In a Bellevue condo on a concrete slab, and in a modern home with radiant floor heat, wide planks or a lower level set into the ground, engineered hardwood usually holds up better. Its layered construction moves less as indoor humidity changes through the year, and it can be glued straight to concrete, floated over it, or installed below grade, all places where solid wood is limited. Solid hardwood holds up best in a different sense: nailed over a wood subfloor on an above-ground level, it can be sanded back to fresh wood and refinished again and again.
What settles the choice for most homes is what's under the floor, how wide you want the boards and, if you lean toward engineered, how thick its top layer of real wood is. Neither type is waterproof, so neither one belongs where water sits on the floor.
What's the difference between solid and engineered hardwood?
Solid hardwood is one piece of wood from top to bottom, most often 3/4 inch thick. Engineered hardwood has a top layer of real wood, called the wear layer, bonded to core layers of wood veneer, lumber or a composite panel, and the finished boards run from about 3/8 to 3/4 inch thick. The wear layer is the species you pick, so an engineered white oak floor looks like white oak once it's down. The National Wood Flooring Association (NWFA), whose installation guidelines are the standard installers work from, counts both as real wood floors.
The core is what changes how the two behave. A solid board swells and shrinks across its whole width as it takes on and gives up moisture, while an engineered board's thin top layer is bonded to a core that resists that movement. NWFA's guidelines describe engineered flooring as, in general, more dimensionally stable than solid, and nearly every difference in the table below follows from that.
Solid vs. engineered hardwood at a glance
| What you're weighing | Solid hardwood | Engineered hardwood |
|---|---|---|
| Seasonal gaps and cupping | Moves more, most of all in wide boards | Generally more stable |
| Concrete slab (many condos, lower levels) | Usually needs a plywood subfloor or sleepers on the slab first | Glued to the slab or floated over it |
| Below grade (basements, lower levels) | Not recommended unless the maker allows it | Allowed |
| Floating installation | Not recommended unless the maker warrants it | Allowed |
| Radiant floor heat | Possible with care, in narrower boards and stable species | Generally the better fit, if the product is approved for it |
| Wide planks (over 5 inches) | Winter gaps show more | Holds its width better |
| Sanding and refinishing | Many times over its life | Depends on the wear layer; 2.5 mm or more for a full sanding |
| Floor height over a slab | 3/4 inch plus the subfloor under it | 3/8 to 3/4 inch, plus any underlayment |
| Sunlight and color change | Changes color with age and light | Same, since the top is the same wood |
| Standing water | Damaged | Damaged |
How Bellevue's seasons affect solid and engineered floors
For a floor inside a heated home, the change that matters most over a year is indoor humidity, and around here it doesn't follow the weather the way you might expect. Outdoors, the Seattle area is damp for much of the year: the U.S. Forest Service's Forest Products Laboratory, the federal lab that studies how wood behaves, figures that wood left outside in Seattle holds about 17 percent moisture in December and about 12 percent in July. Indoors, the furnace dries the winter air, and the lab's Wood Handbook explains that cracks open in wood flooring when it shrinks as a building is heated. So a solid floor here tends to show its gaps in the heating season and close them again once the heat goes off.
NWFA's guidelines, as a general rule for solid wood, call for keeping a home between 30 and 50 percent relative humidity and 60 to 80°F, with a factory-finished floor's own requirements taking priority. At room temperature, the Forest Products Laboratory's tables put wood in that humidity range at roughly 6 to 9 percent moisture, so even a floor kept inside the recommended band swings about three points over a year. A correctly installed floor handles that. How much of the movement you see depends on the board: its construction, its width and its species.
Why wide planks favor engineered hardwood
Wood changes size in proportion to its width, so a wide board opens a wider gap than a narrow one when it dries. Using the Forest Products Laboratory's shrinkage figures for white oak, a flat-sawn 7-inch solid plank can change width by up to about 2 millimeters (a little under 1/12 inch) across that three-point moisture swing, while a traditional 2 1/4-inch strip moves about a third as much. Boards that aren't perfectly flat-sawn move somewhat less, but the difference between wide and narrow boards remains, and it's why a wide solid floor shows seasonal gaps that a strip floor hides.
Species matters too. In NWFA's comparison of how much common flooring species shrink, white oak moves more than red oak, and hickory moves more than either. Wide boards of a less stable species are where solid wood is most likely to gap in winter or cup when it takes on moisture, and that combination is where an engineered core does the most good. If you're still choosing a species, our hardwood buyer's guide compares oak, maple, hickory, walnut and cherry.
If you want wide solid boards anyway, two things help: rift-sawn or quartersawn wood, which is more stable in width than plain-sawn, and a home held within that humidity range all year, which may mean running a humidifier through the heating season. For the wide-plank look with less of that risk, the engineered oak and maple in our hardwood catalog come in several widths and finishes.
Engineered hardwood in Bellevue condos: concrete, height and the slab
Condo buildings vary. Some units sit on concrete slabs and others on wood-framed floors, so find out which you have, from the building's plans or its management, before you shop. On concrete, the two floors part ways. Standard 3/4-inch solid hardwood is nailed down, and nails need wood, so over a slab solid usually calls for a plywood subfloor or a grid of wood sleepers on top of the concrete first; some solid products can be glued directly when the maker allows it, but the choices narrow. Engineered hardwood can be glued straight to a properly prepared slab or floated over it on an underlayment, and NWFA's guidelines say engineered is the only type of wood floor that can be floated.
The build-up matters in a condo. Solid wood over a plywood layer raises the floor by roughly an inch and a half, more with sleepers, while a glued engineered floor adds only its own thickness. The extra height has to meet the hallway, the bathroom tile and the entry door, and it cuts into the space for anything that slides under a counter, so planning transitions and thresholds before installation is part of the choice.
Then there's the slab itself. Concrete floors in condo buildings may be post-tensioned, meaning steel tendons inside the slab are pulled tight to hold the concrete in compression. The Post-Tensioning Institute, the technical association for that construction method, lists residential apartments and high-rise condominiums among its uses, and names coring and drilling after construction as one of the ways tendons get damaged. Before anyone fastens anything into a condo slab, ask the building's management whether it's post-tensioned and what they allow. Glued and floating installations don't fasten into the slab, and neither does a floated plywood subfloor under solid wood, so either floor can avoid it; the point is to settle it before the crew arrives.
Whichever floor you choose, the slab gets tested for moisture first. NWFA's guidelines call moisture testing compulsory practice, whatever the conditions look like, because a slab's moisture can change over time and damage wood from below. Why that testing and acclimation weigh so heavily here is covered in our guide to engineered hardwood in Bellevue's damp climate.
Basements and lower levels
NWFA's guidelines treat any part of a floor 3 inches or more below the surrounding ground as below grade. Engineered hardwood can go above, on or below grade; solid should stay out of below-grade rooms unless its maker says otherwise. A daylight basement or a lower level cut into a hillside can be partly below grade, and the below-ground part is what counts. On slabs at or below ground level, NWFA recommends a vapor retarder over the concrete every time, whatever the test readings.
Condo sound rules and HOA approval
In a condo, the association's rules can narrow your options before you've picked a color. What stops footsteps from reaching the unit below is the whole floor-and-ceiling assembly, so the underlayment and the installation method count for more than whether the plank is solid or engineered. Sound requirements are written as IIC and STC ratings, and our guide to HOA-friendly flooring, sound ratings and underlayment explains what those numbers mean and how a floor meets them.
Before you order anything for a condo:
- Get the association's flooring rules in writing: any required sound rating, approved underlayments, the approval process, working hours, elevator reservations and where materials can be staged.
- Find out whether your floor is a concrete slab or wood-framed, and if it's concrete, whether it's post-tensioned.
- Measure the height you have to work with at the entry door, other doors and where the wood will meet tile.
- Have the slab tested for moisture before the product is final.
- Choose the installation method with the building in mind: glued, floating, or solid over a subfloor.
Radiant floor heat in modern homes
Radiant heat sits right under the boards and dries them through the heating season, and engineered hardwood usually copes with that better than solid. NWFA's guidelines rate engineered flooring as generally more stable over radiant heat, with two cautions: not every engineered product is approved for it, and less stable species such as hickory, beech and maple aren't normally the best choice, even as a wear layer. Narrower boards also do better than wide ones, since wood moves in proportion to its width. Check that the maker approves the specific product for radiant heat before you commit to it.
How the system is run matters as much as the floor. Unless the flooring maker says otherwise, NWFA's guidelines keep the floor's surface at or below 80°F, limit changes in floor temperature to 5°F a day, and advise against setback thermostats that swing the temperature more than that. They also call for humidity control to hold the air between 30 and 50 percent, and they warn that thick rugs, mats, mattresses and pet beds trap heat and can damage the floor underneath. If your home already has radiant heat, have the system's details on hand when you choose the floor.
How many times can solid and engineered hardwood be refinished?
Solid hardwood can be sanded to bare wood and refinished numerous times, so an old solid floor can often be brought back instead of replaced. If your house already has solid floors, price hardwood refinishing and restoration before you price a new floor.
Engineered hardwood can be refinished too, as many times as its wear layer allows. A careful full sanding removes a little under 1/32 inch of wood, and NWFA's sanding guidelines advise against sanding a wear layer thinner than 3/32 inch, about 2.5 millimeters. NWFA's certified-refinishable program, which labels engineered products that can be sanded and refinished, sets its minimum at 2.5 mm for factory-finished boards and 3.2 mm for unfinished ones. Below that, a floor can be recoated but not sanded; above it, each extra millimeter or so allows roughly one more sanding. How many sandings a floor gets in practice also depends on the refinisher's skill, the equipment and how flat the floor is.
A lighter option works on both types. In a maintenance coat, the existing finish is cleaned, lightly sanded and given a fresh coat, without cutting into the wood. A full sand and refinish is for deep scratches and dents, or finish worn through to bare wood. Recoating before the finish wears through saves the wear layer for when it's needed.
That's also the fair way to compare lifespans. Either floor lasts as long as it can keep being renewed, and the difference is how much wood there is to sand. An engineered floor with a thin wear layer gets replaced when it's worn out, while one with a thick wear layer can be sanded back more than once, like solid. For dogs and busy households, scratch resistance comes mostly from the species and the finish, since the wood you walk on is the same either way; what the construction changes is whether a badly scratched floor can later be sanded smooth.
Big windows, sunlight and color change
Light changes the color of solid and engineered floors alike, because both have real wood on top. As wood ages indoors, the Forest Products Laboratory's Wood Handbook says, dark woods generally get lighter and light woods get darker. The handbook also notes that ordinary window glass already blocks most ultraviolet light, so visible light causes most indoor color change, and UV blockers in a finish don't necessarily prevent it.
With a wall of windows, plan for the change instead of fighting it. The Wood Handbook suggests checking under rugs on a newly installed floor after a few weeks and moving them if a line is forming; once exposed, wood usually evens out within several months, though cherry takes much longer. Sheen matters in bright rooms too: the handbook notes that high-gloss finishes accentuate imperfections, and joints seen in direct sunlight are especially hard to hide under them, so a satin or matte finish is the easier choice beside big windows.
Water, entries and kitchens
Neither solid nor engineered hardwood is waterproof. Engineered stays flatter through humidity swings, but a leak or water left standing damages both, so the choice between them doesn't solve a wet entry on a rainy day or a laundry room. Where water is routine, a waterproof floor such as luxury vinyl plank can take the wet zones while wood runs through the living areas. In a kitchen, either type suits a household that wipes up spills promptly, and a mat at the sink catches most of the rest.
What changes the cost in a condo or a house
Species, grade, plank width and, for engineered, wear-layer thickness set the price of the boards. Around them, the installation is where solid and engineered separate. In a concrete condo, solid wood brings a plywood subfloor or sleepers, more height to deal with at doors and transitions, and more labor, while engineered goes onto the slab with adhesive or an underlayment. In a house with a sound wood subfloor, solid nails straight down and the comparison evens out. If you already have solid floors, refinishing them avoids buying new material at all.
When you compare quotes, make sure each one spells out subfloor prep, moisture testing, tear-out and transitions, so you're comparing the same job. If you'd rather spread the cost over months, we offer financing.
Other questions about choosing solid or engineered
Does engineered hardwood count as real hardwood?
Yes. The surface you see and walk on is real wood of the species you chose, and NWFA's guidelines define a wood floor as any flooring with real wood as its top, wearable surface. That separates engineered hardwood from laminate and vinyl, which carry a printed image of wood. When you're comparing engineered floors, the wear-layer thickness tells you more about long-term value than the word "engineered" does.
Can I put solid upstairs and engineered on the lower level?
Yes, and in a house with a slab or basement level it's often the sensible split: solid over the wood subfloors of the above-ground floors, engineered on the slab or below grade. In the same species and a matching finish, the two can look alike once installed, since the top layer is what you see. Plan for the thicknesses, because a 3/4-inch solid floor and a thinner engineered one meet at different heights.
Choosing for your condo or home
If you're weighing the two for a condo, have your association's flooring rules and anything you know about the slab on hand; for a house, note any radiant heat and which floors sit below grade. Then book a free in-home estimate so we can help you match the floor and the installation method to your home.
