In this blog we talk more about the technical aspects of project managing ICF self-build homes.
We originally met our self-builder client at the National Self Build and Renovation Centre (NSBRC) in Swindon, Wiltshire back in 2014. Since then have been supporting our client, who is building a new home in Buckinghamshire, helping with him with energy performance advice, as well as the selection of the build team and finally helping to project manage the construction works onsite.
This large new build went onsite a year ago and started with the demolition of the client’s existing house. The new, replacement house is being built on a sloping site, and has two levels at the front and three at the rear, together with a loft area. The new house is being constructed using insulated concrete form-work, known as ICF.
ICF involves using interconnected blocks or panels (usually, but not always made of expanded polystyrene) as moulds into which a special type of ready-mixed concrete is poured. These mixes have been specially developed for use in ICF to give better flow-ability of the concrete with reduced water content and more cohesiveness. This, together with the use of a pencil vibrator tool which ensures the form-work fills properly and eliminates rock pockets and voids.
This method has been around for decades and is commonly used in the USA, Canada and Europe but has only recently become a popular choice with self-builders and commercial clients here in the UK.
It’s quick to build and the walls have great thermal properties. These enhanced U values, as well as a high level of air tightness and superior acoustic properties make the ICF method popular with those who want their home to have exceptional levels of energy performance.
Our clients decided to use ICFs early on in their project planning. Once outline planning permission was achieved they used an architect who was experienced in ICF project design, together a structural engineer to complete the building regulations drawings.
A specialist ICF contractor was then used to coordinate the supply of both the materials and the labour to build the ICF walls. There are several systems on the market. Our client chose IntegraSpec, in which expanded polystyrene panels are fixed together with webs made from a strong plastic material to create a form-work to which horizontal and vertical steel reinforcements are added for extra strength.
In this photograph you can see the ready mix concrete being pumped and vibrated into the void between the ICF walls.
Once braced, the form-work is simply filled with vibrated concrete. The expanded polystyrene panels stay in place, resulting in a super-insulated monolithic solid concrete structure. The panels are available in various widths and lengths as well as depths of the insulating polystyrene foam meaning it is very flexible from a design perspective and you can also choose how energy efficient you want your building to be.
In this photograph we took onsite you can see the specialist ICF contractors checking the ready mix concrete is being correctly applied to the ICF formwork.
Here you can see the IntegraSpec Panels showing bracing and core of concrete concrete
The ICF walls can be clad with stone or wood or rendered. Our client has chosen to simply render the external walls with a through colour K rend which is a very easy process. Equally there is no need to dot and dab to attach the internal plaster-boarding. With this ICF system the internal walls will have plasterboard screwed directly into the plastic inserts which are within the expanded polystyrene panels.
Frank Elliot, who is our project manager for the Buckinghamshire area, is supporting our client with full trade by trade project management.
Frank’s 3 top tips are :-
- Select your ICF contractor carefully, and see the work they’ve completed in the past, as well as taking up references. Whilst the ICF build method is relatively simple, many things can go wrong and you want to be dealing with experts! For example, beware of voids in the concrete – a special aggregate with round stones must be used, plus the vibration methods need to be right to ensure the concrete is fully compacted. This is particularly true above windows where there should be additional steel bars which form the in-situ lintels.
- Instruct the ICF contractor to be responsible for installing the mid-floors and structural steels as well as the construction of the ICF walls, as this will make things easier. This way you won’t be caught in-between trying to negotiate and resolve things with 2 different trades if there are any problems. Having a single contractor for this crucial part of the build will prevent potential delays and issues relating to responsibility and accountability.
- Don’t forget that every aperture needs to be thought of ahead. You’ll need holes not only for the obvious things like windows and doors but also for ductwork, flues, water, gas and electric services etc. Plan ahead. It’s no joke cutting through reinforced concrete at a later date!
To get a better idea of what’s involved in ICF construction it’s worth looking online – there are videos on YouTube which show whole houses being constructed to create a waterproof shell in a matter of a few days!
If you are planning a self-build construction project and considering using Insulated Concrete Formwork then why not get in touch? CLPM are experienced in project managing ICF self-build homes as well as commercial construction projects with the ICF building method. Call 01923 896550 or email us at info@cl-pm.com to find out more.
