Cost guide
Loft conversion cost: what you actually pay, and why
There is no honest single number for a loft conversion, because the roof you already have decides most of the price before anyone picks up a tool. What we can do is show you the cost drivers in the order they hit the budget, then put a fixed price written quote in front of you after a free site visit.
"We had our loft insulated and boarded. From start to finish the process was smooth, professional and stress-free. Malcolm upgraded the insulation and …"
The one thing that moves the price most
Structure. A rooflight conversion keeps the existing roof line and simply strengthens the floor, so the shell work is modest. A dormer cuts the roof open and builds a new box out of it, which brings steels, a new flat roof, new walls and new windows. A hip to gable rebuilds a whole sloping end of the roof in blockwork or timber before the dormer is even started. Each of those steps is a genuine jump in labour and materials, not a percentage tweak.
The second driver is the staircase. Getting a compliant stair into an existing house is often the hardest design problem in the whole job, and the answer sometimes means moving a bathroom wall or losing part of a landing. We build stairs in our Biddenden workshop, so where a standard flight will not work we can make one that does rather than force the layout around a stock product.
The third is what goes inside. An ensuite means drainage, a pump in most cases, tiling and ventilation. Fitted eaves storage, built in wardrobes and a made to measure balustrade are all workshop items. None of them change the shell price, all of them change the final figure.
How the cost stacks up by conversion type
Relative cost, not a price list. Use it to understand where your project sits before you get a quote.
| Conversion type | Structural work involved | Relative cost |
|---|---|---|
| Rooflight / Velux | Floor strengthening, rooflights, insulation, stair | Lowest |
| Rear dormer | Roof opened, steels, flat roof box, new walls and windows | Moderate |
| L shaped dormer | Two dormer boxes joined over the main roof and the back addition | Higher |
| Hip to gable plus dormer | Sloping end rebuilt as a gable, then a dormer formed | Highest |
Adding an ensuite, bespoke joinery or a structural opening downstairs sits on top of any of these.
What a proper loft conversion quote should include
If a quote does not name these items, you are not comparing like with like.
- Structural engineer's calculations and the steel schedule, not just an allowance
- Building control application and inspections through to completion certificate
- Floor structure, insulation to current standards and fire protection to the stair
- The staircase itself, specified by type, and any alterations needed to fit it
- Roof windows or dormer windows by make and size rather than a generic sum
- Plastering, electrics, heating, decoration and who supplies the sanitaryware
- Scaffolding, waste removal and making good the areas the work passes through
Where loft budgets get blown
Head height found late. If the existing ridge is marginal, the fix is either lowering the ceilings below or raising part of the roof, and both are decisions best made at survey rather than week three. We measure floor to ridge on the first visit and tell you straight away if the numbers are tight.
Drainage for an ensuite. Where the soil stack is on the far side of the house, the run costs more than the shower it serves. Worth designing around early.
Discovering the existing roof is tired. If the tiles are at the end of their life, doing a conversion under them is money spent twice. We say so at the survey and quote both options separately so you can choose.
Fixed price, in writing, before anything starts
We survey for free, then issue a fixed price written quote you can hold us to, with a 5 year workmanship guarantee behind the finished job. Forty years of Kent roofs means the survey catches the surprises before they become variations.
FAQs
Common questions
Why do loft conversion quotes vary so much?
Usually because they cover different work. One may include steels, building control and the staircase while another prices the shell only. Compare the item list, not the total.
Is a loft conversion cheaper than an extension?
Per square metre it usually is, because the roof, walls and foundations already exist. The saving disappears if the roof needs rebuilding or the stair forces changes on the floor below.
Do you charge for the survey and the quote?
No. The site visit is free and the written quote is fixed, so the figure you sign is the figure you pay unless you ask for changes.
What is the most common unexpected cost?
Getting a compliant staircase in. If the obvious position does not work, the fix touches the floor below, and that is a real cost rather than a tidy up.
Does a loft conversion add value?
An extra bedroom, particularly with an ensuite, is generally the strongest return of any conversion type. Local ceiling prices decide how much of that you keep, so check comparable sales in your street before you spend.
Do I pay everything up front?
No. Work is invoiced in stages against progress, and the stages are written into the quote before you commit.
Ready to price your loft conversion cost: what you actually pay, and why in Kent?
Free site visit, fixed-price written quote and a 5 year workmanship guarantee — backed by 40+ years on the tools and our workshop in Biddenden.
"We had our loft insulated and boarded. From start to finish the process was smooth, professional and stress-free. Malcolm upgraded the insulation and …"
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Free site visit, fixed price written quote, 5 year workmanship guarantee.