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Extension costs


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Householder Planning Fee. (Payable to Local Authority.)


All planning applications require an O/S site plan to be accepted as a valid application. These are often attached to house documents i.e. land registry documents. Your solicitor may have a copy.

They are generally on an A4 sheet and show your property and the houses round about and are at a scale of 1:1250 Householders often find they can obtain them from their central Libraries. We would like to point out that they are copyright to the Ordnance Survey.

If you do not have your own copy of the site plan we have to purchase one from the Local Authority on an average cost basis they charge 25.00 for them though the price varies from department to department.

The Ordnance Survey also has a network of superplan agents where these maps can be purchased for 30.00.

Generally Planning departments require four sets of the proposed plans to be submitted.

How long does a planning application take?

The average time for a Local Authority to process a Planning Application is 8 weeks. We often find that telephone enquiries to Local Authorities will be told six weeks but in fifteen years I am still waiting for the first planning application returned in less than six weeks. I have had several in seven weeks but this is the exception to the rule.

Building Control Fees. ( Payable to Local Authority.)

Local Authorities have been freed to set their own fees for this work so it is essential that you obtain a definitive quote from your own Local Authority. The average and standard fees are quoted below and all figures include VAT.

Find your local Building Control Department http://www.labc-services.co.uk/

Charges for Certain Small Buildings, Extensions and Alterations

Type of Work Plan Charge () Inspection
Charge ()
Erection of a detached building which consists of a garage or carport or both having a floor area not exceeding 40m2 in total and intended to be used in common with an existing building, and which is not an exempt building. 150.00  
Any extension of a dwelling, the total floor area of which does not exceed 10m2 including means of access and work in connection with that extension. 340.00  
Any extension of a dwelling, the total floor area of which exceeds 10m2 but does not exceed 40m2 including means of access and work in connection with that extension. 150.00 £348.00
Any extension of a dwelling, the total floor area of which exceeds 40m2 but does not exceed 60m2, including means of access and work in with connection with that extension. 150.00 £502.00
Any extension of a dwelling consisting of one or more rooms in roof space including means of access. 150.00 £502.00

How long does a Building Regulation submission take?

Generally good. It can take from three weeks to six. There are provisions within the Building Regulations that allow you to commence work before approval, provided you have made contact with the Building Control department at least two working days before you commence Building work.

Other Local Authority Costs.

Apart from the above, the only other cost to check is if a Local Authority formerly owned your house. In this case you should check whether a separate fee is payable to the estates departments.

It is not always the case but in many of these sales there is a clause in the deeds requiring the permission of the above department. In many cases there is a fee involved, generally 70.00 but in all cases even when there is no fee involved the relevant department usually requires a copy of the drawing.

Other Costs.

This is particularly relevant to modern houses and those modern houses constructed by volume builders. It is relevant to both freeholders and leaseholders. There is normally a clause in your deeds requiring that you get permission for any and all alterations to your property from the original developer.

There is normally a fee involved. Despite how much you resent paying this fee always obtain approval before you start building work as it seems to have a habit of inflation afterwards or when you try to sell your property.

I personally regard this charge as a form of theft designed to boost the profits of the volume builders. It merits investigation by the consumer watchdogs.

Take note at this point: The above applies to garages, extensions, porches and conservatories. Sometimes it even applies to fences on open plan estates.

If you do not check this matter you may find out about it when you try to sell your property.

Other Occasional Costs.

Your proposed extension may be over or close to a public sewer. When this is the case a separate Legal Agreement must be entered into prior to obtaining your Building Control Approval from the Local Authority. Charges vary between the water boards.

Public sewers can be difficult to spot but are rarely a problem. Main indicators are very big manhole covers i.e. not standard domestic. Lots of manholes on your site. Drainage shared with several adjacent properties.

Can I find out if my property has a Public sewer?


You can request your Local Water board for information usually by telephone providing your address and postcode. The more officious will tend to ask you to put the request in writing.

A reply in either case should generally take about seven days. Public sewers are quite rare on domestic property.


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