Structural External Wall Insulation For The Refurbishment Of Non-Traditional Low & High Rise Properties

When it comes to the refurbishment of non-traditional properties the Structural External Wall Insulation System (SEWI) is what sets Structherm apart from the rest. Whilst a standard EWI system can significantly improve the thermal properties and the aesthetics of a building, the unique, BBA accredited, Structherm system can go one major step further by adding to the structural integrity of a building too. This applies to low rise and high rise properties alike.

This is what makes Structherm the UK’s number one “go-to” company when it comes to the external refurbishment of non-traditional properties in the UK.

Why Structural External Wall Insulation?

The majority of non-traditional built properties were built with little regard to thermal performance. With the most significant heat loss being through the walls the need for an external wall insulation system is obvious.

This unique system provides an alternative solution when the substrate is defective or not in a condition to provide the anchorage for a directly bonded standard EWI system.

BRE designated defective house types? Not a problem – SEWI can even provide a solution. Even an alternative to demolition!

Structherm Structural External Wall Insulation – Our Panel

The Structherm external wall insulation system is based on a unique, lightweight prefabricated panel. This is composed of a rigid insulation core encased in a steel wire cage.

The panels do not attach to the substrate but are instead fixed to the structure of the building itself. This, in effect, forms a new substrate which is structural in a reinforcing capacity – not load-bearing.

These panels are then joined together with a rigid mesh. This provides a stable, continuous envelope around the building which adds structural integrity to the entire property.

The panels are immensely strong and rigid. Yet they are light enough to be carried by one man. They can be installed both vertically or horizontally to suit the existing building. The diagram to the right shows a typical build up of the system.

A layer of base-coat render is then applied directly to the panels. This works with the system to provide extensive spanning / racking strength.

To finish there’s a wide choice of renders in a variety of colours and textures. Alternatively we can create finishes to resemble any existing brick in various ways.

Structherm – The Non-Traditional Housing Refurbishment Experts…

Before Refurbishment

After Refurbishment

Following the First and Second World Wars and up until the late 1960s approximately 1.5 million properties were built in the UK using non-traditional methods. With a population boom, these homes needed to be built fast. Skilled labour was not readily available and traditional building materials were in short supply. Factories set up to support the war efforts also needed to diversify. That’s why new building methods were created.

Most of the resulting non-trad built properties were only designed to last for the short term. Around just 20 years in many cases! Unbelievably though, people are still living in these properties today! Properties which have very little, if any, insulation. Worse still, many are designated as DEFECTIVE by the Building Research Establishment (BRE).

Structural External Wall Insulation – It’s Not Just Low Rise Housing!

When it comes to non-trad construction we’re not just talking about low rise homes. Many high rise housing blocks were also built, particularly in the 1960s and 70s. You’ll still see them in most major UK cities today. Many of these blocks were built from non-traditional materials such as Wimpey No-fines concrete. These again have very poor thermal performance and problematic substrates.

The unique Structherm EWI system is a cost effective way of improving and extending the life of these non-traditional and defective properties. It can be used on both low and high rise. It can work even when a standard refurbishment system will not.

Structural EWI & Low Rise Non-Trad Housing Refurbishment

Whilst a standard EWI system may be all you need if low rise properties have corroded wall ties or problem substrates, a structural external wall insulation system may be appropriate.

If your property type appears on the official BRE “Designated Defective” listing then a standard EWI system CANNOT be used.


BRE Designated Defective Non-Traditional Houses List:

  • Airey
  • Ayrshire County Council
  • Blackburn Orlit
  • Boot Beaucrete
  • Boot Pier & Panel
  • Boswell
  • Cornish Unit Type I
  • Cornish Unit Type II
  • Dorran
  • Dyke
  • Gregory
  • Mac-Girling
  • Myton
  • Newland
  • Orlit Type I
  • Orlit Type II
  • Parkinson
  • Reema Hollow Panel
  • Schindler
  • Smith
  • Stent
  • Stonecrete
  • Tarran Temporary Bungalow
  • Tee Beam
  • Ulster Cottage
  • Unitroy
  • Unity Type I
  • Unity Type II
  • Waller
  • Wates
  • Wessex
  • Whitson – Fairhurst
  • Winget
  • Woolaway

There are literally hundreds of different specific types of non-traditional houses. However, they will all fall into one of four categories: those built around a metal frame, a timber frame, precast concrete or in-situ concrete. A standard EWI system fixes back to the existing substrate but the structural external wall insulation system differs significantly. The larger metal cased insulation panels are fixed together and back into the actual frame or load bearing columns of the building as per the sections below:

Metal Frame Non-Trads

The construction of metal framed properties involves the erection of the main load bearing frame using metal columns, beams, joists and roof trusses.

The framework is then clad using a variety of materials.

In this case the panels are fixed through the existing substrate and into the load bearing columns. They are then joined together with a rigid mesh prior to base-coat render and finish of choice.

Timber Frame Non-Trads

The direct platform frame construction method was often used to build timber properties. Construction consists of storey height timber frame panels, sheathed internally and externally clad.

The solution for these type of properties is for the structural panels to be fixed through the existing cladding panels and into the load-bearing timber frame itself.

The panels are then joined with a rigid mesh to create a continuous envelope. A thick-coat render base and finish of choice can then be applied.

In Situ Concrete Non-Trads

The construction of in situ concrete properties involves three basic elements; formwork, concrete and reinforcement. Steel reinforcement is added between the formwork after which the liquid concrete material was poured in.

In this case the panels are installed by using primary resin anchor fixings which connect both the inner and outer in situ concrete loadbearing panels with restraint ties used to tie the system to the floor joists. The panels are then connected together with a rigid mesh and finished to suit.

Precast Concrete (PRC) Non-Trads

Precast concrete (PRC) is produced by casting concrete in a reusable mould or “form”. This is then transported to site and lifted into place. Construction therefore consists of load bearing concrete columns with external concrete cladding panels.

As some PRC properties are designated as defective the panels are fixed using primary fixings through the the existing cladding panels into the load bearing concrete columns. Secondary fixings are also used to restrain the cladding panels. The system is then joined with a rigid mesh. A base-coat render and finish of choice is then applied.

Our experience in this sector means we are thoroughly familiar with the problems likely to be encountered in these and other types of non-traditional built properties.

Brochure, Standard Details, BBA Certs, Finishes / Colours

Structural External Wall Insulation & High Rise Refurbishment

The structural external wall insulation system can also extend the life of defective medium and high rise blocks to transform them into modern, thermally efficient and structurally sound buildings.

There are many different types of medium and high rise buildings which were built between the 1950s and the late 1970s. Most of these buildings now exhibit one or more significant defects. They are also prone to poor thermal performance and penetrating damp. The Structherm SEWI provides a unique solution for this scenario too.

Refurbishment programmes in this sector can include all of the solutions for low rise properties as well as the following options:

  • Enclosing balconies or walkways to increase internal floor area for residents. Particularly useful when balconies are infested with roosting birds. Also an extremely popular choice among residents.
  • Re-modelling of parapet / gables to increase safety and transform the skyline. An important factor for many Local Authorities as these buildings can often be seen for miles around. It can therefore improve the appearance of the whole surrounding area.

The illustration to the right shows the usual fixing method on to a typical high rise building.

Vertical and Horizontal Panel Spanning

The Structherm panels can be fixed to span both floor to floor vertically and column to column horizontally. This is assuming the building has a structurally sound frame.

In both cases a unique fixing bracket is used. This allows the transfer of shear forces into the building frame. Thus providing the necessary structural support to prevent movement and cracking.

Again, Structherm are highly experience and familiar with all issues you may be facing so why not contact us to discuss the specifics of your project.

Brochure, Standard Details, BBA Certs, Finishes / Colours

Structural EWI & System Built School Solutions

Of course it’s not all about housing – around 46% of the 1,300 schools built in England and Wales between 1945 and 1975 were system or modular built.

Whilst other types of modular / system school buildings exist, construction predominately consisted of a relatively light-weight steel girder framework with panel infill. They incorporated little in the way of insulation.

The structural system can be used to over clad failing infill panels. Alternatively, the panels can be removed and the SEWI system used to infill between the original load bearing steel columns.

As an added benefit the system can be used to reconfigure the facade. Specifically, this can reduce the amount of glazed areas in order to improve thermal performance and reduce solar glare in the classrooms. In this case the existing panels and windows are first removed. A lightweight steel frame is then constructed to house the required size of window. The SEWI panels then connect the existing frame to these new frames with primary and secondary fixings.

Contact us for further details and to discuss the specifics of your system / modular build schools project.

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