The three questions that decide it
Whatever is on the floor now, an installer is asking the same three things.
Is it flat? Floating floors span dips and hump over ridges, and the locking joints are what break first when they flex. Flatness is measured with a straightedge against the product's tolerance, typically 3/16 inch over 10 feet. Low spots are filled with leveling compound; high spots are ground or the material comes out.
Is it dry? Moisture is what ruins floors in Seattle. Concrete slabs are tested with a relative-humidity probe or a calcium chloride kit; wood subfloors with a pin meter, and the crawl space underneath gets a look. A floor over a damp base cups, gaps or grows mold underneath regardless of what the top layer is made of. The moisture, crawl spaces and floating floors guide explains why half the houses in the city need this check.
Does the height work? Adding a 6 to 8 millimeter plank plus underlayment on top of an existing floor raises the surface by roughly a quarter to half an inch. That changes door clearances, the step at exterior doors and at transitions to rooms you are not redoing, and the gap under appliances, especially a dishwasher that has to come out someday.
If the existing floor passes all three, it usually stays. If it fails any one, it is fixed or removed. Here is how that plays out by surface.
Ceramic or porcelain tile
Usually stays. Well-bonded tile is one of the best bases for vinyl plank: flat, hard and stable. The installer taps for hollow tiles, re-sets or removes any that are loose, and fills the grout lines if they are wide and deep, because plank will telegraph a deep grout joint over time. Cracked tile across a slab is a sign of slab movement and gets a closer look.
Comes out when many tiles are loose or cracked, the floor has a large hump or dip, or the added height will not work at doors and cabinets. Tile removal is dusty, slow and the most expensive tear-out, which is the main reason to keep it when you can. See floor removal and subfloor prep.
Sheet vinyl and old vinyl tile
Often stays. A single layer of sheet vinyl that is fully adhered and flat is fine under a floating floor; the plank rides on top with its underlayment. Cushioned vinyl, loose or bubbled vinyl, or two or more layers stacked over decades should come out, because soft or shifting layers let the locking joints flex.
A caution for older homes. Vinyl flooring and the black adhesive under it installed before the mid-1980s may contain asbestos. In that case the usual answer is to leave it in place and go over it, which is permitted and safe when the material is intact, rather than disturb it. If it is damaged or has to come out, that is abatement work by a licensed firm, not a flooring crew. Any installer working on a pre-1985 Seattle house should raise this at the measure.
Old hardwood
Depends on its condition. Flat, tight, well-fastened hardwood is an acceptable base for laminate or vinyl plank laid perpendicular to the boards. Cupped, crowned or loose boards are not; the floating floor will telegraph the cupping within a season. Sometimes the right fix is screwing the old floor down and sanding the high spots; sometimes it is a layer of quarter-inch underlayment plywood over the top; and sometimes the honest advice is that the old fir or oak is worth refinishing rather than covering.
Concrete slab
Stays, almost always, after the moisture test. Basements, daylight basements and slab-on-grade houses are the most common place to find a floating floor in Seattle, and the slab itself is a good base. Everything hinges on the moisture reading and on a vapor retarder between the slab and the floor. Rigid-core vinyl plank tolerates slab moisture better than laminate, which is why installers steer basements toward it. Cracks are filled, low spots leveled, and any old adhesive is removed or encapsulated so it cannot react with the new underlayment. Luxury vinyl plank installation covers the product side.
Carpet
Always comes out. Carpet and pad are soft, and a floating floor over them flexes and fails at the joints. Tack strips come out too, and the subfloor under old carpet usually needs staples pulled and a few screws added. The upside is that carpet removal is fast and cheap compared to tile.
Laminate or vinyl plank you already have
Comes out. Floating floors are not stacked. Two floating layers move independently and the top one will gap and peak. Removal is quick since the planks unlock, and the old underlayment comes with it.
Particleboard underlayment
Comes out, or gets covered. Many Seattle houses from the 1960s through the 1980s have particleboard under the carpet or vinyl. It swells with any moisture, holds no fastener and cannot be leveled. The standard fix is removal down to the plywood subfloor, or a new layer of plywood over it when removal would disturb walls and cabinets.
What this means for the quote
Going over an existing floor removes a tear-out line and a disposal line from the estimate and usually a day from the schedule. What it can add is leveling compound, grout filling, a plywood overlay, or transition pieces to manage the new height at doorways. The measure is where this gets decided: the installer checks flatness with a straightedge, takes moisture readings, looks at the doors and the appliances, and writes the quote for the base that will actually hold the floor. The preparing for installation day guide covers what happens next, and the cost guide shows how removal and prep show up as line items.
Call or text (844) 543-5757 with a photo of the floor you have and the room sizes. You will get a straight answer about whether it can stay, and a free in-home measure if you want the written quote.
