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Wood is also the floor most affected by the house around it. Boards gain and lose moisture with the seasons, so the choice between solid and engineered wood, the installation method, the gap left at the walls and the humidity kept indoors all decide whether the floor stays tight and flat. Concrete slabs, radiant heat and basements narrow the choices further.
This page explains solid versus engineered wood, species and grades, prefinished versus site-finished boards, installation methods, moisture, expansion gaps, concrete and heated floors, stairs and care. For renewing an existing floor, see the hardwood refinishing page.
Solid vs engineered hardwood: how each is built and where each works
Solid hardwood is milled from a single piece of wood. Engineered hardwood has a top layer of real hardwood, the wear layer, bonded to a core of plywood or other cross-laid wood layers, which makes each board more stable when humidity changes. From above, a good engineered floor can look identical to solid.
- Solid: can be sanded and refinished many times over its life, is traditionally nailed to a wood subfloor, and is best kept above grade in rooms with steady humidity.
- Engineered: moves less, so it copes better with wide boards, concrete slabs and radiant heat approved by the manufacturer, but the number of possible sandings depends on the thickness of its wear layer.
- Wide planks: in solid wood, the wider the board, the more it shows seasonal gaps and cupping, one reason wide-plank floors are often engineered.
- Basements: solid wood generally isn't installed below grade, while some engineered products are approved there over a proper moisture barrier.
Hardwood species and grades: hardness, colour and character
Species affects colour, grain, how the wood takes stain and how well it resists dents. Grade describes appearance, not strength: how many knots, colour variations and mineral streaks the boards may show.
- Maple: pale, tight-grained and hard, a long-time favourite in Canadian homes, though it can look blotchy under dark stain.
- Red and white oak: open grain that hides wear and takes stain evenly, with white oak giving a cooler, more uniform tone.
- Yellow birch: a warm, lightly figured wood long used for floors in Quebec, where it's known as merisier.
- Clear or select grades: uniform colour and few knots for a calm, formal look.
- Character or rustic grades: knots, colour contrast and streaks for a lively look that disguises everyday wear.
Prefinished vs site-finished hardwood: speed, dust and a custom colour
Prefinished boards arrive sanded, stained and coated at the factory, usually with slightly bevelled edges. Installation is faster, there's no sanding dust or finish odour in the house, and the room can be used soon after. Site-finished boards go down raw and are then sanded flat, stained and coated in place. That takes longer and calls for dust control, ventilation and drying time, but it gives a perfectly flush surface, any stain colour you want and a continuous coat over the joints.
When new wood has to blend with an older site-finished floor, for instance after a wall is removed, the new section is usually installed raw and finished in place, often along with the rest of the room, so the colour matches.
Hardwood installation methods: nail-down, glue-down and floating
The right method depends on the product, the subfloor and the room, and the manufacturer's instructions list which ones are allowed.
- Nail-down: the traditional method for solid wood over a wood subfloor, with cleats or staples driven at an angle through the tongue so they stay hidden.
- Glue-down: boards bonded to a prepared subfloor or slab with the adhesive the manufacturer specifies, common for engineered wood on concrete; it feels solid but is harder to repair.
- Floating: engineered boards clicked or glued to each other over an underlay without being fastened to the floor, handy on concrete but sometimes more hollow-sounding.
- Layout: boards usually run across the floor joists for stiffness, or along the longest wall, with end joints staggered so they don't line up.
- Stairs: treads, risers and nosings are cut, fitted, glued and fastened one step at a time; it's slow, precise work, often quoted separately from the floors.
Moisture, relative humidity and expansion gaps in hardwood floors
Before installing, a careful installer measures the moisture content of both the subfloor and the new wood with a meter and compares the readings with the manufacturer's limits: a subfloor much wetter than the flooring will push moisture into it. The house should be at normal living conditions, with the heat running in winter and wet trades done. Once the floor is down, stable air keeps it quiet. Health Canada's moisture and mould guidance calls for indoor relative humidity between 30% and 50%, and holding the home within that band also limits how much the boards shrink in January and swell in August.
Wood also needs room to move. The installer leaves an expansion gap at every wall, column, threshold and fixed object, sized according to the instructions, then hides it under baseboards, quarter round or transition strips. A floor laid tight to the walls can buckle in humid weather, and a heavy island or cabinet set on a floating floor can pin it and cause the same damage.
Hardwood over concrete slabs and radiant heat: why engineered wood is the usual choice
Solid boards can't be nailed into concrete, and a slab, especially below grade, can keep giving off moisture. That's why engineered wood is the usual answer on concrete: glued to the slab, floated over an underlay, or nailed to a wood subfloor built on top. In every case the slab is tested first and covered with the barrier the manufacturer requires, and a damp or leaky basement is dealt with before any wood goes down.
Radiant heat adds a second stress, drying and warming the floor from below. Many engineered products are approved for hot-water or electric systems, with conditions on surface temperature, a gradual start-up and the attachment method. Solid wood over radiant heat is riskier, so read the flooring instructions and involve the heating contractor before choosing the product.
Caring for hardwood floors through the seasons
- Sweep or vacuum often with a soft brush head, since grit wears the finish like sandpaper.
- Clean with a barely damp mop and a cleaner suited to the finish; never flood the floor or use a steam mop unless the maker allows it.
- Put mats at every entrance in winter to stop snow, salt and gravel at the door, and wipe up meltwater promptly.
- Fit felt pads under furniture and lift, rather than drag, heavy pieces.
- Keep humidity steady all year, with a humidifier in the driest months.
- Recoat a lacquered floor when it dulls, before wear reaches bare wood, and re-oil an oiled floor as its maker recommends.
Hardwood Flooring: frequently asked questions
How long should hardwood acclimatize before it's installed?
There's no single answer: it depends on the product, the season and how different the storage conditions were from your home. The manufacturer's instructions set the requirement, and a good installer checks the wood's moisture content with a meter instead of simply counting days.
Is engineered hardwood real wood?
Yes. The surface you see and walk on is real hardwood; only the core beneath is plywood or other wood layers. That's what separates it from laminate, which carries a printed image of wood.
Can new boards be matched to my existing hardwood floor?
Often, if the same species, width and thickness can be found. Colour is the hard part, since the old wood has aged under its finish, so installers usually weave in the new boards, then sand and refinish the whole area together.
Why is my new hardwood floor cupping?
Cupping, where board edges sit higher than their centres, means the underside is wetter than the top. A damp basement or crawl space, a leak or wood installed before it matched the house are common causes. Fix the moisture first: boards often flatten as they dry, and sanding too soon can leave them crowned later.
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Written by the LokalMatch editorial team. Reviewed by Zubair Afzal on September 10, 2026. How we write and check our guides