Hardwood Floors on a Concrete Slab, in a Condo or Under HOA Rules in San Diego: What Changes

Most San Diego houses built after the 1950s sit on a slab-on-grade foundation, and nearly all condos sit on a slab or a concrete deck. Older homes in Point Loma, North Park, Mission Hills and Coronado are the exception: raised foundations with wood joists and a plank or plywood subfloor, which is why their original red oak was nailed down.

Solid hardwood is installed with nails or staples driven through the tongue into wood. Concrete does not take a nail, so solid planks cannot go straight onto a slab. That single fact drives every decision below.

Tidal Flooring installs hardwood over concrete three ways. The right one depends on the product, the building and the budget.

Concrete holds and releases water for the life of the building, and a slab that looks dry can still push enough vapor to cup wood or fail an adhesive. Before any route is chosen, the slab is tested. The two common methods are the calcium chloride test, which measures the vapor leaving the surface over a set period, and in-situ relative humidity probes, which are drilled into the slab and read its internal humidity. Flooring and adhesive manufacturers publish the limits their products accept, and the readings are compared to those limits, not to a rule of thumb.

If the slab reads high, the fix is a moisture-mitigating primer, an adhesive rated as a vapor barrier, or in some cases a change to a floating floor with a vapor retarder under the pad. Slabs under kitchens, baths and former garages are the usual offenders. The test results belong in your file next to the estimate.

Hardwood needs a flat surface, not a level one. A slab can slope toward a drain and still be fine; it cannot have humps and dips that leave boards unsupported. Manufacturers state a flatness tolerance over a 10-foot span in their installation instructions, and the installer checks the slab against that figure with a straightedge before anything is mixed or opened.

High spots are ground down and low spots are filled with a cementitious patch or self-leveling underlayment. San Diego market guides price subfloor prep at about $2 to $5 per sq ft in 2026, which is why two quotes for the same plank can differ once one installer has looked at the slab and the other has not.

Wood arrives at the moisture content of the warehouse, and the house is somewhere else. Acclimation lets the boards settle to the room before they are fixed in place, so the seasonal movement afterward is small. Every manufacturer publishes its own instruction: how long, in what conditions, with the house's heating or cooling running as it will be lived in.

The period is typically measured in days, not hours, and the installer confirms it with a moisture meter on the boards and the subfloor rather than by the calendar alone. Engineered products need less than solid; some rigid-core products need almost none. Follow the sheet for the product you bought, because the warranty does.

A condo adds a second set of rules on top of the manufacturer's. Most CC&Rs set a minimum sound rating for hard flooring in units above another unit, written as an IIC (impact insulation class) for footfall and sometimes an STC (sound transmission class) for airborne noise. The association approves an underlayment that meets the number, usually by asking for the manufacturer's test letter, and often requires written approval of the whole installation before work starts.

Then come the building rules: work hours, elevator reservations and protection, where debris goes, and a certificate of insurance naming the association. Tidal Flooring provides the certificate and the underlayment documentation; the owner usually submits the application. Allow time for the board to meet. Floating engineered over an acoustic pad, or LVP over the same pad, is the usual condo answer, because a glue-down floor needs an acoustic membrane under the adhesive to reach the rating.

In houses and apartments built before about 1980, lifting carpet or old vinyl sometimes reveals 9-by-9-inch floor tiles, or a black adhesive left where tiles once were. Both can contain asbestos. The material is not dangerous sitting still; it is dangerous when it is sanded, ground, broken or scraped, which is exactly what floor prep does.

Have suspect materials tested by a certified asbestos consultant before anyone disturbs them. If the result is positive, removal is done by a licensed abatement contractor, and the San Diego County Air Pollution Control District regulates asbestos removal. Tidal Flooring stops and refers at this point rather than grinding through. In some cases the old tile stays in place and a new floor is floated over it, a call the installer and the consultant make together.

Flooring over a slab is priced as the plank plus what the slab needs. San Diego market guides published in 2026 put removal and disposal of the old floor at about $1.50 to $5 per sq ft and subfloor prep at about $2 to $5 per sq ft; a sleeper or plywood system for solid is a separate line, and asbestos testing and abatement are quoted by the specialists who do them. The installed range for the hardwood itself is $8 to $18 per sq ft, Swell's planning range and the figure San Diego guides agree on.

Ask that the estimate list the moisture test method and result, the flatness check, the leveling allowance, the adhesive or underlayment by name, the HOA documentation and the acclimation plan. In the City of San Diego new flooring needs no building permit, so the HOA letter is the only approval, and it is the one that stops a job on day one if it is missing.