Sloping the "Flat" Roof, a.k.a. the Sleeping Porch

  

The part of the house which seems to generate the most confusion is the section of the roof which juts up and out from the rest of the roof line. This has also been one of the slowest areas to finish building. When it's finished, the area beneath will be a 2nd story porch (actually it's about five feet above the second story). Although it's covered by the "fly-away" portion of the roof, it will still receive a certain amount of windblown rain, so I've been working on creating a means of drainage. I began by including two scuppers in the layout of the parapet wall on the East side which will be cut out later when we know the precise dimensions of the actual scuppers. Then I made a crude tapered jig which I used to rip four foot lengths of 2x4's and 2x6's to taper evenly. I started with pieces that tapered from 1" to nothing. It would have been easy enough to create an even slope from West to East, but this would have meant that water would flow evenly towards the entire parapet wall, and would pool up where there was no scupper. So I began by sloping the floor along the bottom of the wall. This solved the problem of water pooling along the wall's edge, but it meant that at the East end of each joist, the desired height to achieve was slightly different. So with the rest of my first batch of shims, I cut off either a little or a lot off the thin end so that the height matched the shim at the edge. In the photos you can see the resulting wave pattern of shims. Although the shims all came out to different distances from the wall depending on how much I had to cut off the thin end, each is exactly the same thickness which made it easy to extend the slope. I just ripped a second batch of shims that tapered from 2" down to 1" and butted the 1" end to the already attached shim. Because the shims are structural in the sense that they will in effect become the bearing portion of the floor joists when I lay plywood down, I glued each shim before I nailed it. I'm not sure if this is necessary, but it certainly seems like a good idea and the small extra step seems well worth it. I also had to use a large nailset to drive the framing nails deep enough into the taller 3" to 2" shims so that the nails would catch deeply enough into the joist. Once the subfloor is down I'll apply flat roofing material ("flat roof" refers to roofs which are in actuality only nearly flat, 1/4" per foot is the minimal slope). On top of that I'll put down sections of decking (which won't be nailed down since that would puncture the roofing), rainwater will pass through the decking, run down the roofing material to the scupper, and leave the building. Of course, the entire process of shimming will have to be repeated in reverse in order to create a deck which is level on top of a roof which slopes! Now that it's basically just me working, the immensity of the work remaining to be done is pretty daunting. But I'm enjoying the problem solving, and seeing real progress day by day. 

In the above photo you can see the word "SCUPPER" scrawled on the bottom plate, and see that the shims along the wall and on the joist tapper away to nothing at this spot.

By notching the shims around the columns, I've created a place to nail the plywood, which will also wrap around the columns.

Here you can see clearly the "wave" pattern in the layout of the shims.