Doug, according to Barratt's regional office in the Midlands, they stopped using bitumen coverings, and confirmed that it certainly would not have been used in a property built only 5 years ago. So, being the nosey so-and-so that I am, I've just been and dug my land registry stuff out about the house.
Looking back, I can see that the house was repossed (Jan 08, we purchased it May 08, knowing that it would need some work, and got it for 10k under asking price), the previous owner by the looks of it had rented it from new, but digging further back, it looks like Barratts originally sold the house to a local construction company before selling it on to the owner who had it repossessed!
So that's got me thinking that maybe Barratts sold it to the local company before completing the build, and hence me now having to contend with building materials that haven't been used in the industry for a long while.
I'm going to see if the local construction company is still in existence and see whether they were responsible for laying the bitumen covering.
And when I can figure out how to get photo's from my camera phone to download to my pc, I'll upload some pics of this black bitumen stuff for all to see..... :joker: