Hello all, I'm in the process of getting quotes for a 18.5'x18.5' slab. The forms are already in place (existing rock wall). The grade is pretty level.

If my math is correct, I have 342 sq.ft. of slab and at 4" thick that is about 114 cubic feet, or about 4.25 cubic yards.

I have been getting quotes all over the place. So far I have quotes for $900, $1450, $2150, and $3200! They are all over the place.

The price per sq.ft. is varying between $2.63 and $9.87!

The material may have to be wheelbarreled to the slab, which is only 25ft from the end of the driveway. The septic system is in between.

Could anyone give me any advice? What is a reasonable price in MA?

 

Are they all the same mix?

 

Who is supplying the concrete, you or the contractor? Maybe the $900 guy assumes you are buying it and he's just supplying labor. Are they all figuring on pulling the concrete truck onto your driveway and only wheeling it 25 feet, or do some of them figure they'll have to wheel it all the way from the road to save potential damage to your drive?
Don't know about MA, but for a plain gray exterior concrete slab in Indianapolis, I would charge about $2,000 and buy the concrete.
Are they all bidding the same finish (brushed, trowelled, stamped, exposed aggregate, etc.)? Your estimates are indeed all over the place. I suspect the $3,200 guy is so busy that he doesn't want to mess with your job, so he bid it high. If you take his price, it would be worth his time. If not, it's all the same to him because he really didn't want it anyway.
I'd go with one of the mid-range estimates if it were me. Good luck.

 

While this may seem to be obvious be sure they plan to use a mix truck for the concrete. I had a customer with a dirt floor garage who wanted a slab pored in it. I happened to be there doing another job. They pulled up with a truck full of concrete sand but no larger aggregate and bags of cement. They then proceeded to throw a sheet of old plywood on the ground and started mixing the concrete with a shovel. Until I said something to my customer they weren't even planing to use rebar or rewire.

 

Nice comments guys! I'm not a concrete pro so I may have missed some things but here goes.... They all said they would put some sort of base down, I don't exactly remember the details. The truck would be parked at the end of the driveway, 25 feet from the slab and would have to be wheeled that distance. The concrete would be supplied by them.

The concrete surface would be "smooth". I don't remember the terminology they used but I told them I want a reletively smooth surface consistent with what you'd find in a garage. They said no problem. It would not be sealed, I will do that later.

By the way, the $900 dude seemed a little shady and just gave me a word of mouth quote. The $1450 quote was just a price written on a business card. The other two were somewhat more formal but the details where pretty vague. They essentially just list the size, thickness and cubic feet needed.

 

Don't pour a smooth surface if it's going to be exterior. it would be very slippery when wet. Also, in freeze/thaw climates like yours, air-entrained concrete should always be used for exteriors to help with scaling issues. Air-entrained concrete should not be hard-trowelled or it will scale. You may want to re-think your plan. By the way, what will this slab be used for?

 

Talking about a smooth surface, what made that tine look so popular? Smooth looks so much better.

 

The existing rock foundation was part of a large shed that originally had dirt floors. The structure has deteriorated over the past 100 years and had to be taken down. The foundation is in good enough shape where I'd like to get a smooth slab put down instead of the original dirt floor and frame a new shed on the existing foundation.

The shed/small garage is 19.5x19.5 and is big enough to park a car in plus a lawn tractor and other outdoor goodies.

During the discussions with the concrete people, I said I would like a somewhat smooth surface. Not exactly polished like you would find at Home Depot/Lowes, but not exactly rough like a sidewalk....somewhere in between. I told them i would like a surface similar to what you would find on a typical garage floor. If I spill oil in there it would be nice to be able to just wipe it up (after I seal it of course).

 

If you are doing a floor for a garage /shed you may want to slope the floor towards the door and have a slight curb where the garage door would sit to keep water out.

 

If it's going to be enclosed, then a smooth finish is fine. It should be slightly sloped toward the door as dan0661 said so water will run out when it drips off your car.

 

Thanks for all the help guys! I'll get a few more quotes before I move forward and I'll also have my friends brother come over and take a look at it.

He is in the commercial concrete business and has done all the concrete work at my friends house (on the side, of course). The patios and walkways he did there look great so I would trust his work. Plus, maybe I'll get the "friends and family" discount. Never know.

Thanks again for the good info, I feel well informed now.