The whole issue of consolidating voids is very complex. There are numerous articles, research papers and discussions on this subject. Therefore, it is important to question some important points. Among the questions that must be asked:

■ Have the voids been present since the original construction of the buidling?
■ How were the voids caused?
■ Is it necessary to fill these voids?
■ What is the budget you have?

Since there are many questions, it is therefore important to consult with a structural engineer before work begins.

As with mortars, it is important that the selected material (binder and ratios) for consolidation is compatible with the entire building envelope. Because of this, it is better to use the same binder that was used for the original construction of the building. 


Grouts, by definition, are very fluid. Unlike mortars, it is difficult to contain. So you have to understand – to the best of your knowledge – the path the grout will take before starting the injection process. This understanding will avoid many unpleasant surprises.


■ Building dated before 1900: King® HL-5
■ Building dated from 1900 to 1975: King® RPL-6 or King® HL-5
■ Building dated from 1975 until today: King® RPL-6 or King® RPL-20