Fill with foam


Building foam is used in many ways. Above all, the use in building connection joints is extremely popular. Again and again it may happen that then on the foamed PU foam should also be filled. What you should pay attention to when filling with construction foam is explained in this guide.

Application examples for construction foam

With construction foam the most different challenges can be mastered. Among other things, the assembly and insulating foam is used for the following work:

  • the filling and closing of construction joints
  • for insulating pipes
  • for the roof insulation
  • for backfilling cavities
  • for gluing ETICS boards

Fill with foam

Especially in the window and door assembly must then be plastered or filled. What has to be taken into account when filling construction foam is summarized here. The filling of PU foam is basically possible. However, it depends on what you want to fill with or on which surface the assembly and filling foam should be foamed.

Commonly used putty: gypsum

At the same time, gypsum plasterboard is increasingly being used in refurbishment and modernization, as well as in the interior construction of new buildings. This in turn is filled with plaster. Again, many do-it-yourselfers may initially think that construction foam is basically well suited. That is not so. On plaster, for example, does not hold the mounting foam.

Plaster on PU foam

On the other hand, even plastering plaster on construction foam can be problematic. In particular, if the foam was merely applied, it could cure and was not further processed. Like the plaster, the surface of the mounting foam is really smooth. That is, neither the plaster keeps on construction foam nor vice versa.

However, if you disperse the mounting foam after foaming and hardening, the plaster may stick to it because the foam is fine-pored so that the plaster can penetrate. However, complete drying out is important. Explicit 1-component construction foam needs moisture to cure, so curing can take a relatively long time.

Building foam and gypsum filler are permeable, so vapor-permeable

In addition, when applying plaster to construction foam, make sure that the mounting foam is permeable. Gypsum also absorbs moisture. This in turn means that the steam can pass through the gypsum and the mounting foam on the underlying material. Although construction foam can not mold, but very many building materials that may be present in the masonry.

Tips & Tricks

Another important question for DIY enthusiasts is with regard to mounting foams: is construction foam toxic? Follow our link and learn everything worth knowing.


Video Board: FILL DEEP HOLES WITH EXPANDING FOAM FILLER (FILLS DEEP HOLES)