Housing Solutions

Insulating Concrete Formwork (ICF) Frequently Asked questions

How are the walls erected?

CEMEX Ready Wallform ICF components are delivered to site in packs or bags. They are light and easy to handle, and can be quickly cut with hot wire or hand saw as required. They interlock vertically and horizontally to form a continuous void that is filled with concrete.

How robust is the system?

Buildings built with Ready Wallform have been in use on the Continent, North America and Australasia for over 30 years with no record of failure.

How many pours are required per storey?

The pattern of concreting will vary from project to project, depending on circumstances and resources available. A storey height pour is the ideal height to be completed in one operation, supplied by one or more ready-mixed concrete deliveries, working round the perimeter of the formwork several times until it is full.

What holds the leaves together?

The two leaves of the insulating concrete formwork system are connected and held together by a matrix of polystyrene or metal connectors which become cast into the concrete core.

What is the U-value of the walls?

The U-values of the Ready Wallform system varies according to the overall thickness of the EPS, and can be as low as 0.10 W/m2K. Even the least insulating Ready Wallform components offer significantly better performance than current standards.

Is a special concrete required?

CEMEX can provide a designated pumpable concrete with an ideal slump of 75-100 mm with a 10 mm aggregate. All of our concrete is supplied under the QSRMC quality assurance scheme.

What happens at foundation level?

Ready Wallform can be built off any foundation, the wallblocks being held in position by their self-weight, just as for traditional masonry construction. The normal procedure would be to build a couple of courses of the Wallform system around the perimeter, adjust it to the correct alignment and level and then pour in the first 150 – 300 mm of concrete to fix the position of the system on the foundations.

Why is the insulation thicker on the outside in some systems?

The thicker leaf gives additional protection to the structure, enhances the use of concrete’s thermal mass and improves energy efficiency.

How thick are the walls?

The thickness of the walls will vary according to the performance specification required. The concrete core may vary from 140 mm to over 300 mm depending upon the structural design, while the two leaves of insulation may vary from 100 mm to 300 mm depending on the thermal insulation specification. Consequently, total wall thickness may be between 250 mm and 600 mm.

How are upper floors attached to walls?

Floors are normally built into the wall as the work proceeds, providing a solid connection between the two building elements.

How are internal and external finishes applied?

Finishes are normally applied directly onto the surface of the insulation. Plasters and lightweight renders will adhere directly to the insulation. Timber, masonry, curtain walling and other claddings are applied over the insulation with appropriate mechanical fixings to the concrete core. Dry lining can be attached to the internal leaf using proprietary adhesives.

How are operatives trained?

Operatives are usually trained through on-site experience. We offer on-site support as part of the package, or alternatively can provide details of local contractors with experience of Ready Wallform construction.

How is the concrete placed and does it need vibrating?

The pump grade concrete is placed into the formwork by means of a pump or skip and fills the system through gravity flow. The correct pump grade concrete will flow, fill and self-compact without the need for mechanical vibration.

Is there a limit to the number of storeys?

The number of storeys or height of the building is limited only by the structural design and local legislation.

How is a DPC introduced?

Normally a waterproof concrete, such as CEMEX Permatitie, is specified for that section of wall where the traditional DPC would be located. Alternatively, a non-solvent based liquid DPC system may be applied onto the concrete at DPC level.

Is a specialist architect required and is there a source of technical information?

The design process is quite practical and, once familiar with the system, most designers find it simple to use since there are fewer components involved, all manufactured to modular sizes. We can provide details of local architects with Ready Wallform expertise, or alternatively provide technical support to architects who are specifying the system for the first time.

How stable are the walls during construction?

During construction, it is necessary to support the formwork system and check for alignment during the pour, adjusting if necessary. (Temporary bracing systems are available)

How are lintels formed?

Lintels are light preformed components delivered as part of the Ready Wallform package. Manufactured to suit the various opening sizes required for the building, they interlink with the other components. Reinforcing bars are laid inside and the lintels are then filled with concrete at the same time as the wall is poured, integrating the reinforced lintel with the overall wall construction.

Has Ready Wallform undergone fire testing?

Ready Wallform has to achieve the minimum fire performance standards to satisfy the Building Regulations applicable to the project. From a minimum 30 minute fire rating the design of the wall may be adjusted and fire tested to achieve the highest fire standards required.

Does a Ready Wallform house burn?

he concrete cannot burn, and the EPS foam is self-extinguishing. In a really fierce blaze, well after the occupants have left, the main gases produced are CO2 and water vapour, with a minute amount of styrene, bromide and CO, which are less harmful than the compounds produced by the same volume of other building materials burning eg. timber. The structural stability of the concrete reduces the risk of building collapse.

Is steel reinforcement required?

It is quite practical to design buildings up to three storeys as concrete masonry structures, i.e. without reinforcement. Any requirement for steel reinforcement will be dependent on the type, size and location of the building and will be recommended by the specifier/designer or structural engineer.

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