A tenant must not make any alterations or additions, or add fixtures, to a property without the written permission of the owner.
If the tenant causes damage making alterations – even if they have permission – the tenant should notify the owner as soon as possible. The owner may allow the tenant to repair the damage or ask for compensation for reasonable costs of repairing the damage.
At the end of the lease, the tenant is responsible for the removal costs of any unauthorised alterations, additions or added fixtures. A common example is satellite dishes on the roof.