Most people plan the build and forget everything in front of it. The construction is often the shortest part of a double storey extension, and the months before a single brick is laid are where the real timeline lives. In Esher, with Green Belt and Elmbridge planning to factor in, that front end matters even more.
Here is a realistic stage by stage timeline, and where Esher projects specifically tend to gain or lose weeks.
The Honest Total First
A double storey extension in this area typically takes 9 to 15 months from first meeting to moving back in.
That surprises people who were quoted a build time of a few months. The build itself is real, but it sits at the end of a queue of design, planning, party wall and building regulations work that runs far longer than the construction.
The homeowners who end up frustrated are the ones given a build figure that ignored everything ahead of it. So here is the whole queue.
Stage One: Survey and Design, 4 to 8 Weeks
It starts with a measured survey of the existing house, usually a week or two, because accurate drawings depend on it.
Then the design itself. A double storey extension takes longer to design than a single storey one, because you are resolving two floors, the structural tie into the existing house, and how the new roof meets the old. Expect four to eight weeks to reach a design ready to submit, longer if the brief changes partway through.
This is the stage you control most. Slow decisions here push everything behind them, so agreeing the design promptly is the single biggest thing a homeowner can do to protect the programme.
Stage Two: Planning, 8 to 13 Weeks, Longer in Esher
Double storey extensions almost always need full planning permission. The statutory target is eight weeks from validation, but the reality across England is longer, with applications averaging well beyond target as councils run short staffed.
Esher adds two specific factors. Around three quarters of Surrey is Green Belt, and much of Esher sits within it, which means the application is judged not just on design but on whether the addition is a disproportionate addition over the original dwelling. That assessment takes officer time and often a round of revisions.
Realistically, budget 10 to 14 weeks here, and more if the scheme sits in the Green Belt or draws neighbour objections. A pre application enquiry to Elmbridge before submitting can add a few weeks up front but often saves more later by surfacing the officer’s concerns early.
Stage Three: Party Wall, Running in Parallel, 2 to 3 Months
A double storey extension almost always engages the Party Wall Act 1996, because you are building near or on a boundary and tying into shared structure.
The notice periods are fixed by law. Two months for a new wall on the boundary, one month for work to an existing party wall. If a neighbour dissents, surveyors are appointed and an award prepared, which can add four to eight weeks.
The good news is this runs alongside planning and building regulations rather than after them, so it need not extend the total if you serve notice early. Serving late is a classic self inflicted delay. A neighbour given two months of warning behaves very differently to one handed a notice a fortnight before the digger arrives.
Stage Four: Building Regulations, 4 to 8 Weeks
Separate from planning and about how you build rather than whether you can. On a double storey scheme this stage is heavier, because there is structural design at two levels, foundations, and the connections into the existing house.
Building regulations drawings and the structural calculation pack are produced here, and they can run in parallel with the tail of the planning stage. Four to eight weeks is typical for a two storey scheme with structural alterations.
Stage Five: Construction, 14 to 18 Weeks
Now the visible part. A double storey extension takes roughly 14 to 18 weeks on site, against 10 to 12 for a single storey rear.
The sequence runs groundworks and foundations, then structure and steel, then the first floor and roof, then first fix, plastering, second fix and finishing. A double storey roughly doubles the structural stages compared with a single storey, which is where the extra weeks go.
Two Esher specific cost the programme here. Foundation depth on the clay soils common across the area can run to 1.5 metres or more, and mature trees push it deeper still, so groundworks take longer than on straightforward ground. And scaffolding stands for two to three months on a two storey job, longer than most people expect.
The Timeline at a Glance
| Stage | Typical duration | Runs in parallel? |
| Survey and design | 4 to 8 weeks | No, comes first |
| Planning (Esher, Green Belt) | 10 to 14 weeks | No |
| Party wall | 2 to 3 months | Yes, alongside planning and building regs |
| Building regulations | 4 to 8 weeks | Partly, with late planning |
| Construction | 14 to 18 weeks | No, comes last |
Where Esher Projects Gain Time
The single biggest lever is getting the planning position right before submission, because a refused or revised application can add two to four months.
Extension Architecture handled a project in Weybridge, also under Elmbridge, that sat in both a flood zone and a conservation area, two of the harder constraints to combine. By mapping both up front and answering them in the submission rather than arguing them afterwards, it was approved in around seven weeks. That is well inside the statutory target, on a genuinely difficult site, and it came from front loading the work rather than rushing to submit.
The lesson for any Esher double storey scheme is the same. The weeks are won at the design and planning stage, not on site. Working with architects esher homeowners who know the Elmbridge Green Belt position and the local ground conditions is what keeps the front end of the programme from quietly stretching by months.
The Takeaway
Plan for 9 to 15 months, not for the build time alone. Design and planning are the long poles, party wall runs alongside if you serve early, and construction is a predictable 14 to 18 weeks at the end.
Get the planning right first time and the whole thing holds together. Rush the front end and you pay for it in the middle, when the delays are hardest to recover.