Building standards - managing fire risks associated with use of external wall systems: research

Executive Summary

Purpose, Aims, and Objectives

Following the tragic events at the Grenfell Tower fire, London on 14 June 2017, the Building and Fire Safety Ministerial Working Group (MWG/) was set up to oversee a review of building and fire safety regulatory frameworks and any other relevant matters, to help ensure that people are safe in Scotland’s buildings.

The aim of this project is to develop guidance for consideration by the Building Standards Division (BSD/) of the Scottish Government to assist local authority verifiers manage the fire risk associated with external wall systems (EWS/). The research includes qualitative analysis of the design, verification, installation, inspection, and certification of external wall systems. The outcome of the research will be used to develop guidance that may be included in the Compliant Handbook that will be developed to support the Compliance Plan Approach work stream of the Futures Board.

The research focused on compliance issues, both physical and procedural. The developed guidance is intended to assist local authority verifiers to manage the fire risk associated with external wall systems through the design and construction phase of a project and as a result improve compliance with building regulations.

The objectives of the project were to:

• Undertake a transparent, rigorous, and systematic analysis of a sample of domestic high rise (above 18m) building warrant applications dated from 1 May 2005 and a sample of building warrant applications above 11m (domestic or non-domestic) dated from 1 October 2019 in a mix of local authorities. The brief was to sample four applications of each of the above (total of eight) from six local authorities; six local authorities were initially approached as per the brief, three local authorities responded to this request. As a result, the actual number of case studies was subsequently reduced to five, from three cities. The authors are indebted to the cooperation from the three cities that participated. The review involved records for each project, including all available pre and post building warrant documentation made available by the local authorities.
• Provide quantitative as well as qualitative analysis and identify any recurring themes in the verification process, and suggest possible solutions to provide appropriate, effective, and robust verification and compliance processes to ensuring safe external wall system design and construction. Local authority verifiers advised during the interview process that a record is not kept on time spent on each aspect of the Building Standards guidance in the Technical Handbook (including external wall systems), therefore a quantitative analysis was not possible.
• Draft guidance should be targeted at assisting relevant persons (see Section 1) which may be included in or cross-referenced by the Compliance Handbook (Note: this guidance should also be helpful to local authority verifiers, designers, installers, fire risk assessors, fire engineers, and external wall system appraisal experts).

Methodology

The authors created a Guidance Tool (see Section 4) based on their external wall experience. The Guidance Tool was then applied to the design information, correspondence, and site inspection records provided by the relevant local authority for each of the five case studies included in this research; this was intended to identify any gaps in the Guidance Tool. Interviews were held with the local authority case officers for these five building warrant applications which were intended to understand how the local authority verifier arrived at the decisions taken specific to that case study in their own words.

The Guidance Tool (see Section 4) includes a methodology for carrying out site inspections.

In order to inform the research and encourage open feedback, the project addresses and local authorities have been anonymised. Data Protection legislation and copyright will be adhered to at all times.

Conclusions and Recommendations

The Guidance Tool has a place in the Building Warrant process. The outcome of this research is that the most useful aspect will be as a formalised checklist/process for Building Warrant applicants to follow, and act as an aide memoir to local authority verifiers.

Local authority verifiers often rely on their experience with products’ fire performance and decide on the suitability of non-standard external wall designs with limited recording of the decision making process. Advice received externally from experts/manufacturers is saved on file. It is the authors’ opinion that better record keeping is important for external wall designs as products’ fire performance is tied closely to the tested configuration, and reference material should be consulted to prevent inappropriate or untested arrangements from being approved/constructed.

Local authority verifiers carry out spot checks of construction quality of external wall systems on site. This is in theory satisfactory as the responsibility for construction quality sits with the “relevant person”, however as construction quality is constantly in question (in the experience of the authors) additional oversight is advisable.

Additional oversight could come in the form of additional site inspections by local authority verifiers or a qualified independent third party acting for the “relevant person” (such as a Clerk of Works). Such site inspections would still be subject to review by local authority verifiers. Input would be needed from the BSD/ to achieve this, including guidance for all and a suitable accreditation scheme.

There is no strong evidence that a separate stage for external wall systems should automatically be introduced for every project, although this is done routinely for large projects.

As local authority verifiers were unable to estimate the percentage of time devoted to reviewing external wall systems, quantitative analysis has not been possible.

To address construction quality issues, clear guidance should be given to local authority verifiers and Building Warrant applicants on how to most efficiently obtain the services of a qualified independent third party acting for the applicant to carry out suitable site inspections (suitable is explained by the Guidance Tool). See Section 1 of this report for the role of the relevant person.

Where decisions are made regarding the suitability of external wall systems, local authority verifiers should be encouraged to record the decision making process to reach the conclusion, particularly where the conclusion is to accept the proposal.