What to clean it with, and what will wreck it.

How do you clean hardwood floors, and what should you never use on them?

Dry dust mop regularly, damp mop with the finish manufacturer's approved cleaner, and wipe spills immediately.[1] The guidelines name what not to use, and two of them are things people do every day: vinegar and steam.

On vinegar the wording is unambiguous: "Do not use vinegar on wood floor finishes. Vinegar is acidic and will degrade the floor finish."[1] On steam: "Do not use steam-cleaners on wood floors."[1]

Also on the do-not list: a traditional mop and bucket, which applies too much moisture and can leave the floor sticky or slippery; household cleaning products and products made for other flooring types; self-polishing acrylic waxes; sheet vinyl or tile floor care products; and the beater bar setting on a vacuum.[1] The guidelines also warn that excessive use of any wood floor cleaner can cause finish adhesion problems when the floor later needs recoating.[1]

For streaks, the cause is usually too much product or too much water rather than the wrong cleaner. Less liquid, and a clean pad.

How do you clean vinyl plank floors, and is vinegar all right?

Sweep or vacuum, then damp mop with a cleaner the plank's manufacturer approves. Vinyl plank does not have a wood finish for acid to degrade, so diluted vinegar is not the same hazard it is on hardwood, but it is still not what the manufacturers recommend and it can dull an embossed surface over time.

The rule that matters more on vinyl plank is the amount of water. Flooding a floating floor sends water down the seams to the subfloor, which is where the actual damage happens. Damp, not wet. See what happens when vinyl gets wet underneath.

How do you protect hardwood floors from dog nails, furniture and rolling chairs?

Felt pads under every leg, replaced when they load up with grit, and a hard-floor caster or a chair mat under anything that rolls. Mats at every entry, because the damage is done by grit tracked in, not by the traffic itself. Keep dogs' nails trimmed.

The guidelines make the mechanism explicit: particles have the potential to be ground into floors, potentially damaging the finish, which is why regular dry dust mopping with a cloth that removes dirt rather than pushing it around matters more than any product.[1] Felt pads and floor registers are among the things Max brings to the estimate.

How often should hardwood floors be refinished, and can you refinish without sanding?

Yes, often you can. A floor whose finish is worn but not worn through can be recoated, which means abrading the existing finish and applying a fresh coat rather than sanding back to bare wood. Full sanding is for when the wear has reached the wood, or there is damage a coat will not hide.

The thing that prevents a recoat is contamination. The guidelines warn that excessive cleaner use can cause finish adhesion problems when the time comes to recoat, and that acrylic waxes and products meant for other floors do not belong on wood.[1] A floor that has been waxed or over-cleaned may need full sanding purely because nothing new will stick.

How often is a function of traffic rather than a calendar. Recoat when the sheen goes and before the wear reaches the wood, because that is the cheap intervention. The refinishing page covers all three levels of work.

Do you need a humidifier for hardwood floors, and can one damage them?

In an Ontario house, usually yes in winter. The target is the published range for solid wood, 30% to 50% relative humidity at 60 to 80°F.[1] A house running well below 30% through February is why boards shrink and gaps open. And yes, a humidifier can do damage, by overshooting.

Too much humidity swells boards against each other, which is the other half of the same problem and shows up as cupping or, at the extreme, buckling. The guidelines note that a supplemental humidity control system is often necessary and should be specified into a wood flooring project to support the ambient conditions.[1] The point is control within the range, not more moisture.

Buy a hygrometer before you buy a humidifier. It costs almost nothing and it tells you whether you have a problem at all.

Can you replace one plank of vinyl, laminate or engineered hardwood?

Usually yes, and how easily depends on how the floor was installed. A glued or nailed board can be cut out and a replacement fitted in place. A click-lock floating plank in the middle of a room means either unlocking rows back to it, or cutting it out and gluing the replacement, which is a repair rather than a reversal.

On wood, the guidelines add a condition that surprises people: the replacement board's moisture content should be within 2 percent of the existing floor, and if it is not, the new board acclimates until it is.[1]

Which is the argument for keeping a box. Ask for the leftover material at the end of the job and store it flat somewhere dry. Dye lots change and product lines get discontinued, and a matched plank from your own original run is worth far more than a close guess in three years.