When it comes to specifying a roof, whether it be a new build or refurbishment project, we know all too well that there are a number of key considerations to ensuring a successful roof installation. From waterproofing system and design to aesthetics and concerns around foot traffic, here at Polyroof, we understand the various challenges associated with roofing specification and the impact they pose on the finished result. Whilst there are undoubtedly many important factors to bear in mind when specifying a roof, below we discuss three of the top considerations when undertaking your next roofing project. 


Ensuring that your roof is watertight not only extends the lifespan of the roof itself, but it also prevents damage to the internal structure of the building.  One of the primary elements of roofing specification to consider, is the choice of waterproofing membrane. There are various types of flat roofing waterproof membranes available, ranging from rollout systems such as felt and single ply, to cold liquid applied coatings, and traditional asphalt. Therefore, a key element of the process is to evaluate the different systems available and assess which is the most suitable system for the project. Considering factors such as location, roof complexities, and applications constraints (e.g. is the building occupied?), will affect which is the most appropriate waterproofing solution. 

In the case of a refurbishment project, not only do you need to choose the most suitable waterproofing membrane, but you also need to assess the condition and build-up of the existing roof to establish if it is suitable to be overlaid. There is no point overlaying a saturated or incorrectly designed roof, as any existing issues would remain and potentially create further problems.  

Polyroof’s liquid waterproofing membranes have been specified for both commercial and residential roofing projects for 40 years, encompassing the perfect combination of RapidCure technology and versatile application capabilities, complete with key accreditations from leading certification bodies, such as the BBA, UKTA, and ETA.   

Take our flagship Protec Evolve system, for example, which is an ultra-low odour, sustainable, liquid-applied membrane that provides long-lasting waterproofing for a wide range of both refurbishment and new-build projects. Protec Evolve is carbon neutral and assists towards achieving vital renewable energy targets, reducing climate change, and helping you and your clients on the journey to achieving your sustainability goals.

Thermal Performance 

Creating a thermally efficient roofing system is high up on the agenda of many building owners in today’s environment, with the ever-increasing focus on enhancing building performance and living quality for inhabitants, whilst improving the sustainability credentials of the structure. Architects can look to amplify the thermal performance of roofs by utilising energy-efficient systems that incorporate high-performance insulation. 

The thickness and type of the insulation used in a roof will inevitably affect the thermal performance of the overall system, which is important when looking to make buildings more energy efficient and help reduce the CO2 emissions. Part L of the Building Regulation Guidance provides advice on the thermal performance (U-value) criteria that needs to be met on new build and refurbishment projects alike, as a function of the building type and location.    

Polyisocyanurate (PIR) insulation is the most frequently specified insulation board on projects, due to its thermal properties.  For guidance on the indicative U Value for associated thicknesses, please refer to the Thermal Performance Guidance Sheet on the Polyroof website. 

Should you require assistance on selecting the right insulation for your roofing project, our technical team will be happy to guide you and carry out thermal calculations to ensure that your target U-values are met.  

Once you have achieved sufficient insulation within your roofing system, you may wish to consider further heightening the environmental benefits of the roof through the inclusion of green roof technology 

Falls and Drainage 

The last topic we are going to explore in our list of key considerations for roofing specification, is falls and drainage.  

BS guidelines recommend that all flat roofs should be designed with a 1:40 fall to ensure a finished fall of 1:80 is achieved on the completed roof. This helps to direct water from the roof into the gutters and outlets, which in effect reduces the risk of standing water and leaks. Where this is not possible or very difficult to achieve, following discussions with the relevant local authority building control, a waterproofing solution that is approved for zero-fall applications needs to be chosen. Falls can be created in a variety of ways, via timber firrings, screed, and tapered insulation. According to NHBC standards, where tapered insulation is used on new build projects to ensure efficient drainage, the drainage should be designed by the insulation manufacturer, with falls of no less than 1:60.   

Taking the above into consideration, architects need to consider the most appropriate option on a project-by-project basis. Therefore, why not take the stress out of your roofing project by allowing Polyroof to take the strain and help you find the right solution to meet your needs.  Where required, a tapered scheme using Polyroof Cut-to-Falls insulation can be designed to ensure adequate drainage from the roof for use in conjunction with one of our cold liquid-applied waterproofing systems. 

Polyroof is here to help 

For the last 40 years, Polyroof’s liquid waterproofing membranes have been applied to residential and commercial properties across the UK. As a spearhead in liquid roofing technology, we pride ourselves on being more than just a manufacturer, with a dedicated focus on our relationship and service levels to our valued customers.  

Our highly experienced technical team produce some of the most comprehensive and bespoke specifications in the roofing industry. Sharing multiple decades worth of knowledge and experience between them, our experts will be able to tailor a solution to make sure all of your roofing needs are met in the most efficient manner.  

Request a specification through our website today or for further information, please get in touch.

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