Building Standards technical handbook 2017: domestic buildings

The structure of a building is fundamental to ensuring the safety of people in or around new and existing buildings and can be affected by a number of factors inside and outside the building including environmental factors. These factors should be considered to prevent the collapse, excessive deformation or the disproportionate collapse of buildings.

The climatic conditions in Scotland including temperature, snow, wind, driving rain and flooding and the impact of climate change should be carefully considered in the assessment of loadings (actions) and in the structural design of buildings.

The Standing Committee on Structural Safety (SCOSS) is an independent body supported by the Institution of Civil Engineers, the Institution of Structural Engineers and the Health and Safety Executive to maintain a continuing review of building and civil engineering matters affecting the safety of structures. The prime function of SCOSS is to identify in advance those trends and developments that might contribute to an increasing risk to structural safety. The collation and dissemination of information relating to matters of structural concern is a vital element of achieving safe structures. SCOSS has established a UK wide confidential reporting system (CROSS) to gather data on structural problems.

Appraisal of existing buildings - conversions to existing buildings present particular problems and an appraisal of the existing structure for its new occupation or use should be undertaken to ensure that appropriate measures are taken to meet the requirements of regulation 12. Guidance on how a structural appraisal may be undertaken is given in 'Appraisal of Existing Structures', 1996 published by the Institution of Structural Engineers.

Procurement - the contractual arrangements used by clients to procure a building can have important consequences for the reliability of the design and the adequacy of the construction. Frequently, building design procurement will involve the appointment of a number of designers who may be employed by more than one organisation. Detailed design of individual structural details and components can be passed to specialist contractors. In these circumstances the client should appoint a lead designer or other appropriately experienced and qualified person to oversee the design process.

The intention of this section is to ensure that the structure of a building shall be designed and executed in such a way that, during its intended life, it will not pose a threat to the safety of people in and around the building with an appropriate degree of reliability. To achieve a structure with adequate structural resistance, serviceability and durability the following should be taken into account:

The actions on the building will comprise a set of loads applied directly to the structure that will include dynamic, concentrated and peak load effects, together with a set of imposed deformations caused for example by temperature changes or uneven settlement.

The following is a summary of the changes made to this section since 1 May 2009.

1.0.1 reference to SCOSS updated

1.0.1 guidance for clients on procurement added

1.0.2 aims re-written to reflect Structural Eurocodes

1.0.4 guidance on relevant legislation added for CDM regulations

1.0.5 guidance on alternative approaches added including the use of withdrawn British Standards

1.0.7 clause on certification introduced

1.1.1 reference to guidance on fixings and stone masonry added

1.1.2 reference to Structural Eurocodes added for loadings

1.1.3 reference to Structural Eurocodes added for design and construction

1.1.4 reference to BS EN 1997-2:2007 added for geotechnical investigation of the site

1.1.5 reference to BS EN 1997-1:2004 added for design of foundations adjacent to existing buildings

1.2.1 guidance in relation to disproportionate collapse updated to align with Structural Eurocodes, and

1.A. Annex A - list of structural Eurocodes and corresponding British Standards to be withdrawn added.

The previous annexes forming the Small Buildings Structural Guidance (SBSG) have been removed from the Technical Handbook and are now referenced in clause 1.0.5.

Minor alterations and corrections have also been made. A full list of changes to this edition of the Technical Handbooks is available on the Building Standards website.

The Construction (Design and Management) Regulations 2007 are intended to protect people working in construction and others who may be affected by their activities. The regulations require the systematic management of projects from concept to completion and throughout the life cycle of the structure, including eventual demolition. Clients have a duty to ensure that competent people are employed to do the work, that sufficient time is allocated for the work to be undertaken and that the various members of the design and construction teams co-operate and exchange information.

Where alternative approaches to the structural design are proposed other than using the guidance contained in this section, the structural design should take account of all of the factors identified in clause 1.0.2 above. For example, care should be taken where alternative numerical values are placed on factors of safety as this may have a detrimental effect on the overall stability of the structure.

The British Standards Institution (BSI) agreement with the European Committee for Standardisation (CEN) obliges it to withdraw UK national standards after a harmonised European Standard with the same scope and field of application has been produced. Withdrawal of a standard implies that while documents will still be available there will be no support or five-year review by a BSI committee to consider the currency of the standard and to decide whether it should be confirmed, revised or withdrawn. BSI, in line with this commitment, will be 31 March 2010 replace the British Standards relating to loading and structural design with the European Standards and associated National Annexes listed in Sections 1.1.2 and 1.1.3 of this guidance.

Whilst other guidance documents or international standards, including withdrawn national standards might be used in alternative approaches to satisfy building regulations, designers, verifiers, or in the case of certified projects, the approved certifiers of design (building structures) will need to satisfy themselves that the use of such guidance is appropriate for a specific project. Care should be exercised, particularly with withdrawn standards, in relation to wind and snow loadings (actions) where the effects of climate change may render these unsafe.

Where alternative approaches use design methods or codes other than those listed in this guidance then these must be used within the context of the assumptions set out in Section 1.1.3. Designs must be checked in order to deliver similar levels of design reliability.

The Small Buildings Structural Guidance (SBSG) provides structural guidance to designers of small domestic buildings on how to comply with Standard 1.1. The guidance was published in Section 1 (Annexes 1.A to 1.F) of the Technical Handbooks in May 2005 (updated in 2007) and based on British Standards which have now been withdrawn. The SBSG, together with research on the impact of the Structural Eurocodes on masonry construction, is available on the Building Standards Division website http://www.scotland.gov.uk/Topics/Built-Environment/Building/Building-standards. The SBSG has been written for those with expertise in building design and construction but not necessarily in structural engineering design. Where the conditions or parameters fall outside the scope of the guidance, then specialist advice should be sought from approved certifiers of design, chartered engineers or other appropriately qualified persons.

A list of structural Eurocodes and corresponding British Standards to be withdrawn is contained in Annex 1A.

Scottish Ministers can, under Section 7 of the Building (Scotland) Act 2003, approve schemes for the certification of design or construction for compliance with the mandatory functional standards. Such schemes are approved on the basis that the procedures adopted by the scheme will take account of the need to co-ordinate the work of various designers and specialist contractors. Individuals approved to provide certification services under the scheme are assessed to ensure that they have the qualifications, skills and experience required to certify compliance for the work covered by the scope of the scheme. Checking procedures adopted by Approved Certifiers will deliver design or installation reliability in accordance with legislation.

The Certification of Design (Building Structures) scheme has been approved by Scottish Ministers to confirm compliance with Standards 1.1 and 1.2. Details are available on the Building Standards Division website http://www.scotland.gov.uk/Topics/Built-Environment/Building/Building-standards.