How to Install Hardwood Flooring on Concrete
Two weeks ago I unveiled my new office, complete with hardwood planked floors. Since the room is located in the basement, I had to figure out a way to install the flooring on concrete.
I came up with three options and chose the best one for this particular project. Can you guess which one I used?
The first approach is to glue the boards directly onto the concrete pad. This is the fastest way to install flooring, but there are drawbacks. I count three:
- Since concrete pads are rarely perfectly flat (or smooth), the flooring would probably not lay level.
- I lack enough weights to brace the wood down until the glue cured. Without the weights, you risk having air bubbles/pockets between the boards and the concrete.
- If any boards need straightened, which will always be the case when installing wood flooring, it would be impossible to use a pry bar in the concrete.
The second option is to glue down a subfloor of OSB or other sheet wood directly to the concrete, then secure the hardwood to the subfloor. This will give you a flat surface and also allow you to sink a pry bar into the wood subfloor to persuade any crooked boards to fit snugly with its neighbor.
There are shortcomings too:
- It takes longer to install because you need to first wait for the subfloor to bind to the concrete before installing the flooring.
- Since the planks are much wider than traditional hardwood floors, you cannot fully nail down the entire board without exposing some nails or screws.
The final solution has some similarities with Method 2. You start by securing the flooring to the OSB subfloor before gluing the OSB to the concrete. The main advantage is that you can hide the screws/nails because the boards can be screwed from the OSB side vs. from the face of the boards into the OSB. Just make sure you buy screws that are about 1 1/4″ long or there will be sharp points sticking through.
The disadvantages to this approach are:
- Each sheet will weigh a lot so it becomes a chore to muscle each one around.
- It’s difficult, though not impossible, to use a pry bar to help straighten boards since you are attaching screws from the backside.
- You need to make sure the flooring aligns up with each sheet. In other words, you are stuck to exactly 4 ft wide sections. Not a big deal, but ripping 10-11 ft long oak boards by yourself isn’t that much fun either.
I chose….Method 2. For a while I planned on Method 3. If I had an extra set of hands and could find 12 ft OSB sheets, then I probably would have stayed with that approach. Since my room is 11 feet x 11 feet, I was concerned about the unsightly seams that would be caused by having to use 8 ft and 3 ft sheets of OSB, which ultimately made me change to Method 2.
It’s also a good idea to install a moisture barrier between the OSB and the concrete. Concrete is known to sweat, which could damage the subfloor.
To hide the nails, I first considered boring out small holes for screws and then pound in plugs. It would be impossible, however, to completely hide the plugs. Instead, I glued each board using tubed glue similar to liquid nails. I then nailed brads into the boards for extra support while the glue cured. The brads were easily hid by tapping them into the wood and then applying a small amount of wood putty into the hole.
The brads were not strong enough to hold the board stationary if it needed straightened more than 1/8 inch, but otherwise fulfilled their purpose.
With large planks like this, I still ended up with some unsightly gaps. Watch this video to learn what I did to fix the problem.
Here is a picture showing the subfloor.