Hi,
If a property is acquired in a dilapidated condition, expenditure incurred in repairing it and putting it into a fit state for letting (including expenditure on decorations) may be inadmissible as a deduction for Profits of a Property Business, see PIM2020.
For Capital Gains purposes, however, such expenditure as cannot be deducted in computing income may be regarded as allowable expenditure under TCGA92/S38 (1)(b).
This is confirmed at:
CG15200 - Expenditure: enhancement expenditure: demolition costs
Thank you.