Flooring installed flat, and installed to stay flat

Solid hardwood can be sanded and refinished several times over its life, and it moves with moisture: in a house that swings from thirty percent humidity in February to seventy in August you will see winter gaps that close by June, and it does not belong below grade. Engineered hardwood puts a real wood wear layer over a cross-laminated core that moves far less, which makes it the choice over concrete and radiant heat; the spec that separates two identical-looking boxes is wear-layer thickness, because a thick sawn face can be resanded and a thin peeled veneer cannot.

Rigid-core LVP is waterproof, dimensionally stable and warm underfoot, which makes it the right call for basements, mudrooms where boots come in wet nine months a year, and households with large dogs and small children. When it wears out it gets replaced rather than refinished, and cheap LVP telegraphs every bump in the subfloor because it is thin and flexible.

Every flooring manufacturer publishes a flatness tolerance, usually a maximum deviation over a six or ten foot span, and every warranty assumes it was met, which in an old Seacoast house it usually was not. We put a straightedge on the floor and map the highs and lows before quoting the material, because grinding down peaks, filling valleys with self-leveler, and adding a layer of underlayment are meaningfully different amounts of work.

While the subfloor is exposed we screw it off to the joists and deal with any panel that has delaminated, because once the finish floor is down the only access to a squeak is from the basement or through the finish.

The material acclimates inside the actual conditioned room, not an unheated garage or a house still full of construction moisture, and on a slab or over a crawlspace we take moisture readings and install a vapor retarder where the reading calls for it. Every wood and floating floor gets a perimeter expansion gap, held at door jambs, hearths, toe kicks and pipe penetrations too, because buckled floors almost always trace back to a gap somebody filled or never left.

Transitions are where flooring meets the rest of the job: hardwood, tile and LVP have different total build-ups, and if nobody adds those numbers before the tile goes down you get a lip at the doorway. On a Nova job the flooring, tile and cabinet build-ups get reconciled on paper while everything is still adjustable, and the same arithmetic decides whether the dishwasher can ever come out again.