Careful planning and finishing of concrete provide a shop floor you can live with for a long time. A smooth, durable concrete floor is literally the foundation for a farm shop. Here are 12 considerations to achieve the best work surface possible.
1. Final floor height is a necessary but convoluted calculation that’s part of initial site preparation.
“You need to coordinate with your grading contractor and your concrete contractor to work out the final floor height,” says Dave Flewelling, owner of Flewelling Earthmoving, Moville, Iowa. “Your earthmoving contractor needs to know in advance how much sand the concrete guy intends to use, and if you’re going to have any foam insulation sheets laid under the concrete for an in-floor heating system.”
2. A concrete floor is only as good as what’s underneath it.
Building crews often create ruts or holes in the compacted earth pad during building erection. If those ruts or irregularities are merely filled with sand or limestone fines prior to placing the floor, problems could appear in the future. It’s essential to relevel and recompact the base to optimize the concrete floor.
3. “Stiff” concrete is strong concrete.
“Some people pour concrete that’s like soup because it’s sort of self-leveling and easier to work with,” says Dave Harland, owner of Harland Concrete, Perry, Iowa. “Wet concrete isn’t as strong, and the extra moisture increases the chance of shrinkage that creates cracks during curing. I want concrete to come out of the truck stiff, so the floor is as strong as possible.”
4. General shop floors work well with a 1"-to-2"-wide slot drain in the center and the concrete’s surface sloped to that drain.
Wash bays, where there will be lots of debris washed off trucks and machinery, need drain pits. Some farmers design their pits large enough to use their backhoe or mini-excavator to remove sediment when the pits are full.
5. Sidewalk-grade concrete is usually rated at a crush strength of 3,000 psi.
Custom mixes that might require special handling and finishing can achieve ratings in excess of 6,000 psi. “Concrete in the 4,000-psi range works well for most
flat work on farm operations,” says Alan Sparkman, executive director, Tennessee Concrete Association. “In most cases, the best way to increase load-carrying capacity is to increase slab thickness. Going from a thickness of 4" to 6" increases the load-bearing capacity by 50% using the same mix.”
6. Some contractors recommend mixing tiny, high-strength synthetic fibers into the concrete mix rather than laying panels of reinforcing wire or a grid of rebar.
“All those fibers can provide the same strength and support as wire or rebar,” Harland says. “I prefer rebar to provide strong support under every cut or crack. Plus, when you put a smooth finish on fiber-reinforced concrete, the fibers stick up and give the floor a ‘hairy’ look. They’ll eventually wear off, or you can use a propane torch to singe them off.”
7. “Four inches and finished” no longer describes a durable shop floor.
“For today’s farm shops, I recommend 6" of concrete with ½" rebar every 2',” Harland says. “Six inches with rebar will easily handle loaded semis and grain carts that are parked or moving at slow speeds. If you’re pouring concrete that will handle equipment moving at higher speeds, go with 8".”
8. Be aware of regional differences in concrete.
“Sand in our area [glacial drift region of the Midwest] has a small percentage of expansive aggregates like coal and shale,” Harland says. “The light weight of those aggregates means they can float to the top of the slab during finishing. When a slab is hard-troweled for a shop floor, it traps moisture in the surface. Those lightweight aggregates can expand from the moisture and cause ‘pop-outs.’ They don’t hurt the strength of the floor, but it’s a cosmetic issue. We can use ‘import sand’ that doesn’t have those lightweight aggregates and avoid that problem, but the import sand costs about $25 extra per yard of concrete.”
9. Install bollards at the inside and outside corners of overhead doors.
The concrete-filled posts prevent damage to door frames. Consider installing bollards inside to protect supports for balconies or the office.
10. “Cutting” finished concrete will control cracks.
Concrete will crack, so cutting is an attempt to control where the cracks will occur. Harland recommends cutting 6"-thick concrete every 10'.
11. Joint sealant in cuts inside buildings is primarily cosmetic, but cuts in outdoor concrete slabs benefit from caulking.
“Joint sealant in outdoor concrete slabs keeps water and ice-melting products from getting into the cuts and causing problems,” Harland says.
12. Beware of concrete coatings that can flake and wear under traffic.
Sealants that soak into new concrete might not leave a glossy surface, but they reduce oil and chemical absorption and have other benefits.
Read more from Dan Anderson’s shop building series:
Start Here When Building A Farm Shop
Expert Tips to Avoid Remorse When Designing A Farm Shop
