Concrete Slabs and Foundations in Arlington, TX and the DFW Metroplex

Most of our slab work is a pad for something that arrives afterward: a metal shop or storage building, a prefab shed, a detached garage or workshop, a carport, a hot tub, a generator or an AC condenser. We work from the building's footprint and anchor layout, so the slab matches the structure instead of the structure being shimmed to fit the slab.

Carport pads are a family job. We pour the slab and set the anchor bolts to the post layout, and CJM Metals builds the steel carport on top of it. One crew owns the concrete, one owns the steel, and the two are planned together so the posts land where the bolts are.

Equipment pads are small but they are not casual. An AC pad that tilts toward the house sends condensate at the foundation, and a generator pad poured on loose fill will rock under the first hard start. We compact the base and pitch the pad away from the structure, same as a big slab.

A slab that only carries foot traffic and a lawn mower can be 4 inches thick. A shop floor that will see a vehicle, a lift, or a loaded trailer should be 5 to 6 inches, and anything that carries a heavy point load gets a thickened footing under it. We size the thickness to what will actually sit on the slab, and if a building supplier or engineer gives us a spec, we pour to the spec.

Reinforcement is a rebar grid, typically #3 or #4 bar at 16 to 24 inches on center both ways, tied and held on chairs so it sits in the middle of the slab instead of on the dirt. Rebar does not stop concrete from cracking; it holds the crack tight so the two sides stay level. Welded wire mesh does the same job only if it is lifted into the slab, which is why we prefer bar you can see on chairs at the pre-pour.

For a building, we pour a monolithic turn-down slab: the edge thickens to 12 inches or more with two runs of bar in the bottom of the beam, poured in one piece with the floor. That thickened edge is the footing for the walls, and pouring it with the floor means there is no cold joint for water to find. Interior thickened sections go under post lines and heavy equipment.

The ground under a slab in Arlington is clay that swells when wet and shrinks when dry. The slab can only be as stable as what it sits on, so we strip topsoil and organics, grade to a consistent depth and compact a layer of crushed base, usually 4 inches, so the slab bears evenly instead of bridging soft spots. Pouring directly onto raked dirt is the fastest way to a cracked floor.

Under an enclosed building we lay a polyethylene vapor barrier on top of the base before the steel goes in. Without it, ground moisture migrates up through the slab and shows up as sweating floors, rusted tools, peeling paint and mold on anything stored against the wall. Open carports and outdoor equipment pads do not need one.

Drainage gets decided before the forms go up. Finished slab elevation sits above the surrounding grade, the ground slopes away from it, and where a slab meets an existing driveway or the house we set an expansion joint so the two can move independently.

Anchor bolts, straps or post bases go in wet, set to the building's bolt pattern and held to line while the concrete takes its set. Drilled-in anchors after the fact work, but cast-in bolts placed to the manufacturer's layout are stronger and save the installer a day. Send us the anchor drawing and we set to it.

Concrete shrinks as it cures and it will crack; control joints decide where. We cut joints at roughly 2 to 2.5 times the slab thickness in feet, so a 4-inch slab is jointed every 8 to 10 feet and a 6-inch slab every 12 to 15, cut within the first day before the slab decides for itself. Isolation joints separate the slab from posts, walls and other concrete.

Plan the build schedule around the cure. You can walk a slab the next day and frame light walls in a few days. We ask that cars and pickups stay off for 7 days on a 4 or 5-inch slab and 10 days on a 6-inch slab, and that heavy equipment and loaded trailers wait 14 days on a 4 or 5-inch slab and 28 days on a 6-inch slab, which is about when concrete reaches full strength. Details are on the curing time FAQ.

The City of Arlington's own DIY permit guide says a storage shed over 100 square feet requires a permit, so only the smallest sheds are exempt. A larger shed, a shop or a detached garage needs a building permit before work starts, carports and patio covers have their own placement and permit rules, and even an exempt shed still has to respect setbacks, easements and any HOA rules. Confirm what your lot allows with the City's One Start Development Center at 101 W. Abram St, 817-459-6502.

For a larger garage or workshop the City may ask for a foundation plan, and on expansive clay it is common for a sealed slab design from an engineer to be requested; confirm with the City of Arlington what your project needs. Many metal-building suppliers ship engineered foundation drawings with the kit; if yours does, we pour to those. If not, we will tell you up front whether your project needs an engineer and can point you to one.

We walk you through the concrete permit process and put in writing who is pulling the permit. If the slab supports a structure, confirm the permit path with the City before you order the building, because the foundation is the first thing the inspector looks at and the hardest thing to change.