A typical extension project in Poole takes between five and nine months from initial design to completion. Construction on site usually takes eight to fourteen weeks for a single storey extension, or up to six months for a double-storey extension, depending on size, planning route, and ground conditions.
Extension Project Timeline at a Glance
The table below summarises typical timescales for each stage of an extension project take in Poole, based on a standard single storey rear extension of around 20 to 30 square metres.
| Project Stage | Typical Duration |
| Design and architectural drawings | 3 to 6 weeks |
| Planning permission (if required) | 8 to 13 weeks |
| Building regulations approval | 4 to 6 weeks (can run alongside planning) |
| Contractor procurement and quotation | 2 to 4 weeks |
| Groundworks and foundations | 1 to 2 weeks |
| Superstructure and roofing | 3 to 5 weeks |
| First fix (plumbing, electrics, carpentry) | 2 to 3 weeks |
| Plastering, second fix and finishing | 3 to 4 weeks |
| Snagging and handover | 1 to 2 weeks |
These figures assume a Permitted Development extension with no major delays. Double storey extensions, wrap-around designs, and projects requiring full planning permission will generally add several weeks to several months to this overall timeline.
Design and Planning — How Long Does This Take?
Design and planning typically take eight to nineteen weeks in total, combining the architectural design phase with the planning permission process where applicable.
Architectural Design Phase
The design phase usually takes three to six weeks. During this time, your architect develops floor plans, elevations, and specifications based on your brief, often going through two or three rounds of revisions before the design is finalised and ready for submission.
Planning Permission Timescale
If your extension requires full planning permission, BCP Council aims to issue a decision within eight weeks of a valid application being submitted, rising to thirteen weeks for larger or more complex schemes. Many single storey rear extensions avoid this step entirely by falling within Permitted Development rights.
Building Regulations Timescale
Building regulations approval typically takes four to six weeks to process and can run alongside your planning application, helping to avoid adding extra time to your overall project timeline.
Contractor Procurement — How Long Does This Take?
Selecting and confirming a building contractor typically takes two to four weeks, covering site visits, detailed quotations, contract agreement, and scheduling your start date. This stage is often underestimated by homeowners eager to get started. Reputable contractors such as Builders in Poole often have a forward booking schedule, so confirming your contractor early — even while planning permission is still being decided — helps avoid unnecessary delays once approvals are in place.
Construction — How Long Does the Build Itself Take?
Construction on site for a standard single storey extension in Poole typically takes eight to fourteen weeks from groundworks to practical completion. Double storey extensions usually take sixteen to twenty-six weeks due to the additional structural work involved.
Groundworks and Foundations: 1 to 2 Weeks
Groundworks involve excavation, drainage installation, and foundation construction. In Poole, where ground conditions vary considerably by location, this stage can occasionally extend if unexpected ground conditions are discovered during excavation.
Superstructure and Roofing: 3 to 5 Weeks
This stage covers the construction of external walls, internal structures, and the roof. Weather conditions can affect this phase more than any other, as roofing work in particular benefits from dry conditions.
First Fix: 2 to 3 Weeks
First fix covers the structural carpentry, plumbing pipework, and electrical cabling that will be concealed within the walls and floors once plastering begins. All installations are tested before being signed off.
Plastering, Second Fix and Finishing: 3 to 4 Weeks
Plastering transforms the shell into finished rooms, followed by second fix works including doors, skirting, kitchen units, and sanitaryware. Decoration and flooring are completed towards the end of this stage.
Snagging and Handover: 1 to 2 Weeks
A final snagging inspection identifies and resolves any outstanding defects before your Completion Certificate is issued and the keys are formally handed over.
What Can Cause Delays to an Extension Project in Poole?
The most common causes of delays are planning objections, poor ground conditions discovered during groundworks, adverse weather during the roofing stage, and late decisions on fixtures, fittings, and finishes by the homeowner.
- Planning permission objections or requests for amended drawings
- Unexpected ground conditions requiring revised foundation design
- Extended periods of poor weather, particularly during roofing
- Late material orders or extended lead times on bespoke items
- Late decisions on kitchen, bathroom, or finishing specifications
- Party wall disputes with neighbouring properties
At Builders in Poole, we build realistic contingency into every project programme and communicate proactively with our clients the moment any potential delay is identified, so there are never any unwelcome surprises.
How to Keep Your Extension Project on Schedule
The single biggest factor in keeping an extension project on schedule is appointing an experienced, well-organised contractor with a realistic programme from day one.
- Confirm your contractor early, even while planning permission is being decided
- Make all fixtures and fittings decisions before construction begins
- Commission a ground investigation survey ahead of foundation design
- Build in a realistic contingency of two to three weeks for weather and unforeseen issues
- Maintain regular communication with your building contractor throughout the project
Why Choose Builders in Poole for Your Extension Project?
Builders in Poole has delivered extension projects of every size and type across Poole and the wider Dorset area, giving us a realistic, experience-based understanding of how long each stage genuinely takes — not just the textbook estimate.
- Realistic, experience-based project programmes from day one
- Free, no-obligation consultations and site assessments
- Full project management from planning to handover
- Transparent, itemised quotations with no hidden costs
- Proven track record across Poole, Bournemouth, Wimborne and Wareham
Conclusion
An extension project in Poole typically takes five to nine months from first design sketch to final handover, with construction itself lasting eight to fourteen weeks for a single storey build. Understanding each stage in advance — and working with an experienced local contractor who plans realistically — is the best way to keep your project on track and stress-free from start to finish.
Frequently Asked Questions (FAQs)
How long does a single storey extension take to build in Poole?
Construction typically takes eight to fourteen weeks on site. Including design and planning, the full process usually takes five to seven months from start to finish.
How long does a double storey extension take in Poole?
Construction on site usually takes sixteen to twenty-six weeks. Including design, planning permission, and contractor procurement, the full project typically spans eight to twelve months.
How long does planning permission take for an extension in Poole?
BCP Council aims to decide standard applications within eight weeks, rising to thirteen weeks for larger or more complex extensions. Many single storey rear extensions avoid this stage under Permitted Development rights.
What is the fastest type of extension to build?
A garage conversion is typically the fastest option, often completed within four to six weeks, since it works within an existing structure rather than requiring new foundations and a new roof.