Building projects tend to fail in the same few ways. For instance, materials are specified without determining load requirements. Contractors are appointed before CDM duty holders. Design approval documents are consulted after the design is completed, rather than before. The guidance presented on this hub aims to provide users with the necessary information required to make better decisions, but it will not prevent the occurrence of poor decisions.
It is vital to understand how different materials respond to different stresses, as well as how those materials respond under the influence of time and fire. Most structural steel design practices in the UK employ BS EN 1993 (Eurocode 3). For refurbishment projects, you may see BS 5950 calculations if that is the design standard of the existing structure. Knowing which standard applies affects your interpretation of load calculations and connection details.
BS EN 1995 (Eurocode 5) design timber frame construction. Moisture content of the timber is a critical factor. If you install green timber with 20% or greater moisture content, that timber will shrink, causing a previously tight connection to become loose. Compared to regular timber, engineered timber products such as CLT and glulam have smaller tolerances and less movement.
Concrete is specified based on exposure and strength, in addition to cover of the reinforcement. One of the most common causes of early carbonation and spalling is cover. In most of the UK’s residential and commercial building projects, the concrete has a strength of either C25/30 or C30/37. Reinforcement of the concrete is designed based on BS EN 1992 (Eurocode 2).
Building Regulations and Compliance
Every construction project in the UK must comply with the Building Regulations. Approved Document A deals with structural safety and Approved Document B deals with fire safety. This includes the requirements for the periods of fire resistance and the requirements for fire compartmentalisation. Approved Document L deals with energy efficiency. The changes to Part L in 2022 introduced even stricter requirements for the energy performance and thermal performance of the building fabric for new building.
Compliance is more than just passing a Building Control inspection. Building Control sign-off will only confirm that the minimum standard has been achieved. There are many buildings that have passed inspection that have underperformed in regards to energy, acoustics, and comfort; and this is the result of the specification of the building meeting said minimum standards with no regard for what would be appropriate.
The CDM 2015 is often misapplied in smaller projects. The construction (design and management) regulations are of course applicable to all construction work. This includes all project sizes. The duty holder structure applicable to single contractor projects is different to that of multiple contractor projects. In multiple contractor projects, the principal designer and principal contractor must be appointed prior to the commencement of work; as opposed to when work has commenced.
Project Delivery and Procurement
The quality of a project’s specification directly correlates to the outcomes of the project. Poor specifications, by default, result in poor and ambiguous tenders, disputes, and delays to contract completion. The specification, the contract, and the inspection arrangements during construction are the most important project documents.
Standard form contracts – JCT, NEC, FIDIC – each have different ways these contracts deal with risk. JCT Minor Works is good for simple projects and has only one contractor. Examples of the NEC Engineering and Construction Contracts are often found in public sector projects and require the contract manager to be proactive and use early warning techniques. One form is not better than the other, but some types of contracts are more appropriate to certain types of projects, and some types of contracts are more appropriate to certain types of client management.
The chosen procurement route has an influence over a projects programme as much as it influences cost. Design and Build relies on the contractor for design and construction and limits control over the design’s specifications, but is useful for clients who don’t want to manage a professional design team. Contracts based on traditional procurement maintain the separation of the professional team, offering the client more control, but requires the client to manage the interface of design and construction.
Procurement of materials also has its own challenges. Commercial projects may face long lead times of 16 to 20 weeks for structural steel and specialist cladding. Late specification for these or other materials may change the structural design and will have significant impacts on the project programme.
Site Safety and Operations
The construction phase plan is a requirement under CDM 2015 and must be in place before the phase commences. While it does not have to be lengthy, it must be specific to that project. Using a generic template fails to identify site specific risks, and so does not fulfill the requirement.
Scaffolding, temporary falsework, and excavation support systems present design challenges and risks for construction project managers. Unlike permanent works, design of temporary works is largely independent. When construction falsework systems fail during a concrete pour, the results can be devastating. Design and construction of temporary works systems is often inadequately supervised.
The greatest risks to construction workers’ health and lives stem from working at height. Consider the Work at Height Regulations 2005. Of most relevance to construction managers and project supervisors is the prescribed hierarchy of control. Of most relevance to construction managers and project supervisors is the prescribed hierarchy of control. First, employers and project supervisors must avoid working at height whenever possible. Where that is not possible, employers and project supervisors must use collective protective measures, and, only then, personal protective equipment. Most working at height injuries stem from unsafe practices and unreasonably unprotected falls, slip, and collapses.