What is an Upstand on a Flat Roof?

“What is an upstand on a flat roof?” is a common question answered by the PermaRoof UK expert team. The answer is not standard and depends on the type of project you’re working on. We’re here to help and in this article, we’ll look at what an upstand is, how you deal with them and what the UK building regs say.

This is a revised 2025 version of a popular post from 2022.

Why do you need an upstand on a flat roof?

Upstands on flat roofing are a part of the British building standards and are needed to ensure that walls, windows and doors are properly protected from water ingress. In short, where there are adjoining walls, skylights and any other types of abutments within the scope of your project, you’ll need to consider your upstands.

Upstands are needed because without them, water can easily track into the property. This can quickly lead to damage – first to timbers and exposed brickwork and eventually interiors and the goods stored inside.

The minimum requirements for upstands

According to current UK building regulations, upstands a minimum of 150mm above the finished roof surface are required at abutments, roof windows and parapets. This minimum height also covers rainwater splashback against exposed brickwork, which causes erosion of the courses in addition to the risk of water ingress.

UK Regs to refer to:

BS 6229:2018 specifies that at all abutments, the waterproof layer should be turned up to a level not less than 150mm above the adjacent finished roof system.

The NHBC Standards 2025 define an upstand as perimeter waterproofing that provides continuity between a flat roof or deck and adjoining vertical wall construction, with a minimum upstand height normally of 150mm, unless serving an accessible threshold where this height may be reduced to 75mm.

You can find the full NHBC standards for this here >

Skylights, doors and thresholds

Skylights must have weatherproofed upstands at a height of 150mm. Some manufacturers include rain check kerbs that can sandwich and ‘trap’ membranes to ensure a watertight seal.

Doors and thresholds have a minimum upstand requirement of 75mm at the opening. However, this is only accepted for building regs if there is either a drainage channel or an extended waterproofing membrane and flashing installed instead.

These are the current minimum guidelines in the building regulations. However, it is worth considering the project type and scope before planning your upstands. This is because 150mm is measured above the finished roof level for exposed membrane installations. Projects such as biodiverse and green roofing will need a deeper upstand to avoid water damage and the risk of ingress.

A note about green roofing

If you’re planning a green roofing project, there is a specific set of considerations for upstands. Best practice includes measuring from the finished surface, rather than the base layer. This is important to understand, with several layers – waterproofing, insulating layers, drainage and planting materials – to consider.

Calculate the approximate height of the upstands in advance and allow for the additional height measurement to be on the safe side. Take this into consideration for all types of green roof, terracing and walkways that use the roofing as a base.

How to waterproof an upstand with rubber roofing

EPDM as a complete system means that handling upstands is fast and easy when it comes to waterproofing. We provide step-by-step installation guidance, with both video tutorials and downloadable PDF guide to show you how it’s done.

Further resources:

Waterproofing a flat roof yourself

Many homowners will have the flat roof deck and timbers installed professionally, but often tackle the waterproofing themselves. When it comes to covering a flat roof, EPDM roofing membrane is widely available and among the best flat roofing materials on the market today. It has a proven high performance over an exceptional life expectancy of more than 50 years, unmatched when compared to more traditional flat roofing materials.

For DIY waterproofing, EPDM offers a range of benefits:

• Fast and easy to install
• Single piece with no joins (up to 15.4m x 30m)
• Available in a complete flat roof kit
• Requires little or no maintenance
• Suitable for a range of surfaces
• Exceptional cost vs. value over extended lifespan

PermaRoof UK stocks everything you need for trade and DIY flat roofing from high performance membranes and adhesives to insulation to skylights in our one-stop shop. We also offer industry-leading customer support and a library of free installation guides and video tutorials to help you get it right first time.

Related products to buy online:

More video content

Watch: How to apply EPDM around a skylight

Can we help?

If you’re still asking ‘what is an upstand? or you’re unsure about how to calculate them or work the standards into the project, let us help. We offer expert advice and product guidance and have an extensive resource library to guide you through the install process. Give our expert team a call on 01773 608 839 or use the live chat for a quick query.

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