Install a Plywood Floor

Author: Karen McBride
Photos: Karen McBride
Published: August September 2021
plywood floor
plywood floor

When you need a cost-effective flooring solution but still want the character of wide planks, consider a quality plywood for the job.

  • DIFFICULTY
    3/5
  • LENGTH/TIME
    3/5
  • COST
    3/5

It was time to lay the floor in our new three-season sunroom created from our recently rebuilt back porch. I wanted a wide plank painted wood floor that suited our 150-year-old farm­house, but worried about wood movement in wide, solid wood boards. It seemed like the perfect opportunity to try a ply­wood floor, but I was initially hesitant. How would it look? Would it hold up to the dog’s nails and foot traffic? After a bit of research, I decided to give it a go. How could I lose? In the worst-case sce­nario, it could always be an over-the-top subfloor. For a bit of wasted time and minimal materials, it seemed like a good gamble.

Rip it Up
The first strip should be ripped slightly wider, then turned end-for-end and ripped a second time to remove the factory edge. Careful cutting will give you the maximum number of strips, all of the same width, to use.

rip it up

Pin it Down
McBride uses 15-gauge nails to secure the floor in place. Her first row was lined up with the center of the room.

pin it down

Minimal Gaps
With a bit of care, McBride ensured the boards fitted together nicely. Any gaps that remain add to the character of using this approach to install a floor.

Lots of Holes to Fill
It’s a time-consuming task, but an important one. Filling the nail holes leaves you with a much nicer finished look

lots of holes to fill

Almost Done
Although McBride opted for a painted finish, using a clear finish, or even applying a stain first, is an option.

almost done

Quality plywood

For floor material I bought the best 1/2″ plywood I could find: Good One Side (GIS) sanded fir plywood for approximately $50 a sheet. Four sheets of plywood would cover the 160 square feet of the sunporch, but I bought a fifth sheet for good measure.

After cleaning up the plywood’s factory edges, ripping strips at 7-3/4″ produced six planks per 4′ × 8′ sheet. For aesthetic reasons, I didn’t want any plywood patches on the floor. In the end all five sheets were used, which was roughly 25 per cent wastage.

Start ripping

To clean the factory edge, I ripped one 8″ wide strip from each plywood sheet and set these five 8″ pieces aside. Then I ripped the remainder of the sheets into 7-3/4″ width planks being careful to always place my clean cut against the fence. When all the sheets were cut, I ripped the 8″ wide pieces to 7-3/4″, once again, with the clean cut against the fence.

Before taking the planks to the work site, I trimmed one end of each flooring plank clean and square. I marked the uncut factory end with a red lumber crayon to indicate it was the untrimmed end.

Start in the middle

It’s always advantageous to start laying wide plank flooring in the center of the room and to work outward from there, thus balanc­ing the width of the partially cut pieces needed at each end of the room. To find the center, measure across the room from the end walls and mark center in two places, close to the side walls. Snap a chalk line between those two points and lay the first run of flooring against the chalk line.

The plywood’s sanded surface is smooth enough to be a fin­ished floor so no sanding is needed once the floor is laid. To avoid mistakes, carefully stack the plank flooring on-site with the good sanded side up and the good cut ends all facing the same way. If a piece is flipped over accidentally and installed, it will need to be sanded in place.

Lay them down

To lay the floor, select a plank from the top of the pile and cut it to maximum length, eliminating any patches in the plywood. Lay and nail the next planks along the chalk line until you reach a wall. If you wanted to be extra sure the initial line was straight you could place a few other lengths beside the first row, making sure the joints were staggered. Next, lightly clamp them together and then nail the first row in place.

Use the remaining length from the final board in each row to start the next run, thus generating a random-length pattern in the flooring. Watch for the red lumber crayon mark. A red crayon mark can be placed against the wall where it will be covered with quarter round, but not in the middle of the room. The flooring can be laid tight against the walls as there is no need to worry about expan­sion and contraction with plywood. Adjacent planks should be held tightly together when nailing. Hand pressure is enough to hold them in place.

Pin selection

I chose to nail with a 15-gauge brad nailer. A heavier nail could be used, but don’t opt for anything lighter than 15-gauge. The planks were nailed along both sides at a 10″ to 16″ spacing and four nails were used to secure the planks at the corners where boards meet. When a board did not look like it was sitting flush, I stood on the high spot then nailed it down. The nail holes blend in well after fill­ing and sanding so don’t hesitate to bang in extra nails where needed.

It can be fiddly work fitting the last planks against the end walls since a partial board will need to be ripped to width. To fit these last pieces, cut a full width plank to length and lay it in place with the good side down. At each end of the board carefully mark where the board must be cut. Rip the plank then flip it over for a test fit, with the ripped edge against the wall. If the piece is close to square, the plank can be ripped on the table saw. If it must be ripped out of square, cut it with a circular saw on a piece of foam insulation or a sacrificial board. A block plane can be used to make fine adjustments, remembering that gaps can be covered with quarter round.

Don’t forget the details

To check for high spots, loose boards or joints that don’t sit level, walk around the floor in stocking feet to feel for snags and/or boards that move under your weight. Nail any high spots down and hand sand the snags with 80 grit sandpaper glued to an MDF block.

Now it’s time to fill the nail holes with wood filler using a flex­ible putty knife followed by a quick sand with 80-grit when the filler is dry. Work your way around the room in a methodical fashion so no holes are missed. With that done, the only remaining task is to install quarter round and finish the floor with paint or a clear floor finish of your choice.

My floor has been in use for over a year now and it’s holding up well. It wouldn’t be suitable for a high traffic area like a front entranceway, but a plywood floor is an economical alternative that can always be covered with a more expensive floor covering at a later date.


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