A basic house addition calculator to help you manage your finances. According to a Design for Me survey of architects and designers, these estimates have been revised in response to current increases in building prices.
House extension cost calculator
The above calculator uses estimates as a starting point for a house extension. The costs shown above assume basic finishes, fixtures, electricity, and lighting.
According to our current research and survey of architects, the beginning cost per square meter is £2,400 m/2 INC.VAT (or from £2,800 m/2 INC.VAT in London/South East England).
Double storey extension
As a rule of thumb, we have added 50% to the build cost of a single-story expansion.
Kitchen Cost
We budgeted £10,000 for a kitchen (including VAT). This should allow for a basic, average-sized kitchen with basic appliances (from IKEA or similar). You can add more to the amount as needed for your specifications.
Bathroom cost
We budgeted £5,000 for a WC/bathroom (including VAT). Again, this is the beginning price for basic finishes and fixtures.
Large format glazing (including sliding doors/ bifolds)
We have budgeted £2,000 (including VAT) per linear metre for large format glazing. Please keep in mind that this is the beginning price for a good-quality, but basic, system. The expenses of personalized embellishments, thermal enhancements, and extra large panes of glass will rise.
Professional fees
We allotted 15% of the construction expenditures for professional fees.
Are there any complex site constraints?
If any of the following apply, your builder must include additional expenses in their proposal.
- Your soil type and ground conditions may need more expensive construction methods and approaches.
- There is limited access to the website. Will the builder be able to bring in tools and machinery easily?
- Existing structure. Are you eliminating any structural walls? If that’s the case, steelwork will most likely cost more.
- Are you moving any pipes, drainage, or gas meters?
Managing or decreasing project expenses
Before you begin work, obtain three to five estimates from recognized builders (your architect can assist you in compiling a tender list).
Shop around. Designers and constructors frequently benefit from trade discounts.
