I know variations of this question have been discussed here and over at TBN, but never really got consensus on my particular situation so I'll throw it out here.
I have an existing 32x26 shop building with a dirt/gravel floor. The building has been up for about 40 years and has been used to store tractors etc for most of that time (point being the floor is pretty well compacted I would think).
The foundation is cinder-block, and I assume, but am not positive, that it extends all the way down to the frost line and most likely has footers in place.
I want to pour a cement floor into this building by fall (I am in New England), and here is what I am thinking I should do:
Use 2x6 (or 2x8) boards laid on edge(and secured) in front of the doorways to hold in the pour. (i.e. a form). I was hoping I could use the existing cinder-block walls as the rest of the "form"...any reasons I can't pour right up against the wall? or do I need to put in a form and remove it later so that I have an expansion joint between the existing wall and floor around the whole outside perimeter?
Also, I'd like to pour directly onto the existing floor without excavating down...I was thinking 4-6 inches thick with proper amounts of wiremesh in place...raising the floor this way would solve two problems: first make it less work [img]/forums/images/icons/smile.gif[/img] and two, it would leave the finish grade high enough to prevent water from running in the front; keeping all my tools nice and dry.
Is there any need to "subdivide" the floor? i.e. leave expansion joints thru the middle? I am hoping not, so that I end up with a smooth 32x26 slab w/no obstructions...
Lastly, I have done small amounts of cemet work myself, but his would be the largest pour by far...how much skill is required to end up with a nice smooth finished surface?...I'll only get one try to get it right and don't want a real irregular surface when I am done..
Don't have much in the way of cement specific tools, but might be able to borrow (or rent) some. The cement would come on a truck (I figure about 10 yards for a 4inch slab)
Was planning on one other helper, with about the same skill level as me (i.e. not a pro).
If you have a pro available they can pretty much get a level floor by evenly spreading the concrete with the chute. Otherwise I would suggest some forms to allow you to screed the concrete in place. These can be removed after they have served their purpose and the space filled with concrete. Eight to 10 foot width is about nice to work with.
You should have a large wooden bull float for the initial finishing. Try not to work it to much. A long plank to place on the fresh pour to stand on. You move this around as required. then for the finish a metal bull float or a motorized float with metal paddles. This will do the best job. After the final floating and the concrete has set up a little keeping it damp will make for a stronger floor.
Rubber boots, gloves and some square nosed shovels. Leave the rakes and hoes somewhere else as they will segregate the mix.
Be pepared for lots of backbreaking work. If the weather is hot time is important and you may want to order a concrete with a higher slump.
Insure the cement truck has enough chute to reach to the back. They can bring extra if needed.
Your original plan sounds okay to me but others will suggest the expansion joints.
I'll wait and see if anyone else chimes in with other tips, but thanks so far for the advice. Plastic is probably a good idea, I'll add that to the list. Also may try to drum up another helper or two...
I'd use a fiber reinforced concrete it you want to try it without joints. But you'll probably want to come back and put a couple saw cuts in.
Better rent a power trowel (if you're wanting a smooth surface) - that's a lot of area to hand trowel for 2 guys.
When I had my 20 x 36 floor poured, they set a laser level at one end of the building and checked several times/places to ensure the center was level.
I put down plastic as well.
Dig a test hole next to your block wall to see if you have footers or not. Is the block mortared in place? My thoughts are leaning towards whether or not you would have to backfill to keep the concrete from blowing out your "forms". Of course, Egon hit all of the other high points. Ask around about finishing work. I know 2 local guys that do pour and finish only work on Saturdays charging ~$0.65/sf. Yes, that would be an extra $550. but get them to show you how while they are there.
If you want to be 'hands on" yet still be assured of a good finished product since concrete isn't very forgiving and doesn't wait for anyone, you might want to consider hiring some people who know what they're doing to run and manage the job while you and your buddy act as "labor" for the job.
You'll do a lot of the work yourselves and also know when everything's done, the job will be what you want.
I've used this method a lot of time on all sorts of tasks. I always tease about being the "owner/lotboy" at my business. The fact of the matter is that if you get someone who'll work a deal like this with you you'll not only save some money but also learn how to do it yourself the next time.
Good luck with whatever you decide. I hope this helps. [img]/forums/images/icons/smile.gif[/img]
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