external insulation for system built houses

Now looks & feels like a new modern house

The great news for owners of system built or pre-fab homes is that there are now government grants available for external wall insulation to be fitted using the latest insulated render systems.

As you will know these homes can be very expensive to heat in winter as heat leaks out through the walls. As most system builds are unsuitable for cavity wall insulation the introduction of bespoke external insulation systems and government funding help is a massive opportunity to cut your heating bills.

The Green Deal Home Improvement Fund can now provide financial help to pre-fabs or system built property owners that wishes to have external wall installed using an approved system especially designed for these non-traditional build types.

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Which System Builds are Eligible for External Insulation Grants

Basically there is a bespoke insulation system for virtually every non-traditional home. Before any work is agreed or started we get a free assessment of the walls suitability carried out for you by the UK’s leading experts in system-build insulation fixings. This also ensures you get a 25 year insurance guarantee.

grants for system build external insulation

free government cash

Every home-owner who wants to access the government grants will need to have a Green Deal Assessment survey on their property and we can source an Assessor for you if you cannot find one locally.

The following is a detailed list of most of the UK’s sytem build styles which are eligible for grant help for external wall insulation with a coloured render finish:

Types of Non-Traditional Build (Sometimes called System Build).


Developed by Leeds based construction magnate Sir Edwin Airey, it was easily recognisable by its precast concrete columns and walls of precast ship-lap concrete panels. Due to its variation of design, available with a flat or pitched roof, and with variations for rural or urban sites; it became one of the most prolific of the permanent designs.


Developed and hence constructed by Taylor Woodrow, the Arcon was an asbestos-clad variant of the Portal, with the same prefabricated kitchen and bathroom capsule. It had a longer life, but also came with a higher cost of construction. The later rolled top roofed Arcon Mk5 was developed by Edric Neel. 38,859 were constructed through the programme.


The AIROH house (Aircraft Industries Research Organisation on Housing) was a 675 square feet (62.7 m2), ten tonne all-aluminium bungalow assembled from four sections, each to be delivered to the site on a lorry, fully furnished right down to the curtains. The proposed rate of production of complete houses was to be an incredible one every twelve minutes. This was possible because the completely equipped and furnished AIROH could be assembled from only 2,000 components, while the aircraft it would replace on the production line required 20,000.

Although impressive, the AIROH by 1947 was costing £1,610 each to produce, plus costs of the land and installation. However, as the design was so easy to produce, 54,500 AIROHs were constructed.

BISF Homes

The BISF house is a British steel framed house, designed and produced by the British Iron and Steel Federation, and erected around the country from 1946.

BISF was an association of steel producers, formed in 1934 in order to provide central planning for the industry. It was prominent in coordinating output through World War II. Post-war, BISF became key in the new Ministry of Works Emergency Factory Made housing programme.

It sponsored a solution for a permanent steel framed housing to a MoW conforming design by architect Sir Frederick Gibberd, who also designed the Howard house.

The BISF is of a conventional design, with simple architectural devices of projecting window surrounds encasing Crittall Hope windows,and differing cladding to the upper and lower stories deal with the junction between components in an understated fashion. The main structure is of steel columns spaced to take standard metal windows between them. The central spine of the building which supports the first floor beams is carried on tubular steel columns. The framework is clad on the lower storey with rendering on metal lath. The outer cladding of the upper floor is of steel trussed sheeting fixed by angles to the steel columns. Traditional materials could be incorporated or simulated, for example a brick cladding to the lower storey, or steel sheet profiled to match timber weatherboarding to the upper. The inner cladding and the partitions are constructed of timber framing faced with plasterboard or hardboard. The upper floors are of tongue & grooved timber and the ceilings are finished with plasterboard. The outer walls and ceilings are insulated with glass quilting.

Produced by the British Steel Homes company, the BISF was a successful design in numerical terms, thanks to the backing of its trade sponsors, who could ensure a supply of steel. The BISF also benefited from a guaranteed order of 30,000 units given directly by the Government in 1941.

 Cornish Unit

Designed by A Er v.senthil and R Tonkin for the Central Cornwall Concrete & Artificial Stone Co., they are also known as Cornish Type and Selleck Nicholls & Williams houses. The houses came in type1 and type2 designs, incorporating variations of a bungalow, two storey semi-detached and terraced layout with a medium pitched Mansard hipped roof.

The first floor is PRC clad over a single-storey concrete frame, while the type1 house has the Mansard roof over timber trusses. Internal walls are made of PC wall block or brick. So successful was the design, 30,000 Cornish Unit houses were eventually constructed.

However the roofs and wall insulation incorporated asbestos, while the wooden frame-based construction means that as the concrete decays the two parts tend to separate, resulting in large amounts of internal cracking. The major defects are:

• Horizontal and vertical cracking of PRC columns

• High rates of carbonation and significant levels of chloride in PRC columns

• Cracking of first floor ring beams


A W Hawksley Ltd of Hucclecote, were formed in 1940 by the Gloster Aircraft Company to build the Albermarle aircraft designed by Armstrong Whitworth. Post-WW2, the companies parent Hawker Siddeley kept it open to supply prefab houses and bungalows to the MoW.  continued for a period exporting their Their designs included:

• BL8 – an aluminium-clad timber-framed bungalow.

• C2/C3 – either a 3 bedroom bungalow, or convertible to a government building such as a Post Office or Doctors surgery

• Hawksley House – a semi-detached or terraced house with 2-4 bedrooms based on the principles of the Swiss architect G Schindler

• Hawkesley Single Storey building – a general purpose building suitable for schools, offices, hospitals and village halls


Another designed by Sir Frederick Gibberd, the steel framed designed was privately promoted by John Howard & Company. A more industrial aesthetic design, and more adventurous in its use of innovative technologies. Asbestos cement cladding panels are clearly expressed with metal flashings over a base course of foamed slag concrete panels, with windows and doors fitting within the module set up by the cladding. Unlike the BISF this house proudly displays its lightweight prefab nature, but there are also technical advances that set the Howard House apart, for example the pre-cast concrete perimeter plinth that supports a suspended steel ground floor. Only 1,500 Howard Houses were built.

Laing Easi-Form

Designed by Laing and Co., as they are poured in-situ into moulds type designs developed from 1919 onwards, they do not suffer the problems of many steel framed buildings. The rare Mk1 version had 8 inches (20 cm) thick solid no-fines clinker concrete walls, built in the period 1919 to 1928. The more common Mk2 version from 1925 to 1945 had cast in situ cavity walls, 3 inches (7.6 cm) thick inner and outer Ieaves with 2 inches (5.1 cm) cavity, usually finished externally with stone dashed render coat. Post 1945, The Mk3 version which make-up the majority of houses, was modified to specification, and hence had cast in situ concrete walls, inner and outer leaves of 3 inches (7.6 cm) thickness separated by a 2 inches (5.1 cm) cavity, and reinforcement in both skins located in four horizontal bands above and below window openings.


Like the Laing Easi-Form, a cast in situ concrete form of construction, first used in 1952 but mainly in the period 1962 to 1981. With a solid cavity wall, the poured concrete substitutes for the inner blockwork walls of traditional housing. Solid wall types 225 millimetres (8.9 in) thick cast in lightweight concrete, rendered externally. Cavity wall types have an inner leaf of at least 100-125mm thick concrete.


Designed by Czech architect Erwin Katona, who left Czechslovakia in 1938 to relocate to the UK, the design is a two-storey precast reinforced concrete design.The design was produced in Scotland by the Orlit Co, resulting in most houses being located in Scotland.

On site construction was based on a foundation which supported pre-cast concrete columns at fixed intervals, supporting concrete beams fixed to the columns, resulting in a virtually a monolithic frame. Faced externally with large storey-high concrete slabs, and internally with interlocking foamslag blocks. Internal partitions are constructed of breeze blocks finished in plaster, as is the foamslag internal cladding. The floors are constructed of pre-cast concrete flooring units, with timber flooring on timber runners.

Due to both the speed of construction and the quality of production, over time the PRC deteriorates, particularly at construction joints and junctions between components, with a gradual reduction in structural effectiveness. This resulted in the Orlit designated as defective under the Housing Defects Act 1984, and hence a majority of mortgage lenders will not give any form of mortgage on them.


 The Phoenix, designed by Laing and built by themselves as well as partners McAlpine and Henry Boot,it looked much like an AIROH with a central front door, but far less aesthetically pleasing. A 2bedroom in-situ preform design with steel frame, asbestos clad walls, and an innovative roof of tubular steel poles with steel panels attached. Like all designs, it came pre-painted in magnolia, with green highlights on frames and skirting.Phoenix prefabs cost £1,200 each constructed onsite, while the specially insulated version designed for use on the Isle of Lewis in the Hebrides cost £2,000.


Main article: Reema construction

Reema houses are built from large-scale (nominally single storey height) precast reinforced concrete panels, themselves made in factories, before construction is enabled onsite. Reema houses come in two forms:

• Reema Conclad

• Reema Hollow Panel

Due to structural degradation and the use of asbestos in the wall and roof insulation,both are difficult to obtain a mortgage on today. The Reema Hollow Panel is listed universally as defective after a Government sponsored investigation and the subsequent Housing Defects Act 1984, while the Reema Conclad is often mis-recognised as a Hollow Panel.


The Tarran was designed by building firm of Tarran Industires Ltd. of Hull. A wooden frame designed bungalow,over clad with precast concrete panels. 19,014 Tarrans were erected under the Temporary Housing act, but one- and two-storey variants were built in some numbers afterwards.

Unity structures

Unity Structures were a construction company based in Rickmansworth. Using a common storey-level precast reinforced concrete panels, they produced various updated versions of their bungalow and twin-storey house variations. Using metal bracing within the cavity and metal joists connected at column joints, the PRC columns act as mullions. Copper straps tie the inner panel to outer PRC panel on earlier variant, while later the copper strap fixed to column holding just outer PRC cladding panels.

Although the design incorporates significant steelwork resulting in fair current structural condition, the concrete used in casting is decaying, and resultantly leaks chlorides. This results in internal staining through panel joints, and corrosion of the metal reinforcing and straps.

A Unity structures bungalow originally located in Amersham is preserved at the Chiltern Open Air Museum.

Wimpey no-fines

George Wimpey & Co. being a house builder, focused on both design but also speed and ease of construction. Their method used “no-fines” concrete, the composition of which used no fine aggregates. Using huge reuseable moulds, they were held in place as the concrete for the entire outer structure was poured in one operation. The ground floor was also concrete, while the first floor was made of wooden floorboards. Interior walls were a mixture of conventional brick and blockwork construction. Wimpey’s design was particularly successful, resulting in many thousands built, and still occupied today.