Published cost examples
| Conversion | Published figure |
|---|---|
| Rooflight | From £30,000 |
| Dormer | £50,000 |
| Hip-to-gable | £60,000 |
| Mansard | £70,000 |
The Federation of Master Builders guide attributes these examples to member Marken Lofts. Location, complexity and materials affect the price. These are national examples, not Yorkshire quotes. Confirm VAT, scope and current pricing with your builder.
Compare scope before comparing totals
A headline total is difficult to use until you know what it buys. One contractor may price a structural shell; another may include stairs, plastering, decoration and a bathroom. Ask each to price the same written brief. Keep optional work separate so that it cannot quietly become part of the minimum spend.
Shell or finished room: agree the boundary
| Scope described | What to establish in writing |
|---|---|
| Structural shell | Which floor, roof and wall works are included? Is the space weather-tight? Who completes the remaining work? |
| Room ready to decorate | Are stairs, insulation, plastering, doors, heating, electrics and the required approvals included? What remains for you to arrange? |
| Finished bedroom or office | Are decorating, flooring, sockets, lighting and storage included, or only allowed for? |
| Room with a bathroom | Are drainage, ventilation, plumbing, sanitaryware, tiling and installation fully specified? |
These labels are not standard packages. Ask each business to list its inclusions and exclusions rather than relying on the heading alone.
Put both quotes on the same basis
Use one brief and one set of drawings for each business. Keep the base work, optional upgrades and uncertain items separate. An allowance is a budgeting placeholder; ask what happens if the actual cost is different.
- Ask whether the total includes VAT and request the amount payable, not just a net figure.
- Separate surveys, design, applications and inspection fees from construction if they are charged separately.
- Confirm whether work to the landing and rooms below is included.
- Record who supplies each item and who is responsible for installation.
- Ask how changes are authorised and priced before work proceeds.
A lower starting figure may leave more work for you to organise. Compare the whole route to the finished room, using the printable quote checklist.
Comparing local projects
Compare projects with a similar property type, roof alteration, size and finish. Check when the work was priced and whether VAT was included. The national examples above are not a Yorkshire average.
If you already have drawings or a quote, summarise what is included in your enquiry. That gives a proposed builder a clearer starting point.
The budget questions worth asking
- Who pays for drawings, structural calculations and application fees?
- Are scaffolding, waste removal and temporary weather protection included?
- What is allowed for stairs, doors and work to existing rooms?
- Are electrics, heating, plumbing and ventilation specified?
- Are flooring, decorating, sanitaryware and fitted storage included?
- Does the total include VAT, and which items remain provisional?
- What happens financially if opening up reveals additional work?
Allow for unexpected work
Choose a contingency with your designer or builder based on the unknowns in your house and scope. Keep that money separate from optional upgrades. Ask how changes will be described, agreed and priced before the work proceeds.
Use our quote checklist to check what each price includes.
Sources & review
Published by Coalesce Local Ltd. Reviewed 19 September 2026.