ICF, or Insulated Concrete Formwork, was developed in the 1930s and has risen in popularity over the years due to its straightforward process and impressive energy performance.

In ICF construction specialist foam blocks are pieced together, much like LEGO, to form the shape of the building and reinforced with rebar. These blocks serve as a mould for concrete to be poured into and are stacked and filled with concrete in stages – usually every 3m in height.

Because of this simple method of construction ICF is particularly popular among self-builders, and many suppliers offer training and accreditation for those who want to carry out some of the construction work themselves.

ICF is not only popular for new build houses but is used on a variety of structures such as hospitals, schools, and large residential builds.

The benefits of building with ICF:

• Installation speed – blocks can be assembled extremely quickly, and the pouring of concrete takes much less time than any traditional building method. Furthermore, weather conditions such as rain will not hold up the process.
• Energy efficiency and air tightness – ICF homes are extremely energy efficient due to the properties of concrete and the air-tightness of the finished building. This results in buildings with very low energy bills and less mould/damp issues. Because of this ICF is well-suited for constructing Passive Houses (ultra-low energy buildings that require little energy for space heating or cooling).
• Soundproofing – concrete and wall composition mean that far less sound penetrates walls than in traditional builds.
• Ease of use – due to its Lego-like simplicity the blocks assembly can be completed by anyone without the need for previous construction experience. However it is advised inexperienced users take a training course provided by a number of ICF suppliers.
• Flexibility – blocks come in all shapes and sizes, so buildings are not restricted to a rectangular block design.
• Structural integrity – ICF builds are incredibly durable. Buildings can withstand hurricanes and earthquakes, which may not be much of a factor here in the UK, but they also have a typical fire rating of 4 hours whilst retaining structural integrity.

The key points to bear in mind when using ICF:

• A good relationship should be established early on with the ICF supplier, who will be able to accommodate custom block sizes and advise on large openings such as wall openings and overhangs which require special consideration.
• While the stacking of blocks is a simple process, the pouring of concrete is much more critical and requires a professional contractor to ensure breaches do not occur.
• Good coordination and design are a must as any changes once concrete has been poured will be expensive and time-consuming to rectify.
• Walls are thicker than those in traditional builds and may not suit projects where internal floor area needs to be maximised.
• An ICF build can be up to 10% more expensive upfront than traditional brick and block, though some costs are usually saved with the reduced need for labour and equipment such as scaffold, as well as by taking a DIY approach. There are also long-term savings in the form of drastically reduced energy costs.

At Yelo Architects our technical team has attended the ICF Southern training course run by NUDURA in order to gain the best knowledge for designing ICF buildings and producing technical drawings. We now have a number of projects being constructed using ICF – if you are considering using it in the future do get in touch! Pictured below is our Wayland Road project, a new build single storey house that will utilise ICF for the outer walls, which was chosen for its structural strength and energy performance.