bay window felt

Doesn't sound too far off. How many layers of felt and what's this "cover"?

Have you considered lead? My bays are about that size and they were releaded about 10 years ago and I would expect another couple of decades at least. It will cost more and you need a lead capble peson, not a random builder, but it's worth it IMO.

The cover is some sort of reflective layer that stops cracking in hot weather

Lead has gone up apparently. Over double the price of the felt.

Okay now. Found a comparison site with quotes for similar work

I'm not sure about larger areas, but lead flashings, gulleys, etc should last around 70 years. The limit on life is the number of expansions/contractions due to temperature changes, and how well the lead was laid/dressed to allow for that without becoming stressed or falling out of the brickwork.

Another limit on life is how accessible it is to be stolen.

Absolutely.

Not worth it IMHO Do it once and do it properly Lead is the only material to use on a bay flat roof

Yes. If you do go for felt though, the day's diy would save you over =A3200 of that.

White paint, silver paint or white stone will all reflect the sun's heat.

NT

If it's in a secure enough place why not consider copper. You'll only do it once in a lifetime.

Copper is just as good. Remember the correct felt below to deaden the sound of rain. Might be harder to find a suitable plumber.

Next time my dormer felt goes, I may consider copper. Lead will impose too much load.

These days its probably wise to bitumen paint it afterwards so its not obvious

NT

Since we have lead & copper, it seems odd to leave out Zinc :-)

Much shorter life, but less likely to raided by pikeys.

Have you thought about GRP? There are a number of companies out there who will do it for you but you can DIY as well.

Mike

and aluminium

NT