If there’s one thing I’ve learned in my years of flooring work, it’s that moisture is the silent enemy lurking under your laminate. You might think everything looks fine on the surface, but a damp subfloor can lead to warping, mold, or a floor that squeaks louder than a mouse in the attic. I’ve been there—rushing to install laminate only to realize later that the subfloor was holding water like a sponge. Trust me, catching the problem early is worth its weight in gold. In this post, I’m going to walk you through how to spot a wet subfloor, dry it properly, and prevent future moisture nightmares, so your laminate stays snug as a bug for years to come.
Understanding Subfloor Types
Before you roll up your sleeves and start drying a subfloor, it pays to know what you’re dealing with—because not all subfloors are cut from the same cloth. I’ve seen more than a fair share of surprises once the laminate came up.
Plywood is the most common subfloor under laminate, and it’s generally sturdy. But don’t be fooled—if it soaks up water, it can warp or delaminate faster than you can say “wet blanket.”
OSB (Oriented Strand Board) is another popular choice, especially in newer builds. It’s a bit like a sponge—absorbs moisture quickly and swells unevenly, which can turn a smooth installation into a real headache.
Concrete is a whole different ballgame. It doesn’t warp, but it can trap moisture from below, making it a slow-burn problem if you don’t address it right away. I’ve had days spent chasing hidden damp spots in concrete before I even thought about laying laminate.
Existing wood planks in older homes can be tricky, too. Uneven drying, gaps, or hidden mold can make them unpredictable. I always inspect and measure moisture carefully before touching a single plank—better to be safe than sorry.
Knowing your subfloor type helps you pick the right drying method and prevents you from barking up the wrong tree. Each type has its quirks, and ignoring them is a sure-fire way to invite headaches down the line.
Signs Your Subfloor Is Wet
If you’ve ever stepped on a floor and felt it squish or noticed a funny smell, you know that moisture has a way of giving itself away. From my experience, catching a wet subfloor early is half the battle.
One of the first red flags I look for is a musty smell. That damp, earthy odor is like a neon sign screaming, “Check under here!” Another clue is warping or buckling laminate—even small ripples can signal that the subfloor beneath is holding water. I’ve had floors that looked fine at first glance, only to reveal hidden trouble once I pulled back a plank.
Mold spots or discoloration are the more obvious culprits. If you see black, green, or white fuzz appearing along seams or edges, it’s time to act fast—mold spreads quicker than gossip in a small town.
Finally, keep an eye on common triggers like leaks from plumbing, spills, or high humidity. I always say, “Don’t wait for the storm to flood the barn”—catch these issues before they sneak under the floor. Early detection can save you a world of headaches and keep your laminate looking sharp for years.
Immediate Steps to Prevent Further Damage
Once I spot a damp subfloor, I know it’s time to jump into action—nipping the problem in the bud can save a ton of grief down the road. The first thing I do is remove furniture and any flooring covering the wet area. You don’t want heavy pieces trapping moisture or making the floor buckle further.
Next, I ventilate the room like my life depends on it—open windows, crank up fans, and get air circulating. If you’ve got a dehumidifier, plug it in and let it work overtime. I’ve found that even a few hours of proper airflow can make a noticeable difference, but sometimes it’s a marathon, not a sprint.
Safety precautions are also key. If you see mold or suspect contaminated water, I don’t mess around—I wear gloves and a mask. Nobody wants to catch a bug while trying to save a floor.
Taking these immediate steps may not solve everything, but it keeps the situation from snowballing while you figure out the best way to dry the subfloor properly, which is where the heavy lifting begins.
Methods to Dry a Subfloor
Drying a subfloor under laminate flooring isn’t a task to take lightly—trust me, I’ve learned that the hard way. If you rush it or cut corners, you can end up with buckling laminate, mold, or a floor that squeaks like an old mouse in the walls. Here’s how I handle it, step by step, depending on the type of subfloor and severity of moisture.
1. Air Drying:
For mild dampness, I rely on good old airflow. I start by opening every window I can and turning on ceiling fans to push the air around. Then I set up portable fans, aiming them at the wet spots to speed up evaporation. I’ll also move furniture out of the way so nothing is trapping moisture underneath. This method is slow and steady—usually a couple of days for plywood or OSB to dry completely—but it’s gentle and keeps the subfloor intact. I check daily by pressing on the wood and sniffing for any lingering damp smell. If it still feels cool or musty, I leave it alone; rushing it is a surefire way to get problems later.
2. Heat Drying:
When dealing with localized wet spots or stubborn corners, I bring in controlled heat. A small portable heater or even a hair dryer on low can work wonders. I keep the heat moving and never let it linger in one place, because concentrated heat can damage the subfloor or warp the laminate later. I also make sure to ventilate while heating—trapped heat can create condensation elsewhere. Heat drying works best on small areas that the air-drying method can’t reach.
3. Dehumidifiers and Moisture Absorption:
Sometimes airflow and heat aren’t enough, especially in concrete subfloors or in high-humidity climates. That’s when I plug in a dehumidifier and leave it running day and night. It’s like a moisture vacuum, pulling water from the air and speeding up the drying process. I also use absorbent materials like silica gel packs or specialized drying mats for tricky areas. A moisture meter is my best friend here—I measure the subfloor daily to make sure it’s actually drying instead of hiding water in the wood.
4. Professional Equipment:
For major moisture issues, I don’t try to reinvent the wheel. Industrial drying machines, floor mats, and commercial dehumidifiers are lifesavers. I’ve seen floors that looked fine on the surface, but the professionals pulled up readings that made my jaw drop. If the subfloor is concrete or water has been sitting for a while, this is often the only reliable way to get it dry without risking mold or long-term damage.
Tips from Experience:
- Always start with the least invasive method and move to stronger methods if needed.
- Patience pays off. Trying to rush the drying process is like trying to run before you can walk—you’ll only make matters worse.
- Keep monitoring moisture daily; the surface might feel dry, but deeper layers could still be wet.
By combining airflow, heat, moisture absorption, and professional equipment when needed, I’ve been able to save countless floors from damage. Drying a subfloor properly is the difference between a laminate floor that lasts decades and one that becomes a costly headache.
Checking Subfloor Moisture Before Installing Laminate
Before I even think about laying a single plank of laminate, I always check the subfloor moisture. I’ve learned the hard way that skipping this step is like playing Russian roulette with your floor—it might look fine at first, but trouble will show up sooner or later.
1. Using a Moisture Meter:
This is my bread-and-butter tool. I press the meter against different spots on the subfloor—corners, seams, and areas near windows or plumbing. It gives an instant reading of the moisture content. For plywood or OSB, anything above 12–14% is a red flag in my book. Concrete has different tolerances, usually measured with relative humidity probes, but the principle is the same: if it’s too wet, don’t touch it.
2. The Calcium Chloride Test (for Concrete):
For concrete subfloors, I sometimes use the calcium chloride test. It measures the amount of moisture vapor coming up from the slab. I place the test kit on the floor, cover it, and leave it for 24 hours. The reading tells me whether it’s safe to install laminate or if I need more drying time. It’s a little extra work, but it beats peeling up warped laminate later.
3. Digital Hygrometer:
When I’m unsure about the overall room humidity, I’ll use a digital hygrometer. It helps me see if the air itself is too humid, which could slow drying or cause future problems. Even if the subfloor reads dry, high humidity can sneak in trouble from the sides or through the slab.
Personal Tip:
I never lay laminate without taking multiple readings across the room. Moisture can hide in pockets, and it’s better to be safe than sorry. One high reading can save you from a future headache that costs hundreds or even thousands to fix. In my experience, investing a little time in moisture checks upfront is like putting your money where your mouth is—you’ll thank yourself later.
Preventing Future Moisture Problems
Once I’ve dried the subfloor and ensured it’s safe for laminate, I don’t just sit back and hope for the best—I take steps to keep moisture from coming back. From experience, prevention is worth its weight in gold.
1. Use a Vapor Barrier or Moisture-Resistant Underlayment:
Whenever I install laminate over concrete or in areas prone to humidity, I always lay down a quality vapor barrier. It’s like giving your subfloor a raincoat—keeps moisture from sneaking up from below. For wood subfloors, moisture-resistant underlayment adds an extra layer of protection and cushioning, reducing the risk of warping down the line.
2. Seal Subfloor Seams and Gaps:
I make it a habit to inspect seams and gaps in the subfloor before installation. If I spot cracks or openings, I seal them with a suitable sealant. Think of it as plugging the holes before the flood comes—one small gap left unchecked can lead to bigger headaches.
3. Control Indoor Humidity:
I keep a close eye on indoor humidity, especially in bathrooms, kitchens, or basements. Using a dehumidifier during wet seasons or running an exhaust fan while cooking or showering can make a huge difference. High humidity is like the silent thief of laminate floors; you don’t see it at first, but it can do serious damage over time.
4. Regular Maintenance:
I also make it a point to clean up spills immediately, avoid wet-mopping excessively, and periodically inspect the subfloor where possible. Prevention isn’t a one-and-done deal—it’s an ongoing habit. A stitch in time saves nine, as I like to say.
By taking these preventive measures, you can rest easy knowing your laminate floor will stay snug as a bug in a rug, resisting moisture problems for years to come.
When to Call a Professional
Even after all my years of handling subfloor moisture, I know when to throw in the towel and call a professional. Some situations aren’t worth risking your laminate floor—or your health—by trying to DIY.
If you’re dealing with major leaks, prolonged water exposure, or extensive mold, it’s time to bring in the experts. I’ve learned that tackling these problems without the right equipment is like trying to empty the ocean with a teaspoon—you’ll just end up frustrated and behind the eight ball.
Professional equipment like industrial dehumidifiers, floor-drying machines, and moisture meters can do the heavy lifting in ways that household tools simply can’t. I’ve seen pros uncover hidden moisture pockets that I would have never spotted, saving homeowners thousands in future repairs.
