I'm about to build a house with an attached garage and a sun deck on the garage roof. Something like this house: http://a-hus.se/web/Steninge.aspx

Now I'm wondering how to go about building the actual roof? The sun deck will be with decking which means gaps where the water runs between. What should I ideally have under the decking? Roofing felt? Metal roof? Should there be any slope on the roof under the decking?

Grateful for input
 
Ola78
Lay standing seam sheet metal as the substrate, it holds well and looks nice. Did so on our entrance when we made a small roof terrace of 10 square meters. The slope was about 1.5°
Under the metal, I placed roofing felt which I pulled up at the back against the facade under the panel and glued there with asphalt glue, all this on the advice of the sheet metal worker.
 
Ola78
Found a link to an old thread I wrote in, where you can see some pictures of solutions among others http://www.byggahus.se/forum/byggmaterial-byggteknik/150506-snaella-hjaelp-anslutning-mellan-tak-och-vaegg.html Don't make the posts go through the sheet metal, it never turns out well, a serious sheet metal worker will advise against it. It can look nice but sooner or later the metal collar around the post will start to leak due to temperature changes and then it won't be fun. I made the decking as cassettes so I can remove them and clean underneath from dirt and such.
 
An alternative to standing seam metal roofing is rubber membrane. It's cheaper and more watertight. The roof should slope in one direction for drainage, and to level the decking, you can rip cut the joists lengthwise, or support underneath with, for example, plastic spacers. I'm personally considering a system similar to when you build joists indoors against a cement slab and want ventilation, they are made of plastic and can be screwed up and down to adjust for leveling.

Regardless of the material, as Ola describes, it's important to ensure the connection to the wall is watertight. However, roofing and related issues need to be addressed whether or not you plan to have decking.
 
Ola78
I have done exactly as pbengtsson describes, cut the studs lengthwise at the same angle as the roof to level the floor, works perfectly.
 
Thank you for your tips. I understand that the anchoring to the facade is an important point in this construction.

I'm sitting here contemplating the possibility of completing the roof entirely with roofing felt as the outermost layer and then building the decking directly on top of it. Do you think this would be a bad solution? Not tight enough?
 
Ola78
There is always a risk that the roofing felt will break when the decking is placed directly on it, not good. My advice is to lay metal as the outermost layer instead, it also lasts significantly longer than roofing felt.
 
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