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Building Systems ICF insulated concrete forms

ICF Concrete Forms

ICF means “Insulated Concrete Forms”.

Traditionally, concrete was poured into wooden forms, handmade on-site, which are discarded a few weeks later, when the concrete has cured. Others use metal forms, that can be used a couple of times.

A typical ICF, before the concrete is poured in

ICF forms are made of an insulating material, like EPS, that will remain a part of the construction once the concrete has set. This way, one saves on labour ánd

They usually look like very large and light Lego bricks. This makes them extremely easy to stack on top of each other, and an option for self builders.

Most ICF forms have plastic connectors between their two outer walls. These connectors make it easy to put steel reinforcement (rebar) where needed.

They also make it possible to attach finishes by simply screwing them into the plastic connectors.

An ICF from Nudura

ICF insulated concrete forms are smart because:

  • they’re very light to work with, and easy to install
  • they do not have to be dismounted or discarded
  • they provide thermal insulation in one go
  • they result in extremely strong walls, thanks to the concrete core
  • great thermal and acoustical comfort
  • monolithic system without cold bridges
Concrete being poured in a Quadlock ICF

The limitations of ICF

  • the concrete core still makes this a heavy system, requiring sturdy foundations
  • the concrete core makes it very difficult to modify walls later
  • most walls are relatively thick, which may cost you internal space
  • it takes a little planning to hang heavy objects like kitchen cabinets
  • while easy to finish with “dry” materials (like plasterboard, fibre board etc.) that are screwed on the ICF’s connectors, it’s a bit more difficult to finish with “wet” materials like rendering and plastering
  • the builder better have a little experience with ICF, because once the concrete is poured, corrections are very difficult. If the ICF isn’t straight or gets displaced while pouring, walls may end up crooked

Our advice

  • ICF is interesting for self builders and will give great comfort.
  • You may want to consider to internal walls in other, thinner systems
  • Consider lighter systems like SIPs to avoid foundation costs, especially on sloping land or weak soils