The building itself is only part of the timeline. From the first sketch to moving in, most extensions take several months. This guide breaks down each stage so you can plan realistically.
Timings are typical ranges and can vary with the project, the council and builder availability.
Overview
| Stage | Typical time |
|---|---|
| Brief, budget and initial advice | 1–4 weeks |
| Design and drawings | 4–8 weeks |
| Planning permission (if needed) | About 8 weeks after a valid application |
| Building regulations approval | A few weeks |
| Party wall notices (if needed) | 1–2 months |
| Choosing a builder and contract | 2–6 weeks |
| Construction | 8–12 weeks (small), 3–4 months (medium), 4–6 months (large) |
| Finishing and sign-off | 1–3 weeks |
Some stages run at the same time, but you should assume 4–9 months from first idea to completion for many projects, and longer for large or complex schemes.
Stage by stage
1. Brief and budget
Decide what you need and what you can afford. Our cost guide will help.
2. Design
An architect or designer produces drawings, a structural engineer sizes beams and foundations, and you refine the layout.
3. Approvals
Check whether you need planning permission. Almost every extension needs building regulations approval. If you share a wall, allow for party wall notices.
4. Choose a builder
Get detailed written quotes, check references and insurance, and agree a contract and programme. Good builders are often booked weeks or months ahead.
5. Construction
Typical sequence on site:
- Setting out, excavation and foundations
- Drainage and floor slab
- Walls up to roof level
- Roof, windows and external doors
- First fix: electrics, plumbing, heating
- Plastering, floors and screeds
- Second fix, kitchen or bathroom fitting, decoration
6. Finishing
Snagging, final building control inspection and completion certificate.
What causes delays?
- Planning delays or objections
- Late design changes
- Weather, particularly during groundworks
- Material shortages or long lead times, such as bespoke glazing
- Unexpected discoveries, such as poor ground or hidden structural problems
- Slow decisions on kitchens, tiles and fittings
How to keep to the programme
- Complete design and choose key fittings before starting
- Order long-lead items early
- Agree a written programme and review it regularly
- Make decisions promptly
- Keep a contingency of time as well as money
Plan your timeline with us
Abron Contracting can give you a realistic programme for your project in Newport. Contact us or call 01633379170.
Frequently asked questions
How long does a single-storey extension take to build?
Often about 8–12 weeks on site for a small to medium single-storey extension.
How long does a two-storey extension take?
Typically 3–6 months of construction, depending on size and complexity.
How long does planning permission take?
Councils aim to decide householder applications within about eight weeks, but allow extra time to prepare the application.
When should I start looking for a builder?
As early as possible, ideally while the design is being finalised, because good builders are often booked in advance.
Can I live at home during the build?
In most cases, yes, though you may lose the use of a kitchen or other rooms for a time.
