Ross Finnie, Sales Director at SIG Design & Technology, discusses how the company’s innovative Flat Roof Specifier Checklist can help architects achieve best practice with Architecture Today’s Technical Editor John Ramshaw

In association with


Flat roof design can be challenging even for the most experienced architect due to the sheer number of constructional and programmatic variables at play. Failure to properly consider one aspect, for example, the method of removing rainwater from the roof, can impact on other related issues, such as the position or even presence of downpipes on the facade. Similarly, if the works are not properly sequenced, contractors may find themselves trying to dress waterproofing around already installed door thresholds. Basic questions relating to design-life, guarantees and sustainability can also affect the success of flat roofing projects, ultimately determining whether they are fit-for-purpose or not.

SIG Design & Technology has responded to these issues by introducing the Flat Roof Specifier Checklist. Comprising five sections, the document examines 14 key questions that specifiers should consider when designing a flat roof. SIG Design & Technology Sales Director and checklist author Ross Finnie, in conversation with Architecture Today Technical Editor John Ramshaw, discusses the intentions behind the document, what it covers, and why architects should use it.


No consideration for drainage in design; expensive remedial works required

AT: Why was the Flat Roof Specifier Checklist introduced?
The checklist was introduced for two main reasons. First, SIG wanted to dispel ideas that flat roofing can be viewed as an afterthought or separate from the main design process. There is much more to this discipline than simply achieving watertightness and a customer guarantee. Second, we wanted to change opinions – held by some – that flat roofs are problematic and prone to leaks. A properly designed and delivered flat roof not only looks great, but can also deliver high levels of performance and durability.


Balustrade installed without consideration to upstand height, relevant British Standards and codes of practice

AT: How is the checklist organised and what areas does it cover?
The document is subdivided into five parts, covering three key stages: fundamentals, design factors and buildability. It asks 14 questions within these key stages that are aimed at highlighting every aspect of flat roof design. Part 1 is titled Employers Requirements, and deals with elemental questions, such as establishing the design life of the building (and roof), guarantees, and sustainability requirements. Parts 2 and 3 deal specifically with design factors and comprise aesthetics, drainage and falls, insulation and U-values, structural considerations and upstand heights. Part 4 covers material interfaces, including compatibility and programming, as well as penetrations and questions related to cost. Part 5 examines buildability in terms of programming and sequencing, flat roof protection on site, and the cost of construction, maintenance and protection.

Poor Sequencing of works makes it difficult and costly to detail the balustrade and parapet behind

AT: What are the main aims behind the checklist and why should architects use it?
The checklist is a comprehensive resource designed to identify all the considerations that are necessary to successfully design, specify and construct flat roofs. Familiarisation with the areas highlighted in the document give architects a strong basis from which to question manufacturers over aspects such as material choices, interfaces with other products, on-site buildability, and expected design-life, to name but a few. The checklist also allows specifiers to engage with roofing contractors at the earliest opportunity. It can therefore help to highlight and resolve detailing issues, which could otherwise cause problems on site or after the building has been completed. It is critical to get the design element right as this can have a major impact on the programming and sequencing of the work.

Flat roofs can become magnets for follow-on trades. Ensure sufficient protection is specified for working platforms to avoid costly repairs.

AT: What are the key benefits for architects?
One of the most important benefits of the checklist is its ability to design-out problems before the project gets built. This saves both time and money by avoiding costly changes and revisions on site. It also safeguards the sequencing process, ensuring that money is not wasted on undoing works that have or will negatively impact the roofing installation. This in turn will protect the validity of the roof guarantee at the end of the project.

By considering the employer requirements and design factors – discussed in parts 1-3 of the checklist – architects should be better able to identify the most appropriate type or types of flat roofing for a specific project. SIG’s ability to supply a wide range of flat roofing materials and solutions means that it can provide unbiased advice and a comprehensive portfolio of products from which to choose.

The checklist is available as a download or encapsulated with a dry wipe pen

Last but not least, specifiers should remember that there is no ‘magic’ flat roof system that will achieve every aspiration of a design project. However, by using the checklist, design teams can make a highly educated choice that will satisfy all the key criteria and lead to a successful flat roof installation that is fit-for-purpose.

Contact Details
Download the checklist and read a guide to its use at