I live in Westminster Borough and the ceiling of my bathroom fell on my tenants and luckly it did not hurt anyone!   Haus first ignored my emails for 8 days. Then when I complained they told me to deal direct with the flat above me. They wouldn't send anyone to investigate. Then my ceiling fell down. Now I'm complaining why they ignored my emails on the leak. They are ignoring my complaint.  What to do?

Haus have a duty to decide if it is communal or not.  Your question suggests they have without inspection or evidence decided they do not intend to get involved.

Here are 5 reasons why Haus should NOT be ignoring you

1. They hold details of flat above

2. They have duty to tell that flat owner what they need to do

3. You can't make your insurance claim sorted until they or you or someone gets confirmation that the source is resolved

4  you have no rights of entry to the flat above they do

5. They have the ability to recover the insurance policy excess from the flat above, you do not

Alternatively, for 3rd party interventon

- Westminster Council Environmental Health officer  (you can do that online and then send them the reference)

- Health and Safety Executive

If you have the insurance details you can phone up and they will give you a contractor for 'trace and access'  

For longer term resolution 

- Ombudsman

- ARMA

- RICS

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