Conservatory Roof Problem (LONG!)

polybear

I built my own Wickes hardwood lean-to style conservatory about 10 years ago. Originally the roof join to the house was sealed using Lead Flashing, but I quickly found that in bad weather with wind & driving rain that rainwater could be driven up under the flashing and down into the conservatory (even though the lead overlap was quite good). I think it was because the plastic roof sheeting can have a tendency to flex in windy conditions, creating a gap between it and the lead sheet.
To cure the problem I overlaid several layers of self adhesive flashbanding over the joint between lead and plastic roof. It's worked well, lasting nearly 10 years. However, it now needs replacement, and i'm not looking forward to removing it.
Also, beacause the plastic sheeting has a tendency to expand & contract in hot weather, the lead flashing does move back & forth slightly (because it's bonded to the roof with the flashbanding) and in a couple of places there are hairline cracks in the lead.
I can either repeat the technique I used 10 years ago, and seal the cracks using Lead Flashing Sealant (which I've used before & works a treat); alternatively I am thing about adding additional hardwood supports between each of the roof joists. These would be positioned about 12-18 inches away from the wall plate and would provide additional support to the plastic roofing to stop it flexing in windy weather.
I'd also add a wide strip of lead flashing right across the width of the roof, with it's edge tucked underneath the existing flashing. The joint between the two flashing strips would be covered in flashband to secure the new lead flashing in place (or instead maybe use lead flashing sealant as an adhesive). I'd either repair the cracks in the existing flashing or maybe even replace the lot, if I'm feeling really keen.
My idea is that:
1. The extra roof support will stop the roof flexing.
2. The extra width of lead flashing (it could be as wide as 18 inches total, including existing flashing) should stop water getting in.
3. Because the lead flashing is no longer bonded to the plastic sheeting, the roof can expand & contract without the flashing moving with it, so should no longer crack.

Any thoughts/other ideas would be very much appreciated. Thanks.

Polybear.

HugoSP

About 12 years ago I installed a upvc conservatory.

We acually used the flashband first, cutting this into the roof as you would lead, then laid the lead on top.

The lead also has to be laid in 1.5m lengths otherwise it will crack due to heat expansion. Overlap the sections by around 10" and use that sealer you mentioned.

Forget the extra supports etc, the polycarb shouldn't cause you a problem. If you can, use a superior polycarbinate roof, such as 4 or even 5 wall provided it will sit in the rebates in the rafters.

Good luck

polybear

Hi,
Thanks for the reply.
Hadn't thought of this approach. Insofar as the lead is concerned, mine is also in short lengths with overlaps. An approach to consider. Thanks.

Polybear.