Constraints on construction projects
A constraint is a condition, agency or force that impedes progress towards an objective or goal.
Constraints should be identified, and described in as much detail as possible during the early stages of a project, so that awareness of them and their potential impact can be managed. This includes understanding the dynamics of the project, and how different constraints interrelate.
There are a number of different types of constraint that can affect construction projects.
 Design constraints
Design constraints are factors that limit the range of potential design solutions. In the early stage of a project only some of these constraints may be known, while others become apparent as the design progresses.
These could include (among many others):
- Available technology, plant, materials, labour and so on.
- The budget.
- Specific performance requirements.
- Site form, boundaries and conditions.
- Neighbouring properties.
- Planning and building regulations restrictions.
- Completion date.
It is often argued that design constraints are helpful in the development of a design, as they limit the number of feasible options and point towards an obvious solution. In the absence of an constraints at all, it can be difficult to know where to start, or to justify developing one particular solution in preference to any others.
 Technical constraints
Technical constraints generally refer to the processes involved in completing construction activities, and are often based on the practicality of building methods and standards. For example, in constructing a foundation, the site must be leveled before excavation can take place; then formwork can be placed as well as rebar before concrete is poured. Each task must be completed before the next can begin; therefore each task acts as a constraint on the next task.
 Economic constraints
Economic constraints relate to the project budget and the allocation of resources. If the budget is inadequate, or is allocated inappropriately, then it can have a negative impact on the success of the project in terms of quality, safety, functionality and performance.
Construction projects are generally a balance between time, cost and quality. A change in one will impact on the other two.
Economic constraints relate not just to the overall budget, but also to the cash flow through the supply chain. Clients must have available funds to pay for works as they proceed, and prompt payments must be made through the contractual chain. Cash flow is one of the main causes of bankruptcy in the construction industry, and having to find new contractors, subcontractors or suppliers part way through a project can cause very significant delays and additional costs.
 Management constraints
These can include particular shift patterns, overtime requirements, resource allocation, safety procedures, working practices, and so on.
 Legal constraints
Legal constraints refer to the many regulations that the activities and practices on a construction project must conform to. These most commonly relate to employment law, safety requirements, planning and building regulations requirements, environmental requirements, and so on.
Failure to conform to legal constraints can have a considerable negative impact on a project, both in terms of delay, financial penalties and possible criminal proceedings.
See Construction industry legislation and standards for more information.
 Time constraints
Constraints can specify the earliest date on which a task should be completed (‘no earlier than’); the date by which a task should be completed (‘no later than’); and the exact date on which a task must be completed (‘on this date’).
Phased projects may include multiple start and completion dates, with penalties if dates are missed.
 Environmental constraints
Environmental constraints include limiting factors concerning geographical location, geological features, hazardous materials, air pollution, excavation, noise, vibration, traffic, tree and wildlife preservation, and so on. These can often overlap with legal constraints.
 Social constraints
Social constraints include factors that may arise as a result of wider interest in or opposition to a project. Public concern and media pressure can often impose greater scrutiny and tighter constraints on a project, and can sometimes result in major alterations to the original plans.
These kinds of constraints on the part of the public are often labelled as ‘not in my backyard’, or ‘nimbyism’.
Projects funded using public money are often subject to social constraints, as there tends to be greater interest in cost escalations, delays and so on, such as in the case of high speed 2 (HS2), or London’s Garden Bridge proposal which have caused much controversy.
 Third parties
Not every aspect of a project is within the direct control of the client or their project team. Every project is dependent to some extent on third parties. It is important that these third party dependencies are identified and that their potential impacts are understood, quantified and managed.
Third party dependencies may include; central and local government, dependent projects, unions, statutory authorities, statutory undertakers, archaeological or other surveyors, the supply market and so on.
See Third party dependencies for more information.
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