Tiling and insulating a conservatory roof.

I have got my own ideas to insulate a 3x4 metre victorian style conservatory but as to whether in practice it ticks the boxes for been structurally correct is the question.Having already had quotes at around £9000 which is nowhere affordable at this present time, I'm hopeful of cutting the cost but not corners.
My intentions are to keep the materials lightweight so as not to overload the existing structure.
I wish to put in a flat ceiling using angle or T angle aluminuim section as a frame. Clad the underside with upvc hollow section decor panels. Put 300mm depth of fibreglass insulation on the top side. Reason for a flat ceiling is to take away a lot of unnecessary volume of air to heat.
On the roof I would fit treated wood tile battens screwed to the glazing bars. Then cover with waterproof tile undercloak. Fit 4 roof vents to minimise any condensation inside the roof space. Finally fix composite lightweight tiles, ridge tiles and flashing to the adjoining brick wall.
My main concern is the additional weight put on the glazing bars.
Any criticisms or pointers in the right direction would be most appreciated.

The companies offering this service are absolutely milking people. Also be careful lots have issues. I think there are only a few decent systems or methods. A builder or carpenter would probably do much cheaper.

megger said:

Any criticisms or pointers in the right direction would be most appreciated.

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Your methods do not sound at all robust, both in terms of structure and of vapour mitigation.

Your ceiling sounds like it will waft and diaphragm like a slack old tent in the wind, every time you open and close the door. Hollow soffit is awful in long lengths and on flimsy battening. You also need to robustly insulate and VCL or else you risk the membrane dripping like a tap (even if it is breathable) and drenching the quilt.

I don't think a lot of people appreciate how dark everything is going to be, especially without any skylights.
Why don't you use 4x2" timber and construct a normal ceiling.

catlad said:

I don't think a lot of people appreciate how dark everything is going to be, especially without any skylights.
Why don't you use 4x2" timber and construct a normal ceiling.

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What does everything hang off with these hybrid roofs?

Well I don't know
I would almost certainly take the old roof off, fix a wall plate and start from there.

Thank you all for your comments, as they say every little bit helps.
My choice of using plastic soffit panels for ceiling is they are 100% watertight click locked together and finish the edge all round using a finishing trim and mastic. I can also install this without employing a messy plasterer to skim finish plasterboard and be lighter in weight. I will fit an inspection hatch so occasionally I can pop my head up to check it is dry. And by putting air vents through the polycarbonate sheet should allow adequate air flow across the roof space. There will be a 25mm air gap between the outside of the polycarbonate to the underside of the OSB/plywood board to attach the composite tiles to.
My thinking here, is by having a moisture tight ceiling with 300mm of fibreglass insulation laid on it, that any heat or moisture from the room is not going to get through to the underside of the existing polycarbonate roof, and therefore, prevent any chance of condensation forming. Plus having a cool draft across the roof space should keep it dry.
I have since learnt to use 18mm osb/plywood as opposed to tile battens. This is recommended by the supplier of the composite slateskin tile system I will use. As this is then adding more weight onto the glazing bars, instead of using aluminium for the ceiling I will make up 3 timber "A" frames to span the width of the room which will push up under the glazing bars. A timber will be fixed all around the existing ring beam to sit the "A" frames on, and then noggins fixed in so I have a pretty firm ceiling ready to fix the ceiling panels to. Using wood instead of aluminium will be cheaper and easier anyway.
Reason I want to retain the roof is so I can take my time to modify it keeping everything dry because once you remove a roof you then have the big problem of keeping the rain out.
And another thing is this, it is the first time I have realised how much of a waste of money a conservatory is. I might sound a bit harsh but I think a lot of us have been blinkered about exactly what we have put our well earned savings into, in that, it is only when the ambient temperature is comfortable you are allowed to use it. It is actually my son's house he bought last September and if I'd known then I think I would have dissuaded him buying the property.
Again, any additional comments will be helpful to keep me right.

I wonder why you're bothering putting the slates etc on- your major heat gain will be coming from the false ceiling and 300mm of insulation, if you already have skylights in the roof opening them a bit will sort ventilation.
EDIT Have a look at the plastic ceiling options available- designed for bathrooms but would work for your setup on a 2" x 2" frame.

Reasons for the roof tiles are to do away with the ear splitting noise of heavy rain also the noise from a busy road and to protect the roof from water leaks. The conservatory is around 10 year old and the glazing seals are showing signs of cracking where a waterproof tile undercloak and tiles will be a much longer lasting fix.

Fair shout on the waterproofing bit, you'll find the insulation helps a lot with noise reduction. Me being a tightwad i'd be tempted to slather the glaze seals with Acrypol or similar or cover them with flashband...

oldbutnotdead said:

i'd be tempted to slather the glaze seals with Acrypol or similar or cover them with flashband...

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Are we talking about the black rubber gaskets between the frame and glazing? Acrypol or flashband would look sh1t.

pilsbury said:

Are we talking about the black rubber gaskets between the frame and glazing? Acrypol or flashband would look sh1t.

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Very possibly but if cash is tight..and it'll be much cheaper sh1t than some of these reroofs