How Long Does Building Work Take?
A single garage conversion typically takes 3 to 5 weeks on site, a standard loft conversion 6 to 10 weeks, a single-storey rear extension 10 to 14 weeks and a double-storey or wrap-around extension 16 to 24 weeks. Design, drawings and any planning decision come before that, and we confirm a programme before work starts.
How long does each type of project take?
These are the typical times we plan for. Every house is different, so we set out a detailed programme at proposal stage and confirm it before work starts.
| Work | Typical time |
|---|---|
| Single-storey rear extension | 10 to 14 weeks, foundation to completion |
| Double-storey or wrap-around extension | 16 to 24 weeks |
| Standard loft conversion, whether rooflight, dormer or hip-to-gable | 6 to 10 weeks |
| Mansard loft conversion | 10 to 14 weeks |
| Single garage conversion | 3 to 5 weeks on site |
| Double garage, or a garage conversion with significant structural work | 5 to 8 weeks |
| Room built above an existing garage | 12 to 16 weeks on site |
| Standard bathroom renovation | 2 to 3 weeks |
| Bathroom redesign, moved plumbing, structural work or a new en-suite | 3 to 5 weeks |
| Straightforward kitchen replacement | 2 to 3 weeks |
| Kitchen with structural changes, rewiring, replumbing or new flooring | 4 to 6 weeks |
| Whole-house renovation (refurbishment, internal remodelling and structural work on an existing home) | 4 to 6 months on site. A lighter refurbishment with no structural work can be quicker |
| Whole-house renovation combined with an extension or loft conversion | 6 to 9 months |
| Log cabin | Around 3 to 5 weeks on site |
| Before the build: planning decision on a standard application | 8 to 13 weeks |
| Before the build: Permitted Development prior approval | Around 6 to 8 weeks |
What happens before the build starts?
Design and drawings come first, then whichever approvals the project needs. Four of them shape the start date.
Planning permission. GOV.UK says that in most cases planning applications are decided within 8 weeks, and that in England the time limit is 13 weeks for unusually large or complex applications. The council and the applicant can agree a longer period in writing, which GOV.UK's guidance on determining a planning application explains. We allow 8 to 13 weeks for a decision on a standard application. Many projects need no application at all: our guides to planning permission for home extensions and loft conversions set out when one is needed.
In the year to June 2026 the 13 councils in our comparison of approval rates and decision times decided 62% of householder applications within eight weeks with no extension, and 92% within eight weeks or an extension agreed with the applicant.
Prior approval for a larger rear extension. Under Class A of the permitted development order, the work cannot begin until the council has given its decision, or 42 days have passed since it received the application without one. We allow around 6 to 8 weeks.
Party wall notices. GOV.UK's guide to party walls and building work says you must give notice to your neighbour between 2 months and a year before you plan to start. The government's explanatory booklet gives the detail: at least two months before work to an existing party wall, and at least one month before building a new wall at the boundary or excavating near a neighbour's building. A notice is only valid for a year. Not every project needs one, and it is separate from planning permission and Building Regulations approval.
Building Regulations approval. GOV.UK's guide to building regulations approval says it is different from planning permission and that you might need both. The design and the Building Regulations application come before the build, and the completion certificate comes at the end.
How does weekly billing follow the programme?
We agree the programme with you before work begins. We take a 10% deposit three weeks before the start date, then bill weekly against work that has been completed, inspected and signed off. As the build progresses, we value the completed work each week and walk you through it, so you always know where the project and the budget stand. Our guide to weekly billing explains each step.
Where can I read more about each type of project?
Each service page sets out what the work involves: extensions, loft conversions, garage conversions, new kitchens, bathroom renovations, renovations and log cabins. When you are ready, request a free Cost Proposal and we will set out a programme for your own project.
Sources
- GOV.UK: planning permission, after you apply, checked
- Determining a planning application, GOV.UK guidance, checked
- legislation.gov.uk: General Permitted Development Order 2015, Schedule 2, Part 1, Class A, checked
- GOV.UK: party walls and building work, checked
- GOV.UK: the Party Wall etc. Act 1996, explanatory booklet, checked
- GOV.UK: building regulations approval, checked
Get your free Cost Proposal.
Tell us about your project and we'll arrange a free, no-obligation consultation, followed by a clear, itemised Cost Proposal, usually within 24 hours.
“The attention to detail and absolute financial transparency provided by Grand Innovations completely redefined our expectations of what a home renovation could be. High standard of work, the extension is beautiful and has added so much value onto our home. Really appreciated the weekly billing, rather than a big amount upfront.”