How long does a house extension take? Thinking of extending your Edinburgh or Midlothian home? A typical house extension project – from design to handing over the keys – often spans several months to a year. In practice, most extensions take roughly 7–15 months from initial concept to completion. This includes every stage: drawing plans, obtaining permissions, and the build itself. Smaller single-storey additions tend to finish faster, while large two-storey or wraparound projects push toward the longer end of that range.
Whether it’s a new kitchen wing or a garden room, every extension has common phases. By understanding each stage and its typical duration, you can plan realistically and avoid surprises. In Scotland, you’ll generally move through these steps: design & planning, permits & approvals, hiring builders, construction, and finally finishing touches. Each phase adds its own time, and factors like size, weather or local planning rules can slow things down (more on that below).
Key Phases of an Extension
- Initial Design & Planning (4–12 weeks): Early on, you’ll work with an architect or designer to create detailed plans. Sketches and drawings typically take a few weeks (often 2–5 weeks), especially if you need revisions. Good architects also advise on whether your project is a permitted development (under Scottish rules, many modest single-storey rear or side extensions don’t need full planning permission). If full planning permission is needed, factor in extra time. In Scotland, finding an architect and finalizing designs can easily use 1–2 months before you submit applications.
- Permits & Approvals (2–4 months): In Scotland, almost all extensions require a Building Warrant (the Scottish term for building regs approval), and many also need Planning Permission. A local council planning decision typically takes 8–12 weeks once plans are submitted. Meanwhile, a Building Warrant application is often assessed within about 20 working days for a first response. (Midlothian Council reports meeting this target on average.) If your extension is permitted development, you can skip planning permission – but you still need a Building Warrant. In conservation areas or for listed buildings common in Edinburgh, additional consents (like listed building consent) can add more time.
- Tendering and Hiring a Builder (2–4 weeks): Once plans are approved, you’ll choose a contractor. Gathering and comparing quotes (“tenders”) usually takes a few weeks. It’s smart to vet builders carefully: check reviews and past projects. Top contractors (like Sawmill Contracts) often manage this step for you, thanks to our in-house trades team. During this phase you may pay deposits and sign contracts.
- Construction Phase (2–6 months): With permissions in hand, on-site work begins. Actual building time varies by project size. For example:
- Foundations & Structure: Site preparation (excavation, foundations) might take 2–4 weeks, then erecting walls, roof, and framing can run 8–12 weeks or more. In good weather, a straightforward single-storey extension can be “topped out” (roof on) in a few months, whereas a two-storey build takes longer.
- Weatherproofing (Lock-Up): Installing windows, external doors and roofing finishes typically takes 1–4 weeks once the shell is up.
- Services & Interior Works: Next come plumbing, electrics, insulation, plastering and plasterboard. This stage can occupy 1–3 months, as all kitchens, bathrooms, and systems are fitted.
- Finishing Touches: Finally, joinery, painting, flooring and cleaning complete the job (often 2–4 weeks).
Building a well-insulated, weather-tight shell is key, especially in Scotland’s climate. Bad weather can delay work (we’ll discuss this below). As Extension Architecture notes, spring and summer are ideal for heavy construction, while winter months often see quieter sites and slower progress.
All told, a simple single-storey rear extension might need about 3–4 months of construction work, whereas a double-storey or wraparound project could take 5–6 months on site. Remember, these build-times exclude the 3–6 months of design, approvals and tendering beforehand. When you add it all up, even a modest rear extension will generally span 6–9 months total, and larger multi-storey builds often approach a year or more.
Factors That Affect Your Schedule
- Project Size & Complexity: Bigger extensions (double-storey, complex shapes) naturally take longer. A simple single-room kitchen extension is much faster than a multi-room addition or one involving major structural changes (like removing load-bearing walls).
- Planning Requirements: If your design requires full planning permission, expect an extra 8–12 weeks for the council decision. Projects under permitted development rights skip this wait, speeding things up. Always check local rules: often rear extensions up to 30% of the house area are permitted in Scotland, but front/side and large two-storey builds usually need permission.
- Structural Challenges: Difficult site conditions or heavy structural work add time. For example, extensive foundations (for basement or big over-structure) or complex steelwork means more planning and longer build time.
- Weather & Season: Scotland’s weather plays a big role. Wet, cold days can halt groundworks and slow masonry. As Extension Architecture points out, rain, snow or frost can delay exterior works. To minimize weather risk, planning to build through the warmer months (spring/summer) is wise.
- Materials & Labor: Global supply issues or high local demand can push timelines out. If key materials (like bricks, windows or kitchen fittings) have long lead times, your builder may wait weeks for them. Similarly, if skilled trades are busy (or taking summer holidays), the project may extend. Good contractors will order early and schedule carefully to avoid this.
- Unforeseen Issues: Hidden problems often emerge once work starts – for example, poor soil, unexpected drainage, or asbestos. Discovering any of these can add significant time, as can mid-build design changes. A flexible budget and timeline buffer are essential.
Tips to Stay on Schedule
- Plan Thoroughly: Clearly define your needs from the start. A detailed plan and budget help prevent last-minute changes (which cause delays). For instance, knowing exactly how you intend to use the new space (dining area, family room, etc.) guides the design and avoids costly tweaks later.
- Work with Experienced Professionals: Hiring qualified architects and builders (preferably under one roof) is crucial. Sawmill Contracts is a design-&-build firm, so our in-house architects and trades coordinate every step. This means fewer handovers and quicker approvals. As building advisors note, good communication and project management greatly speed things up.
- Use Permitted Development if Possible: Where your extension can fit PD rules, this removes a months-long planning step. Talk to us early about PD limits (Scottish law allows fairly generous extensions by rights).
- Choose the Right Season: If you can, start planning in late winter so that construction kicks off in spring. Building in April–October leverages better weather and longer days. This avoids the worst of Scotland’s winter weather pauses.
- Maintain Clear Communication: Keep in touch with your builder (and local authority) weekly. Promptly answer questions and make decisions when asked. This “clear communication” directly contributes to an on-time build.
- Stay Flexible: Factor in a time buffer. Even with the best planning, most experienced builders advise allowing an extra 1–2 months for potential delays. Having realistic expectations (and a patient mindset) keeps the project smooth.
Why Choose Sawmill Contracts?
At Sawmill Contracts, we manage your extension from concept to completion – a one-stop service that keeps everything on track. Here’s what sets us apart:
- 10+ Years’ Award-Winning Experience: Our team brings over a decade of design-and-build expertise to Edinburgh projects. We know local building regs, Scottish weather quirks, and council processes inside-out.
- End-to-End Service: Our skilled in-house team includes architects, builders, plumbers, electricians, joiners and more. We handle everything – from planning drawings to the final paint job – so there’s no finger-pointing or subcontractor bottlenecks.
- Quality Materials & Craftsmanship: We source the best materials at great prices, and our builders take pride in immaculate work. You’ll see it in the superb finishes and the tidiness of our sites.
- Attention to Detail: We focus on the small things that make a home special – perfect joinery, level floors, crisp paintwork. Our process is highly organised (detailed scheduling, regular on-site checks) to uphold our promise of “unmatched quality”.
- Clear Communication & Customer Satisfaction: From day one, we keep you fully informed. You’ll have one dedicated project manager throughout, and we’re punctual and responsive at every step. Our many 5-star reviews attest to homeowners thrilled by our service.
With Sawmill, you gain a partner who knows how extensions should run – efficiently, transparently and with the homeowner’s priorities in mind.
By understanding the timeline and choosing the right team, you’ll get your dream extension on schedule and within budget. If you’re considering an extension in Edinburgh or Midlothian, contact Sawmill Contracts today for a free consultation. We’ll walk you through the process, provide a realistic schedule and quote, and ensure your project is planned down to the last detail. Your home transformation is closer than you think!