Level 2 Survey question about roof membrane

Pat38493

We had a level 2 survey on a property and one of the comments is 

The roof is lined with a proprietary plastic membrane beneath the tiles. This is a modern replacement fortraditional roofing felt, with greater life expectancy and superior performance. The product is a semi-permeable membrane and, if correctly used, can negate the need for the provision of physical vents to theroof space. It is not possible within the remit of this report to positively determine that such a use has beenachieved here. Your Legal Adviser should seek relevant local authority certification in respect of the use ofthis material.

 Is this the famous issue where the roof is lined with stuff which makes the property unmortgagable later on or something different?  I don't think so but I just want to check.  I think the issue I am thinking about is some kind of spray foam insulation?

Tracet74

No, you're thinking of spray foam insulation is the one lenders don't like.

user1977

And I doubt both that your legal advisor will have a clue or that local authority certification (on this specific point) would have been required.