Most landlords want to maintain the integrity and condition of their buildings and make sure that they are well managed. This preserves and hopefully improves the value of their investments. This can be done by retaining some control over alterations and development. For this purpose most leases contain restrictions regarding alterations. Some alterations (e.g. structural) might be absolutely prohibited while others might be allowed with the landlord’s consent which cannot be withheld unreasonably.
In case building alterations are carried out unlawfully, the landlords can resort to proceedings for an injunction (to remove the alterations), forfeiture, and/or damages. It must be noted that in case a landlord unreasonably refuses consent a tenant does not have a claim in damages, although he may try other remedies which include applying to the court for a declaration that the landlord has withheld consent unreasonably.
Disputes over building alterations are quite common and in many cases avoidable too. They can be prevented by applying for consent or taking advice on the effect of an alterations covenant before (in the case of a tenant) carrying out alterations, or (in the case of a landlord) consenting to or refusing an application.