Which trades does a renovation need, and in what order?

Why do the drawings have to come before you hire anyone?

Because a quote is only meaningful against a defined scope. Ask three builders to price a rear extension from a verbal description and you will get three prices for three different buildings — one has assumed a standard door set, one has allowed for structural glazing, one has not priced the drainage diversion at all. None of them is being dishonest. Each is filling the gaps in the brief with their own assumptions, and from the outside you cannot see which assumptions differ. Put the same measured, dimensioned drawings in front of all three and the prices become comparable for the first time.

The second reason is regulatory. Planning permission and building regulations approval are both decided on drawings, not on conversations, and building control signs off against an approved set. Starting the build before that set exists means either a stop-start programme while approvals catch up, or work that has to be opened up and corrected later. Both outcomes land on the homeowner rather than on the trade that built to an instruction.

There is a third, quieter reason. A drawing set is the only shared reference the trades have. The electrician and the plasterer will rarely be on site in the same week, and the joiner may never meet the plumber at all. What coordinates them is not a conversation but a document — and if that document is a sketch, the coordination happens on site, in argument, at your expense.

Who works on the project before anyone picks up a tool?

Three roles sit ahead of the building work: design, structure, and — where a boundary is involved — party wall. None of them are trades in the site sense. They produce paper, and the paper is what the trades build from and what the council approves.

The architectural designer or technologist produces the measured survey, the existing and proposed drawings, and the technical package for planning and building control. The structural engineer is required whenever a load-bearing wall comes out, a steel goes in, an opening is widened, or new foundations are dug, and issues the calculations building control checks. On a London terrace that covers nearly every meaningful project, because the rear wall almost always comes out.

The party wall surveyor is needed where work affects a shared wall, cuts into it, or excavates within 3 metres of a neighbouring structure — 6 metres for deeper excavations. The Party Wall etc. Act 1996 sets notice periods that run in calendar months: 2 months for work to a party structure, 1 month for excavation and line-of-junction notices. That is why party wall is the item most likely to delay a start date when it is left until the builder is already booked.

Which trades are legally gated, and how do you check?

Most trades in the UK are unregulated. Anyone may call themselves a builder, a carpenter or a tiler, and no qualification is required to do so. A few areas are different, and on these the paperwork is a legal requirement rather than a marketing badge.

Anyone working on gas appliances or pipework must be on the Gas Safe Register, which replaced CORGI as the statutory scheme on 1 April 2009. Fixed electrical work in a dwelling is notifiable under Part P of the Building Regulations, so it should be carried out by an electrician registered with a competent-person scheme such as NICEIC or NAPIT — otherwise the work needs separate inspection by building control before it can be signed off. Party wall surveyors are not statutorily licensed, but a surveyor regulated by RICS or belonging to a recognised party wall faculty is the sensible baseline for a role that can end in an award you are bound by.

Checking takes minutes, and it is worth doing directly rather than accepting a logo on a van. Each scheme publishes a public register; a number that does not appear on it ends the conversation. The same applies to insurance: ask for the public liability certificate itself, check it is current, and check the insured name matches the business you are actually contracting with.

Why do the finishing trades matter more than people expect?

Structural work is judged by whether it stands up. Finishing work is judged by eye, every day, for as long as you live in the house. That asymmetry is why the last third of a renovation deserves more attention than it usually gets, and why the trades in it are worth lining up early rather than taking whoever happens to be free in the week they are needed.

Plastering is the clearest case. It sits between first fix and decoration, and the flatness of the wall it produces determines the quality of everything painted onto it. Poor plastering cannot be corrected by a decorator — it shows under raking light for the life of the wall. A dedicated firm such as London Plastering Service covers skimming, rendering and dry lining across London, and the better plasterers are booked weeks ahead, which is exactly why they should be secured while the structure is still going in rather than phoned once the boards are up.

Bathrooms and kitchens are the other place where specialists outperform generalists. A bathroom compresses drainage falls, electrical zones, waterproofing and tiling setting-out into roughly four square metres, and the elements that fail are the ones nobody can see once the room is finished. A specialist renovation firm such as London Renovate handles design, supply and installation of bathrooms and interior finishes as one package, which removes the familiar argument about whether a defect belongs to the fitter or to the supplier. Whoever you appoint, brief them from the drawing rather than from a mood board: the layout has to work with the soil stack before it can look like the picture.

How many quotes should you get, and what should you compare?

Three written quotes per trade, all priced against the same drawings, is the working minimum. Fewer than three and you have no sense of the market rate. More than about five and you are spending your own time for diminishing returns, and trades notice when they are one of eight — the good ones quietly stop responding.

Compare scope before you compare price. A quote well below the others is usually cheaper because something has been left out: the survey, the structural design, the making-good, waste removal, or VAT. Which one it is takes a single question to establish. Compare what happens when things change, too — a fixed price with a named variations process is worth more than a marginally lower price with no mechanism for the inevitable moment the floor comes up and something unexpected is underneath it.