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Your Build - Spring 2018

Phase 4 Phase 1 Footings & Foundations Phase 1 Phase 2 Aircrete forfoundations: Despite the rising use of aircrete throughout Europe and now the UK, the perception remains that aircrete blocks cannot be used below DPC level, meaning it is being underutilised as a foundation material. In fact, this could not be further from the truth. Although aircrete has been around since the late 1950s, many in the industry still see the material as a new and unconventional method of construction, and choose to continue using familiar methods. The reality is that aircrete provides a simplified and cost-effective method of constructing foundations for residential properties. However, aircrete is often overlooked for these projects. It is typically assumed that higher strength masonry units, which are capable of sustaining their load at the critical points in design, have to be applied to the entire structure. In fact, where strength is most needed is at the lintel-bearing where windows and doors are introduced to the wall structure. As the load spreads down the height of the wall, most of the loading is evenly distributed across the whole length of the wall below the ground floor dampproof course. Although one of the lightest forms of masonry, aircrete blocks, available in a range of strengths, are fully load-bearing and capable of supporting buildings up to three storeys tall. The underestimation of aircrete’s load-bearing properties often means that dense aggregate concrete blockwork is needlessly used on foundations, despite being more expensive overall. A simple approach Builders using traditional methods are used to constructing foundations with two separate leaves of 100mm aggregate concrete blocks laid with the required cavity onto a strip foundation to support the wall above. The cavity is then tied together using wall ties and when completed, the cavity is filled with lean mix to shore up the structure. In contrast, the aircrete solid block approach is far simpler. Requiring only a single leaf of blocks, a solid aircrete block can be laid onto a strip of poured concrete to match the thickness of the wall. This method also requires no mortar at the perpendicular joints; instead, they can be butted against each other. Recently, Calfordseaden – an independent construction and property consultancy firm – conducted a Foundation Cost worth a second look? Phase 3 With construction techniques continually evolving, it is easy to dismiss proven and popular traditional methods. H+H’s technical director, Cliff Fudge, reveals how a simple switch to using aircrete for foundations can immediately benefit both contractors and end-users, whilst lowering construction costs 34 Spring 2018


Your Build - Spring 2018
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