Wouldn't it be nice to have more living space in your house? If you're like most people who tackle this challenge, the obvious solution is to go down - to the basement. But damp, chilly floors can make even the most attractively finished basement room uninviting.
For a comfortable basement floor, you need to address two factors: moisture and temperature. Installing a plywood subfloor can increase warmth underfoot, but it does little to combat the moisture that naturally rises through porous concrete. And moisture turns subfloors into a moldy mess. A more effective alternative to plywood is Subflor, a new subfloor system designed to handle basement moisture and provide warmth. In about a day you can transform a cold, damp concrete floor into a warm, dry, resilient surface ready to accept most floor coverings.
How it works
Subflor consists of 7/8-in.-thick x 2-ft.-square interlocking panels. Each panel is surfaced with oriented strand board (O SB) manufactured with water-resistant natural resins and waxes that minimize moisture penetration. The underside features a layer of 5/16-in. dimpled polyethylene plastic (called Delta FL) that creates an air gap above the concrete. The air space and the OSB panel create a thermal break and act as insulation to keep the floor warm.
Subflor’s polyethylene layer also acts as a barrier to dampness. Any water that collects can flow freely under the panels to the floor drain with no damage to the Subflor or the floor covering.
The product is easy to install — a 1,000-sf floor takes a matter of hours. No glue or nails are required, and just a few common tools (a hammer and tapping block, a circular saw or jigsaw, a tape measure and a marker) will get the job done.
Get to know your basement
Despite its benefits, Subflor is not a cure for basement water problems. Before you begin any floor work, it’s important to identify problems in your basement. Is there any moisture on the floor? Does moisture seep in only occasionally, or is it a constant problem? Where does the water come from? Do you have any condensation buildup that aggravates the problem?
Occasional water seepage after a heavy rain is the most common basement moisture problem. If your basement floor is damp only after heavy rains, the Subflor system may be a suitable solution. But you can take a few preventive measures to mini¬mize future water infiltration.
Check the grading around your home for proper slope (1 in. of vertical drop for every foot of horizontal travel), and make sure you have an adequate gutter system to handle roof-water runoff.
Examine basement windows to make sure water isn’t seeping in and running down the walls onto the floor. Install window wells to help keep water away from windows.
Inspect your foundation walls for cracks. You can fill cracks as wide as 1/4-in. with hydraulic cement (this product expands and dries quickly, even in wet conditions), but larger gaps may indicate structural problems and should be evaluated by a structural engineer.
Check basement rooms for adequate ventilation. One of the most common airflow problems in base¬ments is lack of sufficient cold-air returns. Without enough returns, air does not move effectively, and even minute amounts of water can take a long time to evaporate. By increasing the airflow, you’ll encourage occasional leaks to dry up much faster. If you’re unsure whether the existing air returns are adequate, contact your utility company. Most offer home energy audits that can help identify airflow problems.
To check for condensation prob¬lems, firmly tape a 12-in. square of aluminum foil to a basement wall that is prone to dampness. In a day or two, check whether the side of the foil that was against the wall is wet. If it is, the problem is seepage. If the other side is wet, it’s condensation.
You can combat condensation problems by lowering the relative humidity — try slightly opening a window or installing an exhaust fan in the basement. If possible, raise the temperature in the basement, or install a dehumidifier. Insulate all cold-water pipes and basement walls. If your clothes dryer is in the basement, make sure that it vents to the outside.
Once you’ve solved any moisture problems, the first step in installing Subflor is to allow the panels to acclimate to the basement for a few days. During this time, examine your slab for irregularities. Repair cracks with hydraulic cement, and fill low spots greater than 1/4 in. with a self-leveling compound.
If you plan to build perimeter stud walls, now’s the time to set the sill plates in place. Follow local building codes and obtain necessary building permits. Don’t worry about the placement of future interior partitions; you can add those later directly over the panels (more on that later). If you plan to transition at any point from the Subflor panels to bare concrete (such as in doorways), fasten a 2x4 to the slab at the transition point to serve as a threshold; otherwise, the Subflor panels could slide and work free over time.
Because the Subflor system is free-floating — no glue or fasteners anchor it to the slab beneath — you’ll need to allow for seasonal movement by creating a gap around the perimeter of the floor. Allow 3/8 in. from finished walls (and around all fixed structures such as stairways, poles and cabinets) and 3/4 in. from unfinished walls.
You’ll need to cut some panels to fit your installation. All panels must be at least 6 in. wide, so plan carefully. When measuring, if you find that less into place, connecting the tongue and groove. Use a tapping block and hammer to fit the panels snugly together, and continue down the row.
When fitting the last panel in the row, simply mark the panel to size (again, allowing for the gap) and cut it using a circular saw or jigsaw (see photos.
Start the next row with a panel cut to the same length as the last panel of the first row; this will ensure the Subflor panels are evenly staggered. Continue laying the floor, maintaining a running bond. (The third row should look like the first; the fourth row should look like the second, and so on.) Once the floor is complete, remove all perimeter spacers.
One advantage of the Subflor system is that you don’t need to determine the placement of future interior walls before you lay the floor — you can place partitions directly on top of it. Simply screw the sill plates of the walls to the subfloor using 2-1/4-in. wood screws (or 1/2-in. wood screws for metal studs). Then secure the top plates of the walls to the joists above.
Though Subflor is designed to be a floating system, you can anchor the partition walls to the concrete slab beneath — a practice that’s recommended near door openings. Use 3-1/2-in. concrete nails or self-tapping concrete screws placed at the end of each wall and in the middle.
When you’re ready to add floor covering, you can install carpeting, engineered flooring or vinyl (ceramic tile is not usually recommended) according to the manufacturer’s instructions. Then take off your shoes. With the covering in place, the floor will feel as warm and dry as any room in the house.
Step 1: The dimpled polyethylene base of the Subflor panels creates a thermal break that acts as an insulator as well as a barrier to dampness.
Step 2: Before laying the floor panels, fasten any sill plates for future perimeter walls to the slab using a powder-actuated nailer.
Step 3: To start the Subflor installation, place spacers to allow for the appropriate gap, and set the first panel in a corner. Match a second panel up to it and tap the two together with a block and hammer.
Step 4: When you get to the end of the first row, mark and cut a partial panel to fit into the space (remembering to leave the appropriate gap).
Step 5: Begin the second row of panels — and create a running bond — by laying a partial panel equal in size to the last panel in the first row. Then continue the process for the rest of the floor panels.