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Bills Of Material In Construction


Bills Of Material In Construction

Bills Of Material In Construction

Good project management in construction is essential in order to have the most efficient utilisation of labour, material, and equipment. It therefore obvious that every construction project regardless of size will need a list of all the different materials required in order to complete the project. This list may be broken up into different phases, especially in the case of larger projects. The exercise of defining a detailed list of all the materials required, avoids many of the common problems of insufficient order quantities, out of stock situations, all leading to project completion delays. Additionally, the list assists with defining the costs of the project. This list of materials is commonly referred to as a Bill of Materials (BOM) and lies at the heart of an Enterprise Resource System in the construction industry.

What is a Bill of Materials (BOM)?

BOM can be defined as a list of all the raw materials, sub-assemblies, intermediate assemblies, sub-components, components, parts and the quantities of materials needed in the construction or manufacture of an end item or project. It is also known as a recipe or materials list. It can additionally define the labour and tools required during the construction process.

BOM’s are hierarchical in nature with the top-level being the item to be constructed. The next level will contain the main sections that make up this end product, often called sub-assemblies. Lower levels contain the materials needed to make these sub-assemblies and so on until the whole BOM contains all the materials need to build the end product. Another way to see this is by seeing each sub-assembly level as being a BOM in itself and it, in turn, may contain another BOM. This type of structure can also be referred to as a modular BOM.

BOM explosion breaks apart an assembly at the highest level down into its individual materials and parts right down to the lowest level. Conversely, a BOM implosion links the individual parts at the lower level to the assembly at the highest level.

There are different types of BOMs. The ones used in the construction industry will usually be a combination of an Engineering Bill of Materials (EBOM) and a Manufacturing Bill of Materials (MBOM).

The EBOM is defined when the end product is designed, usually using technical or engineering drawings.  An MBOM is defined before the commencement of the construction or project.


In the construction and engineering industries, the term Material Take Off (MTO) is used to analyse the technical drawings or engineering designs and define the list of all the materials, their types, and quantities which are required to build an item. This list of required materials for construction is also sometimes referred to as the Material Take Off List (MTOL). The MTOL contains the quantities as well as the types and grades of the materials required and may also include the weights of various materials to be used. The weight provides information on the transport constraints of certain materials. The MTO is often used to define and make the BOM. Often the MTO and BOM are the same things.

Advantages of a BOM

Using a Bill of Materials software solution, especially when it is part of an Enterprise Resource Planning (ERP) system has definite advantages.

  • Estimate Costs. The BOM will pick up costs from the Inventory or Stock Control data making it possible to get an accurate overall estimate of the total cost of the project.
  • Streamlined Purchases. Using the BOM the procurement process for the project can be effectively managed. Materials can be bulk ordered; Supplier Lead Times can be factored in and alternative suppliers or substitute materials can be identified.
  • Schedules. Using a BOM and especially when there are sub-assemblies, schedules can be defined and this information can be used to assist with the ordering process as well as identify what resources (labour and tools) are needed for each part of the construction project.
  • Material Requirements. An accurate BOM  is a critical requirement in the construction industry for Material Requirement Planning (MRP). The MRP will answer the questions; What is needed? How much is needed? When is it needed? Without knowing the answers to these questions, the project will suffer many setbacks and difficulties.
  • Accurate records. The integrated nature of an ERP system means that as stock is received or used, the updating of all the different sections where this information is used is done automatically. So, at any time, the data is real-time and current. There is no duplication of capture.
  • Reduce Delays. Using the MRP which relies on BOM’s, materials can be ordered timeously, thereby reducing the problem of stock shortages. Additionally, resources can be allocated and any shortages can be quickly identified avoiding bottlenecks.
  • Reduce Waste. By efficient management of the supply chain, materials can be effectively used which reduces waste and keeps the cost of the project down.


Imagine trying to make a cake without having a recipe. The recipe provides the ingredients needed along with the quantities required. It also provides instructions on how to combine the ingredients as well as how to combine them and the cooking times and temperatures required. Without a recipe, the cake will almost certainly be a flop.

It, therefore, is fairly obvious that a well thought out and detailed BOM is a vital part of the construction industry. Without it, the project is likely to be incorrectly costed and suffer major stock shortages and delays, to mention just two of the main problems. Having a BOM which is part of an Enterprise Resource Planning software solution is even more advantageous, given that the Bill of Materials links into areas such as Inventory Management and Procurement which helps to integrate the whole project into all the different areas of the company.