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Grade Level Is the First Thing to Establish
Flooring people talk about rooms as being above grade, on grade or below grade, and it simply describes where the room sits relative to the ground outside. A second floor bedroom is above grade. A main floor living room on a slab is on grade. A finished basement is below grade. It sounds like jargon until you understand what it is actually describing, which is how much moisture vapour the floor has to cope with from underneath.
Below grade rooms are surrounded by soil, and soil holds moisture that migrates through concrete as vapour even when the slab looks and feels completely dry. Solid hardwood is a single piece of wood that expands and contracts as it takes on and loses moisture, so a below grade installation puts it in an environment it was never designed for. This is why solid hardwood is generally not recommended below grade, and it is a materials limitation rather than a matter of budget or taste.
Engineered Is Built Differently Underneath
An engineered board has a real hardwood wear layer bonded over a core of several layers running in alternating directions. That cross layered construction is the whole point. When one layer wants to expand across its width, the layer glued to it at right angles resists, and the board stays far more dimensionally stable than a solid plank in the same conditions.
That stability is what makes engineered the usual answer over concrete and below grade. It is also worth clearing up an outdated idea while we are here. Engineered flooring is not a disposable substitute for solid. The wear layer on a quality engineered board can be sanded and refinished, just fewer times than solid, and how many times depends on how thick that layer is. If longevity matters to you, the wear layer thickness is the specification to ask about rather than dismissing the category.
Your Subfloor Decides How the Floor Goes Down
There are three ways hardwood attaches to a house. It can be nailed or stapled down, glued down, or floated, meaning the planks lock to each other and rest on the subfloor without being fixed to it. Which of these is available to you comes straight from what the subfloor is made of.
A plywood or OSB subfloor takes nails, which opens up nail down installation and brings solid hardwood into play. A concrete slab does not take nails in any practical sense, so you are looking at glue down or floating, and both of those point toward engineered. This is the mechanism by which the house makes the decision. Nobody chooses to rule out solid hardwood on a slab, the slab rules it out.
Flatness Matters More Than People Expect
Every installation method has a tolerance for how flat the subfloor needs to be, and floating floors are the fussiest of the three. Because the planks are not fixed down, a dip in the subfloor leaves the floor unsupported above it, which you hear as a hollow sound and feel as a slight give underfoot. Over time that deflection also puts stress on the locking joints.
Manufacturers publish a flatness specification for each product, and a good installer will check the subfloor against it rather than assume. If your subfloor needs levelling, that work happens before anything else and it is far cheaper to do properly at the start than to live with afterwards. Ask whether your subfloor has been assessed before you finalise which flooring you are buying, because a subfloor that needs attention can change which products are realistic.
Moisture Testing Is Not the Same as Looking at It
A concrete slab can feel bone dry and still be releasing significant vapour, particularly if it is relatively new or if there is no vapour barrier beneath it. Dryness to the touch tells you about the surface and nothing about what is moving up through it. There are established tests that measure this properly, and they produce a number rather than an impression.
Any flooring going over concrete should follow a moisture test, and most manufacturers make their warranty conditional on one having been done. Skipping it is the single most common way a perfectly good floor fails for reasons that had nothing to do with the flooring. If somebody quotes you for a slab installation without mentioning moisture testing, ask about it.
Let Us Look at What You Are Working With
Grade level, subfloor material, flatness and moisture together narrow the field considerably, and all four can be established quickly. Chicago Flooring By Manas Torcom can walk through them with you and show you solid and engineered options that suit what your house actually allows rather than starting from a catalogue and working backwards.
We serve Park Ridge, Chicago, Arlington Heights, Glenview, and Hinsdale, IL and welcome you at any of our Park Ridge, IL. Browse our hardwood flooring to see both constructions side by side, then contact us to arrange a visit and tell us which rooms you are flooring and what is underneath them.
