Modern Methods of Construction
In this article we describe some of the factory building systems that are widely used in the construction industry throughout the UK today. Modern methods of construction employ a radically different approach to that of the past and minimise the on-site activity. They offer many advantages in terms of shortening construction schedules, a greater degree of predictability in cost, reduced material waste, reduced carbon emissions and greater safety and security on site.
The process of off-site construction involves planning, designing, fabricating, transporting and assembling building elements for rapid site assembly to a greater degree of finish than in the traditional piecemeal on-site construction processes.
We have explained elsewhere that the urgent need for more homes stretches back to the 19th Century when industrialisation drove a huge rise in population. We have explained how historically it was the new technology of the age that enabled the creation of the mass housing projects of those times.
Today, as we live in a digital age we have developed building systems that allow us to create high quality houses at a comparatively low cost though computer aided design and off-site construction. In our article ‘Designing Homes, The Argument for an Authentic Approach’ we explain how authentic buildings can be created with timber frame and other modern methods of construction.
In this discussion we look at the factory built systems that are readily available and why these methods, when coupled with a place-making strategy, can create authentic, successful vernacular houses that are fit for contemporary lifestyles.
Part 1 – Construction Systems in Timber
Timber has been used in the construction of buildings for thousands of years. The main building construction method shifted from timber frame to load bearing masonry at the time of the industrial revolution when bricks, blocks and other building materials were first mass produced. Today’s advances in technology and manufacturing has re-introduced timber construction as the main structural component in house building.
Timber is the central material in off-site construction and as it is a renewable, low carbon material it offers a number of different options within the factory production process. We describe some of these options below.
Timber Frame Construction
Timber frame is probably the most commonly employed off-site construction system in the UK. Walls, floors and roof panels are assembled as cassettes by computer controlled production facilities. This computerised process allows each component to be unique and introducing variety to the design palette i.e. each individual dwelling can be designed to match the needs of its occupants and to its context in the landscape.Cassettes can either be Open or Closed Panels. Open Panel cassettes are simply timber frame structures whereas Closed Panel Cassettes involve a greater level of completion with the factory installation of windows, apertures for services, breather membranes etc.
Oak Frame Construction
Oak frame construction involves the factory fabrication of large oak frames that are delivered to site to be fixed in place. Oak frames can be incorporated into the buildings in a number of ways and can be assembled with SIPS panel infills as described below.Oak frames are popular in self-build projects because they offer speed of construction coupled with the historic and authentic method of construction. They also offer a natural aesthetic if the building fabric is to be used as a external feature.
Cross Laminated Timber
CLT is a structural laminated timber panel system that is used to create solid timber walls, roof and floor panels. CLT is produced by gluing laminates two ways and by finger jointing soft wood in layers that are set at 90 degrees to each other.
CLT is a very successful construction process as it has a high loadbearing capacity, and high levels of acoustic, fire and structural performance. CLT is used in most building types and is popular among architects particularly for its beautiful aesthetic appearance.
Part 2 – Volumetric or Modular Systems
Volumetric construction involves the full fabrication of large components that are delivered to site. An entire house can be built from just a few modules that, when delivered to site, require no more than light finishing and decorating once assembled.
Factory production of such large components that are delivered complete with fixtures and fittings means that there are very few defects in the completed building. The main advantage of Modular Construction is the speed of assembly with houses completed within days.
Volumetric construction does not mean that every component must be identical. Computer controlled construction in factory conditions allows for flexibility and variety in building forms and material finishes. Architects use BIM 3D computer programmes that work hand in hand with manufacturing technology to deliver buildings that are responsive to their location and occupation.
Part 3 – Structurally Insulated Panel System (SIPS)
The SIPS system provides completed cassettes with oriented strand boards (OSB) and a full polyurethane or expanded polystyrene insulation.
SIPS panels are widely used in house building. They provide components that do not require any other form of structural support, offer high levels of insulation and can be rendered fully air tight at the point of assembly.
Part 4 – Lightweight Steel Frame Construction
Lightweight steel frame construction is becoming increasingly popular in the UK. Lightweight loadbearing galvanised steel frames are factory assembled and fixed together on site to create the structural envelope of a building.
Steel frames are dimensionally accurate, embody a very high strength to weight ratio, have longevity, and are adaptable and fully recyclable.
The benefits of lightweight steel construction are similar to those of timber construction. The high strength characteristics of steel reduce the size of structural members and spans can be increased without the need for additional supports. Less structure offers more room for insulation and finishes, steel framed buildings can be highly energy efficient in use.