Please refer to page 3 under ‘Accommodation details’ in Home Office/UKBA Guide to supporting documents: settlement in the link below. It is called a ‘property inspection report’.

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/270197/sup-docs-settlement.pdf

An immigration inspection accommodation report (i.e. a property inspection report) is THE ONLY document in the UKBA supporting documents information guide which proves to the Entry Clearance Officer that you have ‘Obtain[ed] an independent assessment of the number of rooms and occupants of the proposed accommodation.  A report from a suitably qualified body certifying that a personal inspection has been carried out and giving details of accommodation inspected is usually acceptable for this purpose. Above all, the Entry Clearance officer must be satisfied that the accommodation will not become overcrowded within the definition of the Housing Act 1985 or that it will not contravene public health regulations’.