Flooring

Wood and grades

Solid hardwood strip flooring is usually red or white oak, hard maple, beech, or birch; softwood floors are typically southern pine or Douglas-fir, where vertical-grain stock wears better than flat-grain ¹. Oak is graded by appearance, with Clear, Sap Clear, and Select in quartersawn grades and Clear, Select, and No. 1 and No. 2 Common in flatsawn; maple, beech, and birch go by First, Second, and Third grades ¹. The most common pattern is 25/32 inch thick with a 2¼-inch face, tongue-and-groove on edges and ends, in random lengths ¹. The face is a hair wider than the back, so the top edges close tight while the bottoms stay slightly open ¹.

Dry before you lay

Flooring goes in after the drywall is finished, the windows and exterior doors are in, and most of the trim (but not the base) is up, so it isn’t wetted or banged up by other work ¹. Deliver it only in dry weather and store it in the warmest, driest place in the heated house ¹.

The handbook gives target moisture contents at installation: about 6 percent in the dry Southwest, 10 percent in the damp South, and 7 percent for most of the rest of the country ¹. Moisture the flooring absorbs after delivery is one of the most common causes of open joints that appear several months after the floor is laid ¹. A pin moisture meter on the flooring and on the subfloor before starting is cheap insurance.

Lay it

• Prepare the subfloor: clean and flat, covered with building paper or felt, which cuts dust and, over a crawlspace, air leakage. Chalk the joist locations on the paper ¹.
• Direction: lay strips across the joists, and lengthwise in a rectangular room where possible ¹.
• First strip: snap a straight line near the starting wall. Face-nail the first strip close to the wall, where the base and shoe will hide the nails, into the joists ¹. Leave a gap at the wall for the floor to swell into; the base covers it.
• The rest: blind-nail each strip through the tongue where it meets the shoulder, at 45 to 50 degrees, into joists when possible ¹. Finish each nail with a nail set rather than a hammer so you don’t dent the edge ¹; today a pneumatic flooring nailer does both in one blow.
• Tight joints: drive each strip up with a scrap block, never by hitting the tongue directly; wedge crooked pieces into line ¹.
• Stagger end joints well apart from course to course ¹.

Squeaks

A squeak is one board rubbing on another. Light joists, loose tongues, and poor nailing all cause it ¹. Nailing through the subfloor into the joists makes a much better floor than nailing into subfloor alone ¹, and a stiff subfloor glued to the joists (the framing module) prevents most squeaks before the flooring goes down.

What to take from this

Install wood flooring last among the wet and messy trades, with the house heated and the flooring stored inside, at about 7 percent moisture in most of the country. Run strips across the joists and lengthwise in the room, face-nail the first strip near the wall where the base will cover it, blind-nail the rest through the tongue at 45–50° into joists, drive strips tight with a block, and stagger joints. Gaps come from wet flooring; squeaks from loose nailing and soft framing.