How we work
From first visit to completion certificate
Nine stages, in order, with honest timings. Most extension disappointment comes from a programme that was never realistic to begin with.
Written byKaren Whitmore, Client & Project Support Manager
Typical 20 m² build
£40k – £60k · 12 weeks
Glasgow · Scotland
180+
Glasgow extensions delivered
Warrant & completion certificate included
A Glasgow house extension runs through nine stages: site visit, constraints check, design and costing, planning application, building warrant, fixed price, groundworks and structure, weathertight and first fix, then finishes and completion. Total elapsed time is typically nine to fifteen months, of which ten to twenty-six weeks is time on site.
Enquiry and site visit
Week 1–2We visit, measure the property, look at levels, drainage and access, and talk through what the extension needs to achieve. We tell you at this stage if what you want is unlikely to be approved.
Title and constraints check
Week 2–3We check the title position, whether permitted development rights exist, conservation area and listed status, and whether any drainage sits under the proposed footprint.
Design and cost range
Week 3–8Two or three layout options, a structural strategy, and a written cost range with the assumptions stated. You choose a direction before any application is prepared.
Planning application
Month 2–5Where required, we prepare and submit the householder application through ePlanning Scotland, handle officer queries, and keep you updated on neighbour representations.
Building warrant
Month 4–7Technical drawings, structural calculations, thermal calculations and drainage design are submitted to Glasgow City Council building standards. We respond to the first report and secure the grant.
Fixed price and programme
Month 6–8With approvals in hand the design is final, so the price can be fixed properly rather than estimated. We agree a start date, a programme and a payment schedule.
Groundworks and structure
Weeks 1–8 on siteSite set-up, excavation, foundation inspection, drainage, floor slab, walls, steel and roof. This is the stage where hidden conditions surface, and where the contingency exists.
Weathertight and first fix
Weeks 6–12 on siteRoof covering, windows and doors installed, then electrics, plumbing and insulation before boarding. The building becomes dry and the internal programme accelerates.
Finishes and completion
Weeks 10–16 on sitePlaster, joinery, flooring, decoration and kitchen fit. Final inspections are booked, the completion certificate is submitted, and we hand over documentation and warranties.
Timeline
What a realistic programme looks like
| Extension type | Design & approvals | On site | Total |
|---|---|---|---|
| Single-storey rear (permitted development) | 3–4 months | 10–14 weeks | 6–8 months |
| Single-storey rear (full planning) | 5–7 months | 10–16 weeks | 8–11 months |
| Side return | 4–6 months | 10–14 weeks | 7–10 months |
| Wrap-around | 5–7 months | 14–20 weeks | 9–12 months |
| Two-storey | 6–8 months | 16–26 weeks | 11–15 months |
The two things that delay Glasgow extensions most
Slow responses to the building standards first report, and design changes made after the warrant is granted. Both are avoidable, and both are within your control as the client.
Frequently asked questions
How long does a house extension take from start to finish?
Allow nine to fifteen months in total for a Glasgow extension: two to three months for design, three to four months for planning where required, eight to twelve weeks for the building warrant, and ten to twenty-six weeks on site depending on the type.
Can I stay in my house during the build?
Most homeowners stay in the property for a single-storey extension. The kitchen is usually out of use for four to eight weeks near the end, so a temporary kitchen is worth planning for. Two-storey work is more disruptive but is still usually liveable.
When do I pay?
Payment is staged against completed work — typically at foundations, weathertight shell, first fix, and completion. Avoid any arrangement requiring a large payment before materials are on site.
Ready to start at stage one?
Tell us about your property and what you want to gain. We will talk you through the realistic cost, the planning route and the build sequence — no obligation.
