Roof and Wall System

Twin-Therm® Roof Assembly
Twin-Therm® Roof Assembly

Twin-Therm® is a site assembled built-up roof and wall cladding system that has proven itself to offer a consistently reliable building envelope since 1995.

When installed the system is both non-fragile and fully walkable for the duration of its guaranteed life. Twin-Therm® delivers U-values as low as 0.14W/m²K, by increasing the depth of construction without the need for additional components.  Air permeability tests on buildings featuring the system have measured as low as 0.99m³/hr/m².  Twin-Therm® comes with a full system guarantee of up to 25 years.

The entire system and not only its constituent parts, has been independently verified and carries Agrément certification and the Loss Prevention Certification Board (LPCB) accreditation.

No Leaks

The Twin-Therm® roof system does not allow roof fasteners to penetrate from the outside to the inside of the building, eliminating a major source of leaks. Metal built-up roof systems, such as Twin-Therm®, ensure that any risk from mis-drilled or under driven external sheet fasteners do not impact on the weather tightness of the system. If any of the external fasteners were to fail allowing water ingress, water would simply pass through the insulation and onto the liner panel where it would either dissipate or drain out of the cavity into the external gutter.

It is common practice to put a flat flashing below the liner panel at the apex and rely on fillers to provide the protection, but at CA Group, whether we are installing a pitched or curved design, we do not believe in compromising the exceptional air and water barrier created by the liner panel.  When delivering a pitched roof design, all systems from CA Building Products will utilise a cranked ridge liner panel, installed over the adjacent sheets, to ensure continuity.  To deliver the same effect on a curved roof design, the metal and GRP liner panels are taken across the apex.

Twin-Therm® Ridge Detail
Twin-Therm® Ridge Detail

Pitched Roof

Pitched Roof

The main function of profiled roofing and cladding is to create a weather tight envelope, keep the heat in and brace the frame.

In order to make a building weathertight, the actual pitch at the end laps must be considered.  Since the use of steel profiled sheeting was introduced as a waterproof layer, the industry has limited end laps to a minimum of 4° after deflection.  However, in recent years profile manufacturers have developed roof systems which take into account all components used in the tested assembly and, in some cases, it is possible to design a roof with a pitch lower than this recommendation.

All roof systems from CA Building Products have been designed and tested to be installed at roof pitches lower than 4°.  For further information on the design parameters of the systems offered please refer to Technical Information available in the technical section of the website.

Curved Roofs

Curved Roof

A common misconception about curved roofs is that they cost more than a traditional pitched design. Whilst this may be true of very large radius roofs, where the only option is to use a standing seam or secret fix system complete with barrel vault roof lights, Twin-Therm® Quantum or Twin-Therm® Griffon designs are delivered at no extra cost.

Most steelwork roofs, even when curved, will use a portal design with faceted rafters, therefore the only cost difference over a standard pitch design is in the extra height required for some of the cleats to achieve the curve; this has minimal impact on project cost. The reduction in perimeter detailing through the removal of the ridge components outweighs any additional costs associated with the hoisting and distribution of the longer length sheets.

The Twin-Therm® external and liner profiles have exceptional self curving capabilities with a convex design radius as low as 45 metres and crimp curving also available for tighter requirements.

See the Twin-Therm® Quantum and Twin-Therm® Griffon sections for more information on enhancements to the Twin-Therm® design to facilitate lower apex heights.

Non-Fragility & Walkablility

Fully walkable liner
Fully walkable liner

The CA LT 17 1000S 0.4mm thick steel liner panel is classed as non-fragile but it is not walkable. In most applications this is the ideal solution as the thickness provides extreme flexibility to pick up where the secondary steel has settled. This can be enhanced with a CA 32 1000RL 0.7 mm thick steel liner panel which is both non-fragile and walkable. These two solutions provide superior air permeability results in comparison with the (ever increasing) thicker sandwich panel options, which due to their rigidity are unable to pick up on the settled steel.

The complete system assembly has been extensively tested for non-fragility in accordance with ACR[M]001:2011 ‘Test for Non-Fragility of Profiled Sheeted and Large Element Roofing Assemblies (Fourth Edition)’ achieving a Class B certification.  The relevant Technical Information Paper can be downloaded from the technical section of the website.

Health and Safety

Fully walkable systems
Fully walkable systems

With many roofing products and components being well in excess of 20kg/m² the architect and building owner have a responsibility in terms of managing the risks of manual handling. The Twin-Therm® system is simple to install, with no heavy individual components, eliminating these risks, both on the ground and at height.

All of the roof system assemblies delivered by CA Building Products have been tested for non-fragility in accordance with ACR[M]001:2011 ‘Test for Non-Fragility of Profiled Sheeted and Large Element Roofing Assemblies (Fourth Edition)’ achieving Class B certification.

Today, many Horizontal Life Line (HLL) system manufacturers and installers are suggesting that their systems are ‘approved’ or ‘fit for purpose’ in conjunction with CA Building Products’ roof cladding systems, this can only be claimed if the systems, in their entirety, have been subject to the relevant tests. For further information refer to ‘ACR[CP]007: – The use of Horizontal Safety Lines in Roofwork’.

CA Building Products have worked closely with a select few HLL manufacturers to ensure that the safety systems they produce meet the required standards of CA Group’s guarantee.  Contact CA Group Technical Department for a current up to date list of recommended partners.

Thermal Performance

Royal Mail Northampton

The Matrix Spacer System which is used in all CA Building Products roof and wall cladding systems allows for deeper insulation and flexibility in design, with achievable U-values a low as 0.14W/m²K without the need for additional components. All systems available are site assembled and as such allow for specialist components to be added, i.e. acoustic insulation.

All our systems have been comprehensively tested to prove their structural performance at CERAM.

The spacing of the brackets used on the Matrix Spacer System allows the insulation to be installed below the bar without the need for cutting and tucking. U-values and system build-up information is available from the technical section of the website.

Based on current building regulations to meet the minimum backstop U-values, the build-up depths for the Twin-Therm® systems areas follows:

  • Twin-Therm® roof CA LT17 1000S – 0.23W/m²K – 180mm cavity + 32mm external profile = 212mm
  • Twin-Therm® roof CA 32 1000RL – 0.25W/m²K – 180mm cavity + 32mm external profile = 212mm
  • Twin-Therm® Wall CA LT17 1000S – 0.35W/m²K – 120mm cavity + 32mm external profile = 152mm

Good detailing or robust detailing, as it is known, can deliver significant reductions in lost heat and therefore cost.

Previous tests have proven that one of the primary causes of heat loss from buildings is due to poor detailing. Poor detailing allows heat to travel from the inside of a building to the outside often via poorly designed flashings, gutters, junctions and interfaces. To put this into context, some details such as drip flashings, which run around the entire perimeter of the building at the base of the walls can, if they are not designed and installed with care, act as huge heat conductors, drawing heat from the warm interior and allowing it to be wasted by passing to the exterior of the building envelope.

By insisting on robust detailing the ‘heat sink’ effect of detailing which allows a direct connection between the inside (the warm side) and the outside (the cold side) of a building can be minimised and in some cases, completely eradicated.

A thermal performance increase of 7.5% can be achieved at no additional cost just by introducing robust detailing to every junction throughout the building envelope. Attention to detailing like this makes the difference between a good Energy Performance Certificate rating and a poor one.

CA Group Technical Department have compiled an extensive library of ‘robust’ details all of which are offered as standard and delivered at no extra cost, these are available from the technical download section.

Material Choices

Twin-Therm® Profile Options
Twin-Therm® Profile Options

Twin-Therm® offers developers, specifiers and architects a cost effective roof and wall solution with a high degree of flexibility enabling the building designer to choose a profile that caters for their architectural need. Twin-Therm® is available in a number of trapezoidal, shadowline, arc and sinusoidal wall profiles, helping to take on any number of complex aesthetical design challenges. The Twin-Therm® system is available in the full range of pre-finished steel products including Colorcoat HPS200 Ultra® and Colorcoat Prisma®.

Click here to see the full range of profile options available from CA Building Products

Positive Programme Impact

Prologis Kettering under construction

Programme is critical. Reducing the site programme saves money. The ability to supply profiled sheets which are packed sequentially enables the roofing contractor to save a considerable amount of time, reducing damage risk and improving efficiency. The ability to line the building out using lightweight materials eliminates manual handling risks as well as creating a weather and air-tight platform that allows the main contractor to begin internal work such as laying floor slab at the earliest opportunity. No cranes are required to lift panels into final position and in addition to the flexibility of the individual profiles this ensures air tightness levels are significantly better than anything else available. The challenges faced by building designers and the construction teams to meet the aspirations of the latest changes in Building Regulations Part L are simplified by extremely low air leakage performance.

Air Permeability

Waitrose - Chorley with an air permeability rating of 0.99m³/hr/m² @ 50Pa
Waitrose – Chorley with an air permeability rating of 0.99m³/hr/m² @ 50Pa

Air permeability, has been widely identified as the primary source of heat loss from a building’s interior. Reducing air permeability is a major factor in demonstrating compliance with Building Regulations and where heating is required can make the difference between a pass and a fail. A good air permeability result will aid in delivering EPC ratings in Band A, providing high asset values and strong yields.

Heat loss not only contributes to higher building running costs but also increases unnecessary CO2 emissions, due to the additional heating load required to replace it. The critical element to achieve good air tightness is the flexibility of the cladding system in accommodating variances in steelwork tolerances. Inadequately designed or poorly installed steelwork can deflect under its own weight or under the weight of the gutters, directly impacting the cladding system to which it is connected.

Built-up metal cladding systems accommodate this degree of flexibility, the metal liners used follow the variations in steelwork making it easier for the cladding contractor to effect a seal. The fixings and sealing methods adopted on the Twin-Therm® system achieve results as low as 0.99m³/hr/m² @ 50Pa. Download the Waitrose Chorley Air Test certificate.


Mega Phone

Roof and wall cladding systems from CA Building Products have been tested at a number of independent test houses throughout the UK, such as Sound Research Laboratories (SRL) in Suffolk. The tests have included determination of weighted sound reduction and rain noise levels for standard systems as well as absorption coefficients when incorporating perforated lining panels.

In addition, CA Group Technical Department can produce project specific predictions for standard multilayer constructions and where necessary, the more complicated build-ups can be outsourced to recognised independent specialists familiar with these types of cladding system.

Based on standard U-values the Twin-Therm® system achieves the following weighted sound reduction figures without any enhancements;

  • Twin-Therm® roof 0.4mm liner – 42dB
  • Twin-Therm® roof 0.7mm liner – 45dB
  • Twin-Therm® Wall 0.4mm liner – 39dB

For further information on the system capabilities download the relevant Technical Information Paper on Acoustics.


Drops - Condensation

The installed liner panel provides an extremely efficient air barrier, with the lowest known air permeability test of 0.99m³/hr/m² @ 50Pa achieved; this greatly reduces the transfer of heat from inside the building to outside. To further support the durability of the system the Therma-quilt insulation has every fibre coated with silicone to ensure that any moisture in the cavity is not absorbed and is shed to the liner where it is either dissipated or directed away from the building via the gutter.

With over 1 million m² of built-up roof and wall systems from CA Building Products installed every year there are very few reported issues of the cladding itself causing problems. Coating the fibres with silicone negates the need for a separate breather paper, except in humidity Class 5 applications i.e. swimming pools. For further information on this subject download the relevant Technical Information Paper.


Thurrock distribution centre fire
Thurrock distribution centre fire

Many cladding systems sold in the UK claim that they can protect a building from fire but the majority of buildings are far from safe. Twin-Therm®, on the other hand, is made from logically non-combustible materials.

Twin-Therm® has been tested by BRE Loss Prevention Certification Board to LPS 1181 Part 1 achieving ‘EXT-B’ classification as standard. The insulation used in the system is also tested to BS 476 and is classified as non-combustible in its own right, delivering confidence to all parties and in particular to the tenant that in the event of a fire the insulation in their roof and walls will not contribute to the fire load. Many clients also insist that the internal gutters are insulated with Manmade Mineral Fibre (MMMF) to eliminate this critical risk.

CA Building Products also offers dedicated FireWall solutions, the Twin-Therm® FW15 and FW30, which provide 240 minutes of structural integrity & 15 minutes insulation (LPS1181 ‘EXT-A15’) and 30 minutes insulation (LPS1181 ‘EXT-A30’) respectively.


System Guarantees

We know that when choosing a cladding system, confidence in its lifespan is a major factor. Unlike most suppliers of twin skin cladding, CA Building Products offers a full system guarantee for up to 25 years on Twin-Therm®.

The guarantee covers the manufacture and design of the entire system including all of the components supplied by CA Building Products such as: screws, sealants, insulation, spacers, etc. This delivery is offered alongside the Confidex® Guarantee when specified using Colorcoat HPS200 Ultra® and / or Colorcoat Prisma® offering peace of mind for up to 40 years. For further information on this subject download the relevant Technical Information Paper.

If we are to offer meaningful system guarantees of up to 25 years the systems have to be fit for purpose. Twin-Therm® is supported by a number of reputable, recognised third party organisations such as the BRE (LPCB) and Exova Warringtonfire. Many people have Agrément certification for individual components but Twin-Therm® is supported by a Agrément certification for the entire system.

Fibre Insulation

Fibre Insulation
Foam Free – CFC, HCFC & VOC Free

A UNEP report entitled ‘HFCs: A Critical Link in Protecting Climate and the Ozone Layer’*, highlights the potential dangers associated with use of hydrofluorocarbons (HFC’s) as replacements in insulation using chlorofluorocarbons (CFC’s) and hydrochlorofluorocarbons (HCFC’s).

The Therma-quilt insulation supplied as part of the Twin-Therm® roof and wall cladding system is a non-hygroscopic glasswool whose individual fibres are coated with silicone to prevent moisture retention and maintain the thermal efficiency of the system. Therma-quilt is CE Marked, complies with the Lambda 90/90 whilst achieving zero Ozone Depleting Potential (ODP) and zero Global Warming Potential (GWP).

Therma-quilt is produced from fine, non-combustible glass mineral wool (as defined in BS 3533: 1981), bonded with a thermo-setting resin. Therma-quilt is made from natural materials and recycled glass and is free from CFC, HCFC Volatile Organic Compounds (VOC’s). Therma-quilt it does not rot, degrade or sustain vermin and will not encourage the growth of mould, bacteria or fungi.

Therma-quilt insulation has also been assessed by the LPCB and classified “non-combustible” in its own right.

Cite ‘UNEP 2011 HFCs: A Critical Link in Protecting Climate and the Ozone Layer. United Nations Environment Programme (UNEP), 36pp’

Responsible Sourcing

CA Group, take responsibility for the environment seriously without gimmicks or tokenism.

All materials within the Twin-Therm® system are fully recyclable to enable a low ‘cradle to cradle’ carbon footprint, with a net commercial benefit on scrap values at end of life. The Therma-quilt non-combustible insulation is supplied with zero Global Warming Potential and zero Ozone Depletion Potential that never utilises CFC’s, HCFC’s or VOC’s in the production process. The system has minimal environmental impact when being transported to site, due the amount of profiled material that can be transported in each load, as well as reducing fuel costs.


Transportation has to consider not only delivery requirements at the beginning of a project but also at disposal.

It is at this stage as legislation has toughened that building running costs are recognised as punitive. The majority of systems supplied by CA Group are either reused i.e. farm buildings etc or sent back to the steel mill for recycling.  The residue (insulation and fixings) can either be reused as cavity wall insulation or sent to landfill at minimal cost.

CA Group understands the implications of the entire process from ‘cradle to cradle’ through production of Environmental Product Declarations.


Steelwork Aerial

Most roofing and cladding contractors have encountered steelwork tolerance issues when installing both pitched and curved roofs. Care must be taken to minimise deflection on purlins. In some instances, particularly with facetted rafters, purlin cleats can be as deep 500mm. Even a small misalignment can have a significant effect on the position of the top flange of the purlin to which the roof cladding is fixed. To ensure this does not occur, the steelwork contractor must be aware of the system requirements.  To that end we always recommend collaboration between the client, architect, main contractor, steelwork contractor and system supplier to ensure the project is delivered to the highest standard.

All built-up metal roofing assemblies require a positive fall from apex to gutter, whether on a pitched or curved roof, the simplest way to achieve this is for the steelwork contractor to ensure a purlin is located close to the apex, as with all traditional portal frame designs.


Site safety is paramount.  Any worker accessing the roof during maintenance inspections and working procedures must be subject to the proper training.  We also recommend that adequate and appropriate safe access should be provided at all times.  Full risk assessments and method statements can be carried out for each individual project.

Safety precautions must be taken for the whole duration of inspections and works. HSG 33 ‘Health & Safety in Roofwork’, available from the HSE, provides detailed advice in this subject.

For further information on this matter refer to the Technical Information Paper on ‘Walkable, Non-Walkable & Walking on Roof Cladding’.


25,000m2 of Twin-Therm® Roof on 6 trailers
25,000m2 of Twin-Therm® Roof on 6 trailers

Over recent years CA Building Products has focused on the reduction of CO2 emissions resulting from transportation of materials to site. With up to 35 vehicles per day delivering throughout the country, the associated CO2 emissions were high, as were the transport costs.  Following a total review, together with our customers, a number of new procedures have been implemented.

For example, prior to the review, om a typical 10,000m2 retail store , a complete order would be shipped on up to 17 vehicles.  Today this has been reduced to 11 vehicles, which is a 35% reduction in CO2.  By reducing our CO2 emissions we were also able to cut our costs, a saving which was passed on to our customers.

CA Building Products endorses the concept of ‘cradle to cradle’ construction, which requires that building materials used in the conception of a building also take into account its end-of-life impact by being ecologically compatible, economically acceptable and socially responsible in equal measure.


Daylight - Rooflights B&Q Preston

The controlled addition of natural light, either direct or diffuse, into a building will reduce the use of electric lighting and, ultimately, the building’s running costs.

The inclusion of natural daylighting also plays a significant role in compliance with Building Regulations ADL2.  However, in terms of meeting compliance, it is not just the thermal performance of the roof lights that must be considered, further information in regards to the roof light area, light transmission and solar gain is required to ensure that the inclusion of natural daylighting does not generate excessive heat inside the building.

With U-values of 1.3W/m²K available as standard and the ability to offer alternatives down to 0.8W/m²K the Therma-light system from CA Building Products can be easily integrated into any of its built-up roof cladding systems.

When specifying roof lights it is important to ensure that the entire roof covering still retains its performance criteria, especially in relation to non-fragility, system life and required guarantee periods. All CA Building Products roof cladding systems are designed for the inclusion of the Therma-light GRP rooflight system.

Twin-Therm® Downloads & Information


Twin-Therm® FireWall

Twin-Therm® Firewall Assembly

CA Building Products has always developed roof and wall cladding systems to comply with the onerous demands of building regulations in terms of thermal performance, air leakage and acoustics, etc. However, we feel the most critical demand under building regulations is Approved Document B: Fire safety. We have conducted extensive testing and development in order to achieve the best possible fire performance for metal clad buildings.  We design all our systems with fire performance as one of Continue Reading »

Twin-Therm® Chronus

Waitrose - Chorley with an air permeability rating of 0.99m³/hr/m² @ 50Pa

Steel framed buildings are typically operated with a controlled internal temperature of between 1-2ºC and 5-8ºC making them a common choice when developing a chill store. To achieve the controlled environment required of a chill store, low levels of air tightness are of paramount importance.  Heat gains must also be limited, in order to ensure the cold does not escape, putting undue pressure on the chiller units. The flexibility of the liner panel assembly in all built-up Continue Reading »

Twin-Therm® Griffon

Twin-Therm® Griffon

Twin-Therm® Griffon uses the principles of the Twin-Therm® Quantum self-curved design across the apex of the roof to achieve the required external sheet end lap either side of apex. However once at the required end lap pitch, it flows into a straight pitch design with every end lap thereafter being set at the same pitch. The system specification drawing ‘TT-SDR-M05’, available from the technical download section, provides further information. Depending on span this design can facilitate a Continue Reading »

Twin-Therm® Quantum

Twin-Therm® Quantum

Twin-Therm® Quantum is a self-curved roof design running from gutter to gutter incorporating all of the features and benefits that the standard Twin-Therm® system has delivered successfully for almost 20 years. The system specification drawing ‘TT-SDR-M04’, available from the technical download section indicates the system build-up and design parameters required to achieve the minimum external sheet end lap. In addition to all the benefits associated with the Twin-Therm® system, Twin-Therm® Quantum also provides lower apex heights over a Continue Reading »

Thursday, July 26th, 2012