28th August 2020 by Spencer Allen 0 Comments

Summary of BS 8579 2020

BS 8579 2020 was published on 28th August 2020 and offers guidance on the design of balconies and terraces.  This British Standard considers the following design considerations for balconies and terraces:

  • Structural
  • Fire
  • Finishes
  • Wind
  • Accessibility
  • Safety
  • Thermal
  • Drainage
  • Acoustics

The standard makes the distinction between a balcony and a terrace in that a balcony is an external amenity space above ground that is not above a habitable room but is accessed from the building.  A terrace however is a roof.

  • Structural

Structural standards are set out in existing standards and Eurocodes.  But this new standard makes clear that some existing guidance can be applied to balconies by recognising that low natural frequencies can cause discomfort to the users, and proposes a minimum of 5Hz should be designed for.  In addition, the standard clarifies that for reasons of comfort the finished surfaces should not deflect more than 5mm under a 2KN concentrated load

  • Fire

The standard clarifies that dividers between enclosed balconies shall be fire rated to at least the level of the corresponding internal compartment rating.   This requirement was commonly applied via interpretation of the guidance in BS9991, but now it is explicitly clear.

It is made clear that the floor of enclosed balconies shall have the same fire compartmentation performance as the compartment floors inside the building and where the balcony adjoins the building shall be stopped via cavity barrier or fire stopping. 

Additional fire resistance is needed for balconies or terraces that form escape routes. 

All parts of balconies on buildings which are occupied above 11 metres shall be of limited combustibility, i.e A1 or A2-S1-d0 as classified by BS EN 13501-1 in accordance with Regulation 7.  Importantly, the standard introduces, that this shall also apply to stacked balconies on buildings of any height. 

An imperforate drainage tray beneath the finishes serves a further function to prevent flaming droplets falling to the balconies below. 

The standard introduces the criteria that structural components shall provide fire insulation performance to the value of the cavity barriers or fire stopping in the adjoining structure.

The standard states that where this slab edge is thick enough, continuity of the fire stopping shall be maintained, but recognises that the slab edge is not usually thick enough to allow this; in which case the bracket shall incorporate fire stopping performance equivalent to the level achieved by the fire stopping or cavity barrier.  The standard highlights that any such design shall only be suitable where test evidence exists to prove the performance of the bracket in continuation of the fire performance across the whole of the area where the balcony adjoins the building. 

Particular consideration is needed around drainage penetrations in order to maintain fire compartmentation. 

  • Finishes

Finishes even to an enclosed balcony, shall be exterior-grade materials.  The standard highlights the need for the longevity of components to be considered.  The standard states that a safe method of replacing parts of the balcony shall be included in the design. 

  • Wind

Balconies and terraces can be subject to high winds, especially due to proximity effects from the building, like those known as “funnelling”.  During the design of balconies and terraces, consideration should be given to extreme wind events, and these should be mitigated to ensure that items do not become dislodged, and consideration should be given to the balcony doors.  The standard states that where possible, balcony doors should be designed to open inwards or side where this is practicable, or in events where outward opening is the only option, restrictors should be fitted so prevent the door from being blown by the wind.  Mitigation measures against wind can include:

  • Specially designs balustrades
  • Subdivision of the balconies
  • Raised side balustrades
  • Accessibility

The guidance on level thresholds from BS8300 and Approved Document M is brought to light in the context of balconies with the 15mm threshold rule.  The standard highlights that balconies and terraces to areas other than dwellings must accommodate the wheelchair tuning circle provision from Approved Document M.  Gaps between the surface finish such as decking boards are limited to 6-8mm.

  • Safety

The standard highlights the consideration that has often been the complaint of residents of high-rise balconies, that the design should make them feel safe.   As well as being intrinsically designed to address the required structural criteria, slip resistance is an important consideration.  Slip resistance is determined by BS 7976.  Depending on the environment, the most appropriate slider should be chosen to represent shod or unshod feet.  In the relevant case, a PTV value in excess of 36 should be achieved in both wet and dry conditions in order to minimise slip potential to an acceptable level.  The standard highlights that users should be advised of the need to maintain the finishes. 

The design of the balustrades should minimise the opportunity for objects to fall from balconies. 

The standard states that an imperforate layer should be included within the balcony, in order to prevent liquids or solids falling through the gaps in the balcony and presenting a risk to people below, or that the designer should consider the risks in the designs where this is not included. 

Where possible, replacement of components should be designed to be carried out from the balcony itself.  A methodology for replacement should be detailed within the design.  The standard identifies examples of components which may need to be replaced at the end of their service life, the example given is cavity barriers.

  • Thermal

Balconies and terraces act as a source of heat loss and a condensation risk, as their components are often metallic and transmit heat well, which can have an undesired cooling effect to the structure. The standard highlights the importance of correct thermal separation, to avoid condensation, and to meet the thermal criteria of the building. 

  • Drainage

However, designs which collect the water in the aforementioned imperforate tray and channel this to the surface furthers from the building where it can run off the building are proposed, provided the balcony is not deeper than 2.5m

Also, positively drained solutions are proposed, however these are subject to the constraints of firestopping around the drainage pipes as highlighted above. 

As highlighted above, gaps should be limited to 6-8mm between boards, and a 10 – 12mm gap should be allowed around the outside of the finishes in order to enable water to readily drain away.

The standard makes it particularly clear that no opportunity for even small amounts of water to be trapped on the finishes. 

In line with NHBC requirements the drainage layer is noted to be at least 75mm below the threshold, and 150mm below the top of the membrane to adjacent walls. 

Guidance is given on how to calculate the amount of expected rainfall on a balcony and how to design outlet pipework.

  • Acoustics

Balconies can offer some screening against unwanted external sound.  Material selection plays an important part in the acoustic performance of the balcony.  Solid materials should be used where possible for this purpose.  Acoustic absorption of materials is classified by BS EN ISO 11654, with Class A being the best performing.

14th July 2020 by Spencer Allen 0 Comments

Balcony Decking Selection Guide for Architects and Specifiers

Following a number of notable balcony fires and the Hackitt report, Approved Document B was changed in November 2018 (and also as amended in December 2019 and April 2019) in that balconies must now be made from materials of limited combustibility.   The MHCLG followed this up with advice that culminated in January 2020, advising building owners that the removal and replacement of any combustible material used in balcony construction is the clearest way to prevent external fire spread from balconies.  This creates not only a challenge for Architects and specifiers to create designs to meet these new technical requirements, but also to achieve the appearance and feel that is expected in a space that is often an extension of the home.

There are key decisions that need to be made in the selection of the appropriate finish, these are set out in the following section.

Free Draining or Drained

Free-draining is used to describe the design where rain falling on the balcony can fall between the decking boards.  Free draining balconies need to have a gap between the decking for the water to drain through.  Free draining balconies don’t usually have soffits, so this can reduce the cost, but it is important to consider what the decking will look like from underneath as this will be readily visible.  Neat bearers and boards that are attractive from the underside also is important.  Its also important there aren’t too many small crevices that birds or insects can nest in.

Drained balconies can be either surface drained or via a lower drainage layer beneath the decking, this can be either via a soffit that catches the water or, an impermeable structure to the balcony itself (such as precast concrete).  With drained balconies, it is important to ensure that the waterproofing extends up the facade at least 150mm from the drainage layer (at least 75mm at doorways).  The selection of the waterproofing must be carefully checked against the requirements of Part B of the building regulations.

Material Performance

Whilst achieving the right appearance is important, it is also important to choose a balcony finish that fulfils the performance requirements:

  • FIRE: Must be A1 or A2-s1 d0 as classified by EN 13501. Note that this applies to EVERY component of the system (i.e including any pedestals, or fixing clips).
  • STRENGTH: Must have the required strength for the application. The strength is tested via the application of a distributed load, but also a point load at the support centres that you wish to use.  The use class of the balcony or terrace will determine the distributed load and point loads that need to be achieved.
  • SLIP POTENTIAL: Slip potential must be considered and be suitable for the application. PTV vales are used to assess this.  Refer to the HSE website for more guidance on this.
  • THERMAL EXPANSION: The material that the decking is made from will determine the thermal expansion. Aluminium has a coefficient of thermal expansion of 24×10-6m/mK.  This means that for example a 3metre section of aluminium will get around 3mm longer at 40°C than it is at 0°  If this is not accounted for in the fixing design, the fixings can break.  Calcium silicate composites can have a coefficient of thermal expansion of 13×10-6m/m.  So, expansion gaps can be smaller.
  • SCRATCH RESISTANCE: It is common for balconies and terraces to have furniture placed on them. Ensure that scratches don’t become a problem during construction or during the lifecycle of the structure.
  • WEATHERING PERFORMANCE: Make sure that any materials specified have had the material and coating tested for longevity. This can be carried out by accelerated weathering testing.  Where the material is subjected to a cycle of UV, freezing and thawing actions to simulate an appropriate number of years.
  • LIGHTNING PROTECTION: Any conductive elements must be considered as part of the risk assessment conducted for lightning protection in accordance with BS EN 62305.
  • HEAT BUILD-UP: Especially if the balcony or terrace will be accessed barefoot, it must be considered that the surface should not build-up too much heat such that it could cause burning. Metal surfaces generally heat up more in the sun than other materials.
  • NOISE: The surface must not generate excessive noise from wind, rain and hail.
PTV

Conclusion

There are a range of materials available, by considering the key performance factors, it the best material for the application can be selected, and will perform for the long term.

Replacement of old wooden deck with composite material
14th July 2020 by Spencer Allen 0 Comments

The Combustibility of Balcony Decking

It’s not just cladding

Due to recent focus on cladding, we thought it timely to write to you to discuss that the issue is not just about cladding, balconies are as much of a concern yet don’t seem to get as much coverage, and the problem can be more difficult to solve because of the limited design solutions available.

Balconies are an essential part of high-rise living, especially during our current period of lock-down. They provide an essential space for fresh air, reflection, a quiet espresso in the cool morning air, and often, smoking!  Architecturally, balconies frequently define the drama of the façade of a residential building and invite the outside in.

The industry has responded to this challenge with a range of aluminium decking systems and until now, the choice has been between one type of aluminium or another.

“We had experience of developing composites for non-combustible cladding, and when we saw the requirement for decking, we set about trialling the same technology for decking boards”.

“We had a number changes to make to the production ingredients, adding higher strength fibre and eliminating water-based colourants, each time testing the end result. We had to consider properties that we hadn’t had to before, such as slip resistance”.

“We are really pleased with the results, we have achieved a non-combustible decking product that would be at home at home.”

14th July 2020 by Spencer Allen 0 Comments

Message From Our Commercial Director

Following a number of notable fires and the Hackitt report, Approved Document B was changed in November 2018 (and also as amended in December 2019 and April 2019) in a number of respects including that balconies must now be made from materials “of limited combustibility”.

The MHCLG followed this up with advice that culminated in January 2020, advising building owners that “the removal and replacement of any combustible material used in balcony construction is the clearest way to prevent external fire spread from balconies”.

This creates not only a challenge for Architects and specifiers to create designs to meet these new technical requirements, but also to achieve the appearance and feel that is expected in a space that is often an extension of the home.

You are of course aware of a range of aluminium decking systems.

However, a team of Engineers at Blazeboard have applied their combined expertise in building engineering and composite materials to develop a product that achieves the requirements of Approved Document B as well as the MHCLG guidance, whilst having the appearance and tactile properties that are more appropriate for residential applications.

The appearance of Blazeboard is based on the colour of driftwood, because it doesn’t create watermarks like wood, and emulates the silvery sheen that natural hardwood takes on after a couple of years in sunshine.

Blazeboard also has the tactile feel of hardwood that can be comfortably walked on whilst barefoot

Our Engineers can work with you to create a balcony design that is rigid and robust, yet won’t suffer from the thermal expansion issues of aluminium systems. If you would like us to look at a project with you, please let us know, or even just request a copy of our Balcony Finish Selection Guide.

Sincerely
Spencer Allen
Commercial Director
Blazeboard Ltd

Large New Deck in House Backyard
14th July 2020 by Spencer Allen 0 Comments

Advantages of Using Blazeboard for Balcony Decking

The team at Blazeboard is very experienced. They have worked with wood to create attractive designs for flooring and balcony decking. We applied our engineering experience of re-inventing construction materials to create Blazeboard which provides the visual and feel appeal of wood, whilst achieving the non-combustibility requirements demanded by the building regulations.

They are suitable for use in:

  • Balconies at any height
  • Roof terraces
  • Walkways and bridges
  • Fire Escape routes
  • Building cladding

The advantages are many such as the following:

  • “Cut, fix and set out the 145mm wide boards just like wood”
  • “Through-coloured in a range of colours”
  • “fire classification of A2-s1, d0 or A1 when classified in accordance with BS EN 13501:2007+A1:2009.”
  • Quality Materials
  • 15 Year Warranty
  • Unique Technology
  • Highly Experienced Team

15th June 2020 by Spencer Allen 0 Comments

Introduction To Blazeboard: A Premium Balcony Decking Solution

Blazeboard is a non-combustible decking board for balcony decking.

It provides a high-quality, elegant and robust look and feel for both residential and commercial applications. It fully satisfies the requirements set by the Approved Document B 2018 for high-rise residential developments. It is finished in wood grain or grooved anti-slip profiles, making it ideal for balcony decking, terraces and walkways.

Blazeboard was able to achieve this by improving on existing re-enforced cement composite technology. Through rigorous testing, adapting and retesting to optimise the material for high-rise residential balconies.

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