Process7 min read19 May 2026

Do I Need Building Control Drawings Before I Speak to a Builder?

A builder can talk through the job from photos and a sketch, but Building Control drawings and structural information are what turn an idea into something that can be checked, priced and built properly. Here is what to sort first.

The short answer

You do not always need a full Building Control drawing pack before the first conversation with a builder, but you normally need one before you expect a reliable build price or start work.

Planning drawings and Building Control drawings are not the same thing

Planning drawings show what the project will look like and how it fits the property. Building Control drawings are more technical — they help show how the work should meet the Building Regulations. For a home extension, wall removal, kitchen knock-through or RSJ opening, that can include structure, insulation, ventilation, drainage, fire safety, damp protection and the sequence of work that needs checking.

When a rough builder conversation is enough

At the very start, you can usually speak to a builder or drawing team with basic information: your address, a few photos of the rooms and outside walls, a rough sketch or estate-agent floor plan if you have one, what you want to change, and whether there is already planning permission or any council advice. That is enough to work out whether the idea is broadly sensible and what information is missing. It is not enough for a dependable fixed build price if the work involves structure, Building Control checks, drainage changes, a new roof, insulation upgrades, or a new opening between rooms.

When Building Control drawings should come before builder pricing

You should get the Building Control route clear before relying on builder prices if the project includes any of these: removing a load-bearing wall; installing an RSJ or other steel beam; knocking a kitchen through into another room; building a rear or side extension; changing drainage or adding a new utility, WC or kitchen layout; changing the roof, floor or external walls; altering fire escape routes, stairs or protected areas; asking builders to compare like-for-like prices. Without the technical route, one builder may price a light version of the job and another may allow for steels, temporary works, inspections and making good. The cheaper quote can look better at first and still become more expensive later.

Full Plans vs Building Notice in plain English

For domestic work, Building Control approval is often handled through either a Full Plans application or a Building Notice route. A Full Plans route means drawings and supporting information are checked before work starts. For more involved projects, this can reduce uncertainty because questions about structure, insulation, drainage or fire safety can be dealt with before the builder is on site. A Building Notice route can be lighter upfront, but more details may be resolved as the work happens. For homeowner projects where you are spending serious money, the useful question is not simply which route is allowed, but which route gives the builder, inspector and homeowner enough clarity before the expensive work starts.

What to send first if you are not sure

You do not need to know the answer before asking for help. Send the simplest useful pack: your address and postcode; photos of the room, the outside wall and any roof/drainage areas affected; existing floor plan if you have one; a short note explaining what you want to change; any planning decision notice, council letter, structural notes or previous drawings; what stage you are at — idea, planning, ready for Building Control, or trying to get builder quotes. From there, the next step is usually one of four routes: existing and proposed floor plans first; planning or lawful development check; Building Control drawings and structural engineer input; builder quote pack once the scope is clear.

The mistake to avoid

The common mistake is asking several builders for prices before the drawings and structural route are clear, then choosing the cheapest number. If the builders have not priced the same information, the quotes are not really comparable. For a wall removal, the missing detail might be the beam size, bearing detail, temporary propping and making good. For a kitchen knock-through, it might be electrics, plumbing, ventilation, dust control and floor levels. For an extension, it might be foundations, drainage, roof build-up, insulation and glazing specification. Good drawings do not remove every unknown, but they reduce the number of expensive surprises.

Written by the PlanBuildCo team

9 years designing extensions and renovations in Poole, Dorset.

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