Back in October, we wrote about a report compiled by 33 London Local Authorities which suggested that London’s home construction was projected to be 550,000 units behind where it needs to be in 8 years’ time. Solutions touted at the time included methods to reduce construction costs and an emphasis on bringing empty homes back into use. The problem still remains and we look below at two innovative construction methods which could make the difference to Britain’s supply problems. The questions is, would you like to live in a house made like this?
Insulated Concrete Formwork (ICF)
The first method we examine is Insulated Concrete Formwork (ICF), which is thought to have originated in Germany as a way to replenish their bombed out housing stock after World War II.
ICF uses polystyrene as a mould into which ready-mixed concrete is poured. The whole system, including the polystyrene, forms the structure of the house – with what was once the mould then providing substantial levels of insulation and a substrate for internal (typically plasterboard) and external (typically render) finishes.
For normal concrete walled construction, timber formwork is typically used, which, when the concrete has set, is removed. Timber formwork has been considered tricky to make and the majority of it is non-reusable once it has been removed. The introduction of ICF removes these potential issues, as timber formwork is no longer needed – being replaced by the polystyrene mould – and there is no need to remove the insulating polystyrene.
ICF has a number of advantages over traditional brick and block methods; including the exclusion of elements such as lintels, wall ties and cavity trays, which are common with cavity wall construction. ICF is also a lot speedier than traditional methods and the integrated insulation it incorporates typically establishes a wall U-value of 0.15W/m2K – better than almost all competing methods.
The cost of ICF when compared with blockwork wall costs can appear to be more expensive, which may be the main reason why many builders and contractors have previously stuck with traditional methods.
The majority of ICF systems in the UK can cost between £25 and £35/m2 and this, together with ready mixed concrete at £10/m2 and a few additional extras, makes the wall cost over £40/m2, even before the cost of labour has been considered. This is effectively double the cost a blockwork wall can be built for, including labour.
It is important to note however that the construction of a blockwork wall goes beyond just the blockwork. It will require an insulated cavity, lintels and a waterproof outer skin which will in fact add to the costs; revealing a truer value of between £70 and £100/m2.
The labour costs for ICF are very low, with an experienced ICF team able to lay 5m2 of wall per hour; add this to the cost of an external render coat at around £25 – £30/m2 and the original wall cost of £40/m2 and the overall cost will be around £80 – £90/m2 – certainly comparable to a masonry structure in terms of cost, but additionally providing a greater level of insulation and taking less time on-site.
Structural Insulated Panels (SIP)
The second building system that we will explore is Structural Insulated Panels (SIPs). SIPs consist of two parallel faces, most commonly Oriented Strip Board with a solid mass of insulation sandwiched between them. The insulation used is either Polyurethane (PU) Foam or Expanded Polystyrene (EPS).
The insulation sandwiched between the two Oriented Strip Boards not only provides high levels of insulation, but creates an element that can be up to six times stronger than a regular timber frame.
Building with SIPs will have similar results as building with ICF, with regards to the fact that both methods will result in a strong, energy efficient and cost effective property. However the two methods do have their differences.
The process of ICF is wet as it requires the concrete to be added on site, whereas SIPs is a completely dry method; typically resulting in slightly quicker erection times. However, SIPs are usually constructed in a factory and any delay there will create delays onsite. Another difference between the two is that ICF relies on the concrete for its strength, whilst SIPs are inherently strong and therefore result in a narrower wall profile (typically 355mm as against 383mm).
Although the two methods are often seen as competitors, some contractors and builders have recognised that they can actually make quite a good team. The reason being that although both can be used for walls, SIPs cannot be used for basements and ICF can’t be used for roofs. The two in tandem can be a cost effective and architecturally attractive option.
These are just two of many innovative construction methods available to UK constructors and, as demand continues to outstrip supply, we will undoubtedly see both further innovations and a greater uptake of these new technologies. In particular, the attractiveness of a walling system that is quick to construct on site will be of great interest to construction firms who can keep the costs comparable to the masonry alternative, whilst shaving between 1 – 3 months off their overall project completion time.
Yet to appear in the mainstream are 3D printer solutions, but with the most advanced models now able to produce parts strong enough for construction – and with detail control enough to replicate London’s Tower Bridge smaller than a grain of sand – this will undoubtedly be a big part of the UK’s construction future.
If you are in the process of building a new house, considering a self-build or are just purchasing a new home; it would be wise to get professional advice from a Local Chartered Surveyor. Find yours here:
10/01/2014 BT / SRJ / LCB