Ive made myself a fairly large porch area on the front and side of my house. Im in the UK but Ive always liked American style porches, so ive ended up with a porch that is 7.5m along the front and another 7.5m along the side of the house, and it comes 2.5m away from the front and side house walls. So its pretty large. Now I want to make a roof for it and Ive been through many options in my head and Ive ended up deciding on half glass, and half wood. Because its pretty large and deep, if it was all solid roof, I'd lose a lot of light to the house windows. It cant be all glass either though, or might well be too hot in the summer. Im also hoping to have a system where I can roll down material over the glass on hot days, to act as a shade to prevent the glass heating up the porch area too much.

Ive worked out I need toughened glass, and the costs aren't too bad - something like £50 for a single 1500mm x 1500mm piece, and I'd need 5 of those for the front (im leaving the side of the house all wood) so its not too expensive. Im just not sure how I go about fixing this glass to my joists. I have 6x 4" (1000mm) square posts along the front of the porch upto my height of around 2.4m (each one is about 1.5m apart). I have 6x2 size joists connecting the posts along the front at my height, and Im going to run 6x2 joists from the house wall on a slight slope down to the front posts. Not being a professional woodworker, Im just not sure of the best way to secure the glass, and to also ensure it doesnt leak at the joist sides. Do I run a strip of wood along each joist, just below the top, and sit the glass pieces on that? And do I need to use putty to seal each one? Or is there a better way of doing it. Any help on this will be really appreciated, or any links to how this is done well to make a nice waterproof seal. Also am I being too ambitious in thinking I can manoeuvre these large pieces of glass into place on my joists in the first place! And will they be safe enough (toughened clear glass). Thanks all.

  • 1
    Websearch "skylights". Glass in roofs is a solved problem... and it's almost certainly going to be simpler and easier to buy a pre-made unit with built-in flashing that simply drops into a cut-out in the roof than to redesign a leakproof skylight from scratch.
    – keshlam
    Nov 28, 2014 at 18:38
  • Thanks keshlam. I dont want a skylight though - I want the entire roof to be glass. More like a conservatory, or a greenhouse. But this could potentially be a living space, so I want to try and seal the glass in well. Im just wondering if someone could point me to a good technique to do that. I appreciate that in a greenhouse its just a case of putty around the edges of the glass - but that wouldnt suffice for a roof on a living space would it? Thanks
    – Luke Smith
    Dec 4, 2014 at 10:24
  • Leaks don't matter as much in a greenhouse as they do in living space. But if you're willing to live with an occasional leak (use weather-tolerant furnishings, as you would on an open porch) and the maintenance which comes with that, I suppose it could work. "If it happens, it must be possible."
    – keshlam
    Dec 4, 2014 at 14:30


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