my Old Workshop

How to build a basement floor

This time, we’ll look at another option for your basement floor.

If you have the headspace, a raised floor is your ideal choice. It provides some “spring”, which translates into an easier stroll around the room, it allows for insulation, and it raises it above the potential dampness. Count on needing at least a couple of inches to install the floor, but four inches or more is better.

As with any basement renovation for regular use, do what you can to keep things dry. Good drainage outside is key, but sealing the floor or installing a vapor barrier is a good idea, too.

We’ll run through two possible set-ups to give you an idea of your options.

In option one, you lay a series of pressure-treated sleepers directly on the concrete floor. These might be 1″ or 2″ dimensional lumber, laid flat, depending on the space you have available. You’ll likely need to shim these in places in order to get a flat floor. Space the sleepers 16″ apart; the space between them allows for drainage and air circulation. Cover the sleepers with your vapor barrier, and then install OSB subfloor on the sleepers. On top of the subfloor, you can finish with carpet, tile or wood flooring.

Option two is similar, but in this case, you build a more substantial frame of treated wood — and you need a little more headroom. Cover the concrete with vapor barrier, lay a few treated sleepers as necessary to raise the frame above the concrete, and build the frame out of 2x4s (or 2x6s) on edge, 16″ on-center. With this option, you have the opportunity to insulate between the framing lumber (keeping moisture potential in mind), yet you still have an air space for circulation and drainage. Install OSB and your finished floor as above.

In both cases, leave access to the basement drain.

You might also consider products specifically designed for basement floors. These come in tongue-and-groove panels of OSB with a membrane on the bottom, and raised sections to elevate them above the concrete.