Boiler flue query

[rustywhiskers]

hi need to replace existing 35 yr old floor standing boiler which is in its own cupboard with chimney in kitchen.

Understand we cannot use existing chimney for new flu? or do i have this wrong?

One side of cupboard used to be outside wall but now has conservatory on other side but does have a small flat roof above part of it - can the new boiler be vented vertically up through the flat roof or does it have to be a horizontal exit? thanks

[The Builder]

Rusty, I'd be interested to know why you can't use the existing flue. It could be lined if there was a problem with it.

[johnk]

What kind of boiler are you getting? Most vent throug the wall now

[AlBags]

The old boiler .. oil? .. will have a conventional steel flue and an air intake in the room directly from boiler casing?
I expect the new boiler will be a balanced flue type?
That will need it's own flue .. which can rise vertically through the flat roof (use a weather slate .. actually lead/poly, or a special riser) some here ..http://www.roofinglines.co.uk/product/?s=fl
at-roof-ventsoutlets&s=flat-roof-terminals

The boiler INSTALLERS manual will tell you what flue lengths when hor/vert are allowed .. and how many bends.

[The Builder]

Ah, I see what Al means. You have an old steel fluepipe? When you said chimney, I thought you meant a traditional masonry chimney breast.
Vertically, no problem :o)