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Our Build

This site exists because of one real build: a 55m2 kitchen extension wrapping the rear and side of an early 1980s detached house in Oxfordshire, project managed by the owner, documented from the first architect sketch to the final certificate. These chapters are that build, told straight: what happened, what it cost, and what went wrong.

The builder quoted £45,500. The construction bill, kitchen excluded, finished at £122,150. Add the kitchen itself at £58,986 and the whole thing came to £181,136. About fifteen of those months were spent with trades on site. Counting back to the first drawings and forward to the day building control signed the job off, the project stayed open for roughly thirty-five months.

None of that was the plan, and that is the reason these chapters exist. Most guidance describes a phase in the abstract, so you reach your own foundations, or your own steel order, with no sense of what normal looks like and no sense of what a warning sign looks like. Reading somebody else's build in sequence is the cheapest way to find out before you commit any money to your own.

Each chapter carries photographs taken on site while the work was happening, the invoices that were actually paid, and the parts that went badly. A steel order nobody had placed. A ridge beam quietly swapped for timber mid-build, caught by the building control officer, and reinstated in steel a week later. A bifold supplier that went into liquidation holding a five-figure deposit, and the credit card claim that recovered it. Those failures cost real time and real money, and they teach more than the weeks when everything went to plan.

The chapters follow the same eight phases as the task tree on this site, in the same order. Read a chapter to see how a phase played out in practice, then work the matching branch of the tree when your own build gets there.

The build, moment by moment

Thirty-five months on one line

1 of 21 · Feb 2021 – Jan 2024
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Planning17 Feb 2021
The architect’s first visit

A brief for a kitchen wrapping the rear and side of the house, and two roofline concepts to choose between.

Read the full story in the Planning chapter

The build, phase by phase

Approved elevation drawings of a detached house seen from four sides, the existing building shown alongside the proposed kitchen extension with dimensions and notes calling out matching brick, brown clay roof tiles and white framed glazing.Planning

Seven months of planning on one Oxfordshire kitchen extension: two rooflines, an eight week planning decision, a full plans building regs application and a column that had to come out.

Read the chapterThe extension footprint sprayed out in yellow line on the ground along the side and rear of a detached house, photographed in low evening light shortly before work began.Pre-Construction

The five months between planning permission and a digger on one Oxfordshire kitchen extension: a £45,500 quote, a 20% deposit, a RIBA contract, utility service quotes and a start date that slipped.

Read the chapterRainwater pooled across a newly poured sub-floor slab, with blue DPC folded up over the first course of blockwork and held down by loose blocks.Groundwork

How groundwork went on one documented Oxfordshire kitchen extension: foundation trenches, tree roots, a public sewer, a build over agreement and a slab that held water.

Read the chapterCantilever steel arrangement at the glazed corner of a rear extension, painted beams carried on a temporary post and scaffolding above new blockwork.Structure

Blockwork, eleven months of steelwork, the roof, and a glazing supplier that went under, on one owner managed kitchen extension.

Read the chapterThe first roof window with its fresh lead apron and side flashings, patination oil newly applied along the top edge, membrane and battens still open around it.The Roof and the Roof Windows

Two rooflights, a drawing that put the lead on my side of the contract, a roofer who could not do it, and four months of leaks on one Oxfordshire kitchen extension.

Read the chapterA living room filled floor to ceiling with the delivered kitchen, tall flat cardboard cabinet packs leaning against the walls and a boxed fridge freezer stacked in front of the patio doors.Specification

Designing and buying the kitchen on one Oxfordshire extension: a designer we did not buy from, £33,250.07 of cabinets supply only, appliances sourced one at a time, and three months of boxes in the lounge.

Read the chapterAn opened wall cavity during first fix, white push-fit plastic elbows joining onto the soldered copper pipework of the original house, with electrical cables running through the timber studs above.First Fix

Wiring, pipes and roof insulation on one Oxfordshire kitchen extension: circuits branched off the old consumer unit, push-fit joined onto original copper, and what both trades cost against quote.

Read the chapterThe completed kitchen extension viewed from the utility room entrance, showing the island, the rear cabinet run and the glazed rear wallSecond Fix

Boarding, screed, plaster, the December kitchen fit and the January tiling on a real Oxfordshire kitchen extension, with the invoices and the mistakes.

Read the chapterThe finished rear of the extension in early December 2022, with the completed patio and newly planted flowerbeds in front of the new bifold doors, and the gutters not yet fitted.Completion

The last year of one Oxfordshire kitchen extension: outstanding trades, the patio and driveway make good, the certificates that held the file open, and the final bill.

Read the chapter

What it all cost

The full ledger, category by category, with the itemised spreadsheet available as a download.

See the real costs

Want the numbers behind this build?

Every invoice from this extension, category by category, in the spreadsheet used to track it. Reuse it for your own budget.

Get the cost ledger

Planning your own extension? The Access Pass covers the same ground as a step-by-step guide you can work through.