10 Reasons to Build with ICF

What are the key benefits of ICF?

Naturally, the final word on what structural system suits your project will come down to how it matches up with your budget and design requirements – but there are plenty of solid reasons to consider insulating concrete formwork.

1. You get super-fast build speeds

The combination of lightweight, easy-to-handle blocks and poured concrete makes this a quick, all-weather construction system. On a straightforward project, the formwork and pour for a single storey can be completed in as little as two or three days; much faster than traditional masonry.

Plus, the insulating blocks help to retain heat when the concrete is pumped in – so the cure can still take place even in very wet or frosty conditions that might put the clappers on a brick-and-block build.

2. It’s easy to understand

ICF isn’t just quick; it’s intuitive, too. Stacking blocks, adding the rebar to the engineer’s spec and pouring the concrete aren’t rocket science. That said, it’s important these aspects are done correctly – and most ICF suppliers offer training for contractors (more and more of whom have experience in using the system).

The tricky part is the first course, which must be highly accurate – but once this is in place, the rest of the process should be super-smooth. The interlocking profiles mean walls will stay square and true as they go up, for instance. This quality means some intrepid self-builders will even take a DIY approach.

3. It’s energy efficient

With ICF, the polystyrene formwork used to contain the concrete pour stays in place permanently – giving you an instant double thickness of insulation.

When specified to the right depth, this built-in thermal protection can easily achieve U-values as low as 0.11 W/m2K (compared to the Building Regs upper limit of 0.30 W/m2K). That means good heat retention and minimal energy bills.

4. It’s airtight

Another benefit in the energy stakes stems from the system’s monolithic nature. With its solid concrete core and interlocking block profiles, ICF is naturally airtight. This makes it a strong fit for Passivhaus projects, where minimising air leakage is a big priority.

Good air quality can be maintained by installing some form of mechanical ventilation system (usually with heat recovery in order to get a free boost of warmth and maximise performance).

5. You can clad it with anything

External finishes are fixed directly to the blocks, and you can choose anything from render (usually the cheapest option) through to thin-profile brick or stone slips, battened-out timber cladding and more. Internally, dot-and-dab plasterboard is the conventional choice, which is then skimmed and painted to achieve your preferred look.

6. There’s real design freedom

ICF might be built around rectangular forms, but that doesn’t mean you have to end up with a blocky house. Dramatic architectural features such as curved walls, vaulted ceilings and cantilevers are all possible.

In fact, in some cases this kind of element may be easier to achieve than with other systems, thanks to the inherent strength of the steel-reinforced concrete core. The method can support openings of up to around 6.3m as standard, so vast swathes of glazing should be pretty straightforward to incorporate. Add in more steel and concrete, and even bigger spans are possible.

ICF’s structural strength and spanning ability makes it a prime candidate for achieving barrier-free living. As with a masonry house, intermediate floors can be of beam-and-block, which among other benefits (see point 8) minimises the requirement for loadbearing internal partitions.

7. You can hang things off the walls

Drilling into concrete isn’t the easiest of jobs. Thankfully, many ICF suppliers have thought this issue through. One solution is the provision of fixing-strips within the blocks (typically at 200mm spacings). You can attach heavy items such as cupboards, towel rails and radiators directly to these strips using self-tapping screws.

8.  Soundproofing comes as standard

A downside of other quick-to-build systems, such as timber frame, is that they don’t provide the best acoustic performance out of the box. ICF’s heavyweight, monolithic concrete core is extremely dense, which helps block out noise transfer from outside. The use of beam-and-block floor structures can do the same for internal sound.

9. It’s extremely robust

The combination of concrete and EPS foam is a highly durable pairing. The insulation won’t degrade over time, and is treated with flame retardants – so it won’t burn in the event of a fire. The monolithic walling, meanwhile, requires no maintenance in use – so only the claddings
will need regular care and repair.

10. You can use it for basements

Insulating concrete formwork’s innate strength makes it suitable for work below ground. Add to that the fact that it’s relatively easy to waterproof, usually with an external membrane, and the system is a prime candidate for schemes involving basements or retaining walls.

Top image: Built using Beco Wallform’s structural system, this contemporary scheme features a cantilevered, copper-clad upper storey. Credit: Philip Thornton