Our Systems and Products:Systems and Practice
Another major cause of the disjunction between theory and practice is that the designed structure is not actually built as per design. There are two main reasons: firstly the building systems are difficult to build, secondly no one on site cares about building performance and it is unlikely to be checked. The two are somewhat connected. If a building system, whether masonry or lightweight is complicated and involves a lot of processes, often undertaken by different trades, then it is more likely to be built wrong.
Cavity walls, in many peoples’ opinion, are almost impossible to build correctly nowadays. Cavity walls were designed to keep weather and water out and now we are filling the cavity with insulation in an attempt to keep heat in. It is difficult, or almost impossible, to build in the insulation correctly (whether rigid or as batts) and at the same time to get the wall ties, cavity trays, lintels etc into the wall, and, again at same time, to keep mortar and other rubbish from falling down the cavity. It is particularly difficult on UK sites with our site organisation and weather. In many structures insulation is omitted in places altogether as time pressures, lack of materials and other factors make it easier to forget the insulation. And of course no one ever checks insulation installation in any application where it is to be forever hidden.
The same degree of problem applies to timber frame construction and to most types of roof construction for different reasons. These kind of constructions commonly rely on flexible membranes for airtightness, vapour control and weathering which are often very difficult to insert, or are almost inevitably breached or punctured by some other trade in the construction process. We need simpler building systems to be able to deliver buildings that perform as designed.
In addition to the problem of complex building systems we also have fragmented and often adversarial site organisation and practice. Therefore no one on site apart, possibly, from the site manager, has any interest in final building performance or in sorting out interfaces between processes which will so hugely affect this performance.