Published: July, 2021

How Has Roof Space Design Changed Since The Grenfell Disaster?

The Grenfell tragedy marked a line in the sand for fire safety in construction materials, with the result that legislation is now much more stringent, and architects pay greater attention to the fire retardant properties of materials they specify.

  • How Has Roof Space Design Changed Since The Grenfell Disaster? image 1

Grenfell – A day of reckoning for UK building materials

Just before 1:00 am on Wednesday 14th June 2017 a fire caused by a malfunctioning home appliance broke out on the fourth floor of the 24-storey Grenfell Tower in North Kensington, West London. The final death toll of 72 persons made it the deadliest residential building fire in the UK since World War II.

This should never have happened. Just the previous year, a fire safety assessment reported forty serious issues, including concerns about the fire rating of materials used in the building’s construction. Four months later, less than half of these issues had been resolved.

This tragedy marked a line in the sand for fire safety in construction materials, with the result that legislation is now much more stringent, and architects pay greater attention to the fire retardant properties of materials they specify.

The rise of rood spaces and gardens

Roof gardens are an increasingly popular feature of urban development, both residential and commercial. In areas of high-density development, they provide a secluded haven of green space for residents and workers, away from the busy streets.

But roof gardens use a wide variety of materials to create decking areas, planters, seating and other hard landscaping features. How fire retardant are these materials, and should specifiers go further than what regulations stipulate?

What does the law say?

Much of the blame for the extent of the Grenfell fire lay with the highly combustible aluminium and polyethylene foam cladding. As Grenfell didn’t feature any landscaped roof spaces, the subsequent Building (Amendment) Regulations 2018  failed to address materials used for external rooftop landscaping.

But if rooftop landscaping products are exempt from the regulations, do architects and specifiers have no obligation to use materials that comply with them? Legally, no, but they are morally responsible to pay due consideration for the potential risks should a fire break out or spread to these areas, particularly as flat roofs often provide a suitable area from which to conduct helicopter evacuations.

How are materials fire rated?

The old British Standard fire rating system uses Class 0, Class 1, Class 2 and Class 3 ratings. These are based on the time interval in which the material can withstand fire.

Euroclass fire ratings were introduced to harmonise and simplify fire ratings, but these are based on the release of smoke and flaming particles rather than the time the materials resist the fire.

The Euroclass ratings are as follows:

A1: Non-combustible materials - no contribution to fire

A2: Non-combustible materials - no noticeable contribution to fire

B: Combustible materials - little or no contribution to fire

C: Combustible materials - limited contribution to fire

D: Combustible materials - contributes to fire

E: Combustible materials - major contribution to fire

FB: Combustible materials - not within classes A1-E

How do these fire ratings relate to materials used on roof spaces?

Let’s look at the materials most commonly used for hard landscaping in roof gardens, and their fire resistance.

  • Timber

While regulations prohibit the use of untreated timber for cladding on residential buildings above a height of 30 metres, there is nothing to prevent it from being used for external furniture. When untreated, timber has a Euroclass D rating, but with treatment, this can be raised to C or even B.

  • Plastic – Glass-reinforced (GRP) and Composite

Although glass-reinforced and composite plastic can be treated with fire-retardant coatings, the material itself is even more flammable than timber. It also emits large volumes of highly toxic black smoke when exposed to flame.

  • Steel – Corten, Powder-Coated and Mild Steel

Most steel used in hard landscaping has excellent fire-resistant properties with a Euroclass A1 or A2 rating. With good heat resistance, it can also isolate fire, creating a barrier that prevents it from spreading to other areas.

  • Porcelain

Wood- and stone-effect porcelain tiles are becoming increasingly popular for outdoor landscaping as they combine excellent weather resistance and low maintenance with stunning visual results.

Porcelain is also totally non-combustible and will give off no toxic fumes or smoke. Like steel, it can create an effective barrier to fire spreading.


How Grenfell paid the cost of cheap materials

The Grenfell disaster revealed the flaws of value engineering in the construction industry. While the building was originally clad in non-combustible material, during refurbishment a few years before the fire this was replaced with a combustible material that offered considerable cost savings. What had been designed as safe housing for West London residents had now become a death trap, a powder keg that only needed a faulty fridge-freezer to set it ablaze.

How can roof spaces be designed to minimise fire hazard?

Porcelain tiles such as those in Atria and Farrino and ranges create stylish, natural-toned decks and walkways. The wood-effect finishes of Farrino and Novento are a low-maintenance, fireproof alternative to real wood. They are also easy to keep clean of moss and other deposits that make wood unsightly, and dangerous when wet.

Preventa Class A fire rated modular terrace system is the popular partner for porcelain decking tiles, with height-adjustable pedestals and aluminium support rails aiding installation and offering durability.

If real wood is an important component of the design – for seating, as an example – we recommend that it is treated to improve its fire rating and frequently interspersed with materials that will limit the potential for fire to spread. Our attractive steel planters, available in natural-looking Corten or striking powder coated finishes are a good example of how fire safety can be combined with spectacular design.

How can I learn more?

Under our Continuing Professional Development (CPD) program we run regular training seminars for our clients on a range of subjects, including the popular Creating a Safe, Class A Terrace. This is essential learning for anyone involved in creating terrace areas ranging from small balconies to extensive roof gardens.

Alternatively, you can contact our friendly, knowledgeable sales team by emailing [email protected] or calling us on 01580 830688.

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