Given that productivity levels are low, that build quality is still an issue and that projects are frequently late and over budget, you would think that the construction sector and procurement bodies would be eager to embrace new methods.
The reality is different. Offsite methods still contribute a very small percentage of total construction projects. This is despite the fact that they are proven to save time, improve budget surety, and improve quality. The reason often given for sluggish take up is confusion about what the term ‘offsite’ really means.
There are certainly different types and varying degrees of ‘offsiteness.’ At the lowest level, you find building elements such as concrete foundations and structural elements created offsite rather than being poured onsite. This results in some timing efficiencies as subsequent operations don’t have to wait for concrete to set.
At the next level, up you see components such as bathrooms shipped more or less finished to the site for installation and connection of services. The remainder of the structure is still traditionally built and therefore subject to the normal risks of timing and budget overruns and quality issues.
‘True’ Offsite
What you might call ‘true’ offsite arguably starts with volumetric prefabricated structures that are shipped in modular form and fitted together onsite. This method certainly brings greater efficiency. The limitations come in where site access is tight or restricted, or when non-standardised building designs are needed. This format of offsite is strong on efficiency but often compromised in effectiveness for anything other than a standard build.
Where design flexibility is needed, the solution is to use a panelised system. Candidates here are metal frame construction, cross-laminated timber (CLT) and Structural Insulated Panels (SIPs).
Metal frame construction uses light gauge steel to form the building skeleton, which is assembled on site. External cladding, insulation, floors and the rest of the structure are then added. CLT uses large format panels made from layers of timber glued together, each layer is glued at 900 to the previous one.
The big advantage of SIPs is that the structural and thermal properties are combined in a single panel that is precision made in a factory environment. The amount of additional onsite work needed is minimal compared with both CLT and metal frame. The insulated panels form the structure of the building, including roof and floor cassettes. The airtightness and minimal thermal bridging losses also guarantee the performance of the finished building,
As you consider the different types of onsite it becomes clear there are differing gains in both quality, productivity, and design flexibility. Offsite is not a single technology but a range of options that can be deployed to improve speed, reliability, and quality of construction projects. If you want to understand more about how panelised offsite could bring benefits to your planned project get in touch with Innovaré or take a look at our case studies.
