Registered Contractor Newman Building Solutions has recently completed a programme of structural repairs for Oxford City Council. Several low-level flats, occupied by elderly tenants, had suffered from cracked brick walls, requiring immediate diagnosis of the cause of the cracking and the design of an appropriate repair scheme
The initial survey carried out by NBS confirmed a number of cracks in the brickwork, both at ground level and at lintel level. Their in-house soil investigation and drainage team also carried out a full check below-ground. “We found no defects to the drainage system but did discover that the foundation of the flats, originally assumed to be deep concrete slabs, was in fact simple non-reinforced raft built directly onto made-up ground on top of a medium to stiff Oxford clay” says Mr Wiggins of NBS. “The investigation concluded that the cracking was caused by foundation movement, which may have been exasperated by the close proximity of a railway embankment and vibrations from the high speed trains running just 15m from the flats”.
Engineers from Newman Building Solutions designed a pile and beam reinforcement system that would cause minimal disruption to the tenants. The design incorporated ten pile caps each with a pair of 10m deep 300mm augured piles - one pile acting in compression and the other in tension. Spanning between the pile caps were brick beams formed by retrofitting Twistfix helical bars discretely into bed joints. BRE Load Tables were used to determine the span between the piles and the depth of the load bearing brick beams or vertical distance between the bars in order to ensure the beams were strong enough to carry the applied vertical loads.
Additional helical reinforcement was introduced to the band of brickwork above the window lintels to form beams over the openings and shorter crack stitching bars were installed to tie together brickwork on either side of the cracks. The long helical bars were wrapped around the walls to tie the gable closest to the embankment back to the longer elevations. In all more than 300m of hidden helical bars were used to reinforce and strengthen the superstructure. Once the structural work was completed, several brick repairs to the front of the property were carried out to preserve aesthetic appeal as the brickwork had come out of line due to the subsidence. The entire project took just ten days and was completed well within budget.
Twistfix are proud suppliers of structural crack repair and masonry reinforcement products to Newman Building Solutions along with a diverse array of clients who carry out masonry repair work. Our brand is well known and trusted in the repair and renovation trade and we always seek to bring our customers the best quality at the most competitive price.
For more information on the Twistfix range of masonry repair products, including cavity wall ties and long helical bars and crack stitching kits, please contact our team on 0845 123 6006 or email us at firstname.lastname@example.org.