Cost: basement conversion
Define two scopes: making the space suitable for its intended use, then fitting it out. Identify assessed, included, provisional and excluded work. Prerequisites should not disappear behind a total square-metre rate.
Editorial update on 19 September 2026
Separate corrective work and fit-out
Distinguish investigations, water management, ventilation changes and structural alterations from partitions, floors and equipment. Avoid double counting shared items. Undefined corrections should remain explicit allowances.
State areas and heights
Request treated areas and finished heights, including beneath services. Compare matching rooms and equipment. Storage, a bathroom and an independent dwelling have different scopes.
Plan operation
For equipment, request commissioning, settings, instructions, maintenance access and stated consumption assumptions. Specify disposal, site access, external repairs, taxes and exclusions. Installation price does not describe all running costs.
The three budget levels
Where your money goes
- AssessmentOn quotationUse, condition and investigations.
- PreparationOn quotationDefined corrective work.
- Fit-outOn quotationDetailed rooms and equipment.
- Follow-upOn quotationChecks and maintenance.
What makes the price vary
Use
Frequency and equipment.
Water
Causes and exposure.
Services
Ventilation and drainage.
Access
Work and future maintenance.
Indicative scenarios
Assume neither general conversion funding nor exclusion from every scheme. Assess potentially eligible work for the case without deducting aid before confirmation.
Frequently asked questions
Is visibly dry enough?
No. Assess the space for future use and necessary investigations rather than one visit alone.
Does a dehumidifier replace ventilation?
No. Define separate functions: removing moisture alone does not renew the air.
Can it become a bedroom?
Confirm feasibility and conditions before buying materials. A cellar window is not approval.
Can a standard duration be given?
Prior investigations and corrections affect it. Request a schedule stating the conditions for starting finishes.
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