I felt the most comfortable with.

His quote was:
$4700...digging the footers...2500 PSI footer cement pour (8" thick X 24" wide)...compacting fill dirt every 6 inches...then pouring the 5" cement floor with 3500 PSI cement.

Block work - will cost me another $3K (using 12" block for the back wall, and 1/2 of each side wall leading to the front of the garage.

Rebar added to the drilled in holes of the block sidewalls...mesh wire too, included.

John

 

[RickP330]

Sounds like a real interesting project, I LOVE radient heat - it's awsome. A note on the Grade, is it really required for a structure that will be indoors! I have one interior room that was built on a pre existing slab that used to be outdoors and it has that much pitch. You would never notice it untill you install a door like I did.
If you have pics please post. I am very interested in seeing what your project looks like before the pour the concrete.
Rick

 

[PAToyota]

I did my floor in two sections - roughly 20'x24' each - with expansion joints between the two and around the perimeter. You want decent reinforcing mesh. Use the flat sheets, not the rolls - rolls are worthless. Especially with the radiant heat, you want the perimeter expansion joint unless you plan to have it a constant temperature ALL the time...

 

[Nosman]

One other thing to make sure you do is put perimeter insulation around the slab. your heat loss from the slab is greatest at the outside edges. I used 1 1/2" Celfort around the perimeter, and poured the slab out to it, against the block wall.

 

[HoosierBuddy]

One other thing to make sure you do is put perimeter insulation around the slab. your heat loss from the slab is greatest at the outside edges. I used 1 1/2" Celfort around the perimeter, and poured the slab out to it, against the block wall.

Agree...

For radiant heating you have to put high strength polystyrene (suggest 2") and a vapor barrier under the slap and line the insides of the footer with it as well. Normally you bevel the top of the styrofoam and leave it just under the finished level of the concrete so it doesn't show.

As far as sloping. My garage floor is sloped about 3/4" to the floor drains. It wasn't any problem to shim the lift (the lift even came with shims for exactly this reason) BUT it is a royal pain in the *** when I want to do wheel alignment. If you've done any of this, you know the car has to be sitting completely level. I have to put shims under my sliders on the drain side to get the car level before I can even start the work.

It is very nice when I hose it down though. Everything runs to the drains. It's a tradeoff.

On the cuts? My 28 X 35 slab doesn't have any. No cracks anywhere (yet). Knock on wood.

Phil

 

[G M]

Yah you want to have some slope otherwise you will get puddles in the middle of the floor. Don't forget the vapour barrier under the insulation too.

 

[Steve in Mi]

I don't need the expansion joint material that runs along the inside of the cinderblock.

Not needed for expansion but it is good to have as a thermo break.

 

[bmwpower]

I always thought you need expansions joints around the perimeter to allow for slab expansion and control joints within the slab for controlling the cracks.

One thing to note about the control joints:
- Keep them away from areas where you want to roll things.
- Keep them away from lift posts.

 

[Steve in Mi]

bmw, The Coefficient of Thermal Expansion for concrete is ~5.0 X 10 raised to the minus 6 power per degree F. The delta T is the difference between the temperature at the time of pour/cure and the heated temperature in your shop/garage (small to negative effect). I think you will find that shrinkage from curing is greater than any expected thermo expansion. I didn't look up the contraction data for concrete curing but I have seen enough steel formed concrete to know that it does shrink as it cures (pulls away from the forms).

Exposed to the sun, long sections and the heat of thousands of car tires - different story.

 

[Ironcrow]

My floor is level. For cleaning, I sweep and mop...no hose, draining, and puddle concerns...

 

[73GRAND]

I would put expansion joints around the perimeter. I also would saw cut my expansion joints. That way you have only 1/4" line and you won't get your creeper stuck in it.

 

[Steve in Mi]

FWIW, I'll add another point that 73 GRAND reminds me of.

I would put expansion joints around the perimeter. I also would saw cut my expansion joints. That way you have only 1/4" line and you won't get your creeper stuck in it.

For cutting your interior fault or crack propagation lines there are blades and there are blades. My first time out renting the machine to slice up my 28 X 48 slab I took what the guy at the rental offered. Mistake! I think IIRC the blade thickness was 3/16" which lead to chipping off the edges of the saw cuts when rolling creepers and heavy steel wheeled tool cabinets etc. across them. Specify or select the thinnest ~1/8" curf blades and life will be better. Much less to fill with the thinner cut also. I didn't really want to put saw cuts in my beautifully finished floor to start with but didn't want any unsightly random cracking to look at later. Saw cuts that were too wide was a double whammy - one mistake you don't have to make.

 

[brownbagg]

if the floor has a slope, you cant install a lift