This will depend on many factors, including the size of your roof, the structural changes which may be required, and the degree of complexity of the design. If you need access, and your roof needs strengthening, it is unlikely that you'll spend less than £25k. But it is possible to spend less, and a great deal more! We are very skilled in maximising the return for your budget, and can offer value-engineering or phasing of the work as ways to make your money stretch further.