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BS 5250:2011+A1:2016

BS 5250:2011+A1:2016 Code of practice for control of condensation in buildings

Details: A4, 106 pages.

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Stock status: Available to Order (Stock Due)

Publication date: 31/12/2011

Publisher: British Standards Institute (BSI)

ISBN: 9780580938047

Publication Status: Active


BS 5250:2011+A1:2016 Code of practice for control of condensation in buildings


Knowledge of the problems that moisture causes in buildings has advanced very rapidly since the last revision of this standard was published in 2011. Accordingly, this amendment has been produced to address some important issues ahead of a full revision of the standard that is due to be published in 2018.

Who is the standard for?

The standard is for architects, surveyors, building companies, insulation and other material manufacturers, housing managers and all those involved in:

  • Structural design
  • Thermal design
  • Heating equipment
  • Ventilation
  • Mathematical calculations on buildings
  • Condensation
  • Damage prevention
  • Design
  • Surfaces
  • The retrofitting of existing buildings

What does the standard cover?

This standard gives guidance on the risks associated with excessive humidity in buildings, notably mould growth and condensation, which can endanger the health and well-being of building occupants and the integrity of the building fabric. It describes the principal sources of water vapour, its transportation and deposition and provides guidance on how to manage those risks during the design, construction and operation of buildings.

The standard is relevant to buildings of all types, whatever their form, construction or level or type of occupancy, except buildings used for storage at sub-zero temperatures.

What does the amendment cover?

Knowledge of the problems caused by moisture in buildings has advanced rapidly since BS 5250 was last revised in 2011. This has led to the development of more sophisticated structural design and failure analysis techniques. In parallel, concerns have grown over moisture problems that are generally due to climate change (a warmer, wetter climate therefore more driving rain and more flooding), as well as the drive to add insulation to walls, which disturbs the equilibrium of structures that have worked well for many years.  

Consequently, the main amendments are as follows: 

  1. A fuller discussion is provided of the more complex heat and moisture processes involved in the methodology of BS EN 15026, compared to the much simpler methods of BS EN ISO 13788 that are currently recommended.  (Section D.3)
  2. Tables F.1, G.1 and H.1 are introduced to cover the recommended assessment methods for different types of floors, walls and roofs respectively. There had been some confusion about when the different methods that were available should be used and complex calculations were required for situations where the straightforward guidance in BS 5250 can be followed
  3. The most significant change comes in G.4.1.4. The addition of a vapour control layer (VCL) inside internal insulation (IWI) on solid walls was regarded as essential. However it is now agreed that, in many cases, this may cause more harm than good. The revised guidance in G.4.1.4 essentially says 'be careful' and consider all the issues when installing IWI. Work to clarify these issues will continue for the full revision of BS 5250