The application of injected polyurethane is mainly used in the filling of air gaps in façades or partition walls, mainly in cases of renovation works, in order to obtain optimal thermoacoustic insulation. In these cases, great care must be taken when filling the gaps or cavities between partitions to not exceed or fall short of the amount of insulation we inject. There is a danger that the pressure of the foam, when expanding, may crack or even pull the wall down, both by overpressure or shrinkage.
Polyurethane injection techniques are highly developed and require different controls during their execution. The first step is to carry out a preliminary study of the situation of the wall we are dealing with. It is recommended that the air gap has at least 5 cm of thickness, it has to be continuous and the recommended minimum temperature of the substrate during injection should be 5°C.
In order to inject polyurethane correctly into air gaps, we should start by making a series of holes or hollows in the interior walls which must be located at less than one metre from each other. Its worth noting that they cannot be aligned in a grid, but is more ideally applied in a diamond pattern. This ensures that all irregular shapes and voids are filled, which traditional methods of cavity insulation cannot do.
Subsequently, the polyurethane will be injected through these holes, always from the bottom upwards, in order to achieve an optimum filling of the air gap. Inside, the polyurethane will begin to expand, filling it completely and reaching all corners, adapting to the interior surfaces.
Once the injection is completed, the holes or hollows made will be closed and the faces will be uniform. Polyurethane, being a rigid material and filling in all gaps and cracks, helps to improve the structural stability of the walls.
Below are listed some of the most common problems that can arise during the application of injected polyurethane, along with its possible causes and solutions: