Flat roofing (RBM) vapour control layers

This standard covers an introduction in understanding the necessity of a bituminous vapour control layer.

CITB has developed this standard in discussion with industry


Minimum 1 day of 6 learning hours

Purpose / scope

The purpose of training against this standard is to provide candidates with an introduction in understanding the necessity of a bituminous vapour control layer.

The scope includes:

  • vapour barriers
  • vapour checks
  • vapour control layers
  • dew points
  • interstitial condensation

Occupational relevance

Training delivered against this standard is relevant to the following occupational group(s):

  • operative and craft
  • supervision
  • management and leadership.

Candidate prerequisites

For this training, candidates must hold a valid Working at Height certificate. It would be beneficial if candidates had basic knowledge of flat roofing, tools and techniques and also, the ability to read manufacture’s installation drawings.

Before candidates perform the work on a construction site, candidates must have successfully completed roofing-specific training for working at heights.

Instruction / supervision

As a minimum, course instructors must be able to demonstrate that, in relation to this standard, they have:

  • A train the trainer or instructional techniques course certificate
  • Successfully completed training to this standard 
  • At least 10 years relevant industrial experience
  • A verifiable CV.


The following methods may be used in the delivery of this standard:

  • practical training in an off the job simulated environment, using low height roofing rigs
  • theory training, classroom

All materials and equipment must be of a suitable quality and quantity for candidates to achieve learning outcomes and must comply with relevant legislation.

The class size and candidate/instructor ratio must allow training to be delivered in a safe manner and enable candidates to achieve the learning outcomes.

This standard is considered to contain 51 per cent or more theoretical learning.

This standard is considered to be set at an intermediate level.


Methods of assessment considered appropriate for training delivered against this standard are:

  • Written theory test.

For the successful completion of training, candidates must complete a written assessment.

Quality assurance


Quality assurance against this standard will require initial approval of the training organisation and their content mapped to the standard. 

CITB will also conduct an approval intervention, either desk-based or centre visit, to ensure the training organisation can meet the requirements of the training standard. 

Approved training organisations (ATOs) will be required to present information on records of training and assessment upon request to CITB for desk based analysis. They will also be visited annually by the CITB quality assurance team.


There are no mandatory renewal or recommended refreshment requirements for this standard.

Approval date


Review cycle

Either on request or in 3 years from approval date.

Learning outcomes

The candidate will be able to Additional guidance to support learning outcome
Discuss the hazards and risk associated with working on the roof and the precautions to be observed. Visual slides in classroom
Group discussion
Describe different vapour barriers Visual slides in classroom
Group discussion
Describe what a dew point is and the affects on a roof Visual slides in classroom
Group discussion

Describe interstitial condensation and the affect on a roof
Visual slides in classroom
Group discussion

Additional information about this standard

Health and Safety Executive (HSE)

British standards

View all available British Standards at the BSI website

BS 8217:2005 - Reinforced bitumen membranes for roofing. Code of practice

BS 6229:2018 - Flat roofs with continuously supported flexible waterproof coverings. Code of practice