Government issues new guidance on sprinklers, wayfinding signage and boundaries

17 August 2020

a person in a high vis vest an hard hat signing a document

The Government has now published amendments to Approved Document B in England. There are three main changes/additions to the guidance.

Sprinklers in blocks of flats

Paragraph 7.4 of Approved Document B, Volume 1 has been amended to reduce the trigger height for sprinklers in a block of flats from 30m to 11m.  This will apply where the height of the top floor to the lowest ground level outside the building is 11m or more. 

In association with this change, Table B4 of Approved Document B, Volumes 1 and 2  (minimum periods of fire resistance) has been updated to include a new category for height of building ‘Up to 11m’.

Wayfinding signage in blocks of flats

Approved Document B, Volume 1 has been extended to include new paragraphs 15.13-15.16.  These paragraphs provide guidance on signs to assist the fire service identify each floor and flat in the following locations:

  • On the landing of every protected stairway.
  • In every protected lobby or corridor into which a firefighting lift opens.

Again, this applies where the height of the top floor of the block of flats to the lowest ground level outside the building is 11m or more.  The guidance also confirms details of the minimum letter heights, wording, style and the positioning/legibility of the signs.


Approved Document B, Volume 1 (paragraph 11.5) and Volume 2 (paragraph 13.5) have been amended to include purpose group 2 (Residential – Institutional/Other) for application of a ‘notional boundary’ between two buildings on the same site.  This is a correction to an error in the 2019 editions of the documents.

Transitional Provisions

The amended Approved Documents come into force on 26 November 2020, however they will not apply where an initial notice has been given to, or a full plans deposited with, a local authority before 26 November 2020 and the building work to which it relates starts before 29 January 2021.

Commencement of work

MHCLG have confirmed that the usual advice for commencement of work should be followed.  In their opinion, commencement of work would usually be marked by work such as:

  • excavation for strip or trench foundations or for pad footings;
  • digging out and preparation of ground for raft foundations;
  • vibrofloatation (stone columns) piling, boring for piles or pile driving;
  • drainage work specific to the building(s) concerned.

MHCLG considers that the following sorts of work would not be likely to constitute the commencement of work:

  • removal of vegetation
  • demolition of any previous buildings on the site;
  • removal of top soil;
  • removal or treatment of contaminated soil;
  • excavation of trial holes;
  • dynamic compaction;
  • general site servicing works (e.g. roadways)

In some cases, applications will be in respect of several buildings on a site, for example a number of houses. In such cases it is the commencement of work on the first of the buildings within the application which determines whether all the building work can take advantage of the transitional provisions, not each individual building.

Relevant statutory notices, guidance and amendments to the Approved Documents

Read more detail in Technical Extra Issue 26 here.

For more information on the amendments and how these may affect your project please speak to your NHBC Surveyor or Project Manager.

grey line drawing of mouse cursor clicking button

Technical news

Stay ahead of the competition with the latest technical news and updates.

Find out more
grey line drawing of paper with cog wheel, protractor and pencil on it

Technical guidance documents

To help you interpret and apply the NHBC Standards we produce Technical Guidance Documents on the page below.

Find out more
grey line drawing of flip-board

Technical training

NHBC is uniquely placed to offer relevant, best practice technical training.

View courses
grey line drawing of blueprints on scroll

NHBC Standards

Your essential guide to house building from foundations to roofs and finishing.

Read more

Talk to us

Technical queries and quotes