BLOG: Why is passive fire protection vital for masonry facades? 

If you look out of your window, it is almost certain you will see some kind of masonry construction. Brick, stone, clay, and concrete have been used to create buildings for centuries due to their robust characteristics and timeless aesthetic. However, as the demands on our built environment have changed, so too have the ways we approach masonry construction and the standards it must meet. In this blog, we will explore the enduring popularity of masonry facades, how typical build ups have evolved, the impact this has had on their fire performance requirements, and why Siderise is putting its passive fire protection expertise into bricks and mortar.  

What are masonry facades and why do they need cavity barriers?  

Since humans first began to build, they have used masonry materials. From the remains of simple prehistoric stone huts discovered on the Irish Arran Islands to magnificent structures such as the Ancient Egyptian Pyramids in Giza, we have long recognised their ability to stand up to the elements, creating safe and protective internal spaces. Whilst the building technology has evolved, our desire for masonry has not dampened, with these types of facades popular all over the world. We not only value the rich palette of colour and texture it offers, lending a sense of permanence and warmth, but rely on its weather and fire resistance and noise-reduction capabilities to create buildings that will last.  

Today, masonry facades come in all shapes and sizes. From the outside, they appear to be straightforward— and, in the days of single solid wall construction, they were. However, to prevent moisture penetrating through the wall, it became standard in the 20th century to build masonry facades with an inner and outer leaf, creating a cavity in between. Whilst beneficial for preventing damp and providing space for thermal insulation to be installed, these voids can cause serious issues in a fire. They can act as a chimney, allowing flames, heat, and smoke to spread into different building compartments.  

This led to the requirement for cavity barriers and fire stops— blocks of fire-resistant material which seal the cavity and prevent fire spread. Cavity barriers can either be ‘full-fill’ products which are installed between the inner leaf and masonry wall (and therefore should be tested for use against a DPC), or intumescent products which expand when exposed to high heat.  

Typical masonry wall build-up 

1. Inner leaf (main structural wall e.g.SFS, blockwork, precast concrete 
2. Weatherproofing membranes
3. Insulation and cavity barriers
4. DPCs and cavity trays
5. Masonry wall

Potential issues to consider when specifying cavity barriers 

There are also several design elements specific to masonry facades which, if not considered properly, could cause serious fire risk issues: 

Projecting/sunken brickwork design

A popular feature on masonry facades is having some rows of brick laid offset to create projected bands or shapes. This is commonly done around windows and doors to add decorative detail, or on large brickwork elevations to visually break them up and add interest. These stepped-out bricks create a slightly larger cavity in these areas which, if not properly considered, can mean that the cavity barrier cannot fully meet the masonry leaf and seal the gap, and therefore could potentially provide a route for fire spread within the cavity. 

Balconies 

Projecting balconies are a common inclusion on masonry buildings. However, there is no standard way to install cavity barriers or fire stops around the thick steel brackets that tend to take up the entire space of the floor slab. In the past, this has typically been resolved on a project-by-project basis, requiring approval from numerous different people, in one of two ways. You can either fill the web of the typically I-shaped bracket with a non-combustible material such as stone wool held in with mesh – an arrangement which is unlikely to have been tested and may still cause the bracket itself to heat up. Alternatively, it required on-site adaptation of the cavity barriers, again likely resulting in a non-tested detail and dependant on variable workmanship. Lastly you can install cavity barriers underneath the bracket. However, as you are stepping down off the compartment line, you need to be sure that the inner leaf has a suitable fire resistance to allow the cavity barrier to be installed onto it and still maintain the compartmentation.  

Putting our expertise in bricks and mortar 

With ever-tightening regulations around fire and building safety, there is a clear need for solutions that have been specifically engineered and tested for masonry facades. Drawing on our vast experience and knowledge of facades, we have developed a suite of passive fire solutions for masonry constructions which will allow architects, fire engineers and contractors to simply meet the fire safety requirements of their projects without compromise. 

This includes the Siderise External Wall (EW) system of easy-to-install cavity barriers and firestops, and enhanced External Wall Intumescent (EWI) versions which includes integral intumescent material that expands in reaction to heat, sealing external masonry walls that have an irregular cavity (such as those with protruding elements.) Each system is suitable for both masonry inner leaf and SFS constructions and have been tested in conjunction with a DPC. 

The Siderise Balcony Bracket Cavity Barrier range has also been designed to solve the common issues with balconies, as detailed above.  This is aavailable as pre-cut or bespoke kit  which effectively encloses the whole bracket, allowing the firestop to be simply abutted to it. This has been tested to EN ISO 1363-1:2012 for up to 2 hours integrity and 2 hours insulation, giving a fire performance rating of EI 120.  

Stay tuned to learn more about our new Masonry Product Set and the standards they achieve.