New Shop Building

Well, after thinking about it for more than a decade I broke ground
this week on my new shop. I took so long because I wanted to wait
until lumber and steel prices were at their peak...arrgh.
Here's what I learned so far. I didn't spend near enough time
figuring out exactly what it would cost and of course nearly all of my
estimates are low. I wanted to go with concrete block (CMU) walls
partly because we live in a high fire hazard area. I knew it would be
expensive, but got some low estimates that re-assured me. After the
plans were drawn up and the permit issued and I got some firm bids,
the low estimates got pretty darn high. The building permit alone was
over $900. It's gotten so civilized around here that the chances of
getting away with a non-permitted structure were pretty slim.
Also totally underestimated the amount and cost of the base material
that needs to be compacted prior to the concrete pour. I'm planning
to pour a 5 inch deep floor with 5 sack mix and fiber additive. I'm
not sure of the benefit of going any more than 5 inches, but may
decide to go to six. I don't know exactly how I'll have machines
located, so I can't realistically make the floor thicker underneath
them.
Another issue is whether to use all licensed contractors. My neighbor
is a licensed contractor and he suggested that he himself would never
hire a licensed contractor since so much of the money goes to
insurance payments and very little goes toward a quality job. In his
view an unlicensed contractor will do a better job for less. The
downside of course is the risk of someone getting hurt while working
on my property. I guess I could agree with them in advance that
anyone getting hurt gets dragged out back, shot and buried :-).
Bob
Reply to
Bob Thomasson
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Put lots of rebar in the floor. I used the fiber, and don't think it did anything except lighten my wallet. It certainly didn't stop cracking...Paul
Reply to
PJ
Neither will rebar, if you don't also cut some control joints (unless very small, any slab will crack - you simply want to tell it where it's OK with you that it should crack). I have both rebar and fiber in my slab, and there are cracks running out from the ends of the control joints (where the saw couldn't cut right up to the wall). No cracks on the face of the slab (so far anyway), so I assume that the contol joints have done what they are supposed to do.
Reply to
Ecnerwal
You didn't say what part of the country you're in. If you're north of the Mason Dixon line, put hydronic heat tubing in the floor, even if you don't plan to use it now. Installing just the tubing is very inexpensive and leaves open your option for the best heating system their is. Unless you put insulation under the floor, this would only be a supplemental heat.
Karl
Reply to
Karl Townsend
The plans call for control joints every 12 feet but the concrete guy suggested going to joints every 10 feet. They are going to be sawcut to a depth of about three inches. The slab and footing will be poured in one flat monolithic pour. The concrete guy also suggested using wire mesh reinforcing in the floor in addition to the fiber additive.
The most important part seems to be to get a good compacted base that won't settle or expand with moisture to place the concrete on.
Thanks for your comments.
Bob
Reply to
Bob Thomasson
The base material thickness, prep, and compostition are CRITICAL to a good slab. It will depend a lot on your soil and frost condtions but the amount you need will scare you. My clay soil and 4' of frost needs 12" for a small slab and 24" for a larger one. And it needs to be compacted down in layers using a vibrator packer.
Be sure they use a 4mil (or more) plastic sheet under the concrete to help control the moisture migration.
Bob Thomass> The plans call for control joints every 12 feet but the concrete guy
Reply to
Roy J
Karl,
Mason Dixon line, put hydronic heat tubing in the floor, even if you don't
Reply to
Bob Thomasson
while your at it put down some insulation around the outside edges
Reply to
jran
cracking...Paul
The beauty of rebar is even if you get cracking (and you will), it prevents the slab from shifting. My shop floor is a full 6-1/4" thick, 6 sack mix, with rebar on 12" centers two ways. Instead of cutting the floor, the guy that finished it used a bull float and scored lines approximately 12' apart, then finished over the score lines. That provides a weaker zone for the crete to crack where you want it to. It works, and you don't get a big line that fills up with crud like you get from saw cutting. I have cracking, but only where he had scored and finished, so it's very narrow, and there has been absolutely NO shifting of the crete. The floor is now 5 years old. I highly recommend rebar, although it does take a lot of time and money to install it. If you do it yourself, it's not all that bad. In my opinion, it's worth it. Cheap insurance when you consider the cost of the job overall. I fully agree with a properly prepared base, too. Ours was compacted well as the fill was installed, then it sat through a full season of winter rain in Western Washington. We used rock for fill, 3/8"- with fines. Worked out great.
Harold
Reply to
Harold & Susan Vordos
My shop has just such a heating system. I fully agree. Not only is it comfortable, but the overall environment is much dryer, thanks to the heated concrete. The typical shop floor can have 3/8" diameter tubing in 200' runs on 18" centers and do a great job. I used the rebar I mentioned in my other post (above) to tie the tubing in place. In my case, the tubing wasn't cheap, though. Heatway, which is now Watts Heatway, uses a rubber tubing (hose) instead of plastic. They have it made especially for heating. It's three ply, with one of the layers an oxygen barrier. It's important that closed hydronic heating systems do not absorb oxygen. The system has been running for 4 years now and has worked flawlessly once I got it balanced.
Harold
Reply to
Harold & Susan Vordos
Not just the outside edges. Code calls for an R10 under the slab when you heat hydronically in slab. It may cost a little to install the insulation, but it will pay for itself in short order, especially with energy prices headed higher and higher. If you plan to run a fork lift in the shop, or install some very heavy machinery, the insulation comes in grades, up to 100 PSI. The typical stuff you see at the lumber yard is usually either 15 or 25 PSI. I used 40 for my shop, which appears to be more than adequate. I have a fork lift that weighs just under 10,000 lbs, and it can pick three tons. I've hauled one piece inside that taxed the capacity and got no cracking or settling. I did do one thing to help prevent edge cracking, though. I have rebar on 6" centers in the door ways, in a couple feet or so, where you might get edge cracking. A few bucks spent before the crete is poured can save a lot of heartache later.
Harold
Reply to
Harold & Susan Vordos
After vacuuming up the dust from my sawcuts, and squeezing in 2-1/2 tubes of caulk, I don't have any big lines that fill up with crud, either. These cuts are only 1/8 inch wide, so it's not like you're going to drop a wheel in them..
I certainly thought it was pretty reasonable in the overall cost scheme of the project, but I did install my own. You simply cannot go back later and put the stuff in.
I also put extra steel (both bar and mesh) in the at doorways.
Reply to
Ecnerwal

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