O/T Shop Floor...........

I'm planning a new shop building within the next year.

Maybe 30' X 40', pole type construction, eventually insulated and lined. On that type of building, when is the best time to pour a concrete floor? After it's framed, but before the steel is on, or after the entire shell is closed in? Or???

I'm looking for ideas.

Thanks in advance.

If you can be careful while doing the rest of the framing, I'd do it after the poles are set. If you think ya might be a bit clumsy(dropping perlins on a green slab won't make ya happy) I'd pour after the framing is done, but before hanging the tin. Use pressure treated lumber for your forms, with a few smallish lag bolts in the back, to grip into the concrete, and use that to screw your tin off at the bottom.

Ben

Kind of depends on your soil.
When I built mine I had to wait a year before the holes stopped settling in the clay.
On one corner, where we had to dig out a huge bolder, it didn't stop settling for nearly 2 years. I poured that sink hole full of concrete under the floor I had already poured at that point.
It was quite a pain to do the crete work with the walls up. If you can do it, it would be easier without the walls/steel.

There will be opinions and preferences by many I am sure.

Its nice to have adequate light when placing concrete, for the finisher at least, building that size, access for the chute, or for some reason you have a pump, probably not necessary, but its wise to consider how the material will be placed. So roof on or enclosed or not, kind of optional, enough work lights can be set up to illuminate or permanent lights installed before hand. Definitely need light one way or the other.

I'm not familiar with the slab edge and column detail is with pole buildings, maybe there is expansion joint or isolation joint around same for preventing cracking, but would assume the columns and the roof framing, and tin would be up, that would prevent weather effecting the finish, like a sudden rain or what have you. Access through the sides, whatever nailer or blocking for the tin is needed, bracing might be in the way, you could plan areas for the chute to place if the doorways do not provide enough access already.


If placed early, you'll want to wait the 28 days for curing and compressive strength, but afterwards, for remaining work, nice clean surface to work off of, just not something I would do if that is the finished floor surface and theres a bunch of trades that will work off it to complete the building, pole building likely not the case.

Don't forget reinforcing, extra where needed, all the stub ups, conduit, pipe, pex for heated floor and or anything extra like spare conduit, pipe for future use etc. Euclid Chemical Company makes great finishing products for your slab.
Euclid Chemical Company

I would pour after the building is closed in. That way you don't have to worry about weather. It also helps to cure concrete in the shade. You will have a stronger floor. It also helps to keep it wet for about 2 weeks.
Ralph

A good concrete man can pour a 30x40 slab without using forms, only the boards of the barn. My guy did it. Only form was across the door.

Used a laser transit and put 16p nails in each post 8 ft apart as a reference point. He used a Georgia buggy to haul the concrete in the barn. The pour was done after everything was up. That way it cured without the sun hitting it. He came back the next day and cut lines. That was 4 years ago and no cracks. He put down a 6 inch floor with wire. Used the laser transit to set points during the pour.

He put his motorized trowel in the far corner of the barn and raised it up using straps. That is the first place he started pouring and the first place to set up.

3 guys did the job on a Saturday morning and only charged me $500. Also put a 10x30 slap in front of barn. I did all the excavating work.

These guys do this kind of work for a living. My job was just a little side job.
George

If you wait 'till the building is up it may cost you substantially more labor for spreading the concrete since the truck may not be able to move the chute around the perimiter as easily.

Jim

Any way you do it be sure to put visqueen under the slab. Stops those Spring and/or fall floor sweats what may last from three days up to three weeks.
Fernan

my 54x88 floor was poured after the building was up. 11x14 doors, mixer trucks backed right in.Almost 100 yards poured. Bill M.

I poured my 30X60 shop after the roof was on. Pole construction and no walls on it at the time. The front unloader trucks came in from all sides and almost no shovel work. One side was very steep but they had no trouble. Kept it wet for about 10 days and no cracks at all. Laid 2 courses of block between posts and framed walls up on that. Having a roof on first made it cool to work in and helped the curing.
Richard

In my experiance wet concrete floors are almost allways condensation. Tape a two foot by two foot piece of poly to floor to tell if the condenstion is coming from the earth or condensing on the the poly. Think sweaty beer can. The temp of floor might be 60 on a day with thats 90 with 90% humidity. Bubble insulatiom might raise the floor temp enuff to stop condensation and act as a vaper b.

This is why treated bottem plates are used on concrete floors. Concretes gets a lot of condensation.

After 20 years with a dirt floor, I finally broke down and had one poured a few weeks ago. The cement truck simply drove up to the sliding door and aimed his chute into the barn.

First the edges were framed with pressure treated studs as close to the sides as possible. I shoveled gravel in later to seal up the narrow gap against varmits and drafts.

Also consider in-floor hot water heating.

I poured mine after the roof was up but before the siding was on. That way I didn't have to worry about rain, but the truck could put its chute between the girt boards and pour from the sides.