In most Philadelphia rowhome and twin basements, the best floor is one that a little water can't ruin: porcelain or ceramic tile, sealed or coated concrete, or a vinyl plank or tile that its manufacturer rates for below-grade concrete. Engineered wood can work if the product is approved for basements; solid hardwood and wall-to-wall carpet laid straight on the slab are the usual regrets. Before you pick a material, do two things: find out how water gets into your basement and how damp the slab is, and if there's old tile down there, find out whether it contains asbestos before anyone pulls it up.
Start with the water, not the floor
A basement floor fails for one of three reasons, and each has a different fix.
- Seepage through the walls or the floor-wall joint, usually from gutters, downspouts and ground that slopes toward the house. The fixes are mostly outside, and no flooring will solve it.
- Sewer backup through the floor drain, a basement toilet or a laundry tub during heavy storms. The Philadelphia Water Department's Basement Backup Protection Program installs backwater valves for eligible homeowners at no cost.
- Moisture from the slab and the air. Old slabs often have no vapor barrier under them, so moisture moves up through the concrete. In a humid Philadelphia summer, warm air also meets the cool slab, and water condenses on it. A dehumidifier helps with the air; the slab itself needs a floor that tolerates it.
Watch the basement through a few heavy rains before you commit to a floor. Look for damp patches, white mineral deposits on the walls, water at the base of the walls and stains around the drain. If the floor gets wet now, it will get wet after you install a new one.
Test the slab before you buy anything
A simple first check: tape a square of clear plastic tightly to the bare slab on all four sides and leave it for a day or two. Droplets under the plastic mean moisture is coming up through the concrete. Droplets on top usually mean humid air is condensing on a cold floor. It's only a rough check, but it tells you whether you have a problem.
Real numbers come from standard tests. The two most common are the in-slab relative humidity probe (ASTM F2170) and the calcium chloride test (ASTM F1869). Most flooring manufacturers state which test they require and the maximum reading they allow for their warranty. A flooring installer can run the test the product's instructions call for. Ask for the result in writing, because a moisture claim is the first thing a manufacturer will look at.
Old tile and black glue: check for asbestos first
Some older basements still have small, square resilient tiles, often stuck down with black adhesive. Old floor tile, its backing and the adhesive can contain asbestos, and you can't tell by looking.
The EPA's advice for homeowners, from its page on protecting your family from asbestos:
- If suspect material is in good condition and won't be disturbed, you don't need to test it.
- Don't sand or try to level asbestos flooring or its backing, and never use a power stripper on it.
- When asbestos flooring needs replacing, install the new floor covering over it, if possible.
- Sampling should be done by a trained and accredited asbestos professional.
That last point matters for basements, because floating floors and many vinyl products can go right over old tile that's flat and well bonded, leaving it undisturbed.
If the tile has to come up, Philadelphia's Air Management Services regulates the work. According to the City's asbestos project permit page, removing 80 square feet or more (or 40 linear feet or more) of asbestos generally needs a permit that only a licensed asbestos abatement contractor can get, and smaller removal or encapsulation generally needs a notification at least 24 hours ahead. A typical basement floor is well over 80 square feet. Rules have details and exceptions, so call the Asbestos Information Line at (215) 685-7576 before you plan removal.
Basement flooring options, compared
Porcelain or ceramic tile
Tile set in mortar on the slab doesn't care about getting wet, and after a backup it can be cleaned and disinfected. The downsides: it's cold and hard underfoot, the slab has to be fairly flat (old Philadelphia slabs often aren't), and cracks in the concrete can telegraph through. Ask the installer how they'll handle existing cracks and uneven spots. Grout is the weak point after a sewer backup, so a sealed or less porous grout is worth asking about.
Sealed, stained or coated concrete
If the slab is in decent shape, the cheapest durable floor may be the slab itself: cleaned, repaired and finished with a sealer, stain or a coating such as epoxy. Water and cleaning don't hurt it. The catch is that coatings can peel when moisture comes up through the slab, so the moisture test matters here too. The product's instructions will say what preparation and moisture limits it needs.
Vinyl plank and tile
Rigid-core or flexible vinyl plank and tile are popular basement choices because the material itself isn't damaged by water. Read the fine print, though:
- "Waterproof" describes the plank, not the slab under it. Water that gets under a floating floor can sit there, and mold can grow on anything organic underneath.
- Check that the product is approved for below-grade concrete and what moisture limit the warranty sets.
- A floating click floor can be taken up and dried after a flood; a glue-down floor stays put but depends on the adhesive tolerating the slab's moisture.
- Vinyl with an attached foam or cork pad changes how it handles moisture; follow the manufacturer's underlayment rules exactly.
Engineered wood
If you want wood in the basement, it should be engineered. The National Wood Flooring Association's installation guidelines treat solid wood as unsuitable below grade, while engineered and floating floors can be appropriate there. Those guidelines generally count a level as below grade when the surrounding soil is about 3 inches or more above its floor, which describes almost every Philadelphia basement. Even engineered wood won't survive standing water, so it only makes sense in a basement that stays dry, and only with a product rated for it.
Laminate
Many laminates have a wood-fiber core that swells if it gets wet and doesn't recover. Some newer products are sold as water-resistant. If you're considering laminate, check whether the manufacturer approves it for basements and what the warranty says about water from below. In a basement with any history of water, vinyl or tile is the safer bet.
Carpet
Wall-to-wall carpet with a pad, laid straight on the slab, holds water after a leak or backup and usually has to be thrown out. Carpet tiles are the more forgiving version: wet tiles can be lifted, dried or replaced one at a time. If you want carpet for warmth, put it on top of a hard floor as an area rug you can roll up.
Subfloors, height and the floor drain
Raised subfloor panels or a dimpled membrane under the floor let air move over the slab and make the floor warmer. They also take up height. Many Philadelphia basements are already low, and if you're finishing the space into a room, the code sets minimum ceiling heights measured from the finished floor. Our guide to finishing a basement in Philadelphia covers ceiling height, radon testing and moisture in more detail.
Whatever you install, keep the floor drain, the sewer cleanout and any backwater valve uncovered and reachable. If you cover them, the next plumbing emergency starts with someone cutting up your new floor.
Do you need a permit?
L&I says that if your property isn't on the Philadelphia historic register, you often don't need a building permit for conventional floor coverings. Replacing the floor in a basement that's already finished usually falls under that. Turning an unfinished basement into living space with walls, wiring and plumbing is different and generally needs permits. In Bucks and Montgomery counties, permits are handled by your township or borough, so check its building office.
A basement flooring checklist
- Watch the basement through a few heavy rains and note where water shows up.
- Fix outside drainage first: gutters, downspout extensions, grading.
- If the basement has had sewer backups, look into a backwater valve.
- Run a dehumidifier through the humid months.
- Do the plastic-sheet check, then have the slab tested the way the flooring's instructions require.
- If there's old tile or black adhesive, leave it alone until you know whether it contains asbestos; consider covering it instead of removing it.
- Choose a floor rated for below-grade concrete, and keep a copy of the installation instructions and warranty.
- Plan around the floor drain, cleanout and valve so they stay accessible.
- Measure the ceiling height before adding a raised subfloor.
When to call a pro
A floating vinyl floor over a dry, flat slab is a job some homeowners handle themselves. Call a flooring pro when the slab is cracked, uneven or damp, when the floor will be tile or glue-down, or when you want a moisture test done properly. Call an accredited asbestos professional, not a flooring installer, to sample old tile or adhesive, and a licensed abatement contractor if it has to come out. If water comes in through the walls, a flooring pro isn't the first call; deal with the source first.
When you ask for estimates, tell each pro the size of the basement, what's on the floor now, how often it gets wet and from where, and whether the space is finished. Ask which product they'd use, whether it's rated for below grade, how they'll prepare the slab and how they'll handle the drain. Our guide on how to check a contractor in Philadelphia covers the state registration and the written contract.
On HomeKept you can describe your basement floor once, with photos of the slab and any old tile, and compare up to three estimates from local flooring pros in Philadelphia. It's free for homeowners, a person reviews every pro profile, and HomeKept covers Philadelphia, Bucks and Montgomery counties.
HomeKept is a brand of FalconAI LLC, 331 E Street Rd, Feasterville-Trevose, PA 19053.
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