Home Contact Us
Contact Us

Section 1 Sub-contractors

Section 2 Suppliers

Section 3 Effect of On/Off Site Methods                                                     

Description:  The purpose of this unit is to enable you to discuss the issues and implications associated with the size and scope of subcontractors, suppliers and manufacturers, trends in new production method and in the management and organisation of building services works.

Author:  Gates MacBain Associates

Section 1  Sub-contractors

Aims and Objectives

At the end of this section you should be able to:
  • Explain the factors to be considered in the appointment of subcontractors for a contract.

It is very unusual for a contractor to undertake all the work in a contract with their own workforce. Even in minor construction projects the main contractor is likely to require the assistance of a trade or specialist firm.  Work undertaken by firms other than the main contractor are described as sub-contractors, although it is not uncommon to find specialist firms working on site beyond the normal jurisdiction and control of the main contractor, and consequently, not a sub-contractor within the generally understood description. 

Employers may employ these firms directly and as such they are not to be considered as sub-contractors of the main contractor.  Provision is made within the contract so that such firms have access to the site and any facilities. 

The employer may also nominate particular firms for specific work that will be required. This approach is used if the employer wants a greater control over the sub-contractor: Although after nomination they are often treated like one of the main contractors own sub-contractors. 

The architect may also name sub-contractors in the BofQ, who will be acceptable for the execution of some of the measured work.  This procedure avoids the lengthy process of nomination, but still provides a measure of control on the part of the architect. The requirement under JCT is to name at least three firms who would be acceptable by the architect.  This allows for an element of competition and allows the main contractor to select the firm.  The contractor can also add to the list subject to the approval of the architect. 

In addition work can be carried out by sub-contractors who are selected by the main contractor these are referred to as domestic sub-contractors.  Selection of Sub-contractors Sub-contractors should be selected, not only on price, but also: 
  • Business integrity
  • Guarantee of service
  • Quality of workmanship
  • Ability to meet the programmed completion date
  • Financial stability
  • Attendance required with regard to facilities, unloading and handling of materials
  • Ensure a proper understanding of the terms and conditions of the contract.
Control and Coordination of Subcontractors 

It is the main contractor who is responsible for the control and coordination of the subcontractors.  Subcontractors will need to fit in with the main programme in order to ensure that they are available when required; failure to do this can have an adverse effect on the programme and can affect the completion of the contract. It is important therefore, that the subcontractor is involved at the planning stage in order to ensure that they are available when required and are aware of the requirements relating to the contract. Chapter 18 of the Cooke /Williams book should be read in relation to this. 



  • Cooke, B & Williams, P (2009) Construction Planning, Programming and Control (3rd Edition) Blackwell: Chichester (Chapter 6 & 18)

Self-Assessment Task

  • Discuss the implications relevant to the selection of subcontractors and the relevance that the size of the firm is likely to have.

Section 2  Suppliers

Aims and Objectives

At the end of this section you should be able to:
  • Explain the factors to be considered in ensuring the efficient procurement of suitable supplies for a contract.

Products and materials are normally obtained through the purchaser who is responsible for the procurement, storage, and monitoring of goods, machinery, supplies, or other raw goods used for the fulfillment of a contract. The purchaser is the person in charge of this aspect of the contract. For a contract to be profitable it is important that the function of purchasing is carried out effectively.   

The people responsible for purchasing must stay up-to-date on new and emerging products on the market. They will also need an understanding of the products that are available and where they can be obtained.     

Cost of Materials 

In many cases, purchasing will involve negotiating with manufacturers or wholesalers in the process of buying goods or materials in order to obtain the best possible price.  

The cost of materials will depend on the economy and the supply and demand of these materials and their availability. Details of this can be found in the constructionsite units listed below. It will also depend on the buying power of the firm as a company spending many hundreds of thousands of pounds will have a greater prospect of negotiating better rates than one spending only a few thousand.   

The same principles also apply to the acquisition of labour in that if there is not much work available due to the economy then the cost for the labour element is likely to be significantly lower than in a boom time.  

Tracking Supplies 

Maintaining an inventory is also a big part of purchasing in order to compare the stock held against that ordered and purchased. It will also enable the future requirements to be assessed.



  • Ashworth, A (2006) Contractual Procedures in the Construction Industry, 5th Edition, Pearson: Harlow (Chapter 16).

Constructionsite Units

Self-Assessment Task

  • Discuss the tasks of the purchaser within an organisation.

Section 3  Effect of On/Off Site Methods

Aims and Objectives

At the end of this section you should be able to:
  • Discuss the advantages of using off-site production methods on a project.

Off site construction involves the production of a building in modular form in a factory environment, transporting the modules to site and erecting them in position. This has the effect of reducing the on-site time required in the buildings construction which can have cost benefits to the contractor. 

Prefabrication and off-site production is looked at in Chapter 8 of Barry’s Advanced Construction of Buildings. 

The Off-site Construction website below looks at the process and advantages relating to this method of construction.  Advantages  A number of advantages relate to this form of construction can be given, these include:
  • Speed
  • Less Wastage
  • Better Quality Control
It also has the advantage of being able to enable the skills specific to the part of the project to be brought in with the components utilising the advantages of specialisation. More details can be found by visiting the Advantages of off-site construction web link below.



  • Emmitt, S & Gorse, C (2006) Barry’s Advanced Construction of Buildings, Blackwell Publishing; Oxford (Chapter 8) 

Self-Assessment Task

  • Compare the advantages of using off-site construction with that of on-site methods in relation to the supply management of a contract.

Site Map