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Last edited 20 Sep 2021
Constraints on construction projects
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, as well as being clear about any potential risks and who is responsible for them.
Design constraints are factors that limit the range of potential design solutions that can be adopted. In the early stage of a project only some of these constraints may be known, while others become apparent as the design progresses.
- Available technology, skills, plant, materials, labour and so on.
- The budget.
- Specific performance requirements.
- Site form, boundaries, conditions and neighbouring properties.
- Site access, rights of way, rights to light and so on.
- Local infrastructure.
- Planning and building regulations restrictions.
- Completion date.
- Local climatic conditions.
It is often argued that design constraints are actually 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 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 levelled before excavation can take place; then formwork and reinforcement can be placed 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.
All these constraints will be linked to safety, health, and meeting building regulations and control needs, alongside the clients needs and any architectural aspects. Some will be very small and meaningless to some but can have a huge impact such as a floor covering, with a height of 25mm, which could mean the stairs will not work and you will need a new set of stairs to account for the extra 25mm of floor covering. Or the balustrades, which should have no opening larger than 100mm so a babies head cannot fit through and the client wants to use steel wire with 200mm gap, requiring complete redesign.
 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.
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.
These can include particular shift patterns, overtime requirements, resource allocation between projects, safety procedures, working practices, environmental and social policies, agreements with unions and so on.
 Legal constraints
Legal constraints refer to the many regulations that the activities and practices on a construction project must comply with. These most commonly relate to employment law, safety requirements, planning and building regulations requirements, environmental requirements, and so on.
Complying with legal requirements can be very time consuming and requires a thorough understanding of complex, often bureaucratic procedures. However, failure to comply can have a considerable negative impact on a project, both in terms of delay, financial penalties, remedial works and even possible criminal proceedings.
The 2 big laws are Town and country planning and Building Regulations. Any building must first gain planning permission and meet certain criteria for approval and planners can apply restrictions and ask for improvements to gain permission. With building regulations, we have a set of "Approved Documents" which set out in detail a mix of prescribed and performance standards that the finished building must comply with. When compliance is reached a certificate is issued and the building owner can then get insurance on the building.
 Time constraints
These include key dates on the project schedule or project milestones. Conforming with these dates is generally very important in terms of the overall project completion date, and penalties may be applied for failure to meet agreed dates.
Contracts 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.
Other time constraints may be imposed by third parties, such as; planning permission expiry dates, or the need to start or complete work before changes in legislation come into force (such as changes to the building regulations).
- The use of sustainable or hazardous materials.
- Energy consumption and carbon emissions
- Air, water or ground pollution or contamination.
- Waste and water management.
- Noise, vibration, and dust.
- Traffic and transport.
- Preservation of ecology.
- Resilience to climate change.
- Design for deconstruction and disposal.
 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.
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.
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.
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