Design Cost

We appreciate that for most people extending their home is a large undertaking fraught with potential problems and expense and that it may be the first time that they have been involved in the planning and construction process.

To help with this, at the start, and as the project develops, we are completely clear about what will be required and the cost. We aim to ensure that there are no surprises or ‘hidden’ extra costs.

Following our first meeting, which is free of charge or obligation, you will receive a detailed quotation giving the cost of each element of the process.

Where there are elements that cannot be costed – for example, structural calculations which may depend on the final design – we will give you an approximate cost following our first visit and a fixed cost as soon as the final design is agreed.

The quotation will also include explanatory notes of cost items that may occur depending on the individual project.

Beware of very low quotes – they may be just ‘Sketch’ views for planning purposes and not have the detail needed for construction and most good builders will not be able to tender for the project.


Permitted Development – Where the project can be completed within the rules for a ‘Permitted Development’ – we would still advise producing a full design and also to submit an application for a Certificate of Lawful Development.

Permitted development still need to be designed to comply with Building Regulations and almost always need structural calculation.


Planning Applications – Full drawings of existing & proposed floor plans, elevations and sections, submitting the application and any amendments called for by planners.

Some applications may also need topographic surveys, ecological surveys, contamination reports, flood risk assessments, tree surveys and protection plans. WE can discuss whether any of these is likely on your project.


Structural Calculations – If the final design includes major changes to the main structural elements then you may need structural Calculations, the cost of these calculations will vary with the size and design of the works. Your quotation will include guidance on this part of the work.


Building Regulations – For some smaller extensions our planning drawings are all that your builder should need.


Full Plans Application – However, we would always advise preparing and submitting detailed drawings and calculations to the Building Inspector for approval before instructing a builder. This service is covered in the 2nd part of the quotation and is a key component of avoiding a difficult build.


During the build the Building Inspector will check the work at key stages and certify the work upon completion.

This is where we agree all the technical aspects of the works with Building Control in advance of you starting the works themselves and ideally before you go to tender.

Party Wall Agreements – We can advise on the need for party wall agreements.

Payments – At the start of each Phase you will pay a deposit. The balance is payable once the Planning Application is ready to submit or the Building Regulations drawings are ready to issue to the Building Inspector.

All charges are on a Pay-as-you-go basis – you are not committed to stages that are not reached.

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