Cost: additional storey
Alterations to the existing building influence the budget alongside the new storey. Separate studies, defined work and provisional allowances. A square-metre rate does not show whether supports, stairs or making good below are included.
Editorial update on 19 September 2026
Separate studies from construction
Identify surveys, investigations, design and procedures. List unresolved decisions and how newly discovered work will be priced. A strengthening allowance is not a fixed price.
Compare the same completion level
Itemise structure, roof work, facade, windows, insulation, stairs, equipment and finishes. State the reference area and making good below. Compare the same room programme rather than only square-metre rates.
Include temporary works
Check scaffolding, lifting, protection, storage, disposal and cleaning. Allocate costs of postponement, extended protection and temporary accommodation. Request taxes, exclusions and the approval process for changes.
The three budget levels
Where your money goes
- StudiesOn quotationExisting building, design and investigations.
- StructureOn quotationStorey, supports and defined alterations.
- EquipmentOn quotationStairs, services and finishes.
- SiteOn quotationProtection and temporary facilities.
What makes the price vary
Existing building
Capacity and condition to assess.
Roof
Assessed retention or alteration.
Access
Stairs and lifting arrangements.
Occupation
Separation and work stages.
Indicative scenarios
Classify work on the existing building and creation of new space before estimating aid. Do not deduct unconfirmed amounts.
Frequently asked questions
Must foundations always be strengthened?
The building and project assessment determines this. Assume neither automatic strengthening nor no work.
Does timber avoid assessment?
No. Material choice does not confirm supports or connections.
Can the current roof remain?
Some projects can retain part of it; assess the construction approach instead of assuming complete removal.
Can we stay at home?
Confirm which stages allow occupation and which need an alternative, considering safe access, protection and available services.
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