How to Install Nailed Down Hardwood Floors

The Fixer Upper Main House is really coming together now. When my husband and I started working on the house, our original plan was to use inexpensive engineered or laminate flooring. But, since we’ve saved so much money with DIY projects, and since this will be the home we live in at least for a while, we decided to splurge a bit and go with 3/4 inch thick hardwood hickory floors. And yes, this is another DIY project! This post will show you how I leveled the plywood subfloor, planned my flooring layout, what underlayment I used, and how to install nailed down hardwood floors. Ok, let’s get to it!

Leveling Plywood Subfloor for Nailed Down Flooring:

The subfloor needs to be pretty level before installing flooring. The easiest way I know to level a subfloor is to pour leveling cement. However, that doesn’t work for nailed down flooring because the nails either break up the cement or get stopped by it. I could just glue the flooring and use leveling cement. But I don’t want to toxicity of the glue.

So. I really could not find a lot of help online about how to level a plywood subfloor for a nailed down flooring installation. The only suggestions I found were to use builders paper or a roofing felt underlayment, basically tar paper, in layers as needed. Or even use asphalt shingles where thicker fill is needed. I did not like the idea of tar paper releasing vapors into the home.

Instead, I came up with a tedious, perhaps mildly crazy way to level the plywood subfloor using a wood product you can easily nail though. Here’s the plan: Use 1/8 inch thick plywood panels to fill low spots and grind down high spots in the existing plywood subfloor to create an acceptably level subfloor.

Here is a look at my leveling around the wood stove tile surround. You can see the weight of the old wood stove caused some low areas in the subfloor that I’ve filled with 1/8 inch plywood layers.

The steps to install the plywood leveling go like this: First, “contour” the 1/8 inch plywood layers in the low spots. Use a level across the floor to help see what areas need fill. It is easiest to cut the plywood with a utility knife and heavy duty scissors. Then, use some construction adhesive called Liquid Nails and staples to attached the 1/8 inch plywood layers to the subfloor.

Here is a progress photo from the living room to the kitchen area with added plywood leveling. You can also see the grinded down high points in the subfloor along the right side of the photo.

To grind down high spots, I use an angle grinder with a high grit sanding disk. This creates a lot of dust, so have the shop vacuum running along side it.

Here are some more examples of the 1/8 inch thick plywood leveling in the hallway.

This closet area was particularly low. I’m proud of my contouring work here.

Expansion Gap at Walls:

The one thing about nailed down hardwood floors that I don’t like is the shoe molding that is often times installed to cover a gap between the flooring and the wall. That gap is needed to allow for natural wood floors to expand during seasonal moisture changes. So instead of shoe molding, I decided to cut the bottom of the drywall up slightly. This will provide an extra 1/2 inch of expansion.

Here you can see the cut bottom of the drywall. The flooring easily slides beneath it. I cut the drywall up with an oscillating saw and worked around the room. Make sure you include underlayment, if you are using it, when cutting the drywall.

Underlayment for Nailed Down Hardwood Floors:

There are mixed opinions as to whether you should use an underlayment with nailed down hardwood floors. I like the option of adding some sound dampening and little bit of insulation. So I decided to use Quiet Walk Plus underlayment below our nailed down hardwood floors. Quiet Walk is typically used under floating laminate floors. But I asked our flooring supplier, and they said it was fine to use under nailed down floors as well.

Here is the start of the Quiet Walk layout. It is stapled down to the subfloor. It’s OK to use standard duct tape along the underlayment joints.

Nail Down Hardwood Floors:

Before you start laying hardwood flooring, make sure you have a good plan. You don’t want to end up with slivers of floor boards along walls. Also, the flooring should be balanced to help reduce expansion, meaning half the flooring tongues face one direction. Then the direction is flipped so the other half face the opposite direction. More on that later.

Here is my dimensioned layout of house. The arrows show where the hardwood flooring will switch direction. You can see tiled areas at the front and back doors and the wood stove. I used AutoCAD LT to draft this to scale. It does have a learning curve, but they have a 30 day free trial if you want to try it out.

This is the beginning layout of the nailed down hardwood floors! Not going to lie, I was very nervous to finally start nailing down flooring. I started near the middle of the room by screwing leftover trim boards into the subfloor. Those acted as a backer for the first row of flooring. I must have measured at least 10 times to make sure I had them set correctly! No walls are 100% straight, so I estimated my best. Plus the baseboard along the walls should cover any slight variations, so I am happy to report everything turned out to plan.

The 3/4 inch hardwood boards are nailed diagonally through their hidden tongues into the subfloor with a pneumatic flooring nailer that typically need an air compressor to supply the pressurized nailing force. I used 2 inch L-shaped flooring cleats as recommended for this flooring.

This is my husband hard at work using the nailer as he worked around the stove tile. Yes, it does put you in an awkward bent position that can be tough on your back.

Here is a trick I learned to help force a slightly warped board into place to reduce gaps between floor boards. This is called a push block. You screw the block into the subfloor. Then use a crow bar to force the floor board into place while you nail it in place. It takes some coordination for sure but was needed many times during this flooring install.

You end up on your knees a lot while installing flooring. You can see some dinky knee pads I am wearing in the video above. I soon after upgraded to some amazing gel knee pads that I wear to this day.

Nailing at Wall:

We kept working along until we got to close to the wall that we could no longer use the pneumatic nailer. There simply is no room. This is when I switched to hand drilling and nailing. It is tedious, but it gets the job done.

I couldn’t find photos from the hickory flooring install, so here is a photo from the pine flooring I installed at the Front Cabin. The concept is the same. You can see the finish nails through the tongue of the flooring board. Pre-drill those holes to avoid splitting the tongue and nail 6d x 2 inch finish nails in place. Nail punch setters come in real handy here to drive the nail flush.

The last row or two along the wall simply wont have enough room to drive a nail at an angle. These last rows you’ll need to drill vertically through the flooring and finish nail them in place. You can come back later and fill the visible nail holes with colored wood filler to match your flooring. That will make the holes all but disappear completely.

Flip Direction in Nailed Down Hardwood Floor:

Now let me show you how to flip the tongue direction of nailed down flooring. To do this you simply fill the exposed groove end with a wooden dowel that is shaped to fit. This dowel is called a “Slip Tongue and can be found in the flooring section at Home Depot.

Here is a photo of the slip tongue dowel and the flipped flooring. Use wood glue to hold the dowel in place. Nail the dowel in place like a standard tongue board. Then connect and nail the new flipped-direction board and away you go.

This is progress shot of the flooring in the living room. A lot of boards are laid out to choose from.

More progress moving into the kitchen and hallway. The entry area where I am standing will be tiled.

This is looking towards the hallway from the living room. You can see the area for tile at the entry door.

Looking back towards the living room from the kitchen.

Below is the hallway towards the closet and bathroom. You can see a perpendicular board along the hallway closet tile for a finishing touch. That had to be nailed in place before the rest of the flooring. I am so thankful everything came out basically perpendicular.

The bottom section of the hallway closet is tiled as a “fancy” spa bathroom for the cat! Lol. You can check out more details on that here.

Below is the finished nailed down hardwood floor in a bedroom. To avoid a shoe molding, the flooring is installed within 3/8 of an inch from the drywall. With the drywall cut up from the top of the floor, the gives over a 3/4 inch expansion gap which is more than enough. A 5/8 inch thick x 4 inch tall simple baseboard will finish the space.

Nailed Down Hardwood Flooring Close-ups:

I left about a 1/4 inch gap for expansion between the hardwood flooring and the tile at the bathroom. Here is a closeup of the gap where you can see the top of the tile is basically flush with the 3/4 inch thick hardwood flooring.

To keep the transition to between the bathroom and the hallway smooth and simple, I added a bead of gray silicone caulk in the expansion gap. The caulk will compress under the flooring expansion. Here is the cap with the silicon caulk. You can also see the brass inlay I installed in the tile floor. More on that here if you’re interested.

I used black silicone caulking in the small expansion gap between the slate tile at wood stove and the hardwood floor. It’s clean and simple.

Here is the finished floor with the modern looking baseboard and NO shoe molding. I love how simple and clean it turned out.