Thanks for your question.
s11 of the landlord and tenant act 1985 states that it is the landlords responsibility to
a) to keep in repair the structure and exterior of the dwelling, including drains, gutters and external pipes,
(b) to keep in repair and proper working order the installations in the dwelling for the supply of water, gas, electricity and for sanitation (including basins, sinks, baths and sanitary conveniences) but not other fixtures, fittings and appliances for making use of the supply of water, gas or electricity, and
(c) to keep in repair and proper working order the installation in the dwelling for space heating and heating water .
If a property is damp as a result of leaking pipes, a damaged roof or wall or an existing damp-proof course which is no longer effective, then the landlord would be responsible to carry out the necessary repairs.
If the damps results in condensation then it is not their responsibility to repair. It does sound as if there is something wrong with the walls because the problem is not limited to the bath room.
I would try a two pronged approach. Contact the environmental health department and state that you have a damp situation and require an emergency inspection. They will send an officer round and either contact the landlord thereafter requesting emergency repairs, possibly by serving an enforcement notice which he will have to comply with (he will face a fine if he does not) OR they will in the worst cases of damp issue a declaration of uninhabitability. Either of these will quicken the landlord in dealing with it.
You should formally write by registered post to the landlord (copying in the agent, or just writing to the agent if you do not have the landlord's address) specifying the disrepair, making a list of the reasonable repair required and ask that he make those repairs within a reasonable time (eg. 14 days). Refer to earlier insufficient repaid works. State that if the landlord does not make the repair within that time you will pay to have the repairs made and will seek to claim the expense from him and are prepared to make an application to court if necessary.
If the landlord does not make the repair you can pay to have it done and then write formally to him requesting the payment of the cost, again within a reasonable time). If he does not pay you can issue a claim for the money yourself through Her Majesty Courts Service's online service: http://www.moneyclaim.gov.uk/. Write to them first asking for the money and stating that you will issue a claim if it is not received.
Its pretty cheap and straightforward to use.
Open a file, send letters by registered post, keep copies of everything for use in any claim you may choose to issue at a later date.
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