Hello
My neighbor wants me to help build the forms & pour a concrete slab for his work shop. Any assistance would be greatly appreciated. From your own experience. Things to consider. Things to do & things not to do. Maybe a How To website Is it necessary to pour a footing or just pour the concrete on the gravel bed. Any re-bar necessary? The building is 16' X 20' Thanks. ron
Many years ago, I tackled this same task.
Got as far as building forms and getting pricing on concrete and rental equipment such as a powered buggy to get the concrete from the curb to the back yard.
There was a concrete contractor in the neighborhood who reluctantly agreed to look at the job site and give me a price.
Needless to say, he got the job.
Stayed home and watched the day the contractor did the work.
Smartest decision I ever made was not to lay concrete.
After watching the job, I could have written a book about what I didn't know about laying concrete.
I'll try most anything, but two (2) things I won't do:
1) Brain Surgery. 2) Lay concrete.HTH
Been there. Done that. For a 20' X 24' shop.
Hoyt W.
This is also the time to think about things like water lines and electric raceways. It is legal to run electrical type ENT "smurf tube" (the blue flex stuff) in a slab. That is cheap insurance for ideas you might have later. I would be pretty generous with it. For plumbing we use CPVC here but YMMV. The plumbing should be underground but the smurf tube can be on the ground, under the 6x6 wire.
Top on the list of "things not to do" is to try to pour a 16x20 slab yourself, unless you have previous experience working with concrete.
About eight years ago, we needed to have our front porch repaired, to the tune of about $2500 to cut out an repour a 7x8' section that had badly cracked.
As I watched the workmen cutting out the cracked section, I said to myself "I could do that. Why am I paying these guys twenty-five hundred bucks?"
And as I watched them break up the old concrete and dispose of it, I said to myself "I could do that. Why am I paying these guys twenty-five hundred bucks?"
And as I watched them build the forms, and lay in the remesh, I said to myself "I could do that. Why am I paying these guys twenty-five hundred bucks?"
And again, as I watched them pour the concrete into the forms and shovel it around into all the corners, I said to myself again "I could do that. Why am I paying these guys _twenty-five_hundred_bucks_?"
Then the head of the crew got down on his hands and knees and floated the whole thing beautifully smooth in about ten minutes.
And I said to myself, "THAT'S why I'm paying these guys."
IMHO... if you've never floated concrete before, a 16x20 slab is NOT the place to begin practicing. OTOH, if you have, then go for it.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
For a copy of my TrollFilter for NewsProxy/Nfilter, send email to autoresponder at filterinfo-at-milmac-dot-com You must use your REAL email address to get a response.
After 37 years as a Concrete Contractor I have seen it all when it comes to Do-it-Yourselfers. Have no idea how many times over the years I have been called to fix someones mess. This isn't just a sidewalk that can be brushed to hide the imperfections, a shop floor must be level, very flat and smooth. You don't want your TS (etc) rocking on an uneven floor. The smoother the better, should be like glass, making cleanup much easier. The best advice you got here was from Doug and Lew. Hire a licenced, bonded contractor. Get bids from at least 3 and check out thier work references. Low bid is not always the best choice if you want a perfect job. When the slab is finished be sure they spray on a good coat of Sealing Curing Compound, which is better then covering with plastic sheeting. If you are in hot climate, keep it watered down for several days.
My 2 cents, Al in WA
No disrespect intended here, honestly trying to help, but if you have to ask those questions you had best hire a contractor. Concentrate your efforts on what to tell the contractor you want from him.
--
Ron; I agree with the Miller brothers (?) Doug and Al. I thought about doing my own sidewalk a couple of years ago, but decided that the finish work was not for me. I am now in the process of building a garage and home and concrete work is something I refuse to do. Do it wrong and you will be reminded of it for the rest of your life and you may loose the freindship of a good neighbor to boot. DO it right (especially foundations) and the rest of the job goes a lot smoother. Leave this one to the pros.
JAW
R> Hello
I concur with many of the above comments with one exception. Forms and prework. The actual pour and finish, pay somebody. You can research the requirements based on your locale for footing requirements based on frost line. A good place to start is the local building inspector or engineering department of local community for building permits.
BUT if your clueless of the requirements and process, pay for it all!
R> Hello
Hmmm, are you saying you wouldn't lay concrete?!?
Check with your local building permit office for the requirements. When I built my shop last year, I found that almost all structures required a certified concrete plan which basically meant hiring someone to do it since they will have a licensed engineer on staff. I ended up going with a pole-barn structure for a variety of reasons but one main one was that they were except from the concrete plan rule. I still ended up hiring out all the work but not having to pay for the plan did save me quite a bit of money (about $500).
Lance
Did my own a few years ago 16 X 24. Excavated about 3in into the ground and backfilled it with sand, rented a tamper and smoothed and compacted it. Laid out slab forms along the perimeter with 2X6's and laid it directly on to of the ground so outside edges would be 5.5in thick. Pegged the forms on the outside every 3 feet. Used a level and some borrowed survey equipment to get the form extremely level. Backfilled inside the form 16 inches inside the forms with compacted sand to a height 2.5in higher than the bottom of the form to create a footing effect around the perimeter leaving the major portion of the slab 3in thick. Drove pegs into the sand spaced
8ft apart inside the forms and marked them at a height of 3inches above the sand with permanent marker. Got alot of 4X8 sheets of 6X6 wire reinforcing mesh and laid this inside the form overlapping each shhet by 6inches. Ran the cement starting at the farthest corner from the cement truck. Ran the cement along the forms from the corner each way for about 8 feet and then filled arround the closest peg to that corner up to the 3 inch mark. Filled in between the peg and the corner and used a screed (10ft 2X4 with handles on it) to level it from the corner to the mark on the peg. Repeated this around the forms ad to all pegs. Got a bull float to settle and smooth the concrete somewhat. Wait until the concrete is firm to the touch and barely leaves an indentation when applying pressure with the fingers. Get a Cement finisher with a good set of cutting blades and run over the surface to smoot out the surface...................................................................GE T A CONTRACTOR.........you'll never regret it.Bert Newfoundland
Wow, I can't help observing at this point how utterly rare it is to see this kind of unanimity in response to a question on the wreck. Not a single person, in a group that is sometimes absurdly optimistic about our ability (yes I include myself) to do ANYTHING around a house, thinks this would be a good idea. Of course now that I've said it someone will step in to say, "No problem at all, maybe go to the library and take out a book on it, it ain't rocket science..." Personally this would scare the bejesus out of me. At least when I screw up a woodworking project I have some hope of undoing the thing, or REdoing it, or at least being able to get RID of it.... A 16 x 20 concrete slab...
Perhaps I can put it in a little different perspective.
Concrete, lots of it, gets very heavy, very fast.
First is an observation that is to say the least, a little crude.
Don't f**k with the truck unless you are prepared to get run over.
The other comes from my background in sailing.
A small sailboat, fully in the right of way, according to the "rules of the road", got on the radio and asked a 1,000 ft ore boat, carrying 60,000 tons of iron ore while making about 25 knots on one of the Great Lakes which shall remain nameless.
Back came a one word response, TONNAGE!
Dealing with concrete is like wrestling a bear.
You keep wrestling until the bear wants to stop.
Same thing with concrete.
HTH
I am a manager for a small concrete construction company. I would not attempt to finish concrete. I even stayed at a Holiday Express.
If a contractor does your work the cost ofor the contractor will not be as bad as you think. You might work a deal to form the floor but don"t complain if the floor is tilted.
Also a concrete contractor can get the concrete at a lower cost than you can.
I would definiatly have a footer (12"x12" minimum) with at least one run of #5 rebar. If you have alot of weight on the building then two bars of #5. Overlap the rebar at least 24". Buy corner bars for your corners and make sure the rebar is 3-4" from the bottom of the foorer.
Make sure you have recesses at the doors either as a 3/4" lip or a sloped recess. This will keep water from blowing under the doors. Make sure the contractor cuts control joints within 24hr.
If you are framing the walls or installing a metal building go ahead and install anchor bolts in the footer. We poured a slab a while back where we took a PT 2x4 and screw it around the inside of the forms to form a ledge. Then we drilled holes for the anchor bolts. After the pour we removed the screws and PT boards. The walls were built using the PT as bottom boards. When completed the walls just fit perfect on the anchors.
Hope this helps.
I'll take the middle road.
It really is not that hard if you know what to do, have the proper tools, have a plan, and have some help. I poured a 16 x 32 patio, but I did it in two pours. I had help of someone with experience. It has some pitch, but the finish is not the same as I would want in a shop.
My advice: If neither of you has done this before, get the help of someone that had done it. I assume you will be using reddi-mix as you'd have to be nuts to mix that much concrete even with a rented mixer. You will need about 4 yards. You must also have a plan for the excess.
There is no second chance if you have a problem. It is not just the cost of wasted material if you screw up, it is th e cost of removal. At least one person must have experience and take charge of the operation. Ed snipped-for-privacy@snet.net
Where to start!
Lots of great info already, and perhaps you're beginning to see how much knowledge is needed. Well guess what, it's not just knowledge, but skill as well.
16X20 is a large project to do as a first timer. Breaking it into to two 16X10's is an execellent suggestion. Piece of cake if you're a finisher by trade, but a sizeable job for a newbie.So far no one has mentioned the fact that you will need to screed the concrete, use a jitterbug to press the aggregate down, float the surface, edge the corners, joint it, and smooth it out. Oh yeah, all the while fighting to keep the surface flat and level.
Around my neck of the woods (CA,) I wouldn't consider anything less than joints 6' on center. Don't let anybody fool you. Concrete is hard and it will eventually crack. Better to direct those cracks into a joint than have them go where ever they want to go.
Even with the wire mesh, I would consider #3 rebar or better every 30" oc in a grid pattern. That will keep any cracks from lifting, and rebar is just not that expensive.
I'm a farm boy who has poured concrete at least 30 times over the last fifteen years. I'm now at a point where I could do the job you've described with another person of the my caliber.
My tenth job (by myself) was a 10 x 12 shed poured in much the same way as described below. It was a hot day, and the concrete ran about two cu.ft. short. I busted my butt on that job -- mixing the needed 2 feet by hand when I should have been screeding and floating. By the time I finished mixing and pouring, the concrete was firming up, and there was very little I could do to salvage the project. It is ugly, and if it hadn't been a shed, I would have ripped it out.
The best suggestion I can give you is to try a small sidewalk first. For once thing, you don't have to finish on knee boards, and if you don't like it, it's easier to rip out.
"Salthead"
Yes - and while you are busy learning to do all this stuff for the first time ever, the concrete will be getting very hard and completely unreworkable.
- Nate
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