When Do the NHBC Standards Apply to Balconies?

The National House Building Council (NHBC) Standards play a pivotal role in ensuring that new homeowners receive a property that not only meets but often exceeds their expectations for quality and safety. These standards are intricately designed with a focus on reducing risk and enhancing the end-user experience in their new home.

Unlike a British Standard or a Euro Standard, which may form part of the mandatory path to demonstrating compliance with building regulations, NHBC Standards apply specifically when NHBC is selected to provide the warranty for the building. It’s important to note that these standards are not universally mandatory; they are particular to NHBC’s warranty service.

NHBC is recognised as one of the most reputable leaders in the field, setting a benchmark for excellence in warranty protection. Although other providers like Premier Guarantee are also common, especially for high-rise buildings, they typically do not operate a separate set of standards. This doesn’t diminish the influence of NHBC standards; on the contrary, in the absence of balcony specific guidance prior to the BS8579:2020, they were really the only independent source of guidance so often served as a reference point for balconies.

One area where the NHBC Standards have been particularly focused, for various products but especially balconies, is in preventing water ingress into buildings. This issue has been a significant aspect of warranty claims over the years. With the lack of specific guidance in British Standard BS8579:2020 and Part H (or Document H in Ireland) regarding balcony-related drainage, the NHBC standards have often been adopted as a reference point for best practice, regardless of the warranty provider.

Ultimately, NHBC Standards are applied to projects that they will warranty. However, when a warranty provider has not yet been chosen at the early stages of a project, it is considered good practice to ‘start with the end in mind.’ Given that NHBC’s balcony guidance is more stringent than BS8579:2020 and what is typically required by other warranty providers, it is prudent for developers to aim to meet or exceed these standards from the outset.

Doing so ensures that the project is prepared to meet the NHBC’s rigorous requirements should they be engaged as the warranty provider. Additionally, by adhering to these more onerous guidelines, developers are able to guarantee a higher standard of construction, thereby reducing risks associated with water ingress and enhancing the overall quality of the living experience for the end-user. This forward-thinking approach is not only beneficial for meeting NHBC standards but also serves as a mark of quality and diligence that is valued throughout the industry.

2024 Changes to the NHBC standard which particularly impact balcony design

In 2024, a significant update was rolled out, especially effecting thermal efficiency and sustainable design. However there are a number of ‘minor points’ of change which have been tweaked which will be impacting balcony design. Some have already been applied for a while on projects but some are a little more surprising.

The 2024 balcony related updates focus particularly on drainage, loosely based on BS8579:2020.

Changes to 7.1

7.1.4 Has been updated to add a clause to stop balcony drainage from dripping onto balustrades below. The statement This is additional to previous requirements which is loosely based on the BS8579:2020 interpretated in NHBC’s perspective. Not draining onto vertical surfaces below reflects BS8579:2020 however the difference lies in the requirement for not flowing onto barrier edges and fascia’s of balconies which is not referred to in the British Standard.

In real terms this means that any stacks of balconies will need to have a drip edge projecting beyond the balustrade. The clause says:

“The rainwater drainage system may be based on conventional piped drainage or an edge drained design. In all cases the downpipes, overflows and edge drainage outlets should be positioned in the construction to provide effective drainage that will not cause water to flow directly down onto the walls and fascia surfaces below or barrier edges of balconies installed in any stacked multi-storey arrangement”.

There is also a new requirement to:

“designed with a projecting profile that prevents rainwater from either tracking back into any soffit or running straight down onto vertical surfaces situated below”

This change doesn’t change anything for the way that Sapphire balconies are designed but in essence means balconies need to have some kind of drip edge at the lip where it is discharged. Again, there is reference to vertical surfaces which matches the BS8579:2020 diagram and guidance.

Another new point relating to where the controlled drainage is being done using RWP (Rainwater Pipes). It would generally be considered standard practise and does not affect Sapphire Balconies design:

“designed with a downpipe shoe fitted where any downpipe outlet discharges above finished ground level, including above a drainage gulley.”

And also a standard not point balcony drainage to BS8579:2020. It has always been the case of what we would point people to for balcony guidance and again is best practise advise which doesn’t have an impact on what Sapphire do or the way we design.

Designs for drainage of balconies and terraces should follow BS 8579 guidance for the provision of discharge outlets with effective clearance, capacity and profile shape to throw rainwater clear of the edge and prevent residual dripping onto other parts of the building beneath.

Another couple of new clauses but ones we have seen multiple times on the more recent NHBC Warranty projects are now included on the new version of their standards. These points cover guidance around ground floor and entrances to buildings, generally following the common NHBC interpretation of BS8579:2020. Secondly, there is a point about water cascading down the building. Whilst our opinions differ considerably from this statement, based on the research and testing we have done which tends to suggests otherwise there is now the following wording:

“A design approach for free draining balconies can be accepted if rainwater will always be routed away from the building to drain via a suitably formed soffit drainage tray that directs water to run outwards over a continuous formed perimeter edge. But where this drainage design is installed for stacked balconies on multi-storey elevations – the rainwater will tend to cascade down from these edge drainage slots as water runs off each balcony.

Under typical wind driven rainstorm conditions the water runoff volumes from these balcony catchment surfaces will progressively increase in a downward direction until the full volume of water reaches ground level. This can adversely affect locations such as main entrances to apartment buildings as well as any access doorways and private gardens of individual homes situated at ground level. Therefore, in addition to the free draining balcony design there is a requirement for design of ground level drainage to effectively prevent ponding or flooding of water. This drainage design is required along all building perimeter locations where thresholds, access locations and other places of regular use will exist.”

There is new guidance specifically referencing free draining balconies. This is assumed to be what is called controlled edge draining in BS8579:2020. It here references a continuous formed perimeter edge. Again requiring a drip edge along the edge where drainage is being dispersed.

“A design approach for free draining balconies can be accepted if rainwater will always be routed away from the building to drain via a suitably formed soffit drainage tray that directs water to run outwards over a continuous formed perimeter edge.”

Guidance has been updated for 7.1.5 Flat roof, terrace and balcony structural design. Again this doesn’t effect the design of Sapphire balconies.

“Flat roofs, terraces and balconies shall support and transmit loads safely to the structure. The structure of the flat roof, terrace or balcony should:

be produced by an engineer in accordance with Technical Requirement R5, and BS EN 1991-1-1, BS EN 1991-1-3, BS EN 1991-1-4 and BS 8579: 2020 for balconies

be designed to address both short term and long-term deflection to provide an effective drainage strategy with no back falls or ponding. resist wind uplift by self-weight or by being anchored to the main structure – where required, holding down straps should be provided at maximum 2m centres at the perimeters

have adequate provision for the additional loads where a flat roof is to act as a terrace, roof garden, for support of permanent service equipment, and for additional loads during construction”.

There is however a reference to holding down straps which may see an increase in request relating to this.

Specific requirements for gaps around decking also remain in the standard and are split between edges and gaps between boards. Again not a change in intentions nor of our balcony design.

“As-built gaps of 10mm – 12mm should be provided between decking/paving units along perimeter upstands/thresholds. As-built gaps of 6mm – 8mm should be provided between individual units of decking or paving. Spacers and supports which raise the decking or paving should not obstruct the flow of rainwater to outlet(s).”

There is a new section referring to the use of metal balconies referring back to BS8579:2020. Again a welcome reference to a document we have been following for a long time.

“7.1.17 Metal balcony decking systems

Metal balcony framework structures and metal balcony decking systems should be designed and constructed as recommended in BS 8579 guidance for the design of balconies and terraces and their component parts.”

There is also new guidance relating to glass use specifically mentioning glass compliant with Part B fire regulations but it does not mention limitations under Regulation 7. It seems to indicate that the use of monolithic glass in a guarding is permissible for balustrading.

“be toughened glass, laminated glass (subject to meeting fire regulations) or glass blocks (suitably reinforced) where glazed balustrading is used”

What were Sapphire expecting to see which isn’t in the updated standards?

Previously the 30mm drip edge, referred to in BS 8579:2020, for where there is a vertical surface of the building (i.e. in scenarios where there is a warm space below a balcony or terrace) had been a frequent topic of conversation on projecting balconies. This has been the result of what we believe is a uncommon interpretation and application of one different application rather than the correct for the scenario show in the edge drained sketch in BS8579:2020. The only balcony and terrace related reference to 30mm drip edges in the 2024 standards is for where there are scenarios matching the BS8579:2020 sketch and guidance, for example parapet walls copings on top of inset balconies and similar scenarios. This matches the Sapphire interpretation of this guidance as these scenarios have a vertical surface of the building below and therefore needs a drip edge to avoid unsightly staining, water ingress etc.

NHBC Future direction of travel

At the Building For Tomorrow, London Conference on 27/02/2024, the NHBC provided insights into the evolving landscape of construction standards, particularly for balcony design and high-rise buildings. This section summarises the key points from the speeches delivered at the conference, outlining the “direction of travel” for the NHBC standards.

NHBC Standard Direction of Travel: Chris Hall presentation

Chris Hall, the technical innovation manager at NHBC, shared that the process of updating the standards is ongoing and typically operates on an 18-month rolling update cycle. Coastal standards are revisited every three years to reflect the latest in environmental and technical requirements. He highlighted the focus in England on future homes and building standard consultations, with Wales adopting the 2022 version of Part F, L, and O. Scotland is pushing towards a ‘passive house like’ standard as a mandatory building regulation.

In 2024, a new chapter was added to the NHBC standards focusing on engineering fill. Five chapters received major updates, including those on external walls and pitched roof guidance, complemented by 70 new CAD drawings. Minor updates were made to other chapters, such as chapter 7.1, and the 2025 process will aim for consolidation of these changes.

Overview of the Implications of Building Safety Act for High-Risk Buildings: Steve Evans’ Speech

Steve Evans, the Head of Technical Operations at NHBC, provided an overview of how the Building Safety Regulator’s new regime, operated by the Health and Safety Executive (HSE), will function and its implications for NHBC. Following the post-Grenfell changes to the building control regime, as of 1 October, high-risk buildings (HRBs) can no longer be part of the NHBC Building Control Scope, with building control set to become a regulated profession under the BSR Rules from 6 April 2024.

For NHBC, this means:

Continuation as warranty providers for buildings.
Managing HRB transitional provisions on projects still working to old regime.
Implementing warranty pilot schemes for full compliance.
Assisting the BSR on multi-disciplinary teams, ensuring teams demonstrate competency by 6/4/24.

Standards for High-Rise and Complex Buildings: Philip Smith’s speech

Philip Smith, a principal technical specialist at NHBC, discussed the need for a new standard for high-rise and complex buildings. The NHBC recognises the need to shift its focus from traditionally low-rise buildings to create specific and more focused guidance on the unique challenges posed by high-rise and complex building’s.

The NHBC has identified some particular areas where there is a gap between their standards and changing landscape in the high-rise sector includes legislation and regulation changes, the climate change and carbon-neutral agenda, future homes, and building standard consultations. There’s also an emphasis on Modern Methods of Construction (MMC) innovation, systemisation, and product certification changes highlighted by the OPSS. Particularly volumetric and panelised systems are increasingly common so that is an area of specific focus too.

Cladding and fire-related claims have significantly influenced the loss both in numbers and in value, prompting a new change control regime that impacts how changes are made and recorded throughout construction and the supply chain. NHBC standards are set to start aligning with the pace of change on MMC, particularly with volumetrics and panelised systems, as part of the PAS 8700 standard. NHBC continues to map out risks and changes in construction techniques, aiming to be simple, consistent, clear, and collaborative.

What Are the Practical Implications of NHBC Standards on Balconies?

The NHBC Standards, particularly those related to balconies, have practical implications that extend beyond compliance; they guide the design and construction processes to ensure the long-term integrity and usability of buildings. Here are three key points to consider:

A) Implementation of a Drip Edge

A drip edge is required at the front drainage edge of most balcony scenarios. This component is deemed crucial to fulfil the latest NHBC 2024 standards as it is aims at preventing water from dripping onto the guarding of the balcony below. It’s an essential consideration that serves to protect lower balconies in a stack or the building’s façade from water staining or nuisance. Sapphire has multiple ways of achieving this. The below images show how this can be done effectively and without the drainage having to run through small drainage slots which could be susceptible to becoming blocked or being too small outlets to deal with storm drainage.

B) Ground Floor Drainage Considerations

At the ground floor level, especially at main entrances needs more careful planning of the drainage is imperative to meet the newest guidelines. It’s essential to ensure that rainwater from balconies has been designed to minimise the nuisance of water discharged onto ground floor areas, especially the main access areas of buildings. This not only affects the aesthetic appeal but can also pose a safety hazard, especially in adverse weather conditions. Strategic placement of drainage solutions can help avoid creating slippery conditions or pooling of water in high-traffic areas. Design consideration needs to be made on how the balcony drains but equally how ground drainage is also done.

C) Sustainable Urban Drainage Systems (SUDS) Strategy

In line with sustainable building practices, it’s necessary to consider how your Sustainable Urban Drainage Systems (SUDS) will function, particularly in preventing ice formation on pathways below where balcony drainage may discharge. This is especially crucial in areas/locations prone to freezing temperatures, where improperly managed drainage can lead to hazardous ice patches. To meet the NHBC standards it should be a consideration of principle designers and landscape designers, etc as to how the design should ensure that water is channelled away safely and does not contribute to potential hazards or damage landscaping.

Conclusion and Recommendations

Adhering to the NHBC Standards for balconies puts increased focus on dealing with drainage appropriately. Therefore it necessitates thoughtful design and engineering solutions to manage rainwater effectively. The spirt and guidance in the standards aims to prevent immediate water related damage, whilst mitigating long-term risks and ensure safety and comfort for building occupants. For balconies, achieving the NHBC 2024 standards does require more than building regulation and compliance with BS and EN standards. It will cost more and will mean considering this early. We are happy to assist at an early stage with this to give project specific guidance.

For those seeking to deepen their understanding of this topic and to explore innovative drainage solutions and approaches, reach out to use to book a rainwater CPD presentation. Additionally, Sapphire’s Drainage Whitepaper offers an in-depth look at effective drainage strategies, providing valuable insights and guidance. Both resources can prove instrumental in achieving a design that is both compliant and conducive to a safe and sustainable living environment.

Do bear in mind that if you are designing to NHBC guidance early on because it is a change to a façade related component, under the new Building Safety Regulator regime, once it is submitted through Gateway 1, then it is going to need to be used. Our advice is; be prepared, or make the decision on warranty providers at an early stage. Your choice, just remember façade related changes will not be easy and neither will cost be an acceptable justification.

You may also find this video useful in understanding the BS8579:2020 statistics.

When Do the NHBC Standards Apply to Balconies?