How to Clean Subfloors (with Video Tutorials)

how to clean subfloor

Photo by Pete Brown / CC BY

Subfloors are notorious for getting dirty. Subfloors are the platforms underneath your existing floors that were probably last seen (and cleaned) when they were installed. Depending on the age of your home, that could’ve been decades or, if you live in Philadelphia, even centuries ago.

As a result, you won’t have to clean you subfloors that often — if at all — unless you have a persistent issue with your floors or rooms in general. For example, is there an odor that you can’t locate and eliminate? Do you hear an uncharacteristic noise, like a wet or spongy sound, when you step on a certain area? Or, otherwise, do you just want to clean your subfloors as part of your home maintenance?

Regardless of your reason, cleaning your subfloors is surprisingly easy. The methods differ depending on what kind of subfloor you have, so we’ll discuss the two main types of subfloors in this blog — plywood and concrete.

We’ll focus on these two subfloors because they’re by far the most common that you’ll find. Plywood subfloors are often used in modern buildings on every story of a home. Concrete is sometimes seen at the foundation of a house, such as in an unfinished basement or a foundation-based patio. As a result, you don’t often see much more in a subfloor than plywood or concrete.

Let’s start with the more common type of subfloor today — plywood.

How to Clean Plywood Subfloors

Cleaning plywood subfloors is trickier than cleaning concrete subfloors because plywood is absorbent. This means you can’t just “mop” your subfloor or use an excessive amount of cleaning solution. Instead, you have to be more tactical.

The first step is to expose your subfloor. Do this by safely removing your current floor and keeping it in tact to the best of your ability. Once your plywood is exposed, it’s time to grab a vacuum cleaner. We recommend a Shop-Vac since they’re the heavy-duty cleaning solution with a wide hose that can accommodate large shards of wood, glass, and dust.

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Vacuuming is a crucial part of cleaning plywood subfloors because, as we’ve established, plywood is absorbent. Because of that, it’s crucial to get as much of your subfloor cleaned with a Shop-Vac as possible.

Also take the time to clean the spaces between the subfloor and the walls, if any exist, and any cracks, openings, or gaps that are between the subfloor plywood sheets. By the end of vacuuming, your plywood subfloor will most likely still look dirty — but when you drag your finger across the surface, you should only get a light dusting of dirt on your fingertip.

If you’re still seeing black or dark brown streaks of dust on your subfloor, continue cleaning with a Shop-Vac until they’re gone. Once you’re done vacuuming, it’s time to start using your cleaning solution. This can be tricky because, again, plywood is absorbent.

In fact, plywood is more absorbent than almost every other kind of wood because it’s made of wood pulp, meaning there’s even more space between the wood particles than conventional wood. As a result, plywood can absorb liquids exceptionally quickly unless it’s treated, but treated plywood is almost exclusively for outdoor use, so you probably don’t have it on your subfloor.

Depending on your comfort level with cleaner, use a cleaning solution of one of the following (but not all three):

  1. Water & soap
  2. Water & vinegar
  3. Water & bleach

Water and soap will be enough to clean most conventional stains and mildews off of plywood. Vinegar is a little stronger, so it can take care of some more stubborn stains. Obviously, bleach is the strongest solution here and it should only be used with great care and in a well-ventilated area, in addition to wearing face and respiratory protection.

Regardless of your choice, less is more when it comes to cleaning plywood with a liquid. Use a rough sponge or even wire gauze to add some extra grit and pressure to what you need to clean.

Then spot-clean the areas you need. This is crucial to maintaining the integrity of your subfloor’s structure. If you use too much cleaner, it could soak into the plywood and cause issues in the future. But if you dab a small amount onto your cleaning implement and then work on a few spots at a time, there won’t be much (if any) excess liquid to absorb.

This will allow you to wipe away any problematic stains on your subfloor while allowing your implement to catch and soak the excess.

Once you’re done, let your subfloor sit and air dry, preferably with fans to circulate air. Let them work until the plywood is dry and odorless, and then cover with your floor.

Subfloor Preparation for New Flooring

How to Clean Concrete Subfloors

Concrete subfloors are much more straightforward. Concrete is not nearly as porous as plywood, and it strengthens as it ages. This means that your concrete subfloor is a solid, single slab — except for any areas that you’ve drilled or nailed.

Otherwise, you can clean your concrete subfloor by first removing your floor and vacuuming the entire surface. Again, we recommend a Shop-Vac for this, but you could get away with a conventional vacuum cleaner since concrete is often so level.

Next, mix the cleaning solution of your choice in a well-ventilated area, ensure your work area is ventilated, and start cleaning with your liquid option. Because you’re working on concrete, you can use liquid cleaner much more liberally than on plywood.

In this case, you can use a mop to fully douse and clean the subfloor, ensuring you wipe down every single spot on the subfloor’s surface.

If you do use something like a mop, watch for liquid buildup that could move toward your walls, especially if you have drywall. This excess liquid could end up soaking into your drywall and causing water damage. Otherwise, you’re most likely in a position to clean without much consideration for anything else.

Once you’re done, you can soak up the excess liquid with towels or use fans to air-dry the subfloor. Then you’re done!

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  • Founder of Mechanical Caveman, Beau is an unrepentant tool enthusiast and, sporting deadlift-callused hands and an incongruous beer belly, all-around macho guy. When he doesn’t know re tools, he consults with his handyman and car-repairman buds to give you well-reasoned and cutting-edge info.

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