Q. I have been told that my property needs new wall ties as the originals have corroded. How do I find out how many new wall ties need to be put in?

Submitted by: TG 

A. The installation position and density requirement for the installation of wall ties is set out in document BS 5628. To rapidly assess the number required for a plain wall the calculation is 2½ wall ties per m². In a plain wall they should be installed in a regular pattern at centres not exceeding 900mm horizontally and 450mm vertically. Around window and door openings the vertical centres should be reduced to 300mm and they should be installed no further than 250mm in from an adjacent window/door reveal.