Concrete floor sweating under carpet can occur when warm air comes in contact with a cool concrete slab and thereafter causes the concrete floor to sweat. Most times, warm humid air from outside the house find its way to the cold concrete to make it wet, and in the process, condensation happens.
As time goes on, the concrete floor will become darker if nothing is done about the situation. Efflorescence then kicks in. This will make the floor develop white patches because the water which was long in the concrete slab comes to the surface and evaporates leaving mineral deposits on the floor.
Concrete sweating is also known as sweating slab syndrome (SSS). It is also important to note that if your concrete slab is colder than the dew point temperature of the air above, moisture must have its way. This situation can be a strong problem if nothing is done about it because other floor complications can result from it. Concrete floors are vulnerable to moisture and that is the main reason why it suffers from different effects of moisture.
Concrete floor sweating under carpet tends to stop some functions in the house which are expensive to repair. Also, it can pose a danger because it will leave the floor slippery which can be bad when the concrete floor has a lot of traffic. The source of this said moisture can be from the proportion of water added to the cement. Failure to do something about it early enough can cause mold growth because mold lives in damp areas. It can also cause an alkali attack and as well cause dangerous slick conditions to your floor.
What Causes Moisture on the Concrete Floor
1. Dew Point Condensation
This is a leading cause of moisture on the floor. This takes place when warm or moist air encounters cooler floors below dew point temperature. When this happens, the floor will have no other option than to sweat and by doing so, causes moisture on the floor.
2. Use of Excess Floor Treatments
The constant use of floor treatments tends to cause moisture on the floor. Make sure to avoid surface densifiers, paints and sealers that will damage the porousness of the concrete. By doing this, you are exposing the concrete to seeping moisture. Before cleaning your floor, you should note that it should be free from any adhesives.
3. Dirty Slabs
When there is the presence of dirt, tire marks, debris and other grime, you get to expose your concrete floor. This will also make moisture build up on the surface of your floor. To prevent this, you need to clean off all dirt immediately to prevent it from seeping into the concrete slab.
4. Inadequate Drainage
Inadequate drainage around the slab can worsen the risk of any source of moisture at all. In a situation whereby there was a little rainfall, good drainage can take the water away and keep it from coming to the concrete slab. Even the smallest source of water will store right under the concrete slab because the drainage is not functional.
5. Poor Subfloor
If a subfloor is not protected well it can cause moisture on the floor. Excessive water can also invade due to poor subfloor protection. Using the wrong vapor retarder is the main cause of this problem. The groundwater will move into the concrete once no vapor retarder sits between the ground and subfloor.
How do I Keep my Concrete Floor From Sweating
It is important to solve the problems before it leads to more complications. It is also important to take measures to prevent moisture even before you install your floor. There are remedies that can solve the problems and these remedies are applied according to the problem in question.
These remedies come in two groups. You can apply each of them before a slab construction or in an already existing slab.
Before Slab Construction
1. Application of Low-Permeance Vapor Barrier/ Retarder
This method can prevent moisture that exists below the slab from getting to the floor. To accomplish this, you will need to pour out a thick layer of sand to the floor, then lay a durable polyethylene, and finally, lay another layer of sand above the polyethylene. When this process is done, you can then install your concrete slab and a top flooring if needed.
2. Enable Natural Drying of Concrete Slab
When you create your concrete slab, it must dry well before placing any type of flooring on it. You should not be in a hurry to dry out because the consequences will outweigh that. Open windows, ventilate the room and avoid quick methods of drying a concrete slab. Whenever you feel it is ready, carry out some tests on your floor to be sure.
3. Keep Excavation Free of Water
You should be able to keep below-grade excavations free of water to avoid waterholes of moisture going upwards to the slab. Moisture below the slab can also make soil bearing strength to be weak and cause shrinkage and swelling of the soil.
After Slab Construction
1. Apply Damping Agent to the Existing Concrete Floor
A liquid epoxy damp proof membrane can serve as a damping agent and should be applied to the existing flooring. This method is for slabs that suffer from moisture problems due to lack of preventive measures for moisture during the creation of the concrete slab. This damping agent will serve as a layer that will prevent the moisture from coming up the floor, rather it will remain in the concrete slab.
To apply, keep the surface from dirt and dust and use a roller to apply the damping agent on it and brush. You can apply more layers after the first, but each layer must be set before applying another. Apply according to the moisture in the concrete.
How Long does Moisture Stay in Concrete
The moisture in your floor can stay up to 24 to 48 hours to dry for you to be able to walk on it. The drying continues and usually takes 28 days to regain its full strength. Most times the surface of the concrete might look dry but it still has moisture in it.
When you then install flooring or paint with the moisture then it will cause problems thereafter. Drying sets in when the water on the surface is not available. If curing is present on your floor, it will make the moisture stay longer on your concrete floor because it contains curing compounds.
In the need to taste the moisture condition, you need to measure the relative humidity of air in the concrete pore system. Your concrete should avoid anything that relates to water in order to dry up fast. The moisture can stay in the concrete longer than it should because of the thickness of the concrete, moisture content, concrete density and even the temperature it is at.
Does Sealing Concrete Stop Moisture
Yes, it does. Water from under your home can seep into your concrete and surface on your flooring thereby making it damp. This problem can cause the invasion of mold and mildew especially when you are using a carpet or hardwood flooring.
Sealing your concrete in this condition can help eliminate moisture. You can apply this method even though you have products that will stop moisture problems.
When you put on a seal on your floor, you are sealing the subfloor to create an impenetrable barrier between your subfloor and your flooring. This sealant traps any moisture on the floor irrespective of where it came from. In order to seal your floor, this guide will go a long way.
a. Check for Dampness
Before sealing your floor, check for dampness. By doing this, you need to measure out a clear plastic to the floor and leave for 24 hours. Then check if there is the presence of condensation on it. If there is then it is still damp. If not, it is dry.
b. Clean and Dry the Floor
Clean your floor using a vacuum and then scrub with a mop. Use bleach and water to clean off the dirt. Rinse afterward and dry vacuum to remove water. Drying the floor will take days to achieve. You can use a dehumidifier to draw out the moisture and make sure it is dry for the next process to take place.
c. Seal the Floor
Maintaining a thin layer while sealing the floor is important because too many sealers can lead to bubbles when it dries. To do this, you need to seal a portion at a time. A sealer made for concrete moisture protection is advisable to use. You can get it as an epoxy concrete sealer. Read instructions properly before application sets in.
Target all the corners and edges of the floor. Allow the first layer to dry for 24 hours. Then apply the second coat after the first. You can keep repeating the layers of your sealant to your taste.