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If you anticipate a need for longer working times,...the best thing is to tell the concrete supplier. They can add retardant to extend the working time and slow the set up. Adding excessive water will weaken the concrete. When I built my hangar (50 X 50 steel bldg with 16' eaves, made of I-beams, etc., 12/2 sloped roof, etc. ...all my own design) I needed a slab poured. I originally thought I could get a couple of buddies over to help me, but when I talked to the local gravel company (I needed to buy fill because the site was not level...it was 26" lower at the rear of the bldg than the front)....the driver of the first delivery truck began to laugh...and gave me the business card of a local crew which normally poured/worked slabs for local homebuilders. His son was one of them. They were between jobs and gave me a break on the price. (Or so they said.) Anyway, when it was all over,....I was so glad that guy laughed and gave me that business card. That crew laid out the work-site, put up the batter-boards, set it level with a sextant, set up forms, had 15 loads of crushed granite gravel delivered, and compacted it with their "bobcat" miniature dozer, laid all the steel re-bar, set out the proper reinforced perimeter walls, and the reinforced cross-beam channels (to strengthen the entire slab). The slab was to be a 4.5" general thickness, with 10" walls/cross-beams 24" deep, reinforced with 5/8" rebar. The general floor was reinforced with 3/8" rebar. They went home after an entire two days setting up, before they called for the concrete. They used six-sack concrete. The trucks arrived starting at 5AM on the third day, and by noon, the pour was over. I'd specified a drain in the center, and the plumbing was pre-laid before the pour, and the crew used long boards with one end at the outer perimeter and the inner end at the drain to "level" it such that the center drain was one-inch lower than the outer edges. They'd also set the weld-plates I'd had the local metal/welding shop build up, in the proper places during the pour. (This is a welded up structure rather than a pre-engineered bolt-together, and the uprights of the bldg are welded to plates anchored/set in the concrete.) The crew of 4 workers settled the aggregate by hand with a "walker" type shaker, then used a vibrator to shake out the bubbles/voids, etc. Then a jitterbug was used to bring it to a near final grade. By 5 PM they were using a rotary finisher (like a floor polisher with spatulas instead of brushes, to give a satin finish.) By 6:30 or so, they were opening cold beer and admiring the work. They told me to stay off it for 48 hours and not to water it. They came back the next day and poured by sloping apron with leads up to the front door opening. (It was 12' X 44', and has a brushed finish.) The next day, they came back after they got off their regular job about 20 miles away and took up their forms. They told me I could walk on it but to keep heavy equipment off it for 28 days. The total slab costs were approx. $9K. Two weeks later, Mueller Steel Bldgs delivered all my materials. I hired some off work erectors who welded up my main structure, including the girts and purlins, over a 4 week period on their off weekends. They also installed about 2/3d's of my sheet metal and insulation. Total labor came to slightly more than $1200. By this time, I'd gotten most of the education to finish the job with a buddy or two. We put up the skin/insulation on the last two walls, and all the roof. Two years later, my cousin (professional welder) and I built an overhead door of my own design. It's a rigid door made of 2 X 6 rect. tubing, measureing 44' wide by 14' tall. It's covered with insulation and more R panel, just like the rest of the bldg. The top, bottom, and ends are weatherstipped with EPDM I purchased in 14" widths, in the lengths necessary for the door. (two 44' and two 14') Folded in half and inserted below the R panel before the final screws are installed. When raised to the overhead, level position, the door is half inside and half outside the bldg. (Makes a great awning to watch the rain while enjoying a beer with my labrador.) It's raised/lowered using a $350 boat lift motor/gear. Takes 3 minutes to go full open or full closed with the flick of a switch. I wanted my own door design because I didn't like the commercial doors available for various reasons, (like they cannot be operated in wind) and also didn't care for their costs. (My door can be operated in any wind without adverse effects, and I lose only the thickness of my door, 8-inches, from the headroom.) I also have a personel door on the side of the bldg. facing my home. I have 4, vertical, opaque light-panels installed in the upper areas of the east and west walls for ambient lighting. (I didn't want such panels in the roof where they would be susceptible to hail damage and rain leaks.) Total costs of my completed hangar came to less than $26K, while virtually identical (but un-insulated) hangars at the local fly in community were costing $84K and up, with much less desireable doors (IMHO). My electrical work is not yet finished. I expect to finish it myself this year for about $600 in materials. I plan 200 Amp service for overhead lighting, wall outlets, 240 volt service for my welder and air compressor, etc. Sorry for the long post, but thought the info might be useful for planning purposes for others. Large project concrete work is best left
for those who know how and have the tools and experience. I almost messed up by trying it myself.
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