ICF Basements

History

Basements, or cellars as they were called then, were often built in Victorian times as a place to store food and fruit and fuel in the form of coal. These were normally constructed in solid brickwork and in the better quality buildings very dense, hard, engineering bricks were used and these were often quite successful in keeping out moisture – but not always!

Cellars are traditionally damp, smelly places that people avoided like the plague! Fortunately Insulated Concrete Forms now allow anyone to build a modern basement where the environment is as comfortable as the ground floor rooms.

During the early part of the 20th century between 1900 and the First World War not much housing was built and the quality of the housing stock was very poor and the housing that was built did not include cellars.

Between 1919 and 1939 there was a massive housing boom and the housing stock increased by about 180,000 houses per year as the builders took maximum advantage from the lack of planning laws. It was rare for cellars to be built because they were being built for profit and they were expensive to build!

After the Second World war building in the UK did not get under way until the 1950,s. People were still using coal but above ground storage bunkers were being provided and the new refrigerators meant that food storage in the summer did not justify a cellar.

Over the last 20 years, and particularly in London, building land has become so expensive, that basements, as they are now called became increasingly incorporated in new buildings, to provide more living space on restricted plots.

The problem with modern basements is that the only way to build them and comply with the building regulations is with reinforced concrete. But reinforced concrete walls have always been built with plywood or steel faced forms that are held apart by a temporary tie system whilst the concrete is poured between them. After the concrete has hardened the forms are removed. The primary drawback to this process is that it is very costly and there are very few joiners with the skill and experience required to carry out this work. Furthermore, the concrete was frequently of very poor quality and the basement s were often damp and smelly as a consequence.

Basement Design

Hence, ICF walls that can be erected in a day or so and filled with concrete to form a very high quality wall that also provides all the insulation required, would appear to the obvious answer. But there is one drawback – it is difficult to use reinforcement that has a diameter greater than 12 mm in ICF because there is not enough space in a wall that is only 150mm or 200mm wide and they clash with the ties in the wall and cannot be bent out of the way.

Structural designers tend to use large diameter (16 to 20 mm) reinforcing bars in their basement wall designs in the same way that they design heavy retaining walls for reservoirs etc. Furthermore, they often ignore the propping effect from the ground floor of the building that allows the reduction of the amount of wall reinforcement by at least 50%. This does mean that the backfilling cannot be placed around the basement until the beam and block ground floor has been built and the blocks have been grouted into place, but this does not normally affect the build schedule particularly.

As a result many structural designers are reluctant to use ICF in their designs even though it is absolutely perfect for this use. The appropriateness of ICF is increased even more because the very slow curing of the concrete reduces the amount of shrinkage cracks in the concrete and the Neopor leaves of the ICF forms also act as an additional moisture barrier.

Basements used to be designed to BS8110 and even though the building industry now uses BS EN 1992-1-1:2023, many designers still use the prescriptive processes of BS8110.and do not take advantage of the flexibility provided by the new code.

A modern ICF basement that is about 2.5m deep and probably about 10 m x 8 m on plan forms a very rigid box that is not susceptible to stresses from settlement and is ideal for basement construction. Furthermore the new code allows the use of the tension capacity of concrete provided that minimum areas of reinforcement are provided to control cracking.

At ICF Design we apply these principles to basement design so that you can make use of this technology without incorporating the large diameter reinforcing bars that are so difficult to use in ICF walls.

ICF is Ideal for Basements

In summary, ICF technology can ensure that your basement is a warm, dry, quiet, and highly energy-efficient living space. This makes it a smart investment for homeowners looking for increased comfort, lower utility bills, and long-term durability, as well as for builders seeking efficiency and a high-performance product.