Est. 1998 — 27 years of woodworking knowledge
New shop concrete poured
john lucas
It's taking shape. They said it will be about a week before they can get back to it but then it should only take a few days to get the building up. The insides are up to me and my electrician so it might take a while but at least it's moving. 
Re: New shop concrete poured
John K Jordan
Great! It's nice to see progress. Don't forget to put up some construction progress pictures!
JKJ
Re: New shop concrete poured
George Balock
Congrats John. That didn’t take long.
Re: New shop concrete poured
Barry Irby
Congrats. It will be good for it to cure for a week anyway. It would be wise to keep it wet, it will cure stronger.
Re: New shop concrete poured
John K Jordan
I always hose it down then cover with plastic sheeting, let cure for a week minimum. When I was a concrete inspector/tester I learned how much stronger concrete can get with time. 30 days wet really makes a difference, but not needed for a floor slab.
JKJ
Re: New shop concrete poured
Sam Scalzo
What size will it be?
Re: New shop concrete poured
Barry Irby
I used to be in commercial construction and a home builder after that. Poured acres of concrete, literally acres.
I started to suggest covering it with poly, but figured it would be a waste. At this time of year probably doing nothing will produce a floor entirely adequate for a shop. John has enough to do what with moving and all, but I figured wetting it occasionally for a few days might help and couldn't hurt. It's March and if its dry and windy there it might help. OTOH, we have had so much rain we could grow rice. 45 degrees is ideal for concrete and I doubt he will get a hard freeze in time to hurt it.
So John, hose it down or don't worry about it, you can't go wrong.
Re: New shop concrete poured
Reed Gray
In the hot summer time, we would hose the slabs down, and best to keep wet for a week or so. Cool high humidity weather is best for curing a slab. The plastic can 'steam' it a bit in hot weather.
Only 2 guarantees you can give for concrete is 1) it will crack, and 2) no body is going to steal it.....
robo hippy
Re: New shop concrete poured
John K Jordan
>>> Only 2 guarantees you can give for concrete is 1) it will crack, and 2) no body is going to steal it.....
My concrete finisher guaranteed it will set up as well as crack. After I told him he added the theft line item.
My shop slab is 24x62 with a couple outdoor extensions. I installed rebar on a 2' grid in the main shop and 1' grid in the maintenance end. The finisher cut shallow expansion relief "joints" every 12', all of it welded. (It's easy to go crazy if you are not paying for someone's labor.) He visited several years afterwards and was surprised/pleased to find no cracks except for almost microscopic cracks where expected, in the expansion cuts. I did keep it under wet plastic for over a week and since the roof was up it was mostly protected from the sun.
JKJ
Re: New shop concrete poured
Barry Irby
A friend of a friend builds warehouses for giant companies like Amazon. they use very tall robotic pickers to remove items from the shelves and in many cases to pick up and deliver the shelving units to human pickers. Because the robots are very tall and have a fairly small footprint the floors must be extremely level/flat or the tops of the robots would tip and sway. They pour the concrete to very tight tolerances and then may still have to grind them. they are measuring to a few hundredths in four feet.
I realize this has nothing to do with nothing, but I thought is was interesting. I poured a runway once. the test was, after it rained we walked it and any puddle, we threw a quarter in it. If water covered the quarter, we had to re pour it.
It's 24x30.
john lucas
A little smaller than my previous shop and I also has 2 outbuilding filled with wood, photo gear, metal, and all my parts bins. That all has to fit into this slab although the extra extension to hold my dust collector is a foot wider and may allow me to store some blanks in there.
Re: It's 24x30.
mikeee12345
With 3 floors you should have plenty of room, make sure you install an elevator. :-)
Re: New shop concrete poured
Reed Gray
Well, most of the time it sets up.... One local concrete dispatch place always seemed to have problems. Some times normal set up, some times setting up in the chutes, and some times you could pull the stem wall forms the next day and the concrete would slump.....
I did a couple of slabs with fiber mesh, one name for it anyway, but micro fibers. Probably the most crack resistant mix I have seen, some times better than rebar. Wire mesh is nasty and belongs in the scrap heap, unless you use the sheet stuff rather than what comes in rolls....
I have seen the laser screeds in use. pretty fancy machines that take most of the work out of the slab pours. You can feel the ground shake a good distance away... More toys!!!!
robo hippy
Re: New shop concrete poured
John K Jordan
>>>Well, most of the time it sets up.... One local concrete dispatch place always seemed to have problems.
That concrete supplier better not guarantee it setting then! I've never seen it not set up but have seen it set up without the spec strength. We made cylinders and took enough for subsequent testing after curing for intervals in a mist room. If the cylinder still failed after the final test it had to be removed and re-poured. There was a lot of opportunity for a dishonest inspector to make money to lie about the test. I remember one parking garage that had to be nearly dismantled when the footers failed all tests even after a month curing!
I like the fiber mixes but I always use rebar plus heavy wire mesh. I built one corner of my shop over fill but with way I reinforced it the dirt under that corner could wash away and still hold the weight of a vehicle. I also agree with the uselessness of roll mesh, even if embedded at the proper position in the slab which is rarely the case. Never use plastic chairs - finishers tell me how they collapse when they walk on them, pushing the wire/rebar to the bottom of the slab where it's about useless.
JKJ
Re: It's 24x30.
John K Jordan
That actually doesn't sound like bad size. High shelves and a step stool should help.
The wood area of my shop is 24x40 but that space also includes my dust collector/compressor closet, a corner cut out for a little weld shop, and an office area. You should have a lot more room inside than mine! (I did recently expand my wood storage into the back end of the shop to give more room in the wood end.)
JKJ
JKJ, plastic chairs, 'splain please!
Not JKJ,.....
Barry Irby
but "Chairs" Support the reinforcing steel inside the concrete while it's poured. For structural slabs the steel needs to be near the bottom and another layer near the top, thus low and high chairs. They are often made of metal, small slightly serpentine rods with a series of legs that support the rods that in turn support the steel. The steel chairs usually have plastic covers on the feet to keep the steel from being exposed on the bottom of the slab. Plastic chairs are similar, but can be flimsy enough that they get damaged during the pour. Sometimes stepped on. The steel gets moved out position and the slab may be weakened.
The reason the reinforcing steel is "buried" in the concrete is so the concrete gets a full grip on it and thus the strength, but also to help keep moisture away from the steel, rusting it and destroying the bond. (A huge topic)
Re: Not JKJ,.....
Reed Gray
Always used the cinder block ones with feed sack wires, or the knock out parts of the cinder blocks themselves. Ever see post tension slabs? Stainless cables about 3 feet on center. After curing for a bit, they put up to 10,000 lbs. of tension on the wires. Your house or shop could slide to the bottom of the hill after the big earthquake, but the slab would be in one piece.... Developed for some of the swamp lands in Texas. We have a lot of clay wet lands here where soil volume can change 30%+between wet and dry seasons....
robo hippy
Re: JKJ, plastic chairs, 'splain please!
John K Jordan
Barry explained well. I supported all my rebar on broken up pieces of cinder block, sized to put the rebar in the right place in the concrete. The guys pouring and finishing joked at first about the effort I put into the forms and rebar but afterwards wanted to know if I would come and do the prep when they did built their own shop. The rebar didn't even sag when they walked on it.
BTW, when you buy rebar go to a real steel supplier. The price was 1/2 of what the big box store sold it for. Fortunately, Home Depot matched the price with my receipt from the supplier, handy when I needed a little more since they were closer.
10-4 on the "chairs" but never...
JamieDonaldson
...heard that terminology used before. In my limited concrete experience I used bricks for rebar and grid supports.
Whoa!, 30%????
Barry Irby
Expansive clay/shrink swell soil. We have some of it locally, but AFAIK none of it moves that much. There are two major subdivisions (about 6000 Houses) Built on it locally. As a Home Inspector I dealt with it for years. Unfortunately, it never goes away, so every time we have the wettest or dryest season on record new problems show up. We excavated beside one house and the soil under the footings had subsided enough you could stick your arm under the footing. I did not.
The pretensioned and post tensioned concrete can do amazing things.
OTOH concrete reinforced with ordinary steel is destined to fail in about 50 to 75 years. Moisture gets to the steel almost no matter what they do. That's why so much of the infrastructure need serious repair. The interstate system and other major projects came about in the 50's and soon after.
rebar corrosion
John K Jordan
>>>OTOH concrete reinforced with ordinary steel is destined to fail in about 50 to 75 years.
Thus the move towards using stainless steel rebar, perhaps cheaper in the long run.
Re: Whoa!, 30%????
Reed Gray
We did an apartment complex one year. In the summer you had trouble pounding steel stakes into the ground. In the winter, we were hand pushing 8 foot studs into the muck to hold up 30 inch forms.
Never heard of stainless rebar. I know on some coastal jobs they had special epoxy coated rebar since water soaks all the way through the concrete and the rebar would corrode. I would think stainless would have the same problem. I have torn out some concrete that old, and the rebar and wire looked almost new. Guess it depends on the minerals in the water.
robo hippy
Re: New shop concrete poured
Paul grover
My shop is 20x30 with 9 ft ceilings. My floor has 1 x3 sleepers 2 ft on center,just floating,thenI laid 3/4 plywood screwed to the sleepers. Great on the feet and allows wires to be fished to machine locations.allow 6” at ends of sleeper for ventilation. Just a thought.
stainless
John K Jordan
Some concrete is formulated to help protect from corrosion. Some people say eliminating that is one of the reasons to use stainless. They have other reasons, but of course they are trying to sell you some https://stainlessrebar.com/
It would be interesting to learn how they build for corrosion in salt water environments, such as the replacement bridge over Oregon Inlet in Hatteras, NC, supposedly built to last 100 years. It was amazing to watch it go up.
https://www.youtube.com/watch?v=71lcD-fbuNM
https://www.newsobserver.com/news/traffic/road-worrier-blog/article57707008.html
JKJ