Cavity wall construction – Brickwork outer leaf, tied to block work inner leaf with wall ties and a 75mm cavity.  The cavity acts as a water barrier.  The properties construction prevents damp by a horizontal damp proof course 150mm above ground level and vertical damp proof courses at openings where brickwork and block work meet. 

 

The main failure with this type of construction is based on poor quality work – this was not evident here.  Additional ferrous wall ties can rust therefore it is required that all wall ties are stainless steel and correctly vertically and horizontally spaced. 

 

Cavity walls may be potentially at risk as follows:

 

  • Built between 1900 and 1940 (ferrous wall ties)
  • Constructed with Black Ash Mortar
  • Exposed
  • Post war buildings with vertical twist ties with sub-standard coatings
  • Older than 1970

pwbsl.com serving Thanet, Kent and London

Bruce Spenser MSc MCIOB Managing Director