How to install hardwood flooring: moisture, subfloor, nailing and what 300 sq ft costs

How do you know the hardwood is ready to install?

It is ready when a moisture meter says so, not after a set number of days: the subfloor should read no more than 2% above plank flooring, or 4% above strip, in a room already at living conditions. Wood swells and shrinks with the moisture in the air. Boards installed wetter or drier than their room move after you leave: gaps in winter, cupped edges in summer. The National Wood Flooring Association's 2025 guidelines replace "let it sit a few days" with a measurement. Run the room at living conditions, generally 60 to 80°F and 30% to 50% relative humidity, then compare two numbers.

The subfloor should be no more than 4% moisture content above solid strip flooring (boards under 3 in wide) and no more than 2% above solid plank (3 in and wider). The 3-1/4 in boards in this case are plank, so the limit is 2%. Bruce, whose floor is priced below, writes the same 2% into its instructions and caps the subfloor itself at 12%.

Take enough readings to trust the average. NWFA asks for 40 board readings and 20 subfloor readings for the first 1,000 sq ft, at least three per room, with extra attention along exterior walls and plumbing. Read the boards on their backs so the pin holes do not show. A $15.99 pin meter is enough to spot a problem. NWFA says to set the meter for the species being tested; a basic meter without species settings gives you a trend, and a borderline reading deserves a better meter or a second opinion.

If the numbers are too far apart, open the cartons, keep the heat or air conditioning running and meter again every day. When the gap closes and stays closed, you can start. NWFA is explicit that flooring delivered at the right moisture into a room already at the right conditions may go in right away.

How much hardwood flooring do you need for 300 sq ft?

Buy 15 cartons of 22 sq ft, 330 sq ft in all, for this 15 x 20 ft room. Bruce says to add 5% to the square footage for cutting and grading on a straight lay (10% on a diagonal, 10% to 15% for glue-down). Through the tile calculator's box math, 300 sq ft plus 5% is 315 sq ft, which rounds up to 15 cartons of 22 sq ft. You buy 330 sq ft, so the real overage after carton rounding is 10%. Buy all 15 cartons at once: a carton bought later can come from a different run and a different shade.

The staple count follows the fastening rules below. With boards running the 20 ft length, 15 ft of width at 3-1/4 in is 56 rows. At one staple every 8 in, a 240 in row takes 31, so the room takes about 1,736, and two boxes of 1,000 cover it with room for end-joint extras. The flooring is 92% of the materials, so the species and finish you pick moves the total more than anything else. The same room in Bruce's Windsor Gunstock at $4.25 a sq ft comes to $1,732.98 all in.

Unfinished oak is $3.39 a sq ft, but then you sand and finish in the house, and Angi puts hired finishing at $2 to $7 per sq ft. For a first floor, buy prefinished.

What tools do you need to install hardwood flooring?

The one tool that matters is a flooring nailer or stapler, which drives a fastener at an angle through the tongue of each board. Menards rents a Bostitch industrial floor stapler that shoots 15.5 gauge staples 1-1/2 to 2 in long into 1/2 to 3/4 in flooring. It is pneumatic, so it needs the compressor. Two days of each costs $90, against $449 to buy the same stapler, which makes renting the obvious call for one room.

You also need a miter or circular saw, a jigsaw, a pull bar, a chalk line, a 6 ft level as a straightedge, a finish nailer for the rows by the wall, and spacers. Wear eye and hearing protection around the stapler.

What subfloor do you need under hardwood flooring?

Over joists 16 in on center, NWFA asks for at least 19/32 in plywood or 23/32 in OSB, nailed and preferably glued. Most rooms keep their subfloor. Replace it when it is water-damaged, delaminated, too thin for the joist spacing, or too far out of flat to shim.

Thickness comes first. NWFA's minimum for wood flooring over joists up to 16 in on center is 19/32 in plywood or 23/32 in OSB, and 23/32 in over 16 to 19.2 in spacing. The 2024 IRC is looser. Table R503.2.1.1(1) lets a panel stamped 24/16 (7/16 in) span 16 in as subfloor, and a single-layer combination subfloor-underlayment must be 19/32 in at 16 in on center. The code keeps the floor from breaking; the flooring standard keeps it from squeaking and moving. Build to the NWFA number.

Fastening is where subfloors fail. IRC section R503.2.3 sends you to Table R602.3(1), which for 19/32 to 3/4 in panels calls for 8d common nails (2-1/2 x 0.131 in) or 2-3/8 x 0.113 in deformed nails, 6 in apart along supported panel edges and 12 in apart along the intermediate joists. NWFA asks for the same spacing, recommends gluing as well to prevent squeaks, and requires glue plus fasteners when joists are more than 16 in apart. The adhesive should meet ASTM D3498 or APA AFG-01.

Lay the panels with the long side across the joists, continuous over at least two spans. Land every end on a joist center with at least 1/2 in of bearing, and leave a 1/16 to 1/8 in gap around each panel unless the tongue and groove is milled to gap itself. In the 15 x 20 ft room, 300 sq ft of 4 x 8 sheets plus 10% for the staggered layout is 11 sheets. An 8 ft sheet crosses seven joists: two ends at 6 in spacing take 9 nails each, and five intermediate joists at 12 in take 5 each, 43 per sheet and 473 for the room. Sixteen joists under 15 ft of floor are 240 ft of adhesive bead, and Liquid Nails' data sheet gives 30 ft per 10 oz tube, about 84 ft per 28 oz tube, so three tubes.

Those ring shank nails are 2-1/2 x 0.120 in, longer and thicker than the 2-3/8 x 0.113 in deformed nail the code table accepts. Five boxes hold about 475, too close to 473 for an approximate count, so buy six. T&G plywood is $51.99 a sheet if you prefer it.

Should hardwood be nailed, glued or floated?

Solid 3/4 in boards over a wood subfloor get nailed or stapled; that is the method this page prices. Glue-down is the usual method for engineered flooring over concrete, and Bruce tells you to add 10% to 15% waste for it instead of 5%, because the adhesive leaves no chance to straighten a bowed board. Floating floors (click engineered wood, laminate, click linoleum) are not fastened and move as one sheet.

Flatness targets follow the method. NWFA wants the subfloor within 3/16 in over 6 ft, or 1/4 in over 10 ft, for nail-down with fasteners 1-1/2 in and longer. For glue-down, floating, and short fasteners the target tightens to 1/8 in over 6 ft or 3/16 in over 10 ft. Sand the high seams, and fill low spots with felt layers, plywood or a patch. Bruce allows up to six layers of 15 lb felt for small dips.

How to install hardwood flooring, step by step

1. Measure moisture in the flooring and the subfloor, as above. Check: the subfloor average is at or below 12% and no more than 2% above the plank average. Write the numbers down with the date.
2. Check flatness with a 6 ft straightedge in several directions across the room. Check: no gap under the straightedge over 3/16 in. Sand humps, fill hollows, and drive any nail or screw that has backed out.
3. Remove base shoe and thresholds, and undercut the door casings with a board and a scrap of felt as the height guide. Check: a loose board slides under each casing.
4. Roll out the felt across the room, seams overlapped at least 4 in, stapled flat. Skip it if the crawlspace or basement already has a vapor retarder on the underside of the joists, per NWFA. Check: no wrinkles, no torn patches.
5. Snap a working line parallel to the starting wall, 3/4 in plus the tongue width off the wall. Bruce's minimum expansion space is 3/4 in. Run the boards perpendicular to the joists. Check: the line measures the same distance from the wall at both ends, or you adjust for an out-of-square wall now.
6. Rack the floor: lay out several rows loose, mixing boards from different cartons. Keep end joints in neighboring rows at least twice the board width apart (NWFA; that is 6-1/2 in here, and Bruce asks for 4 to 6 in at least) and avoid H-shaped joint patterns. Check: no two joints line up within three rows.
7. Face-nail the first row along the groove edge and blind-nail through the tongue. NWFA's face-nail spacing for plank is 8 to 10 in with at least an 18 gauge fastener. Check: the row sits exactly on the line from end to end.
8. Switch to the rented stapler once you have room to swing the mallet. Fire one staple every 6 to 8 in and 1 to 3 in from each end, at least two per board. Check: staples sit flush in the tongue pocket, neither proud (the next board will not close) nor sunk through the tongue. Test the air pressure on a scrap first.
9. Keep the gap at every wall, cabinet and pipe with spacers. Check: 3/4 in on a spacer at every wall as you go.
10. Finish the last rows with the finish nailer and the pull bar, face-nailed where the stapler cannot reach. Check: every board tight, gap still at the wall, no hammer marks.
11. Pull the spacers, refit the base shoe to the wall (not the floor) and install thresholds. Check: the shoe moves freely when you press on the floor next to it.

How do you install linoleum flooring?

Real linoleum, made from linseed oil, installs as glued sheet or as floating click panels, and the click panels are the version to try yourself. For Forbo's Marmoleum Cinch LOC Seal panels, the instructions call for storing the cartons flat in the room for 2 to 3 days (about 6 in winter), a room at 68°F or warmer with 50% to 60% humidity, a subfloor flat within 3/32 in over 6 ft, and a 3/8 in gap at every wall. Over concrete the slab must test at or under 75% relative humidity by ASTM F2170 or 3 lb per 1,000 sq ft per 24 hours by ASTM F1869. Sheet linoleum goes down in adhesive and gets rolled with a heavy roller, which Menards rents for $16 per 4 hours. Seaming sheet goods is where DIY jobs go wrong.

Mistakes that cost money

The refinishing range is Angi's $2 to $7 per sq ft on 300 sq ft, and it is the cheap outcome. Severe cupping means new boards.

Is it cheaper to install hardwood flooring yourself?

Yes, by $1,020.03 in direct cost on this room, and by more against a contractor's bid, if the subfloor passes the checks. Floor layers other than carpet (BLS SOC 47-2042) earned a national mean of $29.69 an hour in May 2025. Wages are 69.0% of total compensation in the construction, extraction, farming, fishing and forestry occupations row of the June 2026 employer cost survey ($32.17 of $46.65), so a loaded hour costs $29.69 x 46.65 / 32.17 = $43.05. I allow a two-person crew 24 crew-hours for 300 sq ft of prefinished nail-down, including prep and trim. A pro brings the stapler and compressor, so the rentals and the meter drop out.

Angi's $6 to $12 per sq ft works out to $1,800 to $3,600 for this room, and the direct cost above sits near the top of it because the flooring is a $6.40 prefinished oak. A contractor's bid adds overhead and profit on top.

Doing it yourself saves $3,533.46 − $2,513.43 = $1,020.03 in direct cost, and more against a real bid. Over my 30-hour allowance for a first-timer, that is $34.00 an hour, less than the $43.05 a pro's hour costs. The pro is faster. The saving is worth taking if you have the weekends and the subfloor passes the checks; if the subfloor needs work you are unsure about, the $1,020 does not cover one cupped floor.

For a larger remodel, the renovation financing guide compares cash, a HELOC and a loan.