Thermalite Garage Crack Stitching, Waterlooville

The problem

A homeowner had developed 3–5mm cracking in the Thermalite blockwork of their garage wall. The client came to us with written repair instructions from a structural engineer specifying the method of repair.

The cause

Diagnosed as movement-related cracking, typical of how Thermalite block responds to moisture and temperature changes over two decades where there was limited reinforcement in the original build.

What we did

1. Dust extraction. Because this was inside an occupied garage, dust extraction was used throughout the slot-cutting process — essential when working inside someone’s property.
2. Bar installation. Around 20 6mm stainless steel helical bars, each 1 metre in length, were installed across the affected blockwork and bonded with two-part masonry resin, restoring the structural bond across the crack lines. Stainless steel and two-part resin were chosen for strength and longevity.
3. Making good. Sand and cement finish applied on completion.

The result

Completed by one person in a single day, working to the structural engineer’s specification. Dust extraction was a key consideration on this job — crack stitching involves cutting slots into the masonry which generates significant dust, and working inside a domestic garage without extraction would have been unacceptable.