Seal concrete floor properly and permanently


Basically, there are two ways to seal a concrete floor. The surface can be coated or a sealant can be introduced into the concrete by means of grinding. The porosity of concrete makes it sensitive to liquids of all kinds, which are prevented by seals.

Unstable material

The material concrete is both chemically and physically latently unstable. An unprotected bare concrete floor may decompose or dissolve over time due to various causes. In particular, the internal corrosion threatens a concrete floor.

Penetrating and developing chemical substances such as sulfate, alkali silicic acid or lime have harmful effects. Salts and the change from frost to dew attack the unprotected concrete floor. Embedded reinforcements "rust" the concrete from the inside broken. Sealing not only has to prevent the ingress of moisture, but also prevents chemical and physical reactions.

Individual sealant

If a coating is applied to the concrete floor, the structural situation of the floor must be considered. In a "sealed" full seal, for example, with epoxy resin, the diffusion of the concrete floor is prevented. This can lead to a problem with ascending humidity, for example in the basement.

The impermeable skin of the coating prevents the concrete from releasing moisture into the air. Depending on the construction situation, permeable sealing agents may have to be used.

The seal must also be adapted to the intended use of the concrete floor. In garages, they must withstand hot and cold car tires, large amounts of fluid from rain or snow, and occasionally dripping engine oil. The living area requires a non-evaporative sealant. At high traffic load, the abrasion resistance is important.

How to seal a concrete floor

  • Two-component sealant
  • Primer / impregnation
  • Possible slip-resistant surcharge
  • Possibly special cleaning agent
  • Plastic paint roller
  • extension rod
  • working gloves
  • respiratory protection
  • steel brush
  • Big iron nail
  • Plastic film
  • duct tape

1. Strength test

Using a large nail, scratch a small grid into the surface of the concrete floor. Then brush back and forth around ten times with the steel brush. When the line intersections break, the concrete floor must be sanded down.

2. Moisture test

Stick a plastic film around one square meter to the concrete floor with adhesive tape all around. Check after one day, whether condensation has formed on the underside of the film. If this is the case, the concrete floor must be dried or dried with a blower.

3. Clean

Remove all grease and oil residues with appropriate special cleaning agents according to the manufacturer's instructions and make the surface dust-free.

4. Priming and sealing

Mix according to the manufacturer's instructions on the primer, apply and proceed after drying with the sealant as well. Apply medium thinly in two to four coats evenly with the painter roller.

Tips & Tricks

If the concrete floor is not threatened by moisture, as well as indoors, you can also use the alternative method of sealing by means of sanding.


Video Board: How to paint a concrete floor - Step by step guide on how to paint concrete floors.