Claiming building improvement costs on the sale of a (UK) property

I'm correcting an old tax return in eTax and need to add my UK house sale. I have added purchase price and associated costs (legal fees), added sale price and fees (legal, conveyancing) and everything else including applying for the deductions (family home > 10 years). What I can't find is a place to enter renovation costs. I believe major works can be added to the cost but it doesn't seem right to simply add them to the cost of purchase as they came some time later. I need to add a loft conversion, a new bathroom and a new roof.

Any help appreciated.

Thanks.