U&M Group

Retaining wall rescue

Thursday, March 12th, 2020 AT 11:42AM

  • Type of work: Ground anchors and masonry reinforcement combine to restrain overturning Listed wall
  • Location: North West London

The presence of a tree behind this retaining wall in North West London had created significant problems when root growth created lateral pressures resulting in bowing of the brickwork, and overturning of the wall. Built in soft bricks with lime mortars, the wall is within a Conservation area, and consequently listed. Because of this, wholesale demolition and reconstruction of the wall was not an option, and an alternative approach was therefore required. Additionally, the rigid requirements of the appropriate authorities needed to be taken into account in providing an adequate but sympathetic repair solution.

Where the existing brickwork had fractured and been dislodged beyond making good in-situ, it had to be removed prior to rebuilding. Previous making good with cement mortars resulted in the loss of many bricks, but careful sourcing of matching second hand replacements ensured that the homogenous appearance of the wall was maintained. Traditional lime mortar was also used in the re-construction of the wall, followed by toning down to match the original areas. The entire length of the wall required the introduction of lateral restraint, and this was provided by the installation of stainless steel Duckbill MR3 ground anchors, driven 4 metres into the ground behind the wall, through diamond cored holes in the 230 mm. thick brickwork.

 

In order to provide a ‘period’ appearance, the anchors were terminated with cast iron pattress plates with domed nuts.* In addition to the anchors, the integrity of the brickwork within the wall was restored by the introduction of ‘Helibeams’, bed joint reinforcement comprising Helifix 6 mm. diameter stainless steel helical bars set in Helibond MM2 cementitious grout. Shorter lengths of bar were also used to stitch cracks in the wall.

* In walls of suitable thickness, Duckbill anchors may be terminated invisibly within the thickness of the wall, using patented Combi-Tec concealed fixings.