Adele
Did you obtain a surveyors report when you bought the house? If so, did the survey reveal any issues?
Your new Insurance policy will exclude any pre-existing damage and it will also exclude any building defects.
You need to contact the vendors who sold the property to you, to obtain the name of the Insurer, the policy number and their contact details.
With details of the previous insurance, then contact your new insurers claims department and see how they will take matters forward. They will usually arrange for a loss adjuster to visit to look into the cause of the damage and if it has been caused by an insured peril e.g. subsidence, they will advise you what needs to be done. If it is subsidence, the claim will be referrred to the previous Insurers in line with the ABI Insurers agreement, which is as follows.
Where the Date of Notification is eight weeks or less from the date of inception of the current Insurer's policy, any claim shall be accepted and dealt with by the previous Insurer and no contribution shall be requested from the current Insurer.
From memory I believe what happens is that if subsidence is the issue and the previous insurers are required to take over the claim, is that you have to take out a policy with the same Insurer used by the vendor. They make a note of the vendors previous insurance on the policy and against the claim record, to explain the situation. Please be aware that for subsidence claims you may be responsible for an excess up to £1000. Also if underpinning is required, you could be in for some inconvenience whilst works are carried out.
If subsidence is not the issue and the building is defective, you will need to get a full survey/ structural engineers report and then look to take action against the surveyor who reported on the property before you bought it. The surveyor will have professional indemnity Insurance that you may be able to claim against. If you have a mortgage, you should also advise the mortgage company, who may also wish to take action.
So in summary you need 1) Contact your new Insurers claims department to advise them of the situation, 2) contact the vendors for details of the previous Insurance on the property, as you may need these.
Huckster