Extension plans and drawings across Welwyn Garden City
For Welwyn Garden City homeowners we handle extension plans and drawings, with fees agreed in writing before any work starts.
- Guide price in Welwyn Garden CityFrom £1,250 inc VAT
- PlanningWe find the right route for you
- Timescale2–6 weeks for drawings
- Postcode districtsAL6, AL7, AL8, AL10
Covering Welwyn Garden City
Postcode districts we cover around Welwyn Garden City include AL6, AL7, AL8, AL10. The same team covers Hatfield (3 miles), Hertford (6 miles), St Albans (6 miles), Harpenden (6 miles), all within easy reach.
Just over the Bedfordshire border, Luton is about 10 miles away. The East of England mixes market-town terraces, inter-war semis and modern estates. Clay soils are common in parts of the region, which can affect foundation design.
Do I need planning permission in Welwyn Garden City?
In England the main routes are permitted development (ideally confirmed with a lawful development certificate, £274), larger home extension prior approval (£249, 42 days) and a householder planning application (£548, normally 8 weeks), with council fees as set from 1 April 2026.
Before any drawing is finalised we check whether the house is listed, in a conservation area or subject to an Article 4 direction.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.
Applications are decided by the local planning authority (your district, borough or unitary council).
What it costs in Welwyn Garden City
Guide fees for Welwyn Garden City including VAT, using our East of England factor of ×1.06. Council and building control charges are not included.
| Option | What it covers | Guide price |
|---|---|---|
| Essential | Measured survey and planning drawings | £1,250 – £2,350 |
| Standard | Planning drawings plus building regulations drawings | £2,300 – £4,050 |
| Premium | Full pack with structural calculations and 3D visuals | £3,600 – £5,850 |
Want a range for your exact size? The guide-price tool takes about a minute.
When it helps
- Anyone who wants fixed designs before getting build prices
- Projects that need a planning application or other approval
- Homeowners at the very start of a project
The most expensive changes are the ones made after the steel is ordered. A good design stage settles layout, heights, glazing and services on paper, so the build price is firm.
Our process, step by step
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
We visit your Welwyn Garden City home, measure up, talk through what you want and check the planning position.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
Fixed written price
With the design and specification agreed, you get a fixed written price and a start date.
Build and sign-off
We build it with one project manager, book the building control inspections and hand over the completion certificate.
Questions answered
Will my neighbours in Welwyn Garden City be involved?
If a planning application or prior approval is needed, the council notifies neighbours. If the work is on or near a shared boundary, party wall notices may also be needed.
Do you cover all of Welwyn Garden City?
Yes. We cover Welwyn Garden City and the surrounding parts of Hertfordshire. Site visits are free and there is no obligation.
How long does this take for a Welwyn Garden City home?
2–6 weeks for drawings, depending on the council and the complexity of the project.
Do I need an architect?
Not necessarily. For most extensions an experienced designer or architectural technologist is enough. For listed buildings or complex sites an architect’s input can help.
Can I use your drawings with another builder?
Yes. Once paid for, the drawings are yours to use for your project.
Book a free site visit in Welwyn Garden City
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.