Explanation of the professional fees
When planning any building works, you will need to consider professional fees on top of the building costs. Consider that, 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.
Having the drawings produced by a professional is often a way to save money, as they are a way to put the requirements in writing. Keep in mind that unclear requirements can cause delays and mistakes that can be very expensive to fix after the work is done.
Loft extensions can often be done without planning permission, you will still need to file for a Certificate of Lawfulness from your council (approx fees £100)
Fees for filing for the planning permission vary with the councils and heavily depend on the amount of work the planning authorities need to process the application. Householder applications, needed 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.
On top of this, you will need to budget for structural calculations, if a new beam or other structural alterations are needed. The fee for the structural design would go from £900 to £1,800 for a standard loft conversion.
Any design and drawings produced for a planning application of a loft conversion, if planning permission is needed, can cost between £1,000 and £3,500.
Keep in mind that the design costs vary a lot, according to the architects you appoint and whether the design is straightforward or not. A saving option is to appoint a consultant, rather than choosing an architect practice. A great solution to hire a design and build company, that will quote 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 and 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.
As an average, party wall agreements will cost £700 to £1,500 per neighbour.
Keep in mind that you can serve the notices yourself and won’t 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, that certifies that all the work is in compliance of building regulations. The average cost for a loft conversion is £750 approx, 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 done in compliance and will issue the certificate at completion.