Considering Construction Buildability In CDM Design

As a construction designer, your exposure to health and safety risks is limited. While you may spend some time out on construction sites, most of your work is probably office-based. So health and safety issues during construction mostly fall on to the contractor, don't they? Well, actually, there are a few things that you can do to improve safety on the site without being there. In fact, it's your legal duty to do so. And it all comes down to your design.

Buildability and CDM

Buildability is a term that refers to the ability to build, and under CDM, the ability to build safely. While you won't find the word in the regulations, the need for designers to consider buildability refers to Regulation 9 (2) duties of designers within the Construction (Design and Management) Regulations 2015 (often referred to as the CDM Regulations). This regulation requires designers to avoid foreseeable risks to the health and safety of any person carrying out construction work, or who is involved in using, cleaning or maintaining the structure.

2. When preparing or modifying a design the designer must take into account the general principles of prevention and any pre-construction information to eliminate, so far as is reasonably practicable, foreseeable risks to the health or safety of any person—
   1. carrying out or liable to be affected by construction work;
   2. maintaining or cleaning a structure; or
   3. using a structure designed as a workplace.

Therefore, legally, you must consider the health and safety of the people who will be building your design. You also need to consider those who will be maintaining, cleaning and using the structure, but for now, let's stay focused on buildability.

When a designer is asked for or required to provide information about buildability from a CDM point of view, they need to consider how the design will be built on-site and any hazards or risks that may arise during construction.

Find out more about designer duties under CDM in our free CDM guide for designers.

Considering buildability

So how should you start? Well, this may seem obvious, but you should start at the start. As in, when you start designing.

Because designers have a duty to eliminate foreseeable risks to those who are going to be carrying out the construction work, we know that buildability needs to be a consideration when the designs are being prepared. It shouldn't be an add on. It shouldn't be that after your design is completed you think "OK, now let's look at buildability". Because what would be the point in that? It's too late to develop your design with safety in mind when the design work is complete.

In general terms you can ask yourself:

• How will the design become reality?
• How will the structure be built and maintained?

And during the design process, this should lead to more specific questions like:

• How will that steel beam be fitted?
• How will that 20-foot horizontal glazed screen be installed and cleaned for handover?
• How will the prefabricated cladding get on to the site through narrow access?

Not sure what risks you should assess in your design? Let the A-Z Of CDM Design Risk Assessment For Architects give you some ideas!

Involving other people

You might not have all the answers yourself, and that's OK. CDM is all about cooperation and coordination between the duty holders. That's you, other designers, and contractors.

During the design stage, the early involvement of the project team is encouraged under CDM. That includes the principal designer, principal contractor, contractors and indeed the client. Input from others helps with discussions on buildability, usability and maintainability of the finished structure. Other designers might have come across similar issues before. And contractors are the ones who will be planning how to put everything together.

Early involvement of the contractor may not always be practical given that in traditional tendering, the design is usually completed before selecting a successful contractor. However, the CDM Regulations place a specific duty on clients to appoint a principal contractor "as soon as is practicable, and, in any event, before the construction phase begins".

The early appointment of a principal contractor by the client will allow their construction expertise to be used from the earliest stages of designing and planning a project.

It can be argued that appointing a contractor early in the design process can lead to inflated costs due to variations from the tender quotation. After all, if the planning is not yet complete, how can an accurate price estimate be prepared?

However, the opposite can also be true. As contractors have more practical on-site experience, they can often provide additional expertise to assist the design process. This input can lead to lower costs during construction and reduce unnecessary delays by reducing the risk of problems with the buildability of certain aspects of the design.

Contractors are likely to have experience building other similar structures or features and can offer a different viewpoint and on-site knowledge. And rectifying any problems early in the design stage is much less expensive than making changes if issues with the design are found halfway through the construction.

Early involvement of contractors allows any difficulties with the design to be raised early and solutions found before building work commences. Alternatively, if contractors are appointed after the design work is complete, opportunities to improve buildability are missed. When these problems are identified during the build process, it's harder to make changes, resulting in delays and extra costs. Or worse, the buildability issues lead to accidents and injuries during the project. And this still means more costs and delays.

Reducing risks

Ultimately, putting buildability into your design process is all about reducing risk. Reducing risk for the people on your sites by making sure your design is safe, reducing risk for yourself by eliminating future design problems during the construction and reducing risk for your client by helping them avoid unnecessary costs and delays during the build.

Crucially, considering buildability throughout the design stage will help to ensure that any health and safety risks can be minimised or eliminated, where possible, at the design stages.

When designing, a designer must consider the risks people may be exposed to through the course of both constructing a building and using it once it is constructed.

It's never possible to eliminate all risks, and that's not what is expected of you. You don't even need to list every construction hazard, because contractors should be more than aware of those. The focus should be on high or unusual risks. What is different or difficult about your site and your design?

Where risk can be eliminated from your design, that's great. Where it can't be, it should be reduced as low as reasonably practicable (ALARP). Then provide information on any remaining significant risks to other duty holders on the project so that they can take appropriate action.

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