Editing Underpinning (section)

==Mass concrete  underpinning==

Mass concrete underpinning is one of the simplest forms of remedial underpinning at shallow depths. This type of underpinning is done by excavating "bays" along and under the existing foundation and filling them with mass concrete. It is sometimes called a "traditional" method to distinguish it from other types of underpinning like piling and needling. The latter often require underpinning specialists and may use proprietary underpinning systems. Mass concrete underpinning work is performed in compliance with the Party Wall Act (in the UK) using plans that are designed with engineering calculations to plan a sequence of excavating bays along and underneath the existing foundation without damaging existing walls. In some cases walls have collapsed because lateral support was inadequate leading to disputes among contractors, subcontractors and architects about where the responsibility lay for the mistake.<ref>{{cite book |last1=Gwynne |first1=Anthony |title=Guide to Building Control For Domestic Buildings |date=2013 |publisher=Wiley-Blackwell |isbn=9780470657539}}</ref><ref>{{cite book |title=The JCT 05 Standard Building Contract: Law and Administration |date=2009 |publisher=Butterworth-Heinemann |isbn=9781856176293 |page=88}}</ref><ref>{{cite book |last1=McGuinness |first1=John |title=The Law and Management of Building Subcontracts |date=2008 |publisher=Wiley |isbn=9780470759752 |page=155}}</ref>

Mass concrete underpinning is commonly used when permanent support is needed to comply with the [[Party Wall Act of 1996]] in the construction of a new basement during a restoration, rehabilitation or redevelopment.<ref>{{cite book |last1=Douglas |first1=James |title=Building Adaptation |date=2006 |publisher=Elsevier |isbn=9780750666671 |page=288}}</ref>

In the [[United Kingdom]] most [[subsidence]] claims are for buildings at least 40 years old with shallow [[strip foundations]]. This is one of the most common types of foundations suffering from subsidence-related damage and according to the [[Building Research Establishment]] subsidence database, mass concrete underpinning was the most common underpinning and was often applied only to part of a building. If the soils have a low bearing capacity partial underpinning may increase the risk of differential settlement and localized settlement due to additional load on the soil.<ref>{{cite book |title=Problematic Soils: Proceedings of the symposium held at the Nottingham Trent University School of Property and Construction |date=2001 |publisher=Thomas Telford Publishing |isbn=0727730436 |page=65}}</ref>