Solid Hardwood Flooring

Solid hardwood is nailed down. A flooring nailer drives cleats or staples at an angle through the tongue of each board into the subfloor, where the next board's groove hides them. That needs a plywood, OSB or older plank subfloor thick and stiff enough to hold the fasteners, usually with a layer of building paper or felt on top. The boards generally run across the floor joists, and over an old plank subfloor the direction of those planks matters too, sometimes enough to call for a layer of plywood first. Nailing is a little more forgiving of small dips than a floating floor, but a hump or hollow can still squeak underfoot, so the subfloor is checked and fixed first. A gap is left at every wall so the floor can expand, and the baseboards cover it.

Solid wood takes on moisture from whatever it sits on, so it's generally kept above grade. Over a slab poured on the ground or in a basement, moisture coming up from the ground gets into the boards and they cup, and there's no wood subfloor to nail into without building one first. Many solid hardwood makers also don't approve their boards over in-floor heating, because the heat dries them out and opens wide gaps. In all three places, engineered flooring is the usual answer. It's real wood on top of a cross-laid core that moves far less, and it can float or be glued down instead of nailed.

Bathrooms and laundry rooms are the other places solid hardwood doesn't suit. Splashes around a tub, a toilet tank that sweats in humid weather and the odd washer overflow all find the seams. Luxury vinyl plank or vinyl tile is the better floor there. Kitchens are a judgement call. Many older homes have hardwood in the kitchen and it does fine, as long as spills get wiped up and a leak under the sink or dishwasher is caught early.

Wood takes on and gives off moisture with the air around it. It gets slightly wider when the air is damp and slightly narrower when it's dry, and wide boards move more than narrow ones. So the boards shouldn't go down straight off the truck. They sit in the rooms they're going into, with the heat on and any drywall, paint or concrete work dry, until they're close to the moisture level they'll live at. That isn't a set number of days. A moisture meter on the boards and on the subfloor says when it's done, and the two should read within a few points of each other, closer still for wide boards. Close isn't enough on its own, though. A subfloor that reads wet points to a moisture problem underneath, and that needs finding and fixing before any boards go down. The manufacturer's instructions set the limits, and the warranty is written around them.

In an older Lower Mainland house, look under the floor as well. A crawlspace with bare, damp earth keeps the subfloor moist, and boards over it take on moisture from below and cup, with their edges higher than their centres. Covering the bare ground with a heavy plastic vapour barrier and getting rid of any standing water usually deals with it, as long as the crawlspace is kept vented or heated the way it was built. Water getting in from outside is a drainage job, not a flooring one. It's worth checking before the floor goes in, because no flooring installation fixes a wet crawlspace.

After it's down, a solid floor follows the seasons. The air outside is damp most of the year here, but a heated house in January can be very dry inside. The boards shrink and thin gaps open between them. When the heating goes off in spring and summer, the boards take the moisture back and the gaps close. That's normal behaviour for solid wood, not a defect. Keeping indoor humidity roughly between 35 and 55 per cent, as most manufacturers ask, with a humidifier running in winter, keeps the gaps small. In an older house with single-pane or aluminium windows, watch the glass. If it fogs or drips, the humidity is too high for the house and the humidifier should be turned down.

And it isn't waterproof. A spill you wipe up is fine. Water left standing, a plant pot or pet bowl that leaks over weeks, or a wet mat left down will soak into the wood, and on oak it can leave dark stains that sanding doesn't always remove. Felt pads, mats at the doors and wiping up spills straight away do more for a hardwood floor than anything else.