Insulating Concrete Formwork

Insulating Concrete Formwork (ICF) is used to build insulated structural walls in both residential and commercial buildings, and is one of the most energy efficient and cost effective building materials available to you when you plan your self-build project.

ICF is a simple construct of insulating panels and concrete. The panels are put in place to form the wall’s framework and a concrete shell poured around them which, once hardened, leaves the internal panelling to form an insulating layer. The insulation is usually made from either expanded or extruded polystyrene, which makes the ICF lightweight and easy to manoeuvre on-site.

How Does it Work?

ICF can be designed in a range of sizes, thicknesses and shapes depending on the requirements of your specific self-build project, and can be reinforced with steel for added durability. The insulating panels are simply set up on-site and ready mixed concrete poured so that they are encased within the wall, providing a hardwearing layer of insulation. ICF can be used for both internal and external walls, and once the concrete is dried they can either be rendered, dry-lined or plastered.

Unlike brick and block walls which require the right weather conditions to be installed, ICF walls can be put up even in freezing or damp conditions, allowing your building to be made water-tight very quickly. Because it is so lightweight and easy to assemble, savings can also be made in terms of labour costs.

The Advantages

Using ICF has multiple advantages over other building materials:

  • Greater design flexibility – ICF comes in a wide variety of sizes, thicknesses and shapes, including the ability to create curved walls. This gives you more creative scope when designing your self-build project.
  • Green credentials – ICF is one of the most energy-efficient building techniques, creating a home which has greater thermal performance and is much better insulated than standard timber, steel or brick and block walls. This can be a bonus when applying for planning permission, as local authorities are always keen to see more green homes being built.
  • Concrete means better damage resistance – The concrete shell means walls are more resistant to flooding and fire, with added fire retardant also applied to the layer of insulation. Unsurprisingly, some statistics suggest homes built with ICF are four times more resistant to fire than timber-framed constructs.
  • Savings on build-time and cost – The panels are lightweight and easy to install, meaning reduced labour costs as skilled tradesmen are not needed to erect them. The ability to quickly manoeuvre them into place also means a reduced need to store materials on-site.
  • Better noise reduction – Homes built using ICF are very quiet, with the insulation letting in only about a third of the noise timber-framed houses let in.

The Disadvantages

There are very few disadvantages to using ICF, but…

  • Cost of concrete can vary – Concrete can be a more expensive building material than timber, which may push the price tag of your self-build project up by 5-10%.
  • ICF buildings are difficult to remodel – If you decide later on that you want to add another door or window, you will have to cut directly through concrete, which is much harder than simply altering a brick or timber-built home.
  • Walls are thicker than when using other building materials – Compared to some more traditional building methods, ICF walls tend to be thicker due to the layer of insulation. This might be a disadvantage if your plot and the building under construction are particularly small.