ICF Construction

I. Introduction

What is ICF Formwork?

ICF is an abbreviation of Insulated Concrete Forms. Formwork is an engineering term used to describe the timber structures that are required to hold concrete in place until it is “formed” into a wall, column or beam. Insulated Concrete Forms are used to build walls using sheets of expanded polystyrene that are held together by a system of ties.

Development History

The concept was developed in the US, and put on the market in 1978 by a company called American Polysteel. Since then many other companies have copied the basic idea and developed numerous alternative systems but they are all based on the same principle.

The American company was put into liquidation many years ago but Polysteel (UK) Ltd is still making and selling the same product 45 years later! We now call the Polysteel forms “Polybloks”.

II. The Benefits of ICF

Building with Insulated Concrete Forms (ICF) is a now proven way of creating an eco-friendly, stronger, safer building that’s highly energy efficient, needs minimal maintenance and repair; and one where design possibilities are limitless.

It’s a modern fast-track method of construction (MMC) and is now being adopted by architects, housing associations, developers and local authorities for commercial, residential, industrial, institutional, healthcare and a variety of other building types.

Switching from traditional building methods to ICF technology will significantly reduce labour and increase speed of build. ICF offers considerable benefits over both brick and block and timber frame.


ICF provide the easiest and most cost effective way to comply with the recent changes in the Building Regulations which require a much higher level of insulation. The dense concrete structural core with layers of insulation provides thermal mass benefits that keep the building warm inside in winter and vice versa in summer.

High thermal mass is what keeps old french farmhouses with 600mm thick stone walls cool in the hot summers as it takes all day to heat the walls up. In colder climates thermal mass slows down the cooling effect of a drop in external temperature and so the heating response can be slower and cost a lot less.

Timber frame houses have the lowest thermal mass of all the Modern Methods of Construction.

Structural Integrity

ICF buildings are provided with a rigid concrete box that will never crack or move due to settlement. They can easily resist the loading from heavy storms and high winds up to hurricane and tornado level and will not be damaged by flooding or earthquake.

Air Tightness

Airtightness is the control of air leakage, i.e. the elimination of unwanted draughts through the external fabric of the building envelope. In the future every building will need to be tested and failure could be very costly to the builder. ICF buildings are inherently airtight without a vapour barrier. And the reduced levels of dust and pollen inside the property will benefit occupants with allergies and chest complaints.

Timber frame houses and cavity wall construction are very difficult to make airtight.


The density and thickness of the concrete cores within the ICF provide excellent acoustic insulation and will dramatically minimise unwanted external noise.


Under normal circumstances ICF walls will not require maintenance during the life of the building. This does not of course apply to surface finishes.

III. ICF reduces cost and minimises Project Duration

Fast track construction

It can take 3 or 4 months to order, get delivery and erect the frame for a dwelling. Traditional brick and block construction will also take about the same time to get the roof on.

ICF is normally available within a week, the walls are up to eaves level in 3/4 weeks and the roof is weathertight in 6/8 weeks allowing the follow-on trades to enter the building and start putting utilities and finishes into place months before a traditionally built house.

Reduced labour costs

Labour costs are reduced as ICF systems require semi-skilled labour only and not highly paid, scarce skills such as brick layers. Although there is a need for a certain amount of training, which is offered by all ICF suppliers on site, this can be learned quickly. Construction can proceed in most weather conditions including rain and frost.

Simple service installation

To save time on site, the conduit, cabling and ducting can be installed within the wall space of the empty forms prior to pouring the concrete. The inner wall of polystyrene can also be chased after the concrete wall has been poured and cured.

Less heavy plant and equipment

Due to the light-weight forms and the speed of the build, large forklifts, heavy plant and equipment normally found on the average building site is not required with ICF.

Improved site safety

ICF systems are light to handle so there is less chance of injury. The workplace is easy to keep tidy thereby cutting down the possibility of trips and falls, and because the need for plant and other equipment is minimal, chances of accidents are also minimised.

IV. ICF is a superior material for all types of Building Projects

Variety of finishes

A wide range of external facing materials can be applied to ICF structures, including brick, stone, render and timber, as well as steel, aluminium and cement cladding panels.

Basements, Retaining Walls and Swimming Pools

One of the major assets of ICF is that it can be used to construct very high quality retaining walls for basements and swimming pools very quickly and economically without the need for highly skilled shuttering joiners.

Compatible to other building systems

The ability to use a range of roofing, flooring, utilities and opening systems allows the designer total freedom to choose their preferred supporting non-structural building components. Most ICF systems have compatible flooring systems which can be poured at the same time as the supporting walls, but they also have timber systems where joist hangers penetrate the ICF walls before being concreted in.

Design Details

Detailing is an issue which can be daunting for architects who are new to ICF. The details allow architects to successfully interface a wide spectrum of different construction systems, materials and products. Furthermore the flexible nature of ICF means that important aesthetic considerations, such as whether to recess doors and windows and by how much, are easy to achieve using standard detailing practices. Indeed, some conditions such as corner windows and cantilevered openings, are easier to design with ICF than traditional forms of construction, as they do not require complicated structural solutions.

ICF Mortgage, Insurance and Planning Acceptance

ICF systems are recognised by The Valuation Panel of the Council of Mortgage Lenders for mortgage purposes as a standard form of construction.

To make sure of this it is essential that any ICF system has a current British Board of Agréement certificate.

How to build a pool with ICF Polybloks?

Polyblok Pools