What is plinth wall

Plinth plaster: How to repair damage

A plinth separates the foundation from the house facade and also protects the underlying masonry. But what different types of plinth are actually there and how can damage to the plinth plaster be repaired yourself? We'll explain it to you.

Plinth plaster: How to repair damage
Plinth plaster: this is how you repair damage

Basically, a base is the lowest component to which the elements above it are attached. When building a house, the base connects the foundation with the structure or facade. On the one hand, it acts as a splash guard for the house, on the other hand, the colored plinth plaster serves as an ornament and thus the visual beautification of the house.

In modern houses without a basement, the structure sits directly on the floor slab - although much less of the base can be seen, you still need a base plaster here to hide the perimeter insulation below.

What types of plinth are there?

When building a house, you often find that not all bases are the same. There are different types of plinths depending on the design, appearance and function.

  • The protruding base
    As the name suggests, the protruding base protrudes over the facade. This type of construction is rarely found, as the upper edge of the projection is heavily exposed to the weather and therefore needs a lot of renovation. In the case of architectural monuments, however, the protruding base can still be admired.
  • The flush base
    In contrast to the protruding base, the flush base does not protrude beyond the facade, but is flush with it. Since the exterior plaster is applied continuously, damage to the base can usually only be repaired by specialists, especially if thermal insulation has also been applied. Because of this, you should only opt for a flush base if you have a large roof overhang (it offers additional protection) or if there is only a low risk of splashing water.
  • The recessed base
    This is the most practical and modern base variant. The fact that the house facade protrudes slightly above the base creates a so-called drip edge, from which rainwater can drip off more easily. This means that the base is less stressed. In addition, repairs to the plinth plaster can also be carried out more easily, since the facade does not have to be tackled.

What is plinth plaster?

The base plaster protects and hides the perimeter insulation up to the structure. It measures around 25 centimeters and is often a different color than the house facade in order to visually stand out from it. Since the base is constantly exposed to rain and splashing water, it has to be renewed more often than the house facade itself. But that's not a big problem - experienced craftsmen can easily repair the plinth plaster themselves.

What you should pay attention to with plinth plaster

The classic plinth plaster consists of a basecoat made of cement and lime plaster as well as a decorative colored stone finishing plaster based on acrylic resin. Like all other building materials, it is available in various grades, which then also differ in their function and price. In any case, base plaster should have the following properties:

  • Frost-resistant and waterproof
  • Dirt repellent
  • Shockproof
  • Resistant and washable
  • Highly flexible
  • Solvent free
  • Diffusible
  • Easy to use

What does plinth plaster cost?

Anyone who buys a simple 30 kilo sack of base plaster pays between 15 and 20 euros for it. The classic, ready-to-use colored stone plaster or mosaic plaster is between 30 and 50 euros. Modern new buildings often prefer mineral plaster with a small grain size. This costs from 10 euros for self-mixing up to 70 euros ready-to-use. Anyone who uses renovation plaster due to damage costs around 20 to 50 euros per sack.

How does damage to the plinth plaster occur?

As the lowest, externally visible part of the facade, the base touches both the soil and its moisture as well as the dry structure. Under no circumstances should it, however, transport the moisture upwards or let it penetrate into the masonry. However, execution errors or inadequate sealing repeatedly lead to construction defects such as damage to the plaster, silting, salt efflorescence or moisture horizons. Unevenly compacted subsoil, strong vibrations, the static setting of the masonry or simply processing or material defects can ensure that cracks or bubbles form in the base plaster and that it flakes off over time. Anyone who does not repair the damage directly must expect consequential damage. These include mold growth in living areas or damage to the building fabric. Problems that can be avoided with a few simple steps.

tip: If you notice cracks on the plinth, you should immediately notify a specialist who can best assess whether the damage is easy to repair in the plinth plaster or more dangerous cracks in the masonry.

Typical damage to the plinth plaster

  • Chipping: The stress on the plinth plaster is particularly high due to road salt in winter. Because the salt absorbed by the capillary suction leads to different freezing points in the cross-section of the component. This is accompanied by pressure effects between the layers, which the plaster cannot withstand - it flakes off.
  • Sand: The problem arises particularly with lime plaster, because rainwater "washed out" lime and cement from the plaster - it starts to crumble.
  • Cracks: Water damage, settlement of the subsoil, vibrations from heavy traffic and the settling of the masonry can cause cracks in the plaster. The key here is to act quickly and not watch the cracks for too long.
  • Efflorescence: Water penetrating the wall carries salt with it, which crystallizes as soon as the water evaporates. It becomes visible as efflorescence, which can cause cracks or bubbles in the plinth plaster.

In this context

Renewing the plinth plaster: step-by-step instructions

If you have a bit of technical experience, the renovation of damaged areas in the base plaster should not be a problem for you. We'll explain how it's done in five steps.

1st step: preparations

You should only replace plinth plaster in persistent dry weather and moderate temperatures. In such a weather period, begin to prepare the base zone. To do this, dig the ground about five centimeters deep and push it away from the base.

Step 2: Remove the old plaster

Then knock off the base plaster with a hammer drill and then remove the mortar from the joints of the masonry with a smaller chisel. Particular care is required at the transition to the facade, it should not be damaged. You can widen narrow cracks in the plaster in order to fill them out properly afterwards. Finally, sweep away algae, dirt and dust thoroughly.

3rd step: check the masonry

Examine the surrounding masonry for any damage. If moisture is already penetrating, it is better to leave the problem to the professionals. They know best how to install horizontal barriers against moisture. Every mistake that laypeople make in the plinth area can lead to expensive structural damage. In any case, the masonry must be dry before you can apply the plinth plaster.

4th step: touch up damaged areas

Refill mortarless joints properly and fill in any cracks. In the event of major damage, you should insert reinforcement mesh that absorbs tension between the different building materials. This is also neatly filled. If you have come to the area below the surface of the earth with your repairs, you should apply sealing slurry here in order to effectively protect the base plaster against penetrating moisture.

5th step: Apply plinth plaster

Mix the lime-cement plaster according to the instructions on the package and throw it on the wall with a trowel. Then smooth it out with a smoothing trowel. This layer is called flush and ensures that unevenness is evened out. The reinforcement fabric is placed on top. Then wait until the plaster is dry - this can take a few hours. Then the second, thinner layer of plaster can be applied. This should be carefully smoothed so that the surface is even. After two to three days, the plaster will be completely dry. If you want to beautify your base, you can give it a coat of paint or a colored stone plaster afterwards.