St Albans, Hertfordshire
Double Storey Extension in St Albans
A double storey extension adds significant space on two levels, making it cost-effective per square metre compared to two separate single storey extensions.
Estimated Cost
£60,000 – £95,000
Based on 40m² at local rates
12–20 weeks typical duration
Planning permission: Usually required
Cost Breakdown for Double Storey Extension
Estimated costs for a typical 40m² double storey project, adjusted for local labour and material rates.
| Category | Low Estimate | High Estimate |
|---|---|---|
| Foundations & Groundworks | £7,200 | £11,400 |
| Structural Walls | £9,000 | £14,250 |
| Roof Structure & Covering | £6,000 | £9,500 |
| Windows & Doors | £4,800 | £7,600 |
| Plumbing & Drainage | £4,800 | £7,600 |
| Electrical Installation | £3,600 | £5,700 |
| Plastering & Rendering | £3,600 | £5,700 |
| Flooring | £3,000 | £4,750 |
| Kitchen/Bathroom Fitting | £6,000 | £9,500 |
| Decoration & Finishing | £3,000 | £4,750 |
| Professional Fees | £6,000 | £9,500 |
| Contingency (10%) | £3,000 | £4,750 |
| Total Estimated Cost | £60,000 | £95,000 |
* Costs are estimates based on regional averages and may vary depending on specification, access, and site conditions. Prices include VAT at 20%.
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