Slate roof - Tile roof.. acceptable method of joining?

Here is the problem....
Semi detached house, both properties sharing he same type of slate roof.
One house now has had their roof re-done. New battens, felt and the original slates replaced with tiles.
Now the problems is.. how should the two different roofing areas meet? From the ground view it appears that the original slates are at a lower level than the tiles, but instead of the tiles overlapping the slates, the opposite has taken place.
The slates have now been prised up to go over the tiles, so the run of slates as they approach the tiles gradually rise up like a ski slope to meet the thicker and higher tiles.
From the ground it is not possible to see what, if anything, has been used to seal the joining. The worry is that the slates have been disturbed, and the original nailing holding slates to old battens have been weakened.
Looking at other properties with similar different roofing material there seems to be a variety of joing styles... but none that looks like the roof we have.
What is best practise in a situation like this?
Thanks
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Set fire to your neighbours house and insist that the insurance company replaces the roof with a proper slate one. ;-)
I appreciate that it's a bit "iffy" trying to burn just half of a semi.
Just out of interest, were you consulted? I'd be furious if I lived in a semi and and my neighbour did this. Roofs that were designed for slates just don't look right with tiles. Spoils the whole look of the house IMO. I take it that there are no local planning restrictions that could have been applied to prevent this?
Whatever the rights and wrongs of changing the roof covering I would think that the onus for ensuring a watertight join lies with your neighbour. I would look for similar properties in the same situation as yours and see what's been done there. If you're not happy, it might be worth getting in touch with your local building control officer.
Tim
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Second last question in is FAQ may be helpful.
http://www.sandtoft.com/technical-support/design-advice/faq/?FAQCat=General&subimt=Go
Tim
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On Thu, 18 Jul 2013 13:13:27 +0100, Tim+

Tim.. Does the local building inspector have a remit to inspect and allow (or not allow) roofing jobs, as in the example above?
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On Saturday 20 July 2013 10:20 alo wrote in uk.d-i-y:

Absolutely he does.
On 2 counts at least:
1) Structure;
2) Thermal element if any insulation owrk is being done.
Reroofing is as far as I know, notifiable work.
You'd probably get away with not bothering if it were a like for like, but if the covering materials is being changed, it should be notified.
I changed mine from plain to interlocking tiles. However, I was able to demonstrate that the loading was reduced by doing so, so he was happy.
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On 18/07/2013 12:33 PM, alo wrote:

Jeez, that will look ugly. The cleanest looking and most effective method is a concealed bonding gutter.
http://www.hambleside-danelaw.co.uk/roofing-ventilation/products/bonding-gutters/bonding-gutter-hdlbg.php
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On 18/07/2013 12:33, alo wrote:

My roofer used a hidden gutter. It runs under my tiles and under the neighbour's slates. The slates have straight edge, the tiles have a straight edge with a one inch gap between the two
<http://www.hambleside-danelaw.co.uk/roofing-ventilation/products/bonding-gutters/bonding-gutter-hdlbg.php
http://tinyurl.com/nrm9rnd
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On Thu, 18 Jul 2013 12:33:40 +0100, alo wrote:

What you describe really does sound like a bodge of the first order. Also along the bodge lines did they strengthen the roof at all or just replace the battens and sarking? Tiles weigh considerably more than slates per unit area...
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