Drainage at the terrace - is this necessary?


Again and again, the question arises, whether a terrace needs an underlying drainage system. Whether this is necessary, and what other benefits drainage systems under the terrace offer, you will learn in detail in this post.

Drainage or drainage

Basically, the cover of the terrace is crucial for the use of drainage. Here it can be

  • a water-permeable covering (such as a patch or similar) or
  • a water-impermeable surface (such as laid natural stone tiles or non-oozing plaster in the concrete bed) act.

Soakable coverings

In the case of a permeable surface, surface water seeps through the covering into the substructure. From there, it should also seep into the ground as quickly as possible. If water builds up in the substructure, frost damage (freezing and collapse of the subsoil afterwards) and constant water level can damage the substructure.

Decisive for a possible necessary drainage of the substructure by drainage is the soil condition. Heavy or cohesive soils (such as very loamy soil types) allow water to seep away slowly. In this case, additional water drainage must be provided.

Non-oozing coverings

Here not only the surface should be dewatered (in the case of driveways this is obligatory in many places!), But if possible also the substructure.

This prevents damage to the substructure caused by water penetration. For example, water can infiltrate through tile joints for extended periods of time.

If drainage mats are installed below the lining, penetrating water can be discharged relatively quickly. In addition, the flooring (for example tiles) is also effectively decoupled from the substrate. This also helps to avoid stress cracks.

Especially recommended is the use of such drainage mats under natural stone coverings. They are also available for loosely laid coverings, in which case they also replace any pedestal bearings.

drainage mat

Drainage mats can also be bought at the hardware store. The cost of such a sub-base mat starts at around EUR 10 per meter (for mats one meter wide).

Such drainage mats are resistant to aging and rotting - a wear or reduction in the function of the mat is therefore not to be feared. In many cases, such a drainage can also be useful under a balcony.

Tips & Tricks

In addition to the drainage of the subsoil, of course, you should also pay attention to a sufficient slope in a sealed terrace area. The slope must always lead away from the house and should not be less than 1.5%, so that the sealed surface is dewatered as quickly as possible.


Video Board: Garden terrace rebuild- pt4- drainage and lower wall