Designing roofing with multiple materials can be a risk. SIG Design & Technology look at what you can do to execute your design vision and achieve a robust, efficient outcome.

Benefits of using Multiple Material Roofs
When designing a roof, it isn’t always the case that a single material or system will be suitable, even when the roof form is relatively simple. Using multiple materials can help with design needs in a variety of ways:
• Aesthetic – ability to combine flat and pitched roof elements, curves and angles, or include unusual edge details to tie in with an overall design approach.
• Appearance – SIG may want to tie the appearance of each roof area to the material it is made of, using the materials which suit each roof element. For example, they may wish to use tiles, slate or metals on pitched roofs, and membranes or liquids on flat areas.
• Cost Efficiency – SIG may wish to use relatively costly materials in areas where they will be highly visible, such as a metal cladding to a façade or curved area and apply relatively lower cost materials where they won’t be seen but can perform as well or better.

Some materials lend themselves to multiple use. For example, single ply roofing membranes work well as an alternative to copper, zinc or lead on pitched roofs, and schemes with a mixture of flat and pitched roofs could therefore be single material.

The Problems of Complex Interfaces
When designing roofs with multiple materials, the challenge arises as to how the interfaces will be designed, executed and guaranteed.

A team may design a roof with several materials and interfaces. Many manufacturers will typically only have expertise in the small group of products that they are familiar with. This can become an issue if their work takes them within proximity of products that they are unfamiliar with.
If this inexperience leads to poor care and application at interfaces (where need for care and experience is greatest) then this can become a risky problem for all parties when the project is finished and there are nasty faults hiding across the roof.

A Professional Approach to Multi Material Roof Design
SIG Design and Technology offer a range of roofing materials from membranes and hot and cold applied liquids, to green and blue roofs, metal roofing and cladding and pitched roofing materials such as tiles and natural slate and stone. Their supply chain is backed up by SIG Plc, a FTSE 250 listed company.

They are also experienced designers, accreditors and inspectors of roofing design and construction with their own Professional Indemnity Insurance and their own accredited contractors.

Designing Complex Interfaces
SIG have technical experts in all sorts of materials, who routinely work together to develop solutions to multi material interfaces. They take responsibility for the interface design, allowing the architect the freedom to choose whatever she or he wants to use.

U Value Calculations and Condensation Risk Analysis
SIG can provide U Valve Calculations and Condensation Risk Analysis for all the different roofing systems from one source, giving you a uniform answer that is more reliable than going to several different manufacturers.

Wind Uplift Calculations
SIG Design and Technology conduct thorough wind uplift and rainwater calculations. This reduces the risk of a roof system failing due to insufficient fixings, inadequate gutters or overflows or upstands being too shallow.

Cut to Falls Insulation
SIG can supply a comprehensive survey of your roof if required, together with design and manufacture of a bespoke cut to falls system which avoids ponding water on roofs. With refurbishment projects, SIG’s consultants will always attend on site to carry out a survey to ensure that no inconsistencies are overlooked.

SIG have also tested the membranes they supply to ensure that adhered membranes (which are commonly used) are reliable.

Acoustics Calculations
SIG work with acousticians regularly, partly due to their experience with schools where there are specific acoustic standards to meet. The acoustician produces the acoustic requirement and their technicians then develop a specification for the roof to meet that requirement.

Accredited Installation with Inspections
The DATAC Accredited Contractor Scheme ensures that the roofing contractors that install the products SIG supply are trained, competent and are continually honing their skills. This scheme ensures that DATAC contractors’ work is inspected on site to ensure that their work is consistently of a high standard.

Full System Warranties
On a multi-product roof system, SIG can unify the responsibilities and cover it with one guarantee. They can also design to the SIG One Warranty Scheme.