Question 1

How much does a double storey extension cost in High Wycombe?

Accepted Answer

A double storey extension typically costs between £1,200 and £1,900 per square metre. For a typical 40m² extension (20m² per floor), expect to pay between £48,000 and £76,000. The upper floor is cheaper per m² as foundations and roof are already covered.

Question 2

Do I need planning permission for a double storey extension?

Accepted Answer

Yes, double storey extensions almost always require full planning permission. They must not extend beyond the rear wall of the original house by more than 3 metres and must not be closer than 7 metres to the rear boundary.

Question 3

Is a double storey extension better value than single storey?

Accepted Answer

Yes, a double storey extension typically costs 50-70% more than a single storey but gives you twice the floor space. The shared foundations and roof make the upper floor significantly cheaper per square metre.

Question 4

Will I need a party wall agreement for a double storey extension?

Accepted Answer

If your extension is built on or near a shared boundary with a neighbour, you'll likely need a Party Wall Agreement under the Party Wall Act 1996. This typically costs £700-£1,500 per neighbour for surveyor fees.

Question 5

How long does a double storey extension take?

Accepted Answer

A double storey extension typically takes 12-20 weeks to build. Larger projects with complex designs or difficult access can take longer. Factor in additional time for planning approval, which takes 8-13 weeks.

Category	Low Estimate	High Estimate
Foundations & Groundworks	£6,912	£10,944
Structural Walls	£8,640	£13,680
Roof Structure & Covering	£5,760	£9,120
Windows & Doors	£4,608	£7,296
Plumbing & Drainage	£4,608	£7,296
Electrical Installation	£3,456	£5,472
Plastering & Rendering	£3,456	£5,472
Flooring	£2,880	£4,560
Kitchen/Bathroom Fitting	£5,760	£9,120
Decoration & Finishing	£2,880	£4,560
Professional Fees	£5,760	£9,120
Contingency (10%)	£2,880	£4,560
Total Estimated Cost	£57,600	£91,200

Category	Low Estimate	High Estimate
Foundations & Groundworks	£6,912	£10,944
Structural Walls	£8,640	£13,680
Roof Structure & Covering	£5,760	£9,120
Windows & Doors	£4,608	£7,296
Plumbing & Drainage	£4,608	£7,296
Electrical Installation	£3,456	£5,472
Plastering & Rendering	£3,456	£5,472
Flooring	£2,880	£4,560
Kitchen/Bathroom Fitting	£5,760	£9,120
Decoration & Finishing	£2,880	£4,560
Professional Fees	£5,760	£9,120
Contingency (10%)	£2,880	£4,560
Total Estimated Cost	£57,600	£91,200

Double Storey Extension in High Wycombe

Cost Breakdown for Double Storey Extension

Frequently Asked Questions

Get an Accurate Quote for Your Double Storey in High Wycombe

Double Storey Extension Costs in Nearby Cities

Double Storey Extension in High Wycombe

Cost Breakdown for Double Storey Extension

Frequently Asked Questions

Get an Accurate Quote for Your Double Storey in High Wycombe

Double Storey Extension Costs in Nearby Cities