Case Study
Subsidence – reducing costs and impact to tenants
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Drone image of a street impacted by subsidence caused by trees
WHAT IS SUBSIDENCE? As many as 3,000 cases of subsidence are reported each year aff ecting social housing stock. Subsidence is the downward structural movement of a building; which is the consequence of a change in soil dynamics beneath a building’s foundation. T e downward movement means part of the structure is pulling away and generally results in cracks to the property appearing. Cracks in the walls of a building can be
very alarming for tenants and should be assessed immediately and the cause treated promptly. Subsidence usually occurs as a result of long periods without signifi cant rainfall, meaning trees extend their roots further looking for moisture, drying out the soil and leading to the ground shrinking / swelling. Properties which are built on clay soils and near trees and other vegetation are more prone to subsidence, although other issues which may cause subsidence include properties on granular soils with ageing Victorian drainage systems, or near previous mining activity or subject to frequent fl ooding. Last summer was the driest since 1976, leading
to a surge in properties being aff ected by subsidence. T e Association of British Insurers reports there might be 12,000 to 15,000 subsidence claims in a typical 12 month period. In a so-called ‘surge’ year like 2022, numbers could more than double. Tenants or asset maintainers in impacted areas can expect to see an increase in tell-tale signs such as cracks appearing in walls,
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diffi culty opening windows and doors, or more severe structural problems. With the changes in climate, the prevalence of subsidence events will be more common.
T e challenge for maintenance professionals is how to deal with subsidence quickly,effi ciently and cost eff ectively. Underpinning a building was the traditional
method of dealing with subsidence, however this has been surpassed with modern injection processes provided by suppliers such as Geobear. T eir solutions remove expense and time from subsidence maintenance and they are providing subsidence solutions for housing associations across the country. T e example below illustrates how associations can benefi t from Geobear’s system which can also be used to stabilise blocks of fl ats.
CASE STUDY – GEOBEAR, REMOVING COST AND TIME FROM SUBSIDENCE REPAIR A housing association in the Midlands had a large number of properties that had suff ered from structural movement due to the drying of soils and drainage systems being in a state of disrepair. T e properties were largely Victorian terraced homes located on busy one-way streets. T e traditional solution, mass concrete
underpinning, requires properties to be empty as major excavation is needed in and around the structure. T erefore Geobear was approached to provide an alternative solution to tackle dozens of properties in as short a timeframe as possible. T e managing agent was introduced to Geobear,
Drilling to insert injection tubes in restricted access
a ground engineering company that uses innovative methods to stabilise properties. T e method used by
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