Explanation of the professional fees
When planning any building works, you will need to consider professional fees in addition to the building costs. Even if planning permission is not required, you will still need drawings of your loft conversion to be produced for the council, the building regulation officers and for the building teams.
Ensuring the drawings are produced by a professional is always a sensible approach as they minimise the likelihood of miscalculation and incorrect information. Producing and submitting unclear or incorrect requirements and measurements can cause both delays and mistakes that can be very expensive to rectify at a later point.
Whilst loft extensions can often be completed without planning permission, you will still need to file for a Certificate of Lawfulness from your council. This will cost approximately £100.
Fees for filing for the planning permission differ amongst the councils and heavily depend on the amount of work the planning authorities need to process the application. Householder applications, required for extensions and garden buildings, are around £210.
For more information on the planning process and fees across the UK, you can visit the Planning Portal.
For a loft conversion, you will need to produce at least building regulation drawings. For a standard loft conversion, the design fees would be between £1,000 to £2,000.
Furthermore, you will need to budget for structural calculations, such as whether a new beam or other structural alterations are required. The fee for the structural design will range from £900 to £1,800 for a standard loft conversion.
Design and the associated drawings produced for a loft conversion planning application, can cost between £1,000 and £3,500.
Keep in mind that design costs can vary substantially, depending on the architects you appoint and the complexity of the design A cheaper alternative is to appoint a consultant, rather than choosing an architectural practice. Alternatively you can choose to hire a design and build company, who will quote for your loft conversion including the design fees. In some cases, the planning fees will also be included in a design and build quotation.
Party wall fees
If your loft conversion will need building work to a wall that sits astride a boundary you will need Party Wall agreements with all the neighbours that share that party wall with you.
This is very often the case in terraced or semi detached properties, or if you are extending a flat in a block. The typical cost of a party wall agreement depends on whether your neighbours and you will want or need to appoint a party wall surveyor.
Typically, party wall agreements will cost £700 to £1,500 per neighbour.
Keep in mind it is possible to serve the notices yourself without the need to pay for a surveyor if your neighbour agrees on the proposed work, and they don’t appoint a surveyor themselves.
Building control fees
You will need a Building Control certificate at completion, which certifies that all the work is in compliance of building regulations. The average cost for a loft conversion is approximately £750, depending on the size and the nature of the works.
You can liaise directly with the local authority or engage a government-approved inspection company. Both will check that the work is carried out in compliance and will issue the certificate at completion.