The National House Building Council, (NHBC) is the leading provider of warranties for new build housing in the UK. Each year, the NHBC releases an updated version of its technical standards after working with stakeholders from across the construction industry to improve them. The standards provide the technical requirements and performance standards for the design and construction of new homes registered with an NHBC warranty. 

The NHBC has recently launched its 2021 technical standards. The good news is, these new changes need not be too time-consuming for builders and developers to get their head around as a lot of what’s in the 2021 version is updates rather than starting from scratch. 

But to help, our technical manager, Michael Copley, has reviewed the new guidelines and has picked out the key elements that are worth you paying particular attention to.

Cavity trays, mortar and firestopping

Let’s start with Chapter 6. This has been updated with the main changes focusing on cavity trays, mortar and firestopping. Within this chapter, the key sections to focus on are as follows:

  • 6.1.2 Provision of Information

The alteration here is the position of fire breaks, cavity barriers and other passive fire stopping, plus the required fire resistance period should now be specified. 

  • 6.1.3 Structural Design

Movement joints – Table 1 has been revised and updated, with calcium silicate bricks and dense concrete blocks removed and natural stone masonry added. A new set of notes has also been provided to support this table.  You’ll also find that there’s new guidance on damp proof courses to give extra clarity. 

  • 6.1.4 Fire Resistance

There’s lots changing around all things fire at the moment, so the guidance here has changed to help with building regulation compliance.

  • 6.1.7 Thermal Insulation

Within the Thermal Insulation section, the guidance has been improved overall and particularly in line with currently available products and their installation.You’ll see that Table 2 now allows the use of recessed mortar joints in sheltered locations. Before there were restrictions for retrofit filling of cavities in Scotland, Northern Ireland and Isle of Man but these have been removed in line with current building regulations. Inner leaf of insulated blockwork and dual insulation guidance has also been removed.

Flat roofs, terraces and balconies

Moving on to flat roots, terraces and balconies which are featured in Chapter 7. This section  has had a full NHBC review, so it’s worth focusing in on it.   

The guidance  now includes terraces and podiums, and has more detail on drainage given its importance in the build process.  

Within Chapter 7 the parts we’d concentrate on are as follows:

  • 7.1.3 Provision of information

Roofing wise, deflection analysis is now needed on some roofs and ventilation now needs to be considered on flat roofs too. A welcome addition is that the guidelines now also include references to green and biodiverse roofs alongside blue roofs

Deck surveys are now needed prior to waterproofing, and the testing of a waterproofing layer is now required.

  • 7.1.5 Drainage

Drainage has been moved to the beginning of this chapter to emphasise how  important it is in the design and construction of all new build homes. The drainage section includes guidance on the use and interpretation of ‘zero fall roofs’ and how to maintain effective drainage on the completed waterproofing layer.

Following on from the new BS 8579 standard on balconies, which the NHBC helped to draft, detail on small balcony and terraces drainage has been introduced into the guidelines. This is an important addition given the rising popularity of these kinds of spaces.

Back to decks again, a clause has been added regarding carrying out a deck survey and having a formal handover between the deck erector and waterproofing contractor. The purpose of handover being to ensure a fully drained waterproofed surface is achieved with no back falls.

  • 7.1.6 Flat roof, terrace and balcony structural design

This section has been updated and now includes guidance on both long-term and short-term deflection and the effect that this can have on drainage.

  • 7.1.12 Waterproofing later and Surface treatments

Fully supported flat sheet, hard metal roof waterproofing designs have now been included with illustrations showing you the preferred approach when using these types of  waterproofing systems.

There is also now requirement to check the integrity of waterproofing, either visually or electronically dependent on size and complexity of the roof. This part has also been updated to include more commonly used treatments (as opposed to traditional bitumen membranes).

  • 7.1.13 Green & Biodiverse (Brown) roofs – including roof gardens

Further guidance has been introduced which includes roof gardens’, and both ‘warm’ 

and ‘inverted warm’ green roof build-ups. 

  • 7.1.15 Raised Podiums

A new section on podiums has been added to differentiate between ‘raised podiums’ which are dealt with under Chapter 7.1 and ‘buried podiums’ which are covered in  Chapter 5.4

  • 7.1.18 Parapets and guarding to terraces

This section has been expanded to include new illustrations and revised guidance on the design of copings and waterproofing to parapet walls. There are useful examples included on how to fix balustrade posts through waterproofing layers without causing leakage

Drives, pathways and landscaping

In chapter 10, the old BS Standards specifications have now been harmonised EN Standards throughout. 

In this section more detail on garden areas and decking has been included (in 10.2 in particular) and refences to Highway Works specification has also been updated together with the clause on sub-base thickness.

Working on a new build project?

The new standards apply to every home covered by an NHBC warranty where foundation work started on or after January 1st 2021. 

If you’re a builder or developer looking at ways to make your build process smoother, by saving you time and assisting with the right route to compliance, we have a range of Build Aviator services that can help.  

Full details of the NHBC 2021 technical standards can be found here.