Options.....any opinions?

[CheapCharlie]

New member here, looking for some opinions on pouring a concrete slab.

I'm in Manitoba, Canada for starters.

I'm going to be building a 26'x34'x10' shop. I'm planning on running PEX for in-floor heat.

Questions:
1) Insulating - I've read that you only need insulation around the perimeter of the slab (vertically) and out flat about 16" around the outside (horizonatally).
I've also been told to put insulation under the whole slab with a vapour barrier on top. Which is preffered?

2) Forming - I want to have a 6" curb above the slab to stand my walls on. How to you go about forming this? Would you pour the curb after or at the same time?

3) Rebar or Wire mesh? I plan on having fibre mesh put in the concrete.

I'll leave it at that for now, I'm sure I'll come up with more later.

TIA

 

[dirttracker18]

New member here, looking for some opinions on pouring a concrete slab.

I'm in Manitoba, Canada for starters.

I'm going to be building a 26'x34'x10' shop. I'm planning on running PEX for in-floor heat.

Questions:
1) Insulating - I've read that you only need insulation around the perimeter of the slab (vertically) and out flat about 16" around the outside (horizonatally).
I've also been told to put insulation under the whole slab with a vapour barrier on top. Which is preffered?

Both, no question about it and go farther than 16" out, 4 feet is better to control the frost.

2) Forming - I want to have a 6" curb above the slab to stand my walls on. How to you go about forming this? Would you pour the curb after or at the same time?

I had a row of blocks done after the pad was done. If you want the curb form it at the same time

3) Rebar or Wire mesh? I plan on having fibre mesh put in the concrete.

I prefer rebar, more money but my 30 X 36 slab has NO CRACKS and no "cuts" were made. Your choice though Spend a little more now for the long term.

I'll leave it at that for now, I'm sure I'll come up with more later.

TIA

I am no expert but I did ask a lot of questions before I started.

Just my $0.02, no charge though

 

[Gary S]

Insulating under the slab depends on what you expect from this garage, and what your soil temperature conditions are.
Are you planning on heating the garage? If so, you probably want to insulate under the slab if you expect to heat it warmer than the ground temperature in winter. If you aren't heating, you gain by not insulating under the slab. I have similar cold temperatures here to what you have. I don't heat my garage, and I didn't insulate under the slab. In winter, the ground under the garage is warmer than the outside air temp, so I get warmth through the floor by leaving it uninsulated.
On cold winter mornings the garage is 40-50 degrees warmer than outside with no heat added to the building. Insulating the slab would take away my free heat source.
If you want to heat the garage warmer than expected winter ground temperatures, you need to insulate the floor.

 

[1948]

what about putting in a heated floor?

 

[CheapCharlie]

I am no expert but I did ask a lot of questions before I started.

Just my $0.02, no charge though

Thanks for the replies. Now, I forgot to ask....2" or thicker foam? And I am going to be heating it. Infloor heat with some kind of electric "recovery" heater.

 

[fromnwmt]

Definitely insulate/add vapor barrier I did not think i was going to heat our new 30x40x12 Rhino steel shop so "saved" some $$ BUT it looks like the mono slab is sweating every time I heat it with a 45,000 btu. propane sheet rock dryer (slab 1.5yrs old) although as mentioned above it does stay 38-45 deg inside all winter. I would go Rebar especially if there is a chance you will add a 2 post lift someday. I did not add in floor heat or concrete stub walls.

 

[A_Pmech]

Rebar.

Mesh is for keeping chickens in.

 

[egads74]

1st time out there where your feet are cold, you will think I should have heated... Put the pex in now... can always add a unit later... will be glad you did...

 

[CheapCharlie]

1st time out there where your feet are cold, you will think I should have heated... Put the pex in now... can always add a unit later... will be glad you did...

If you read my original post I said I am putting in PEX.

I like the chicken thing...lol

 

[nkachur]

I am also in Manitoba. I poured my slab last October.

I had to get engineered drawings done up for my build as I exceeded 30' wide.

so the drawings specified:
- 1.5" insulation under the slab except the thickened edges and tapers
- 2" insulation along the edge of the slab
- 2" insulation 2' out around the base of slab perimiter
- Gov inspected poly inside the enire form sides and bottom
- 20mm rebar around thicked edge 4 runs
- 15mm rebar on 16" centers across pad
- 6" of compacted granular fill under entire pour

if you need more info check out the pictures on my build thread (see my signature block below)

 

[CheapCharlie]

I am also in Manitoba. I poured my slab last October.

I had to get engineered drawings done up for my build as I exceeded 30' wide.

so the drawings specified:
- 1.5" insulation under the slab except the thickened edges and tapers
- 2" insulation along the edge of the slab
- 2" insulation 2' out around the base of slab perimiter
- Gov inspected poly inside the enire form sides and bottom
- 20mm rebar around thicked edge 4 runs
- 15mm rebar on 16" centers across pad
- 6" of compacted granular fill under entire pour

if you need more info check out the pictures on my build thread (see my signature block below)

Thanks for the info, in my jurisdiction, as long as I'm under 900 square feet, engineering is not required. But that information gives me something to go on. Did you do everything yourself? How did you tie the runs in the thickened edge to the slab rebar?

 

[nkachur]

Thanks for the info, in my jurisdiction, as long as I'm under 900 square feet, engineering is not required. But that information gives me something to go on. Did you do everything yourself? How did you tie the runs in the thickened edge to the slab rebar?

here is is over 30' in width you can go as long as you like.

I had some help along the way but was involved with everything.

My thickened edge was 16" x 16" and I used edge saddles that I got thru the lumber yard... you could get them thru any re-bar supplier.

you can kind of make them out in the bottom left corner of this picture.

 

[dirttracker18]

Thanks for the replies. Now, I forgot to ask....2" or thicker foam? And I am going to be heating it. Infloor heat with some kind of electric "recovery" heater.

2" is good, what I found most recommended.

Order your foam out of the US (Menards perhaps) as it is half the price it is here in Canada. I am not even kidding about that, half price. Not sure how far you ar from the border but a run into ND would be worth your while or MN if you are more east.

Had I known then I would have order my entire garage out of the US.

Menards delivers for a pretty good price.

 

[Kevin54]

what about putting in a heated floor?

1st time out there where your feet are cold, you will think I should have heated... Put the pex in now... can always add a unit later... will be glad you did...

If anyone really read what he first posted......Oh, never mind

 

[KPSquared]

I looked hard at the heated floor option (alberta) but decided to go with a radiant tube heater.

By the time you set up a "proper" in floor heating system, you'll be in so deep you'll never recover the cost in efficiency.

Radiant tubes are very efficient, cheap to install, and if you're slab is insulated, it will hold a lot if great and stay decently warm.

My father-in-law has a large shop with a heated floor where they maintain their tank trucks. Said his guys hate working on the floor because it's just to warm under the trucks.

Just my $0.02

 

[dirttracker18]

I never understood the "the floor is too warm" arguement. Turn the damn heat down then! Either that or you are putting to hot of water into the floor. I have never had that issue nor had someone say that in my shop. Everyone talks about how comfortable it is in there in the winter!

 

[CheapCharlie]

Just for kicks, I called a local cement pad contractor for a ballpark price on just the pad. Here is what it was:
12" thickened edge slab (5" thick in the middle)
4500psi concrete
all rebar
1" foam under and around pad (including horizontal "wings")
1/2" PEX tubing
10mil vapour barrier
base preperation (packed gravel)

$10.50 per sqft with no PEX or underslab foam
+$3.50 per sqft for PEX and underslab foam

Comes out to just over $12k.

I was hoping to be able to do the slab for about $7k. Am I way out of wack here? I estimated needing about 20 yards of concrete. Got a quote from the local redi-mix and 4500psi with fibre mesh is $3800 (little less than $190 per yard). I already have the forming lumber (free from work). Just need foam (get from the states at half price), rebar, poly, pex (also cheaper in the states) and someone to finish the concrete.

 

[1948]

If anyone really read what he first posted......Oh, never mind

yeah i missed that one. got me.

 

[KPSquared]

Don't forget the $8000 or so you need to set up a proper hot water heating system for the floor once the pex is in.

you'll never pay someone to do that for $7000. If you DIY, then you'll get it a lot cheaper. They love to **** guys for tying re-bar and laying pex and foam. . . it's hard work but way cheaper to do this part yourself.

Please don't use a thickened slab on shop that big. It's way below code here in Alberta. Seen way to many "thickened slabs" crack. Anything over 700 sq ft here has to have an engineered grade beam or frost walls 4' below grade.

I'm about to pour my floor. Inside it measures 28x34. Going with 4" of 32MPa. That works out to 12 yards. I'm at about 160/yard plus $90/truck for delivery. That's with no fibre. So, I'm looking at $2000 for the concrete maybe a bit more with the 2' out side in front I'm planning. I found a great guy to pour and place. I was in a few hangars he did recently and they are beautiful. 1.60/ sq. ft. so that comes out to $1500 ish plus the goof tax. Don't remember what I paid for re-bar. About $5 per 20' length of 10 mil. so I think that was around $500. Grand total for my finished floor, looking at around $4000 with all the prep work done myself.

 

[CheapCharlie]

I'm looking at about $1500-$2000 for a boiler system. I will be doing it all DIY except for finishing the concrete. Anything below 900 sqft here needs a thickened edge slab (12"x12".
My 20 yard estimate includes the thickened edge...5" thick and 6" by 6" curb.

 

[Boyd Who]

I'm also in Manitoba. The shop I built in 2010 is only 20 x 22, but I insulated under the slab. No pex, I use a small overhead electric heater to keep things tolerable. Total cost was just under $5K for the slab.