Concrete floors and slabs for KC-metro barndominiums

Four things, every time:

• Frost-depth footings. Johnson County building officials' residential foundation guideline sets the minimum frost footing depth at 36 inches below grade. Our engineering always follows the requirement of the jurisdiction reviewing your parcel.
• Soil-appropriate design. The same guideline points out that the area has a lot of clay soil with varying expansive behavior. It recommends keeping soil moisture steady during concrete work, because slabs placed on dried-out clay can crack and heave once the soil gets wet again. Unusual sites, such as fill, slopes, high water or rock, get a soils report and an engineered foundation.
• Load planning for shop zones. A tractor bay or vehicle shop doesn't carry the same loads as a bedroom. We thicken and reinforce the slab where equipment will sit, and we design column and door footings to match the building engineering.
• Vapor control under living space. The guideline calls for a 6-mil polyethylene or approved vapor retarder, with joints lapped at least 6 inches, between the slab and the base course in living areas. It isn't required under garage slabs. In a shouse, we handle the living side and the shop side on purpose instead of copying one detail across the whole pour.

The slab is engineered as part of the building, not poured as a generic pad.

Everything that will ever need to come up through the floor:

• Drain, waste and water lines for every bathroom, kitchen, laundry and shop sink
• Floor drains in wash bays or shop areas, sloped to them
• Electrical conduit for islands, shop equipment and any detached circuits
• Sleeves for future lines you're not sure about yet (cheap now, expensive later)
• Radiant tubing and its zone layout, if you choose in-floor heat
• Anchor and embed locations for lifts or heavy equipment

We walk the layout with you on paper and again on site before the inspection and the pour. After the pour, moving a drain means cutting concrete. That's why we lock the floor plan before the slab, as described in our build process.

Hydronic in-floor heat is popular in KC barndominiums because big open rooms with tall ceilings are expensive to heat with forced air. Radiant puts the heat in the floor where people actually stand and work.

What you decide before the pour:

• Zones. Living areas and the shop usually run on separate zones so the shop can be kept cooler.
• Insulation under and at the edge of the slab. Heat should go up into the room, not down into the ground.
• Backup or supplemental heat and cooling. Radiant doesn't cool. Most homes still need a plan for summer cooling and humidity.

If you're unsure, we can lay tubing now and connect the system later. Pouring without tubing closes that door for good.

If the slab is going to be the finished floor, choose the finish before the pour. Polishing needs a flat, carefully finished surface, and saw-cut control joints will show in the final floor.

Mixing finishes often makes sense: polished or sealed in the living space, a coating in the shop, and covered floors in bedrooms. Pick the finish by room, not for the whole slab.

The slab goes in early, and everything else gets built on top of it: lifts, scaffolding, drywall, framing and trades with tools. If it's going to be your finished floor, we:

• Cover it in work areas once the shell is up
• Keep fuel, paint and hydraulic equipment off unprotected concrete
• Schedule final polishing or coating near the end of the job, after the heavy trades are out
• Repair and touch up before closeout, not after move-in

Site work, the foundation and the slab are their own line in our phase-by-phase pricing. They're never buried in a shell price. Our Kansas City barndominium cost guide shows how we break a project into phases and why a kit or shell quote often excludes the foundation entirely.