GUIDE TO SPECIFYING BRICK AND BLOCKWORK
The use of brick and blockwork remains important today both for their functional and aesthetic value and for the fact that their role brings potential risks to the architect.
It is therefore vital that a correct and achievable specification is prepared that reflects the specific circumstances of the project and steers the builder towards the quality of manufacture and workmanship that is expected. An inadequate clause that conflicts with other contractual statements will almost certainly lead to unwanted additional costs.
This article highlights the stages that the architect or specification consultant will pass through when specifying brick and blockwork, and some of the key issues that should be raised during each stage.
SETTING UP It is important to agree among the design team and client/ project manager the type of specification to be developed - either descriptive or prescriptive - for each 'F' Group within the Common Arrangement of Work Sections (CAWS), an industry-wide system that allocates a fixed code to each type of construction.
The main function of a descriptive specification is to define performance, design intent, procedures for completing detailed design and quality control, and to provide the contractor with a fair indication of the solutions that are acceptable. Prescriptive specifications, in contrast, include the proposed manufacturer or supplier, where the architect knows exactly what is required and there is a minimum level of design development by the contractor.
Misunderstanding this distinction can lead to the design team including more detail than is necessary (or not enough). The decision on which sections are descriptive or prescriptive is usually taken by the architect in conjunction with the project manager and cost consultant, based on factors such as size of project, procurement route and complexity of design.
The architect will also need to consider the types of brick and blockwork required and preferred.
The type of masonry unit will be determined by several factors including functional requirement, performance and aesthetics. The architect should liaise with the structural engineer during the process in order to ensure that the products and types specified are also co-ordinated with the structural information.
start the specification process early and agree 'buy-in' of the team. It is recommended that this process starts during RIBA Stages C or D, depending on the procurement route;
agree collaboratively whether 'F' Group sections will be descriptive or prescriptive.
It is typical within the industry that brick and blockwork is prescriptive but both routes should be considered;
start to define systems and types of brickwork and blockwork dependent on their function, required performance and the visual appearance that is expected; and - consult the specialists for advice. Davis Langdon Schumann Smith ( www.schumannsmith. com) can provide advice on specification issues. There are also various specialist groups, such as the Brick Development Association at www. brick. org. uk
TENDER Once the specification sections have been set up, it is essential that the document is updated regularly and reviewed to reflect the design drawings so that at tender, both design documents are fully co-ordinated and the cost consultant has as much information as required. When specifying brick and blockwork for descriptive sections where the contractor will be expected to develop the design, it is important to include achievable performance data (see table on page 30). For specifications relying on performance criteria, evidence should be provided either through testing or through previous test certificates on similar systems where the actual performance has been met. Testing of masonry units should be carried out in accordance with BS EN 772 and results should always be provided in writing to the architect. General specification requirements for mortar are included in CAWS Section Z21.
Nominal mix proportions are included in BS 5628: Part 3, and testing of mortar over seven and 28 days, including crush testing, should be carried out in accordance with BS 5628: Part 1, BS 4551, and BS EN 1015.
ACCESSORIES TO BRICK AND BLOCK WALLING It is important when preparing the specification not to exclude the specific accessories relevant to the brick/block walling.
Such accessories include insulation, ties, joints, restraints and damp proofing, and should be included in Section F30 and covered under BS EN 845.
include relevant performance data for descriptive specifications where the contractor will be expected to complete the design. The architect will be expected to have already incorporated relevant performance data into his/her design for prescriptive sections;
benefit from the advantages of sample panels and benchmarks;
testing of masonry units should be to BS EN 772. Be wary of testing being removed from the scope of work due to possible cost savings - it may backfire;
remember to include necessary accessories including insulation, ties and reinforcement; and - Maintaining quality is not about a single specification document. It is about being on site regularly and talking to people.
This is an abbreviated version of a longer article. To see the full piece, go to www. ajplus.co. uk/material