Sweating Slab Syndrome 6 Tips for Reducing Concrete Floor Condensation
If you have ever been in a warehouse or industrial facility in the south you are most likely familiar with Sweating Slab Syndrome (SSS). The buildup of moisture from temperature swings doesn’t just affect the concrete floors; machinery can sweat, materials can sweat. In addition to the primary safety concerns moisture on concrete slabs presents for employees it can also result in damage to inventory, machinery, and the structure itself.

What Causes Moisture on Concrete Slabs that Cause Sweaty Slabs

Basically, everything that cools down after a hot humid day experiences sweating slab syndrome. Moisture as you would guess is the underlying cause of such sweating on concrete floor slabs. This usually happens when concrete slabs and the other materials that sweat reach dew point temperature. Usually, warm, moist air and relative humidity enters the structure through the several openings (windows, doorways, and vents) and as the air diffuses throughout the structure it condenses on any surface that is at or below the 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 air onto the surface of the slab. Sometimes this salt even draws water from within the concrete.

See How MacroAir Fans Solve Sweating Slab Syndrome!

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Even Metals are Sweating

Interestingly, even metals in most structures can sweat! At an aluminum company in the humid South, they ran into issues with their metals sweating. In particular they had a lot of black iron and once it would sweat it would begin to rust. Rusting of their black metal results in significant loss to the value of their inventory.
When you have these temperature swings mainly in spring and fall, you’ll end up with cool nights and hot days. The metal at an aluminum company is trying to change the temperature and the result is a buildup of condensation. Combating sweaty slab and its impact on valuable product is a very important issue.
Subject matter expert, Jason Hornsby lends insight into the issue of Sweating Slab and the impact it has on facility operations.

“Imagine a forklift sweating oil onto the floor, machinery sweating grease. These lubricants combined with sweating machinery and slabs creates very serious hazards for employees.”

So, what can be done to avoid the risks of 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.”

2. Good Housekeeping Practices to Prevent Moisture

Always remove any deposits from the surface of your slabs. A good 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 as well as protecting your assets.

3. Re-examine Air Movement Within the Facility

Often, sweating slabs occurs because 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 such as an HVLS Fan.

4. Use HVLS Ceiling Fans to Reduce Ceiling-to-Floor Temperature Differential

HVLS fans also increase the surface evaporation rate. These fans provide cost-effective ways to keep your structures cool, increase drying while preventing the buildup of moisture on your floors.

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.

6. Use Low-Permeance, Low-Slab Retarders in Your Stores

This can prove particularly effective where 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, tile, vinyl or wood flooring, moisture and condensation can still cause Sweating Slab Syndrome with temperature fluctuations. Moisture under the flooring that is laid over concrete floors can ruin the adhesive that holds the top flooring in place.



Many industries and companies have concrete flooring and most everyone has experienced sweating concrete floor slabs. Moisture in concrete slabs pose a huge 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 sweaty slab with HVLS fans will help protect your machinery, product, building, minimizes mold and mildew and most importantly the safety of your employees in a cost-effective way.
Jason Hornsby is the owner/ President of Vector Sales and the Regional Sales Rep for MacroAir Fans. An expert with high volume, low speed fans, Jason has spent more than 22 years focused on cooling solutions for industrial facilities that increase employee comfort and decrease energy consumption.
Have you ever had to deal with sweating slab syndrome? Leave a comment below and tell us about your experience.

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