Looking at the pics again, the twinwall is well siliconed in....suspect lead work!

S

theres a few things wrong with that installation any of which could be the cause...
1) ill bet a weeks wages theres no 'cavity trays' installed...
very few instalations of this type actually bother with them and its unlikely to be the cause BUT when you build any time of 'lean to' beit a flat rofe extension or a conservatory, what was once an external wall becomes an internal wall and any water soaking into the brickwork above may wel permeate own below roofline and manifest itsel as damp on the internal wall... unlikely to be the cause if its running down the wall though..

2) high modulus silicon releases acetic acid on curing and that may well be high modulus silicon... that then causes 'plasticiser migration' and will atac any rubber seal... again unlikely although it shouldnt be up there in the first place, if the system was installed and was working correctly there wouldnt be a need for any silicon sealant, the gaskets should hold it perfectly well...

3) that leadwork is a pretty poor job and more than likely the cause...
there should be no peice of lead longer than 1500mm due to possible failure due to expansion and contraction which would explain the over lap..
however, the overlap should be 200mm minimum (100mm either peice) and clipped together (a nick in the lower edge would do nicely when wrapped into the adjoining peice)... the 'upstand' or 'waterline' should be 65mm minimum (it's near enough looking at it) and the roof lap should be at least 100mm ONTO the roof itself, dressed over the glazing bars preferably stuck down with some lead and guter sealant onto the poly to combat 'wind lift'... ill put my money on this being the cause of the ingress...

4) another point to consider...

I went to inspect a 'box gutter' edwardian (hipped) roof against a facia that was leaking....
the box gutter had been manufactured in two peices butted together in the centre...
upon installation, the centre had become the lowest point...
the joint was sealed with a proprietory insert and seale with silicon which had held perfectly well HOWEVER...
the end caps were missing from the box gutter...
a box gutter is a 'channel' with the bottom of the channel being a hollow box section for lightness and strength...
only the inside of the channel had been sealed...
the rain was blowing into the hollow section on the ends, running towards the joint in the centre and because the inside hadnt been sealed it was leaking through into the cover cap, tracking along to the lowest point of the highly flexible cover cap and coming in near the windows...
the solution? remove the cover cap, drill into the lower edge of the box section to remove the rest of the water (i tried an air gun but i was there a while and it just didnt work)
replace the cover cap...
refit the end caps...
problem solved...

what i would do in this case is.....
remove the glazing bar top caps...
remove the roof sheets...
remove the leadwork....
inspect the gaskets (replace the bottom 'fir tree/retainer' gaskets with glazing tape if need be or new gasket, trust me, it works, and it holds the thing together better too, just pull the tape after the sheets go back in, leave a 2 inch tag pulled)
repoint the wall as needed
renew the leadwork properly using patination oil (itll stay a nice dark grey as the oil allows the lead to develop a protective 'patina' just like aluminium without the weather getting to it first)
refit the roof sheets dressing the lead as you go (cleaning the top caps with cif before reinstallation )

days work...

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Very useful information - Thank you.


I see you only like betting on certainties.

The conservatory was, I suspect a DIY job as the previous owner was in the building trade, so he probably did it with a few mates. Apart from the roof having to be replaced, there is no proper drainage. The gutters empty into a large water butt - which has been a problem in the recent very wet weather.

Thanks for the info about high modulus silicon, I agree it shouldn't be needed if the job was done properly.

The lead work is poor, but that's not the fault of the roof repairer. It was like it when my son moved in. Not sure what you mean by 200mm overlap and then say 100mm per piece. Do you mean this?


Your list of what to do is helpful, but a bit out of our DIY range; so will have to get a quote.

Couple of comments.

The lead is not that bad, it is dressed down over the top bar, which is fine, even if it could be a little longer.

Never ever stick or mastic the edge down as it can encourage capillary attraction.

The overlap as your sketch Dave is the minimum, and the lap should be the opposite to the prevailing wind if that makes sense.

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hear what your saying re sticking the edges scruff but ive had problems with wind lift before today, especially in exposed areas and i dont know of any other method of holding down the front edge... maybe if it was just donr in blobs?

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Lead clips, fixed under the flashing and turned over the edge.

Can also use copper strips in extreme conditions.

You can also give the front edge strength by folding or rolling it under.

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never thought...
i like the idea of forming a little 'welt' type fold on the front edge...
be good when trying to dress over the glazing bars too... nice one..

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Update

The problem has not been so bad over the winter, but now it has reappeared with a slight difference. Water is appearing along the top edge of the window frame (see pic) as well as where the conservatory roof joins the house. It looks as if the water is actually coming out the seal between the frame and the opening in the wall.

CW Plastering suggested that there were no cavity trays installed, and I am inclined to agree with this.

There are so many possible causes of the problem - no cavity tray, porous brickwork, failed pointing, poor leadwork etc - that I think the work is beyond a DIY job. So my questions now are:

Who will be the best person (i.e trade) to ask to quote for this type of work?

What sort of cost am I looking at?