SIG Design & Technology’s eight-step guide identifies the challenges to designing and delivering flat roofs that are durable and fit-for-purpose


The roof is central to the performance of all buildings. It not only needs to keep the rain out, but also incorporate suitable insulation, acoustic attenuation, and in some cases capture carbon and generate electricity. The proliferation of different roofing systems combined with legislative changes and ever-present time and budgetary constraints mean that designing the perfect roof has never been more difficult. With this in mind SIG Design & Technology has published an eight-step guide that identifies the challenges and ensures that specifier designs meet client needs.

Step 1: Choose the right roofing products for the job

Some manufacturers will have you believe that they produce solutions for every eventuality, but this is unlikely. The roofing industry is changing and what might have been perfectly suitable in the past may have been superseded by a better, more appropriate and more cost effective alternative.

Don’t rely on a single manufacturer for all your roofing needs; they are likely to recommend their own products exclusively for any application. Instead, get independent support from an experienced supplier who will help you make an informed choice about which waterproofing solution best meets your needs.

Step 2: Get reliable design expertise from one source

Many manufacturers provide design and specification services for their products, but if they are not taking responsibility for the whole roof there is a risk of clashes between their designs and other manufacturers, making the whole process very messy. This is where details can get botched, and you may end up with one part of the roof interfering with another, PV panels puncturing the membrane or untidy detailing making the roof look unsightly and more prone to failure.

Don’t rely on several sources of design input from individual manufacturers. Make sure that the roof is designed, specified and co-ordinated from the deck up by a single PI-insured designer who takes the risk and joins the dots for you.

Step 3: Meet all the statutory requirements

If you’re relying on manufacturers to design your roof, they may not have enough technical expertise and experience to keep up to date with changes in regulations for the building types you work with. If their service stops when the project is tendered or hands over to a third party, there may be gaps in knowledge that you won’t know about until the building inspector starts poking about on site.

Don’t run the risk of having to undertake remedial works to get your roof signed off. Use an independent design service for full technical support throughout the specification process and on site.

Step 4: Have confidence in your supply chain

When you’re selecting products for your roof, the most appropriate product is of no use at all if you can’t get guaranteed delivery within your project programme.

A reliable material supply chain is essential to keeping your project profitable. Don’t run the risk of having to settle for an inferior product with shorter lead times that risks your roof guarantee. Choose a proven product supplier with local availability, shorter lead times and a high level of stock to counter unforeseen circumstances.

Step 5: Use reliable, experienced roofing contractors

Roofing contractors are skilled individuals, with a critical role in the success of your project, both aesthetically and in terms of performance. Working in partnership with the main contractor, a good roofing contractor knows the products, their limitations and how they interface with others.

An inexperienced contractor can cause a failure that may not be detected until later. Make sure you choose an accredited roofing contractor who knows how the entire roof works, and who will integrate the system with the rest of your building so it performs well and looks great too.

Step 6: Monitor the roofing installation on site

The quality of the product is only ever as good as the guys who install it on your roof. How do you know that your roofing contractor does good quality work? Typically if a roofing system fails, it is the product that is blamed at first, but poor installation is much more likely to be the cause.

Buildability issues not identified during the design process may arise on site. If the contractor cannot get technical support, non-standard, unapproved details may be used, invalidating the guarantee. Ensure your materials supplier will monitor the installation and provide quality field support on site for your contractors.

Step 7: Ensure your roof is fully guaranteed

If something goes wrong with a roof you designed, the last thing you want is to find that different manufacturers are disputing with each other about who should look into the matter and who is responsible. A Manufacturer’s Guarantee can provide confidence in the quality of a product, but this is only as good as the company that provides it. To ensure confidence in the companies you choose to work with, make sure they are part of accredited bodies, such as the Single Ply Roofing Association (SPRA) or the National Federation of Roofing Contractors (NFRC). But with more than one manufacturer on the roof, how do you avoid falling between them into a never-ending cycle of phone calls and disputes?

The solution is to have your roof designed, installed and guaranteed by one company. Interfaces between products can be covered by the design without dispute. If anything does go wrong, you’ll have a single point of contact to resolve matters swiftly.

Step 8: Implement appropriate planned maintenance

Flat roofs can create a range of architectural opportunities, solve design problems and produce functional buildings, but they have had a bad press in the past. Whilst waterproofing has come a long way since this reputation was earned, many clients still won’t entertain the idea of a flat roof.

Poor maintenance is often the cause of roof failure. If your client doesn’t want a flat roof, it may be because they aren’t confident about maintenance and will blame you if it becomes a problem later on. To deal with this problem, be sure to have your roof designed for appropriate, safe and efficient maintenance, and tie this into the whole roof service to protect yourself and give your client confidence.

How SIG Design & Technology can help

SIG Design & Technology provides the construction industry with a deck-up design, supply, installation and guarantee service that is product-neutral. We recommend the right products for the job from a broad portfolio. Added to this, our design team can provide much of the information needed to ensure the roof meets expected detail, specification and performance criteria.

SIG Design & Technology is part of SIG Roofing, a division of SIG plc, one of Europe’s leading suppliers of products to the building and construction industry. We have a national network of more than 120 outlets across the UK and a fleet of thousands of vehicles to ensure that the right product gets to the right place at the right time.


The SIG Design & Technology Accredited Contractor scheme (DATAC) provides assurance that that our roofing systems are installed correctly. We also have a team of dedicated field technicians who provide constant site monitoring and support visits on all our projects. Should any difficulties arise on site, your contractor won’t have to wait for technical support or improvise a solution.

SIG Design & Technology provides a single point of contact and responsibility. We can provide guarantees for product and workmanship because our services include all these elements. SIG Design & Technology considers maintenance from the outset of roofing projects, ensuring the right design and products are chosen in line with client needs.

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Find out more about SIG Design & Technology’s 8 Steps to the Perfect Roof.