england-and-wales
Is it ever illegal to change a lock so as to exclude your landlord access?
<p>Most leases say you can never do it without permission but permission wouldn't be unreasonably withheld but if you ever do it then you absolutely must give LL notification and issue of the new key.</p>
<p>Are these terms valid or overridden by the common law covenant doctrine of exclusive possession? I've read that if you change them back to originals upon leaving then you can never be forbidden as an AST to do that in England.</p>

<p>The common law covenants of &quot;quiet enjoyment&quot; and exclusive possession never excluded access in a <em>bona fide</em> emergency, and a landlord would be entitled, and perhaps <strong>required</strong>, to break a door or window open if needed to gain access in the face of an emergency such as a gas leak, where others are potentially endangered and time is of the essence.</p>
<p>That said, a valid and reasonable contract may specify this as the parties please, unless  <strong>specific</strong> law overrides this. For example a local landlord/tenant law could require that the landlord be given access (such as a key) Aside from such laws, the lease can forbid changing locks, permit it only with permission, or permit it freely (perhaps requiring that the landlord be given a key). Any of those provisions would be lawful in the absence of a specific law to the contrary. The lease could also specify when the landlord is to have access, and how much notice. But a provision denying access in a true emergency is probably not valid.</p>
