Worked case: a 500 sq ft great room in wide-plank engineered white oak — what happens and what it costs

The scenario

Picture a two-story house in one of the newer Otay Ranch villages, with a homeowners' association. The ground floor is a concrete slab covered with large tile in the entry and kitchen and carpet in the family room. The owners want one continuous wide plank from the front door to the patio.

Measurements give about 500 square feet. Once the carpet and tile are out, a straightedge laid on the concrete shows a shallow low spot near the kitchen island that would show through a wide plank, so the slab is ground and patched.

New concrete can hold water, so a probe test is done in the slab before any adhesive is spread, and the reading is compared with the written limit from the plank maker. If it is above the limit, the plan changes to a moisture barrier or a floating floor.

The association asks for notice before work, and the CC&Rs are checked for any rule on flooring changes. The planks are brought into the house to sit for the time the maker states, then glued down in the direction the owners prefer, with a small gap left at each wall.

Thresholds are fitted at the patio door and at the hallway where the floor changes to carpet.

What the job involves

1. Tile and carpet come up, the adhesive is scraped, and the slab is checked with a straightedge for flat.
2. Low spots are patched or ground, and an in-slab humidity probe test is read against the plank maker's limit.
3. The planks acclimate in the house for the time the maker states.
4. A moisture barrier and adhesive go on, and the planks are pressed in with a gap at the walls.
5. Baseboards or shoe molding are refitted and thresholds are set where the floor meets other surfaces.

Materials and tools

• Slab grinder or patching compound
• In-slab humidity probes and reader
• Moisture barrier, adhesive and a notched trowel
• Engineered white oak planks, spacers and a flooring roller

Add-ons often paired with this job

• Slab moisture test — +$250–$650. An in-slab humidity probe test is a flat line for a single large room.
• Subfloor leveling or patching — +$300–$1,300. Grinding and patching a low spot is a flat line; the size of the low area sets where it falls in the range.
• Transitions and thresholds — +$100–$400. Thresholds at doors and where floors change height are a flat line.

Why it is done this way

Wide planks make a floor look calm, and they also expose every flaw in the slab. That is why the job pairs the highest-priced plank in the calculator with a slab surcharge, a test and leveling.

The slab surcharge covers the moisture barrier and adhesive work. The test, leveling and thresholds appear as flat lines because they depend on the room and the concrete, not on the number of square feet.

The same arithmetic applies to every install: the plank rate plus the subfloor surcharge, multiplied by the area, plus whatever flat lines the room needs.

What would change the price

• The probe reading is too high and a different barrier or a floating floor is needed.
• The slab needs more grinding than a single low spot.
• Stairs or a second room are added.
• The owners choose a standard plank instead of a wide one.
• The association requires an acoustic underlayment.