Building showing crack

Crack interpretation

29 March 2019

How to establish whether a crack is a serious issue or not.


  • Direction of crack; vertical, horizontal or diagonal. This will show you the direction of movement, which is always perpendicular to the crack itself
  • Is the crack of a consistent width throughout its length, or is it wider at one end (tapered). Tapered cracks indicate a rotational movement
  • Size / width of crack. In general terms, any crack within a structural wall wider than 5mm should be considered as significant and be professionally assessed. Cracks of this size will typically require some form of robust repair and / or strengthening
  • Its position. The positioning of a crack will help determine its cause and therefore the required remedial works.
  • Estimating the age of a crack is not always possible, although if it can be achieved, is a great tool in helping to determine the severity of the issue. Likewise a crack that has clearly been repaired in the past and continues to open up is a sure sign that whatever movement is happening is progressive and will therefore require some form of remedial attention

The photograph within this blog shows the first floor windows within a traditionally constructed property, dating from circa 1890, with a commercial (take away) premises at ground floor level and self-contained residential flats above. In this instance, the diagonal cracks occurring above the left hand window are caused due to a failed structural timber beam which supports the brickwork above the glass shopfront serving the ground floor premises.

Key points to note from the image:

  • The cracks are tapered (wider at the top)
  • The base of the brick arch above the window is lower on the right hand side compared with the left
  • At their widest points the cracks are clearly in excess of 5mm
  • Although not visible from the image, the casement window had suffered significant distortion as a result of the movement and could not be opened

All of the above factors demonstrated that the central column of brickwork situated between the two first floor windows had dropped due to inadequate support offered by a timber beam in place above the ground floor shopfront. On further inspection, following exposure works, the beam was found to have suffered extensive timber decay brought on by poor external maintenance of the building. Extensive temporary propping, a replacement (steel) beam, large scale brick repairs and replacement windows were necessary, all as a consequence from not carrying out routine building maintenance. These cracks were serious!

If you are concerned with cracks to your property, then follow the outlined identification processes above. Following which, if you remain concerned then give one of our team a call!