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Why Does Concrete Sweat | Guide To Stopping Concrete Sweat

Sweating Slab Syndrome (SSS) happens from moisture that accumulates from the difference between the inside air temperature and the floor temperature. When the air vapor cools down and matches the floor temperature, condensation forms on the concrete, this is also known as concrete sweating.

Safety is a top concern for all businesses. When smooth slabs of concrete are wet, it poses additional safety concerns for workers. Many slip-and-fall accidents happen from slippery surfaces and are one of the most common workers’ compensation claims from occupational injuries. On top of slip-and-fall injuries, a slippery surface can cause equipment to slip and slide, causing severe injuries to employees and staff.

Concrete sweating slab syndrome also contributes to poor air quality and undesirable indoor environmental conditions. Moisture causes mold and fungus. Not only can it ruin contents and inventory, but it also poses an air quality safety risk for everyone in the building.

The buildup of moisture from temperature swings doesn’t just affect people and concrete floors. Moisture problems can also cause machinery and materials to sweat. In addition to the primary safety concerns from moisture on concrete slabs, moisture in the air and on surfaces can also damage inventory, machinery, and the building structure itself.

How can you keep your employees safe from sweaty slabs? No sweat no problem! MacroAir has your back and keeps the air moving.

What Causes Moisture on Concrete Slabs or What Causes Concrete to Sweat?

Reduce Moisture

Basically, everything can experience sweating slab syndrome after cooling down during hot or humid temperatures. Moisture, as you would guess, is the underlying cause of sweating on concrete floor slabs.

This usually happens when concrete slabs and other materials that sweat reach dew point temperature. Usually, warm, moist air and relative humidity enter the structure through several openings (windows, doorways, and vents). As air diffuses, moisture comes up through the concrete floor. It condenses on surfaces that are at or below dew point temperature.

Another factor that can cause Sweating Slab Syndrome is salt deposits on the surface of the slab. In such situations, the hygroscopic nature of salt will act to attract moisture from the air onto the surface of the concrete slab. Sometimes this salt even draws water from within the concrete.

So, what can be done to avoid the risks of excessive moisture content and costs associated with sweating concrete slabs? 

How to Spot a Moisture Condition on a Concrete Floor

Warehouse concrete

Moisture vapor transmission can lead to large expenditures, repairs, and even production downtime, which can result in loss of revenue. While your concrete floor may seem fine, there are a few things to look for keeping in mind, the earlier you notice a moisture condition in the building, the quicker you can take necessary measures.

  • Do you notice damp spots or dark discoloration on the concrete slab? This could be slab moisture.
  • Are there unexplainable cracks or splits in the concrete?
  • Does your concrete slab have a white residue? If so, this could be alkali/salt deposits from condensed moisture vapor on your concrete flooring.
  • Do you smell musty, mold growth, or mildew in your building?
  • Do you notice black spots along the bottom of walls, other flooring material, machines, or inventory?
  • Does your building have unusually moist air?

So, what can be done to avoid the risks of excessive moisture content and costs associated with sweating concrete slabs? 

Here are 6 Ways to Reduce Concrete Floor Condensation:

1. Dry Out Your Warehouse and Materials Using Air Movement

Sometimes you come in the early morning, and you find your concrete flooring or slab soaking wet, “just sweating.” Industry expert Jason Hornsby sees this common problem with his clients. 

“For my clients in the South, sweating slab is a big issue due to the humidity. If they have a high volume low-speed fan, they can come into work, turn it on, and within an hour or less, it’s totally dry. Some people even say that if they know they’re going to be getting those temperature swings that certain time of the year, then they could just leave the fans on all night, and the floors won’t sweat.”


One other tip is to try to keep the air and the concrete floor temperature levels close to the same. One way to do this is to turn down the air conditioning and turn up the heat. An HVLS fan can help regulate fluctuating temperatures while keeping costs down, and they can also prevent moisture problems on a concrete floor.

2. Prevent Moisture on Industrial Concrete Floors with Good Housekeeping Practices

Always remove any deposits and excess moisture from the surface of your slabs. An excellent way to do this is to use commercial cleaning agents to scrub your floors and vacuum your machines. This is an important safety measure for employees, and it protects your assets. If possible, seal the concrete to keep out moisture with a penetrating sealer. It is recommended to use a concrete densifier primer, and then a stain repellent that penetrates the concrete. This will help prevent a moisture problem.

3. Re-examine Air Movement Within the Facility

Often, sweating slabs occur because the air inside the structure can’t easily flow out. If the air movement inside the building isn’t sufficient, it is necessary to find a means to de-stratify the air and reduce the relative humidity levels. An HVLS fan not only helps de-stratify the air but also helps keep your employees cool and comfortable by reducing moisture content in the air. We’ve also seen massive improvements in air quality with ceiling fans and other tips.

4. Fans for Sweating Concrete

HVLS, or High Volume Low Speed fans, also increase the floor surface evaporation rate, minimizing moisture content in the air. These fans provide cost-effective ways to keep your structures cool, increasing drying while preventing the buildup of moisture on your floors. The end result is comfort and safety.

5. Install Commercial Dehumidification Units

Although these are costly units that add to your overall energy bill, they are known to alter the interior building humidity environment, which may help reduce or eliminate SSS caused by moisture on a concrete surface.

6. Use Low-Permeance, Low-Slab Retarders to Reduce Moisture Damage

This can prove particularly effective when products are stored directly on the floor. They tend to reduce the possibility of moisture rising and condensing beneath stored products.

Mysteriously enough, even if you do not have bare concrete floors and you have carpet, floor tiles, vinyl, or wood flooring, moisture and condensation can still cause Sweating Slab Syndrome with temperature fluctuations. Moisture under the flooring laid over concrete floor slab can ruin the adhesive that holds the top flooring in place.

A Moisture Issue Affects More Than Concrete – Even Metals Sweat

Interestingly, even metals in most structures can sweat! At an aluminum company in the humid South, the company ran into issues with its metals sweating. In particular, they had a lot of black iron, and once it would sweat, it would begin to rust. The rusting of their black metal resulted in a significant loss to the value of their inventory. The metal was actually trying to change the temperature, and as a result, it caused a buildup of condensation.

When temperatures fluctuate in the spring and fall, you may end up with cool nights and hot days. Many of those days are with high humidity. You can help reduce humidity on your concrete floors and metal surfaces by creating more airflow throughout the building to create a more even temperature with thermal equalization.

Combating sweaty slab and their impact on a valuable product is a very important issue.

See How MacroAir Fans Solve Sweating Slab Syndrome

Eliminate a sweating slab

HVLS fans are the ideal solution to eliminate a sweating slab in your warehouse. HVLS fans move around the air in your building so that the temperatures from the ceiling to the floor are nearly equalized. This reduces the humidity throughout your entire warehouse, which means the concrete slab is much less likely to grow wet and your employees will stay safer.

Your workers have to operate safely, using established safety procedures, inside your warehouse. To increase safety in your warehouse, use a proven solution like HVLS fans to reduce the humidity levels and remove any condensation. Stahl advises that,

“Simply turning the fans on when you arrive at the warehouse is, in most cases, enough to create a safe and comfortable environment for your employees.”


Preventing Moisture on Concrete Floors Starting Now

Stop Contrete Sweat

Many industries and companies have concrete flooring, and almost everyone has experienced sweating concrete floor slabs. Moisture in concrete slabs poses a considerable risk for workers along the corridors, so it’s important that you deal with it as soon as possible. More often than not, this is climate and temperature-related, and blasting your AC won’t get to the root of the problem.

Adequately combating slab moisture with HVLS fans will help protect your machinery, product, and building, by minimizing mold and mildew on a concrete floor slab, and, most importantly, addressing the safety of your employees in a cost-effective way.

Keeping your facility cooler and moisture-free is really as simple as adding MacroAir HVLS fans. Your employees will sing your praise, and your facility would be singing if it could! 

Prevent sweating slab syndrome and moisture accumulation before it ever begins. You can also download the 6 easy ways to reduce concrete floor condensation below. 



Contact us today to talk with an expert about the benefits of MacroAir’s big fans or visit our site by clicking the link below. You will be blown away by the form, function, and life-changing effects provided.

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Frequently Asked Questions

  • How do you stop concrete from sweating?
  • Does all concrete sweat?
  • At what temperature does concrete sweat?
  • Does sealing concrete stop moisture?
  • Can moisture seep up through concrete?
  • How do I stop condensation in my concrete garage?
  • How do I keep my garage floor from sweating?
  • Can you put a vapor barrier over concrete?
  • Why are my basement walls sweating in winter?
  • What is the best waterproofing for concrete?
  • Why is my floor sweating?
  • How do you stop rising damp on a concrete slab?
  • Why does my concrete floor sweat in humidity?
  • Why is my concrete floor always wet?
  • How do I stop my concrete floor from sweating?
  • How do I stop moisture coming through concrete floor?
  • Can moisture come up through concrete?
  • Why does my floor sweat?
  • Why is my basement floor sweating?
  • How can sweat slab syndrome be prevented?
  • How do you dry out a concrete floor?
  • How long does it take for a concrete floor to dry out?
  • Why does my garage floor sweat when it rains?