Retaining walls are a vital structure within the infrastructure of London. They are everywhere and a large number of them are well over 100 years old. Victorian built retaining walls are usually constructed using 13 inch solid brick work construction with a soft lime mortar and usually they haven’t been inspected for signs of failure or disrepair until they are at a critical stage of failure.
At Newman Building Solutions we are regularly required to design a suitable structural stabilisation programme that will restrain further outward movement or collapse as well as retain the original charm of the structure.
Newman Building Solutions specialise in retaining wall restraint and use various modern methods of structural repair such as the Twistfix helical system creating masonry beams and crack stitches tying the masonry together. In some instances ground anchors are required to restrain the outward movement. Twistfix helical systems can be guaranteed for up to 25 years and ground anchor solutions can be guaranteed for up to 99 years.
We like to restore these engineering marvels and relish the opportunity to conserve the original structure. Visit our case study here to view the Twistfix system in use to restore and restrain a Victorian built retaining wall.
Subsidence is a common problem in London and the South East of England with an estimated 3.7 million home owners at risk within the region covering over 140,000 postcodes.
Why is subsidence such a problem in London and the South East? Well the majority of the properties within London and the South East are Edwardian or Victorian built and certainly the vast majority were built before the 1970’s. Built on shallow foundations on a clay sub soil which is susceptible to shrinkage and heave with our ever changing adverse weather condition causing changes in ground conditions causing subsidence.
How is subsidence recognised? The location of the cracking for subsidence is normally located around window and door openings in vertical staggered form with the width of the crack normally wider at the top than at the bottom, Heave is different, it is the expansion of the sub soil lifting the building and this is recognised with similar crack locations but often the crack is wider at the bottom than at the top.
Subsidence is caused by ground movement but in order to locate the source of the ground movement obvious factors are undertaken during our survey such as the location of tress which can suck large volumes of moisture from the soil, drains – which in some instances fail causing the soil beneath to wash away. Excavations beneath the ground such as tunnelling for Londons crossrail, expansion of the water and sewage systems and the increasing number of basements can also be the culprit of subsidence.
Subsidence and heave can in some instances be repaired using the Twistfix Heliforce system by creating masonry beams across the brick panels connecting the whole building allowing it to act as one structure instead of individual brick panels that distributes structural loads.
In instances were subsidence cannot be repaired using the Twistfix Heliforce system alone, it is incorporated with either mass concrete underpinning or more conventionally mini piling systems that drive piles down to bedrock or firm made up ground preventing the structure from subsiding or heaving in the event of further ground movement.
Lintel Failure is a common defect to period properties and cracking and sagging of the masonry is a serious structural defect that should not be ignored.
To restore the structural integrity of the masonry Newman Building Solutions designed a specification that would allow the installation to be carried out in a day but also restore the integrity.
Deep masonry beams were installed above the lintel distributing structural loads and the brick lintel was propped back into position and resin injected creating a load bearing high strength lintel whilst restoring the original aesthetics of the building.
As well as lintel failure a 3mm crack was stitched using 1.2m single crack stitching rods where cracking had occurred caused by a change in loadings where lintel failure had occurred.