Principal designer
Does a loft conversion need a CDM principal designer?
Short answer
Almost always yes. A loft conversion normally involves several contractors, often sequentially: the main builder, a structural steel supplier and installer, a roofer for the dormer, an electrician, and a plasterer. That is more than one contractor, so regulation 5 of CDM 2015 requires the client to appoint a principal designer and a principal contractor in writing before work starts.
Why loft conversions are worth coordinating properly
Two things make a loft different from a ground floor extension, and both are pre-construction problems rather than site problems.
The roof is already there and people have to work on it. The existing roof covering, its condition, whether the boarding is fragile, how the scaffold reaches it, and what is directly below when a section is opened are all questions best answered before somebody is standing on it. On an older house the roof may also carry materials worth knowing about before they are disturbed.
The structure is being cut into while the house stands up. Purlins, rafters and ceiling joists are doing a job. New steels go in to take over that job, and the order in which that happens is a design decision with consequences on site. It belongs in the information the builder gets, not in a phone call on the morning.
What the information pack usually covers on a loft
- The roof construction, its condition and its age, and whether any survey exists.
- The asbestos position for a house of the relevant age, including artex, insulating board and cement sheet in likely locations.
- What is loadbearing, what is being removed or altered, and the propping and sequencing the engineer has specified.
- Occupation: whether the family is living in the house while the roof is open, and what sits directly below the work.
- Access for scaffold, materials and waste, and what the scaffold passes over or stands on, including any neighbour's land.
- Services in the roof space: old wiring, tanks, flues and vent pipes.
- The new escape route and the fire strategy, which usually changes the whole stair.
Who holds what
Same as any other domestic project. You make the appointments, in writing. The principal designer coordinates the design risks and gets the information to whoever is building. The principal contractor runs the site and draws up the construction phase plan. If you appoint nobody, regulation 7(2) makes your designer the principal designer and your builder the principal contractor by default, and regulation 7(1) puts your client duties on the builder as well.
What it costs
A loft conversion is priced as an extension, loft conversion or refurbishment of a single dwelling, from £750 plus VAT for the pre-construction service. Price your project.
Sources
- CDM 2015, regulation 5: appointment of the principal designer and the principal contractor legislation.gov.uk
- CDM 2015, regulation 7: application to domestic clients legislation.gov.uk
- CDM 2015, regulation 11: duties of a principal designer legislation.gov.uk
- HSE: domestic clients, roles and responsibilities hse.gov.uk
Find out where your project stands
The free checker asks six questions and tells you whether the appointment is required, and why.
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