Extension Costs

There are three main areas which make up the total cost of building an extension. Planning permission fees, building regulations fees, and my costs for architectural drawings and structural calculations.

If you’re looking to get an accurate quote for the cost of having plans drawn for your extension, you can visit my get a free quote page.

Council fees

The current planning permission fee for all type of extensions, loft conversions, garage conversions and conservatories is £150. New builds and commercial work are £335.

Building Regulations

This fee is split into two. Submission fee and inspection fees. I submit my plans on what is called a “full plans submission” which means they are checked by a council surveyor and approved before the builder starts on site. The current submission fee is £166.

When the work starts on site, inspection fees are payable. These are fixed depending on the size of the extension and vary between £350 and £550.

My Costs

Prices start from £350. All prices are totally fixed and all inclusive so you can add them to the council fees and know how much you need to budget for on top of the building cost. I will visit free of charge, with no obligation whatsoever and give you design advice to get things started. A maximum price for a large extension including all planning permission drawings, building control drawings and structural calculations as well as helping you appoint a reputable builder is £1250.

As a general rule, my fees are about 4% of the cost of your project. Typical fees can easily be between 10 to 15%.

Build Costs

When I visit site I can give you a good idea of the build costs for your project due to to my experience. As soon as the drawings are done you can get firm quotes.


For budgeting purposes, it is safe to work on £1000 per metre squared for a ground floor extension. So a 3m by 5m extension, making a total of 15m2, would be £15,000. This is completely finished with radiator, electrics, plastered and ready to decorate.

The breakdown of fees for this type of extension would be:

Planning permission, if needed – £150.

Building regulations, £166 plus £350.

My fees, £650, all inclusive. This is approximately 4% of the build cost which is £15,000.

Total project cost would be £16,316

If you are thinking about a two storey extension, use £1000 per square metre for the ground floor and £600 per square metre for the first floor.

The fees would increase by about 30% in comparison to a single storey extension.

Plans For Extensions
5 Hendon Street SheffieldSYS13 9AX UK 
 • 07756 495 241
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