If you are determined to secure the pipe to run across the flat roof, then how about securing it with something like EverBuild Stixall, exterior grade?
Bond and seal virtually everything to anything with Stixall Extreme Power adhesive and sealant. The high strength glue is a versatile nail replacement solution with hybrid PMS polymer technology, and it's specifically designed to stick together most common construction materials. From jointing...
www.toolstation.com
You could just stick the brackets, not the whole run of pipe.
Can any roofers/builders comment on this method?
Felt is there to hide leaks for a small number of years.
WTF? What do you consider a small number of years?
Water does not kill flat roofing felt - full stop. Felt is designed to last decades. Your post makes zero sense.
Also, in context with the OP's post, i.e. he's bothered about the gutter running on to it - makes even less sense. It will do zero harm in terms of durability of the felt.
You certainly didn't attend the lesson on diplomacy in school, did you?
I asked for any roofers/builders to comment on my suggestion.
I certainly don't think it deserves an insulting sarcastic reply.
Saying something along the lines of, "Not a bad idea but Stixall won't adhere to a felt roof".
You may find people will respond more favourably to your replies if you don't post such aggressive, 'I know everything' answers.
It's people with that kind of egotistical attitude that contribute to arguments and name calling to develop.
Out of curiosity, are you a builder/roofer or just a diy'er?
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