where to put trays on chimney?

Hi,

asked some different questions about this chimney earlier however have now decided to get a professional in to do the main chimney flashing.. I do have a question though about the trays - from what I understand my fire supplier has said that the flashing should be sort of the shape of a 'Z' bottom tray just under the bottom of the step flashing, top tray level with the top of the step flashing..

I can see how this would work with an internal chimney mid roof - but don't understand with my external chimney.. surely the bottom tray would have to go through above wall plate height (otherwise there would be lead on the inside wall beneath the plaster?) If it goes above wall plate then it will come through the step flashing about halfway, would have thought this would comprimise the step flashing..?

have done a pic that tries to explain what I mean..

any thoughts welcome.
thanks
Trev

Having been thinking about where I posted this..should it be in the building thread? Seems like a bit of a borderline leadwork/construction question..

cheers

Trev

Its not very clear to me exactly what you're asking! However this may help: http://www.leadsheetassociation.org.uk/html/1405.html except obviously there'd be no flashing on the front, any roofer worth his salt will have no trouble.

sorry, the post was a bit muddled, think I may have left out an essential fact. The chimney is not currently fully built. it is just under soffit height at the moment, the diagram was just to show how it is being built..

The fire suppliers (HETAS) have said that the chimney should have two trays one above and one below any step flashing and I don't see how that can possibly work with this chimney.. I guess the question is do you have to have two trays within the fabric of the chimney?

The lead sheet association page doesn't seem to show any so am a little confused..

Details of trays shown here http://www.zurich.co.uk/NR/rdonlyres/733D6B7F-F137-47D9-A3C4-5B42E59C1DC5/0/Chimneys111284A02.pdf