The area around Baker Street in Central London is a prime location and contains many beautiful listed buildings. One such building is a 5-storey Victorian mansion built in the early 1830s that, although in a state of disrepair, maintains a high value due to its location. During the renovation of the building, as it is converted into high-spec apartments, Twistfix-registered contractor Newman Building Solutions were employed to perform an external survey and provide a plan for structural masonry repair work.
Diagonal cracking above window openings, cracked bricks and obvious bowing masonry were all already evident but the survey revealed further details. Brick arch lintel failure was found to be present alongside a serious lack of lateral restraint: these factors had caused the masonry at floor and ceiling level to bow. Believed to be a 13" solid-wall construction, closer inspection revealed that the construction had only a 9" structural wall and had a single-skin collar jointed external façade. At no point had this the single skin wall been mechanically tied to the structural walls.
The entire project was made more complex by the fact that the specification called for the building's original façade to be disrupted as little as possible in order to maintain the attractive original aesthetic. An ideal solution was provided by installing retrofit bed joint reinforcement in the form of Twistfix helical bars, which were embedded into grout above window openings, to strengthen the brickwork and redistribute structural loads. 450mm long stainless steel wall ties were installed vertically to securely pin the brick lintels to the masonry above and the cracked joints were raked out and filled with Twistfix epoxy resin; these processes eliminated the need for an expensive and disruptive remove-and-rebuild technique.
The delaminating single leaf external facade was then tied back to the main load bearing 9" walls using the unique Airtwist CD Tie designed by the directors of Twistfix. The limiting factor on the performance load of the ties was established as being the outer connection. The remedial wall ties were accordingly driven through the outer leaf and pull-out tests were performed to check for security; all of the ties easily exceeded the required pull-out force. The ties were then driven into the back wall to provide a secure mechanical fixing. Installing these patented replacement wall ties was a rapid process due to efficient and cost effective tool design.
Aesthetic repairs to ornamental features and stone windowsills were also carried out by the team. Utilising stone repair mortar and concrete sealer to match the existing profile, Newman Building Solutions were able to provide perfect results; once decorated, these features showed no sign of any repairs at all and looked as new. More than 200 bricks had suffered from the freeze/thaw cycle and extensive spalling and discolouration had occurred. This was professionally repaired and the mortars were tinted and shaped to exactly match existing masonry.
This entire process was carried out in less than two weeks and fully restored the structural and aesthetic integrity of all external elevations. We would like to thank James Wiggins of NBS for regularly sharing the details of the structural masonry repairs that they carry out in Central London and invite all of our registered contractors and other customers to do the same.
Please contact our team on 0845 123 6006 or by email firstname.lastname@example.org if you require any further information on our damp proofing, replacement wall ties and structural crack repair products or for details on our registered contractor scheme.