How Long Does a Home Extension Take?
Most people picture the building work and forget the months of design, warrant and approvals that come before the first brick. Here is the honest, stage-by-stage timeline for a home extension in Aberdeen, from your first survey through to handover.
When clients ask how long an extension takes, they usually mean the part where the builders are on site. That is a fair question, and for a typical home extension the answer is reasonably predictable. The longer, less visible part is everything that happens before that: design, the building warrant, and any planning permission. Add the two together and you get the real timeline, the one worth planning your year around.
Below we break the project into its natural phases and give typical durations for each. None are guarantees. Every home is different, and the moment a builder opens up a foundation, the ground can have its own opinion. What follows is what a straightforward single-storey extension usually looks like in the North East, and where the time tends to go.
- On site: a single-storey extension is typically 12 to 16 weeks of building work. A double-storey usually runs longer.
- Before site: design, the building warrant and any planning permission commonly add several months on top.
- Start to finish: from first survey to handover, plan for the better part of a year for most projects, sometimes less for a simple build, sometimes more.
- The big variables: planning, the building warrant queue, the size and complexity of the build, and the weather.
The two timelines people confuse
It helps to separate the project into two clocks. The first is the build clock, the weeks the team is physically on your property. The second is the paperwork clock, the design, the planning decision if one is needed, and the building warrant. The build clock is the one most people focus on, but the paperwork clock is usually the one that decides which season you actually break ground in.
The good news is that the two can overlap. While design is being finalised and an application is sitting with the council, nothing is being built, but the work is far from idle. Materials with long lead times, such as large sliding doors or steel beams, can be ordered, and a start date can be pencilled in. A good builder uses that waiting period rather than waving it away.
Stage by stage, from enquiry to handover
Here is how a typical extension unfolds. Treat each duration as a guide for a reasonably straightforward project, not a promise. Your extension cost and your timeline are shaped by the same things, so the two guides are worth reading together.
Free survey and brief
It starts with a site visit. We measure up, look at access, drains and the existing structure, and talk through what you want the new space to do. You leave with a clear sense of what is feasible and a written quote to follow. This stage is quick, usually a single visit and a few days to prepare the quote.
Design and drawings
Once you decide to proceed, an architect or technician produces the drawings. Expect to spend a little time here refining the layout so it is right before anything is submitted. The more decisions you settle now, the smoother everything downstream runs. Choosing between a single or double storey extension early keeps this stage tight.
Planning permission, if required
Many extensions fall under permitted development and skip this step entirely. Where a formal application is needed, the council has a statutory target of around eight weeks to decide, though it can take longer if the case is complex or neighbours raise objections. Our guide to extension planning permission explains when you do and do not need it.
Building warrant
In Scotland a structural extension needs a building warrant from Aberdeen City Council or Aberdeenshire Council before work starts. The council reviews the technical drawings against the building standards. Processing time varies with how busy the local authority is and whether they request changes. We prepare and submit the warrant for you and manage any back and forth.
Scheduling and mobilising
With approvals in hand, we confirm a start date, order materials with long lead times, and arrange the trades in sequence. This is where a pencilled-in slot becomes a firm one. Materials such as steels, large glazing units and bespoke joinery are best ordered now so they arrive when the build needs them.
Groundworks and foundations
On site, work begins below ground. Footings are dug, foundations poured and drainage set out. This is the stage most exposed to the weather and to surprises underground, such as an old drain or poor ground, which is why we build a little contingency into the programme rather than promising the impossible.
Structure, roof and weathertight
Walls go up, any steel is installed, and the roof structure is formed and covered. Reaching a weathertight shell is a real milestone, because once the new space is closed in, the weather matters far less and the interior trades can press on regardless of what the North East sky is doing.
First fix, second fix and finishing
Inside, the electrics and plumbing are run, insulation and plasterboard go in, then plastering, joinery, decorating and flooring follow. Any connection into the existing house, knocking through and making good, happens around here. This finishing run is detailed work and is often where a few extra days quietly accumulate.
Inspection, snagging and handover
The council carries out its final inspection and, once satisfied, issues the completion certificate that confirms the work meets the warrant. We walk the space with you, deal with any snags, clean up and hand over. That completion certificate is an important document to keep, particularly when you come to sell.
"The build clock is the part you can see. The paperwork clock is the part that decides which season you break ground."
Typical durations at a glance
Pulling the phases together, here is a rough shape of a project. The on-site figures align with what a typical single-storey extension involves. A double-storey extension generally extends the build phase, because there is more structure, more roof and a second floor to fit out.
| Phase | What happens | Typical duration |
|---|---|---|
| Survey and quote | Site visit, measure up, written quote | About 1 week |
| Design and drawings | Layout, technical drawings, decisions | A few weeks |
| Planning (if needed) | Council decision on a formal application | Around 8 weeks plus |
| Building warrant | Technical approval before work starts | Several weeks |
| Single-storey build on site | Foundations through to handover | 12 to 16 weeks |
| Double-storey build on site | More structure and a second floor | Typically longer |
What affects how long it takes
Two extensions of the same size can land weeks apart. These are the factors that move the needle most.
Whether you need planning permission
This is the single biggest swing. An extension that sits within permitted development can skip straight to the building warrant, while one that needs a formal planning application adds a council decision period on top, commonly around eight weeks and sometimes more. If you are unsure which camp you are in, our permitted development versus planning permission guide is the place to start.
The building warrant queue
Even when planning is not needed, the building warrant is. How quickly it comes back depends on the local authority's workload at the time and on whether your drawings prompt any questions. It is rarely instant. We explain the whole process, including the completion certificate at the end, in building warrants in Scotland explained.
The size and type of extension
A modest single-storey rear extension is quicker than a double-storey or a wraparound that reconfigures half the ground floor. The more structure, the more steel, and the more the new space ties into the existing house, the longer the build runs. If you are weighing the options, the main types of home extension sets out what each one involves.
Specification and decisions
Long-lead items such as bespoke glazing, structural steel and made-to-order joinery need ordering well ahead. Late changes to the layout or finishes are the most common self-inflicted delay. Settling the important choices before the build starts is the simplest way to protect your timeline.
The North East weather
Aberdeen weather earns its reputation, and the early groundworks phase is the part most exposed to it. Heavy rain can hold up digging and concrete, and a hard frost can stop certain work altogether. Once the extension is weathertight, the weather matters far less, so a sensible programme tries to get the shell closed in before the worst of the winter. We build a realistic allowance for this into the schedule rather than pretending the sky will cooperate.
How we keep an extension on track
Delays are usually caused by gaps between stages, not by the building work itself. As a family-run firm with over twenty years' experience, the way we protect your timeline is straightforward and unglamorous:
- We give you a written quote and a realistic programme up front, not an optimistic guess.
- We prepare and submit the building warrant, and any planning application, so nothing stalls waiting for paperwork.
- We order long-lead materials early so the build is not waiting on a delivery.
- We sequence the trades so each one is ready when the last finishes.
- We keep you informed, so a question never becomes a week's delay.
If you are choosing who to work with, the same habits are worth looking for in any firm. Our wider building work across Aberdeen and our new build projects run on exactly this approach. We work throughout the city and the shire, including towns such as Stonehaven, so a site visit is rarely far away.
Want a realistic timeline for your extension?
Book a free survey and we will talk you through the stages, the likely warrant and planning route, and an honest programme for your home. No vague promises and no pressure to go ahead.
On site, a single-storey extension typically takes 12 to 16 weeks from foundations to handover, depending on the size and specification. That figure covers the building work only. Design, the building warrant and any planning permission happen before the build starts and commonly add several months on top.
Counting design, approvals and the build, most extensions take the better part of a year from your first survey to handover. A simple project that falls within permitted development can move faster, while one needing planning permission and a busy warrant queue takes longer. We give a realistic programme at quote stage.
A building warrant is reviewed by Aberdeen City Council or Aberdeenshire Council and typically takes several weeks, depending on how busy the authority is and whether they request changes to the drawings. It is required before structural work starts. We prepare and submit it for you and handle any queries.
Generally yes. A double-storey extension adds more structure, more roof and a second floor to fit out, so the on-site build phase usually runs longer than a single-storey one. The design and approvals stages are broadly similar. We give an indicative programme for your specific project at survey stage.
It can affect the early stages. Groundworks and foundations are the most exposed to heavy rain and frost in the North East. Once the extension is weathertight, the weather matters far less because the interior trades can work inside. A sensible programme aims to get the shell closed in ahead of the worst of the winter.
In most cases yes. Because an extension is built onto the house rather than within the existing rooms, much of the work happens outside the living space until the final connection through to the house. We plan the disruptive stages, such as knocking through, to keep the impact on daily life as short as possible.