Nail-down is the oldest way to fix a tongue and groove oak floor, and it is still the usual method over a wood subfloor. The tongue does two jobs: it carries the fastener, and it holds the next board level so the fastener stays hidden. This article walks through the sequence an installer follows, from the subfloor to the last row, so a buyer or specifier knows what the board has to support and who decides what. Fastener type, spacing, moisture limits and acclimation belong to the installer, the fastener maker and the NWFA installation guidelines for the project.
When nail-down is the right method
Nail-down needs a subfloor that can hold a fastener: plywood or OSB panels over joists, or solid board subfloors in older buildings. A concrete slab cannot hold a floor nail, so over concrete the floor is normally glued instead (see glue-down installation over concrete).
Both solid and engineered oak can be nailed where the installer approves it. Solid oak is the traditional nail-down floor and is best suited to narrower boards. Engineered boards can also be nailed, with a fastener approved for the board’s thickness and tongue. Our standard builds are 5/8” (15mm) overall with a 3mm sawn wear layer and 3/4” (20mm) overall with a 6mm sawn wear layer. Our Tongue & Groove profile is machined on all four sides and is intended for glue-down or nail-down installation.
A square-edge board has no tongue to fasten through, so it is not a nail-down product in the usual sense.
Who decides what
| Decision | Who makes it |
|---|---|
| Whether the subfloor is sound, flat and dry enough | Installer, testing on site |
| Fastener type (cleat or staple), size and spacing | Fastener maker and installer, following NWFA guidance |
| Underlayment paper or sheet under the floor | Installer, following local guidance |
| Board direction and layout lines | Installer, with the designer where the look matters |
| Construction, thickness, width, profile and finish | Buyer, with the factory, written in the RFQ |
Step 1: Check the subfloor
The subfloor panels should be fastened down firmly, with no squeaks or loose areas, and flat enough that boards will not rock. High spots are sanded down; low spots are built up as the guidance allows. The installer also checks the moisture content of the subfloor and of the flooring, and compares the two, because a large difference between them leads to gaps or cupping after installation. The acceptable difference is set by the installation guidance the installer follows, not by the factory.
If the building is still drying out after wet trades, the floor waits. Our article on subfloor materials for oak flooring covers what each type of subfloor means for the method.
Step 2: Lay the underlayment paper
Over a wood subfloor, most installers lay a sheet material before the floor: asphalt-saturated felt, rosin paper, or another product the local guidance calls for. Depending on the product, it reduces friction noise and slows moisture movement from below. Over a crawl space or a basement, the vapor retarder required depends on the building and the local code. Sheets are kept flat so they do not form ridges under the boards.
Step 3: Decide board direction and snap layout lines
Board direction is usually set by the joists and by the room. Running the boards across the joists gives the fasteners the best hold. Where the design calls for another direction, the installer may add a layer of subfloor panel or follow other guidance to suit it.
The installer then measures the room and snaps a straight working line, parallel to the main starting wall and offset from it by the width of the first rows plus the expansion space at the wall. Walls are rarely straight, so the line is measured from both ends of the room and checked against the far wall. A floor that follows a crooked wall carries that error across the room.
Step 4: Face nail the starter rows
A flooring nailer needs room to swing, and close to the wall there is none. The first one or two rows are therefore set exactly on the working line, groove toward the wall, and face nailed: fasteners driven through the top face near the groove edge, where the base and shoe molding will later cover them. On some floors the first row is also blind nailed through the tongue with a smaller tool.
On a prefinished board, any face nail that will not be covered by molding is set below the surface and filled with a filler matched to the finished color. The aim is to keep visible face nails to the starter and finish rows only.
Step 5: Rack the boards out
Before nailing the field, the installer opens several cartons and lays boards out loosely in installation order, which is called racking. Racking mixes lengths and natural color movement across the room and sets the end-joint stagger, so joints do not line up in neighboring rows. Our article on end-joint stagger and board layout explains how this is planned.
The approved sample remains the reference for color and grade; if anything on site looks different, the installer raises it before the boards go down.
Step 6: Blind nail through the tongue
The field is installed with a flooring nailer that drives a cleat or staple at an angle through the shoulder of the tongue into the subfloor. The next board’s groove slides over the tongue and hides the fastener completely.
The points that make the difference:
- Seat each board before fastening. The board is tapped tight to its neighbor along the long edge and at the end joint with a tapping block or the nailer’s mallet, never by striking the tongue directly.
- Use a face protector on prefinished boards. A nailer shoe or pad suited to finished floors keeps the base of the tool from marking a UV-cured face.
- Set the nailer pressure correctly. Too little and the fastener stands proud in the tongue, so the next board will not close. Too much and the tongue splits or the fastener drives below the pocket and loses hold. The installer tests it on spare boards first.
- Follow the fastener schedule. Spacing along the board and the distance from each end come from the fastener maker and the installation guidance. Wider boards may call for a different schedule, or for adhesive in addition to fasteners, as the guidance for that width sets out.
Step 7: Finish the last rows and the details
At the far wall, the nailer runs out of space again. The last rows are face nailed or fastened with a smaller tool, and the final row is ripped to width, leaving the expansion space at the wall. Base and shoe molding then cover that space and the face nails.
Two other details:
- Changing direction. Where the floor has to run from a groove edge, for example into a hallway, a spline (a loose tongue) is glued into the groove so boards can be laid in the opposite direction.
- Doorways and transitions. Thresholds and reducers are fitted to the height agreed for each opening.
What to put in the RFQ for a nail-down floor
- The installation method: nail-down, with the subfloor type in each area
- Construction, overall thickness and wear layer
- Width, length, grade, color, texture and sheen
- Profile: T&G on four sides, with micro-bevel if specified
- Whether the floor is prefinished or unfinished for site finishing
- Any radiant heating, and any floor-height limit
- Quantity in sq ft per area, and delivery address or port
Working with Vu Uy Wood
Vu Uy Wood manufactures made-to-order solid and engineered French White Oak flooring in Song Than 3 Industrial Park, Ho Chi Minh City, and has done so since 2006. A four-side molder cuts the long-edge profile and a double end tenoner squares and end matches each board, as shown on our Production page; the profile is intended for glue-down or nail-down installation. Tell us the subfloor and installation method along with your selections on the Specify page, and the specification is reviewed with them in mind. We normally reply within one working day.