oil heating pipe

southcoastrgi

it's primarly there to stop rain going down the flue into the boiler, yes it has to be a certain distance above the tiles but without the make & model of the boiler we can't tell you the correct distance, the builders aren't legally allowed to touch the flue & therefore wouldn't have the knowledge to know that, however that doesn't excuse the fact that they should have got someone in that did know, i suspect they took off the terminal to fit a new lead slate (sealing collar) & didn't re-fit it properly hence the reason it's "blown" off in the wind

Spikey2

Out of interest, roughly how much taller should the flue be?

southcoastrgi

clicky "M" is the measurement you need depending on burner type

Mr_Ted

The figures are minimums so if you were to get a standard 1Mtr length of single skin stainless push fit (not twist fit as yours is push fit) flue pipe of the appropriate size you will be OK.

Fixing needs to either a predesigned clamp/band, or screwed through the joints with self tapping screws!

And personally I would get a replacement flue terminal, preferably one with a bird guard