Self-Builder FAQs

Whether you’ve committed to building your new home with Durisol ICF or are still in the planning stages, you’ll likely have many questions about our product.

Here we’ve provided the answers to our most frequently asked questions.

We recommend engaging with us early on in your self-build journey, as this will save you time and money in the long run.

Use the links below to jump to the section you’re most interested in, or scroll down the page to view all the questions.

Design & Planning

The design process is reasonably practical, and the system is simple to use, so you don't need a specialist architect. However, if you'd prefer to use an architect with Durisol expertise, we can provide details of those local to you. We can also provide technical support to architects who are specifying the system for the first time. We've working relationships with structural engineers and specifiers who are conversant in detailing Durisol to the current codes and contractors who have experience building with it. We can put you in contact with these specialists to support these aspects of your project.
Our complete Technical Manual and Build Guide is available to download from our Technical Resources page. Here, you'll also find all the construction drawings you'll need.
CAD details are available to download from our Technical Resources page.
No, we can accommodate other dimensions; the units just need cutting. Ideally the design will allow for full block height such that window cills and tops of walls arrive in full block dimensions. However, vertical cuts for walls and openings of differing lengths are very simple.
If you supply us with your dimensioned drawings, we can do a take-off to estimate the number of units you'll require and help you decide how many to order.

Certification, Insurance & Mortgage

Regarding a structural warranty, Durisol is third-party certified by the BBA (British Board of Agrément). Durisol builds have successfully acquired structural warranties from various warranty providers, including LABC Warranty, Premier Guarantee, Global Home Warranties, and Build-Zone. As each provider has different criteria, we can advise you on the most suitable one for your build.
When it comes to insurance, ICF is considered a non-standard form of construction. However, since many homes fall outside the restrictive 'standard' classification, non-standard insurance is readily available. Provided you've met all the building regulation requirements during your Durisol build, you'll be able to insure your new home with various insurers.
In the UK, the Council of Mortgage Lenders has formally recognised ICF as a standard form of construction for those manufacturers who are members of the industry trade association, the Insulating Concrete Formwork Association (ICFA. As Durisol is a full member of the ICFA, most mortgage lenders will lend on homes built with Durisol ICF.

Performance

The U-values and PSI values achieved through building with Durisol exceed UK building regulation requirements and can surpass types of traditional cavity and timber frame construction values.
As Durisol can deliver very high insulation levels and airtightness in the building fabric, it can contribute to meeting Passivhaus standards.
The Durisol woodcrete is inert. Durisol has a 90-minute certified fire rating in regard to resistance to fire. Other tests have been conducted for up to four hours.

Usage

The highest recorded Durisol build is a reinforced concrete frame hotel in Canada, over 20 storeys tall. So, your self-build home can be several storeys high. Concrete has excellent compressive strength, and a Durisol build creates a monolithic continuous concrete frame within the units that provides exceptional stability.
Yes, it is suitable to be exposed to moisture permanently.
Yes, but it would need to be structurally waterproofed as with traditional construction. We can advise on specialists in this area along with warranty providers who support this approach.
Yes, swimming pools have been built with Durisol, and it is ideal as swimming pools now come under building regulations and need to be insulated.

Specification

Durisol creates a concrete frame within the formwork that can easily incorporate a range of flooring systems. For timber floors, it's quick and easy to bolt a wall plate to the wall and introduce joist hangers in the usual way. Alternatively, for solid floors such as "beam and block" or precast plank floors, these can bear directly onto the concrete core.
Durisol provides excellent flexibility in terms of the finishes that you can apply to it. The woodcrete has a rough surface which provides an excellent key for wet finishes such as plasters and renders. Externally, renders can be applied onto the bare Durisol to provide weather tightness and air tightness as well as an aesthetic finish. Externally, Durisol can also be matched with local brickwork or stonework using synthetic or real brick and stone slips. It is also possible to screw battens and a house wrap membrane to the Durisol and then overlay timber cladding of your choice. Internally, again the options are broad. A wet plaster takes very well to the woodcrete. The added benefit from a plasterer's perspective is that the woodcrete does not support capillary action, and as such, it doesn't suck moisture out of the plaster during its application. This feature gives the plasterer more working time to get a perfect finish. Alternatively, plasterboard can be "dot and dabbed" directly to the Durisol or fixed to battens which are screwed directly into the woodcrete.

Building With Durisol

For detailed instructions on how to build with Durisol, please download our Technical Manual and Build Guide.

Yes, including rain, snow and low temperatures. Concrete can be poured into the insulated formwork down to -6 degrees C.
We recommend building to a maximum of 1.5 metres (six courses) in height per pour for self-builders. Commercial contractors can extend this to 2.5 metres (ten courses) if our Build Guide is followed religiously.
Gables are formed by dry stacking the Durisol units and then screwing timbers to either side of the wall to create the pyramid shape of the intended gable. The units can then be cut off along the line of the timber. To fill the gables, it's necessary to blank off the opening at the top to prevent the wet concrete from spilling out. This can be achieved by screwing timber to the opening.
As Durisol is made of woodcrete, it can be easily chased out with anything that cuts wood. For example, an inexpensive router can be used to chase out channels, and the depth can be controlled by screwing a piece of timber to the wall as a guide and a depth gauge. External Durisol wall units have a 40mm thickness, which is ample depth to sink cables and socket boxes without touching the structural concrete behind them. So, it's straightforward to install all the required services before wet plastering. Alternatively, plasterboard can be placed over the Durisol, which affords space between the wall and the plasterboard to run cables and services in the usual way.
Movement joints are not required. In structural concrete movement, joints are there to guard against two phenomena. Firstly, they help to manage shrinkage cracking during curing, which, while not structural, can be unsightly on an exposed surface. Secondly, they are there to offset the effects of thermal expansion and contraction in the concrete during the structure's life. Durisol is permanent formwork, and as such, the concrete is never visible in the finished condition. Therefore, the aesthetic aspect of shrinkage cracking is not relevant. Furthermore, any tiny movement during this build stage has no relevance to the render because the concrete is poured and allowed to cure long before the walls are rendered. Finally, in terms of thermal expansion and contraction of the concrete during its life, it is sitting within an insulated formwork that wraps it in insulating woodcrete and PIR and means that during the life of the structure, the temperature range that the concrete experiences is minimal.
Durisol used below ground in basement applications requires structural waterproofing like any other structure (masonry, traditionally shuttered concrete etc.). We work with various suppliers such as Wykamol, Delta and RIW and these specialists in structural waterproofing use systems compliant with BS8102. Good practice dictates this process is signed off by a CSSW qualified contractor as well as at the design stage by a CSSW qualified surveyor. Every project is different, and we can advise as required on a project-by-project basis.
The concrete within the Durisol units, in conjunction with rebar, form the lintels. Your structural engineer will define the schedule of reinforcement. However, we have load tables worked up to the current codes to enable designers to specify appropriate rebar schedules depending on the specific loading requirements of the application. The plan will be dictated by wall heights above, intersecting floors, roof loadings, and of course, the span of the opening. Please contact us for design tools or referrals to engineers conversant with Durisol.
The design of the concrete frame inside the Durisol formwork is the responsibility of the structural engineer. There are instances where mass concrete can be used. In other scenarios (retaining walls, vaulted ceilings, tall walls etc.), it may be necessary to design for reinforcement. We have design tools available upon request to assist engineers, or we know engineers conversant in structural design using Durisol as formwork.
The weight of the units means that other than at openings, the walls generally don't need propping during construction. However, bracing the walls in certain locations such as corners, cut units etc., with sheets of ply screwed into the Durisol, will help avoid movement during a concrete pour, which is covered extensively in the Build Guide.
Anything that will cut wood will cut Durisol. For several cuts, a reciprocating saw or alligator saw is ideal.
There are three models of units – a corner unit is used on a corner, face units are used around openings, for lintels and as stop ends, and a standard unit is used in straight wall runs.
The units should be laid with the insulation at the outside of the wall to allow the thermal mass benefits of the concrete.
The concrete specification is critical. It should be C30 strength, 10mm aggregate and a slump between 180 and 220mm, which is a pumpable mix.
No, it can be put in by crane/loader bucket or with a bucket (by hand).
The type of pump is dependent on on-site access and the size of the build. Please speak to a member of the Durisol team for further information.
As a guide, for our D170, D300 and D365 units, you will require one cube of concrete per 10sqm of wall. For D250 units, you will need to allow approximately one cube per 7sqm of wall.

General Product Information & Sizing

All units are 500mm long, 250mm high, with width dependant on the unit chosen.
The number in the product name refers to the width (in mm). So, for example, the D300 has a width of 300mm.
D365 units have 30 in a pack, D300 units have 40 in a pack, D250 units have 50 in a pack, and D170 units have 60 in a pack.
Durisol D300 and D365 units will arrive on-site with insulation pre-installed. D250 and D170 units are non-insulated.

Ordering, Training, Support & Delivery

Please email us at [email protected], and we can provide a price estimate based on your project requirements.
Yes, please check on our training page for upcoming dates.
Yes, please speak to a member of the Durisol team to arrange a visit.
Yes, please speak to a member of the Durisol team to arrange a visit.
Yes, we deliver through a third-party haulier, and there are vehicle and offloading options. Our T&Cs include a checklist in terms of site access and other factors designed to ensure delivery and unloading runs smoothly.
There is a six-week lead time. The newly manufactured units must pass quality checks for 28-day strength development before being packed and booked for transportation.