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CROSS Safety Report

Building regulations checking

Report ID: 33 Published: 1 July 2007 Region: CROSS-UK

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Overview

A reporter’s firm has been carrying out building regulations checks for 25 years, but it is only in the last six or seven years (say 2000-2006) that concerns have arisen, some of which are described below.

Key Learning Outcomes

For civil and structural design engineers:

  • It is good practice to check and verify design calculations prior to submitting them to local building control

  • Checkers of design models should ensure the model and its input data are appropriate, and that the output makes sense. The checker should consider if anything has been omitted or overlooked.

  • It is good practice to check and validate all design outputs from proprietary design software

  • Competent supervision of design by experienced personnel can allow less experienced engineers to develop a feel for the right solution

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A reporter’s firm has been carrying out building regulations checks for 25 years, but it is only in the last six or seven years (say 2000-2006) that concerns have arisen, some of which are described below.

Inadequate co-ordination

There were two instances of partial collapse during the construction of a two storey timber framed educational building. The local authority client nominated a timber frame sub-contractor for a Main Contractor Design & Build contract. The sub-contractor’s design was not reviewed until there was a building regulations check by the reporter’s firm. This revealed defects, some of which had been incorporated in the structure and had to be modified. The foundations, designed by another engineer, also had defects due to no overall co-ordination. There were substantial financial consequences, and the building should, according to the reporter, have been designed (or supervised) by one engineer before going out to tender.

Robustness/disproportionate collapse

There have been, again according to the reporter, problems with single/two storey schools due to difficulties in interpretation of building regulations requirements. The reporter wants definitions of terms such ‘effective tie’ and ‘robust’, and design rules, illustrated with diagrams, for how framing should comply with Regulation A3. The reporter’s firm has seen only one robust building in ten years (presumably in terms of the designs submitted for checking). On one school the steel roof sheeting (0.8mm thick) stabilizes the building. It rocked before the windows were put in but probably won't collapse due to ductility of steel – so does it comply with Part A of the Regulations? Difficult to disprove under BS 5950 - but the structure is not robust. Should a BS to cover ‘robustness’ be drafted?

The reporter wants definitions of terms such ‘effective tie’ and ‘robust’, and design rules, illustrated with diagrams, for how framing should comply with Regulation A3

Sub-contract design

Considerable reliance, according to the reporter, is placed by engineers on ‘guarantees’ provided by timber frame suppliers and foundation contractors. No checks are carried out on suppliers’ designs or specifications to see if their own design assumptions are met. In one case a strip foundation design for a building several storeys high was ‘guaranteed’ to have zero settlement on a stone consolidated site consisting of random fill. In another the design by a supplier for a timber half portal, was accepted by the engineer without comment. This was despite the fact that it was pinned at foot and ridge, with large outward forces, and no allowance was made for these. An engineer with responsibility for the whole design/co-ordination seems to have disappeared. The reporter wonders if it is left to building regulation checkers to do this essential job and where does self-certification fit in?

Inadequate design time

One engineer submitted drawings of a school hall with a brick panel 9m high x 7m wide with 100mm inner and outer leaves and a 75mm cavity. Even the designer’s computer calculations submitted with the application said it would fail. Other panels were inadequately tied to the steel frame or were too large. Substantial remedial works were carried out, but why did the engineer make these mistakes? Another engineer on a shops/flats complex did the same – again resulting in major remedial works. The reporter’s hunch is they simply did not have enough time, or probably the fees, to do the simplest of checks.

Expert Panel Comments

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Regardless of the contractual situation all engineers have a duty of care and there was a failure to exercise this in many of the quoted examples. It is recognized that not all submissions are made by engineers but the CDM regulations require co-operation, co-ordination, and information flow. As a basic step it is recommended that co-ordination issues are discussed between the local authority and the designer when possible to help both sides to appreciate the other’s point of view.

The objective is the same for both parties; to have safe buildings. The observations on robustness reflect a general and widespread lack of understanding about what is required to comply with Part A3 of the Building Regulations. It is a theme of concern to CROSS, and the Institution of Structural Engineers plans to produce a report on the subject. A common thread through these points is that responsibility is divided.

Case law has established that with sub-contracting, including design, there remains a responsibility to monitor the work of others. British Standards, design guides, and indeed common sense dictate that there has to be a single entity with overall responsibility for the design of safe structures. It is fortunate that there are firms like the reporters to find and resolve problems although this should not have to be relied upon.

Inadequate design time would not be an excuse for an engineer faced with legal action over a collapse. CROSS is concerned that there is a lack of competence and professionalism in the quality of submissions in parts of the industry, and that experienced engineers are not engaged when they should be.

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