Plaster steel beams - you should pay attention

When it comes to properly plastering steel beams, such as after a renovation or new construction, you often hear many different opinions on the correct execution. What matters most, and what is important in plastering, you can learn in detail in this post.

Rust protection on steel girders

On a rust protection can be dispensed with the steel beam under any circumstances. A passivating layer should definitely be applied. In any case, painting the steel beam with rust protection will prevent rust from possibly forming later, possibly even cracking.

It is also important that the steel beam can dry sufficiently after brushing. Also, a suitable primer can be recommended before cleaning.

Expanded metal and Rabitz

So that plaster later adheres properly, usually used expanded metal. Expanded metal is a very good plaster carrier, which is also well suited for this purpose. The expanded metal is simply stretched over the carrier and then holds the plaster firmly.

The necessity for the use of expanded metal (or another suitable plaster carrier) results from the fact that a steel beam always responds to temperatures, and then the already poor plaster adhesion by the movements of the steel beam (caused by temperature changes) then significantly worse.


Also Ziegelrabitz is a way to plaster a carrier well. In this (very old) technique, with the help of which you can plaster other, complicated constructions. A load-bearing substructure of steel bars (round and approx. 5 - 8 mm in diameter) is produced, over which the plaster carrier is tensioned. In addition to expanded metal can also serve as plaster carrier here:

  • Rib mesh
  • brick wire
  • different metal wire mesh
  • wired reed (classic variant)

Fiber-reinforced mortar (reinforced with various fibers, such as calf hair or pig bristles) is used, with which the fabric is "expressed" and then roughened. This can then be used ordinary plaster (after curing the expressed plaster).

Admissibility of plastering

It is important, however, to determine whether or not there are special fire protection requirements before doing plastering work. In principle, each load-bearing steel girder must have a fireproof sheathing. The reason for this is that steel beams can lose some of their load capacity even at very low temperatures (from around 100° C).

The very high temperatures that a fire entails can give way in steel girders with a static function within a very short time, causing the building (or part of it) to collapse. For this reason, appropriate fire protection classes may be necessary for the wearer (F 90, F 180, etc.).

Rabitz constructions are - depending on the version - often quite fireproof. For example, a very simple plasterboard ceiling already meets fire protection class F 60A. Important here, however, is the professional execution and a corresponding certificate from a specialist company about it. An alternative would be, for example, disguising a steel beam with appropriate Rigips finished parts.

Tips & Tricks

As an alternative to expanded metal you can also use very good brick wire. It's an old technique, but one that still works very well.

Video Board: How to smooth the beam with cement and sand - the excellent workers