The subject building was a substantial Victorian traditionally built end-of-terrace domestic residence arranged over four floors.
Problem
Outward movement to the gable wall, patress plates and tie bars were
noted, which indicated that a previous attempt to restrain the outward
movement had been made. No significant cracking was noted. Also, a
steel band to the front first floor was found to be heavily corroded
and delaminating.
Causation
The movement noted is progressive, attributable to historic subsidence
(downward movement) compounded by outward movement due to ineffective
or inadequate restraining to the main elevational walls and the bay
window, allowing the brick arch to spread and drop and the brickwork
above to crack.
1. Bed joint reinforcement: The introduction of two rows of twin cord reinforcement, forming a deep masonry beam – As indicated with red double dotted lines on our proposal images.
2. Lateral restraints:
In conjunction with the beam, 8mm stainless steel lateral restraints
were introduced and screwed directly into timber floor joists’ end
grain or into the side grain, all resin bonded to the masonry – As indicated with yellow stars on our proposal images.
3. Crack stitching: To stitch localised cracks, single 8mm stainless steel corded joint reinforcements were introduced – As indicated with red single dotted lines on our proposal images.
4. Wall ties to de-bonding brickwork:
Wherever possible to the centre of a brick, we drilled for and resin
bonded 6mm stainless steel remedial ties. We then re-pointed the
disturbed areas only with coloured sand and cement mixture – As indicated with blue line on our proposal plan images.
5. Making good and pointing:
We then raked out the existing mortar and repaired with new coloured
sand and cement mortar to approximately 20mm in depth. AWT operatives
are highly skilled in traditional building methods and always attempt
to match replacement bricks, pointing styles and mortar colour to be
sympathetic with the existing building.