On Thursday, 13 September 2018 22:21:13 UTC+1, Mathew Newton wrote:
On Thursday, 13 September 2018 21:48:21 UTC+1, JimK wrote:

How much of an upstand is there against the "host" wall?

Good question - I haven't (yet) seen how tall the upstand is as it is covered by the lead flashing (which itself looks to be about 150mm and so I know it's less than that).

What are the chances of water building up on your flat roof to
overtop the upstand?

I'd all honesty I'd say there was very little, if any, chance of that happening. There *is* definitely a fall on the roof and whilst there is still a 200kg roof lantern to go on (hence there may be some deflection of the joists) I don't think I'd ever see water running the 'wrong' way. I think by biggest concern is pooling, particularly once the roof gets dirty and weathered, and the increased risk of the membrane failing.

Incidentally, speaking of the membrane, the BBA certificate for its states that 'for the purposes of this certificate flat roofs are defined as those having a minimum finished fall of 1:80' and so I am assuming from this that the approval the certificate assures in terms of regulation compliance could well be not valid if the product has not been installed in accordance with this?

of course


NT