Barndominium slab construction in Tennessee

Barndominium slab construction in Tennessee

Barndominium slab construction in Tennessee comes down to three calls made before the concrete truck rolls. What each zone carries sets the thickness. The soil sets how hard we pack the ground, and the building plan sets the steel. A typical West Tennessee barndo slab is 4 inches under the living space and 5 or 6 under the shop. Get those calls right and everything on top stays put.

We pour barndo slabs across Tennessee, with teams in Memphis, Nashville, Knoxville, and Chattanooga. This page leans west. Our Memphis team works from the Memphis metro east on I-40 to Jackson and north through Dyer and Lake counties to Dyersburg. The Tennessee state overview shows the rest.

Want polished concrete as the finished floor? Then the slab spec changes on pour day, not after, so read our Tennessee barndominium polished concrete page before anyone orders concrete. National price ranges are in the barndominium slab cost guide, and the basics are in the barndominium slab guide.

How does West Tennessee soil shape the slab?

West Tennessee soil changes from county to county. Matching the slab to the ground costs little at planning; fixing it after the slab cures costs a lot.

Memphis metro and the river plain. Shelby, Tipton, Fayette, and Lauderdale counties sit on silt and silty clay that the Mississippi River laid down. It drains slowly, holds water near the surface, and pushes vapor up through the slab for years. Pour on loose ground, and the slab sinks in spots in its first two to five years. It shows most at inside corners and along plumbing trenches. So we strip the topsoil and bring in a rock base where the native soil can’t hold. Then we pack it to 95 percent standard Proctor density per ASTM D698, a lab test for how tight a soil can pack.

I-40 and the Jackson plateau. Madison, Chester, Henderson, and Haywood counties have a thick cap of loess over silty clay. Loess is a fine silt the wind laid down. It holds more weight than the river plain, and the water table sits deeper. That makes the design simpler.

Dyersburg and the north. In Dyer, Lake, Obion, and Gibson counties, parcels near the Obion, Forked Deer, and Mississippi rivers sit on the softest silt we work on. The water table there is the highest we see, too. Many sit in the old floodplain. There, we lean toward a stem wall or a raised pad, with clean rock under the vapor retarder so water can’t wick up.

A typical West Tennessee barndo slab is 4 inches thick under the living space and 5 or 6 inches under the shop bay. It thickens to 8 to 10 inches under each post-frame column or two-post car lift. On river silt, we use #4 rebar on a 16-inch grid, tied at each crossing. Unbroken bars wrap the edge and follow every column line to meet the New Madrid quake rules. The edge turns down 12 to 18 inches below finished grade. That’s deep enough. Winter frost here rarely gets more than a few inches into the ground. The slab edge thickens to 16 inches to stiffen it and spread quake loads into the soil. Last, a 10 to 15 mil plastic vapor retarder goes right under the concrete on every site, because humid Mississippi basin air pushes vapor up through the slab all year.

What does the pour sequence look like for a Tennessee barndo slab?

Five stages take the slab from bare dirt to a cured surface ready for framing. Half the craft is timing them around West Tennessee weather: humid summers and short dry spells in spring and fall.

1. Site prep and forms. Topsoil comes off down to firm ground. We pack it to 95 percent standard Proctor and set the forms. Silty Memphis sites usually need a rock base brought in. Plumbing trenches get refilled in 4 to 6 inch layers, each one packed, so the slab won’t sink along the trench over the first two winters.
2. Vapor retarder and steel. The 10 to 15 mil plastic sheet lies flat with every seam taped. Then the rebar grid goes up on chairs at mid-depth, and the plumbing and electrical rough-in gets set. Edge and column-line bars get tied and lapped to the seismic drawings before any concrete shows up.
3. Pour and screed. A 2,400 square foot barndo slab takes 35 to 45 cubic yards, poured in one day. Living areas get 4,000 PSI concrete and shop bays get 4,500 PSI, per ACI 332. We aim for a 4 to 5 inch slump at the truck. July and August pours above 90 degrees start at first light, so the finishers stay ahead of a flash set.
4. Finishing. A slab headed for polish gets troweled to FF 35 or better (FF 50 on a premium spec). FF is a measure of how flat a floor is. It gets no curing compound that would gum up a later grind. A slab going under LVP, tile, or carpet gets a broom finish or one light trowel pass.
5. Curing and joints. A 7-day wet cure under plastic, or an approved evaporation retarder per ACI 308R-16, locks in the strength. In Memphis summer humidity, we saw the joints 12 to 24 hours after finishing, 12 to 15 feet apart on a 4-inch slab.

Which foundation fits: monolithic, stem wall, or raised pad?

Three foundation types cover almost every West Tennessee barndo we pour. Soil, slope, and how close you sit to a floodplain or a bluff edge decide which one.

• Pick a monolithic slab on the Jackson plateau or a well-drained spot along I-40. About 70 percent of the slabs we pour in West Tennessee are this kind. The footing and the slab pour as one piece.
• Pick a stem wall near the Mississippi, Obion, Forked Deer, or Hatchie floodplains, or on a sloped Chickasaw Bluffs parcel above Memphis. Footings and short walls cure first, and the slab pours inside them. It costs more than a monolithic pour, but on flood-prone ground the drier floor and the option of a crawl space are worth it.
• Pick a raised pad if your parcel sits 12 to 24 inches below the planned floor. We bring in packed fill, cap it with clean rock, and pour the slab on top. It costs well under a stem wall and still lifts the floor above the old wet-season water line.

How do the columns attach to the slab?

Almost every West Tennessee barndo has a metal frame, either post-frame or red-iron steel. Where each column meets the concrete is what ties the building down.

Post-frame columns drop into galvanized steel brackets set 24 to 36 inches into the concrete. The bracket keeps the wood post off the ground and holds it down in straight-line winds. We cast each bracket in the pour from a steel-and-plywood template, so every post lands inside the framer’s tolerance. In the New Madrid zone, a closed stirrup or hooked bar wraps each bracket.

Steel columns sit on anchor bolts cast into the slab. The bolts have to match the column base plate the first time. Once the concrete cures, there’s no fixing them. We work from the fabricator’s stamped shop drawings and set every bolt in a plywood template fixed to the forms. Placement tolerance is plus or minus 1/16 inch per ACI 117.

How do we manage moisture in Memphis climate?

Two things shape a West Tennessee barndo slab more than anything else: earthquakes and moisture. The New Madrid Seismic Zone puts Memphis and the counties around it at the top of the USGS hazard maps for the eastern United States. The 2018 International Building Code makes that Seismic Design Category C or D for Shelby, Tipton, Lauderdale, Dyer, and Madison counties. That’s why the edge and column-line bars run unbroken and the edge is thicker than a quiet region would need. Moisture pushes from below. The Memphis metro gets 53 to 55 inches of rain a year and 70 to 80 percent relative humidity in the warm months. Vapor pushes up through a cured slab all year. So the vapor retarder and a tightly packed base both have to be there.

The trouble is vapor rising through the slab, not water on top. Before any finished floor goes down, we look the slab over. If it sits on low, wet ground, shows water stains, or you ask, we test it. We use a calcium chloride dome (per ASTM F1869) or a humidity probe set into the slab (per ASTM F2170). The cutoffs are 3 pounds per 1,000 square feet per 24 hours on the dome, and 75 percent humidity inside the slab on the probe. A slab over either one gets a moisture barrier primer before the finished floor goes down.

Plumbing and utility rough-in

The slab buries most of a barndo’s plumbing, its in-floor heat tubing, and the pipe for floor outlets. Once it cures, moving any of it means a saw. That’s why rough-in happens in stage 2, before the vapor retarder seals at the edge.

• Drain lines run at the 1/4 inch per foot minimum slope and stub up right where the framing plan puts the walls. Trench fill goes back in 4 to 6 inch layers.
• Water lines are PEX inside a sleeve, so a future swap won’t mean cutting the slab.
• In-floor heat tubing is tied to the rebar at chair height and kept under pressure through the pour, so any nail hole or kink shows right away.
• Floor-outlet conduit stubs up during forming, with bends set below the finished height of the polished surface.

Moving a drain in cured concrete costs three to five times what the first rough-in cost. So the crew walks every pipe and wire with the plumber and electrician before the rebar gets tied. Measure twice. Pour once.

What does a Tennessee barndo slab cost?

A slab we pour runs $5.32 to $15.61 a square foot. A 40 by 60 barndo (2,400 square feet) comes to $12,750 to $37,100 before the drive cost, our trip out to your site. The soil, truck access, the steel, and the haul from the batch plant move the price. Your number is the base pour plus the options you pick, and the online quote calculator adds them up.

• Good upland ground on the Jackson plateau and along I-40 sits toward the low end, since the loess packs without a rock base.
• Memphis-metro silt needs a rock base. We price it per job after we see the site, because the truckload count depends on how soft the silt is.
• Rebar. The quote tool’s base rebar option is #4 rebar on 18-inch centers, which adds $1.49 a square foot over wire mesh. West Tennessee slabs usually step up to the 16-inch grid, which we price per job.
• Raised pads and stem walls are priced per job after we see the parcel. Fill depth, wall height, and slope set the cost.

The drive cost is its own line on your quote. The first 40 road miles each way from our nearest team are free, and the quote tool adds the rest from your address.

Coordinated services for your Tennessee barndo

Slabs Built for the Finish means the slab pour and the finished floor share one spec. That matters most under polished concrete, since the screed, the cure, and the joint layout all plan for the polish. We also do polished concrete for the living space, concrete flatwork for the apron, and the rest of the barndominium floor catalog. Photos of finished slabs are in our concrete flatwork portfolio.

Next door, our Arkansas barndo slab page covers Ozark and Delta soils. The Texas barndo slab page covers post-tension slabs on North Texas black clay. For towns here, see Memphis, Collierville, Bartlett, Jackson, and Dyersburg on our Tennessee page. Other states are on our list of places we work.