Hello all,

Not that 'Green' a query, but it's part of a timber frame, sheep's wool insulated shed, and someone will know an answer, so here goes. I cannot afford a Velux or similar, and I have a mis-measured 3G unit, so I want to build that into the roof. Roof is 11mm OSB on 100 x 50 at 360 ctrs. Breather membrane on OSB, 19 x 38 battens on top of the BM in line with rafters, and feather-edge board as 'wide shingles' as final rain-screen.

I can vaguely remember how to build it up (and it's not rocket-science anyway), but cannot think of how to do so without lead. I was thinking 75 x 50 upstand, lead soakers at side, lead apron at top wrapping around the soakers, bottom apron slightly oversailed by the soakers. 3G unit will sit inside the 75 x 50 on a stop-lath, and lead ?silicon-ed to the top oversailing the frame.

How does that sound? How can I do it on the cheap without lead?

You'll notice that the above does not open. Improvements (including waterproof opening function!) welcomed.

Ta!

Nick

Thanks Tony. If doing with felt or say alu, how do you prevent ingress at the corner of the 'L' (where lead can be dressed round the corner and onto the roof surface to m,ake a skirt?). Does that description make sense? The only way I can think of is soakers at the side and a top apron flashing wider than the upstand top rail.

Nick

Posted By: tonySit glass on top sealed down, to open wooden frame member at the bottom housed into bottom member with a screw drive opener. top in copper hook-over retainers to top and sides at top

I don't quite understand this, any chance of a sketch, Tony? Also what's the best way of dealing with the edges of a flush fixed (non-opening) rooflight? I've attached a Lumen detail for reference. So, something at the edge of the glass that stops water, UV and vents the seal. (Glazing seals need to be drained and ventilated?)

Viking house had some neat ideas. Probably on his website. E.g. a seperate single pane rainproof layer with the double/triple glazed unit a bit lower in line with the roof insulation - assuming you have insulation there.
Even if you don't have insulation its perhaps easier to get a weatherproof seal on a single pane than a 3g unit.

Posted By: RobinBdouble/triple glazed unit a bit lower in line with the roof insulation

I think Viking's had condensation and dust issues with that design. I think it's preferable to have just one layer of glass rather than two.

Tony, for the insulation I would bring the ceiling up to the glass and insulate behind it. This would eliminate the the bridges through the rafter and window frame.

Posted By: tonyYours might work at the sides but it will not work top and bottom!

Why wouldn't the top work? For the bottom a stepped unit (as in picture), is a good way. I think DIYing this flashing detail would be tricky though. I guess Lumen (and others) use aluminium? Can we see a sketch of your design, or are you patenting it?