Help -my adjoining neighbour has a shallower roof pitch on his rear extension

19 Feb 2020
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United Kingdom
We are building a single storey rear extension wall next to our neighbour’s single storey rear extension wall.

The neighbour has a pre-finished aluminium capping to their parapet.

We intend to form a pitched roof abutting right up to theirs forming a weathering detail - but this is proving decidedly difficult!

Our roof pitch will not match theirs. Their roof pitch on their glass extension I estimate is 12 degrees and ours on our tiled roof is 15 degrees.

Therefore, the lowest part of our roof at wall plate level does not enable a 150mm cover flashing to be formed between the neighbours extension wall and our roof (we can only get say 60-70mm upstand).

At the highest level at rear original house external wall abutment, there is healthy say 300-400mm difference in levels down to their parapet which would enable a detail to be created (subject to their agreement) dressing on to their parapet.

But the ‘cross over’ space between the two creates a troublesome area difficult to weather properly.

It is not really an option to take off the neighbour’s aluminium capping.

I understand an option is to form my own parapet which would resolve the issue, but I may lose internal floor space.

Any ideas?
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I know it's a pain but could you post a pic of the capping.

Maybe it's possible to speak to the manufacturer of the neighbours roof glazing. It could be possible the capping could be changed for one with a wall upstand. Then you could dress down over the upstand.

Ideally you want yours to be higher all the way, a cross over isn't good.

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