Design and permissions · High risk
Who designs it, and how far do they take it?
Decide whether your designer stops at planning or carries on through construction.
- When it lands
- At appointment, before fees are agreed.
- What it costs to get wrong
- A design that stops at planning leaves gaps a builder fills with assumptions — and assumptions become extras.
Appointing a designer is not one decision. It is two: who draws it, and how far they stay involved once it is being built.
The second half is the one homeowners skip, and it is the half that decides who is looking after your interests on site.
Match the designer to the difficulty
A straightforward rear extension in a permissive area is different work from a listed building, a conservation area, or a structurally complex remodelling. Ask for two comparable finished projects, not a general portfolio, and speak to those clients if you can.
Charm is not evidence. A homeowner appointed on personality rather than a written brief and budget; the scheme came back beautiful and unbuildable for the money, tenders landed 38% over, and the redesign cost both fees and a season.
Decide where their service stops
Some designers take you to planning approval and hand over the drawings. Others produce building regulations and tender information, help you compare quotes, and inspect during construction.
Stopping at planning is legitimate and cheaper — but understand what it means. Planning drawings are not construction information, and nobody independent is checking what gets built against what was agreed.
Get the scope of service in writing
The appointment should list stages, deliverables, what triggers each fee instalment, and what is excluded. Ask specifically whether structural engineering, building regulations drawings, planning fees and site inspections are inside or outside the quoted fee.
Ask for the professional indemnity insurance certificate. It is a routine request; anyone reluctant to provide it has told you something useful.
Why this one matters
Planning drawings are not building drawings. The detail between the two is where most disputes live: junctions, insulation, glazing, structural sizes. Someone has to own it, and if nobody does, you do.
Do this week
- Send your one-page brief and budget ceiling to two or three designers.
- Ask each for two comparable completed projects.
- Request a fee proposal that names the stages and states what is excluded.
The realistic choices
Planning only
Cheapest fee. You will need someone else for technical detail.
Planning plus technical package
The usual sweet spot. Builders can price like for like.
Full service including site stage
Most protection, highest fee. Sensible on larger projects.
What good looks like
- A written appointment listing exactly what is and is not included
- You know who produces structural calculations and who applies for building control
Questions worth asking
- What is excluded from your fee?
- Is this drawing enough for a builder to price accurately?
From real projects
Designed £40,000 over
A homeowner appointed on charm rather than a written brief and budget. The scheme came back beautiful and unbuildable at the budget; tenders were 38% over. Redesign and re-tender added four months and £4,800 in extra fees.
The lesson: Give the designer the ceiling in writing and make 'design to budget' part of the appointment.
Putting it into practice
What this decision should leave behind
The steps to work through, the paperwork worth keeping and the questions to send your builder today.
- · Match the designer to the difficulty
- · Ask for two comparable finished projects
- · Agree the scope of service in writing
- · Template: Designer enquiry and fee request
- · Paperwork: Designer appointment / letter of engagement
- · Paperwork: Fee proposal with stages and deliverables
- · Paperwork: Professional indemnity insurance certificate
Next decision
Planning permission or permitted development?