Saturday, October 15, 2011

Green roof nearing completion

I had hoped to beat the rain...of course I didn't. The tiny house got rained on a couple times but had time to dry out after luckily. In typical fashion, the plans were once again changed mid-build. Now that our walls were sheathed (mostly) an the roof was on, we got our first glimpse into how much light would be in the house....and we though it might need more. So, we went skylight shopping. Chose a Velux 14x56 dual pane lowE curb mount, pretty inexpensive actually, around $160.
I laid out 7/16 OSB for the roof then put 2" rigid foam insulation on top (plus one scrap 1.5" piece mostly over the overhang)

Also seen in the picture is the roof edging to keep the soil in place. I ended up with some nice looking redwood 1x8 fence boards; way cheaper than "regular" 1x8 stock at about $4 for a 6' length. The front edge board is held in place by L brackets secured to the rafter tails.
A drip edge was installed and a "drainage basket" was made by securing wire mesh from the front edge board to the roof (for strength) and then filter fabric applied over that (to keep soil from washing out). I've seen designs that use gasketed shower drains but I wanted something a little more fail-proof and with more drainage.
Next came the EPDM liner. We bought a 15x15 liner from a pond supply for $130 but they're apparently also available at roofing supply places. Pretty awkward lugging up and unfurling a 100lb sheet of rubber, getting it positioned correctly isn't the easiest.

The skylight unfortunately adds some complexity and ripples an wrinkles in the EPDM are unavoidable. Should be fine though (famous last words)
Decied on a soil mix of 1/3 compost, 1/3 perlite an 1/3 coconut coir. I calculated I needed about 60 cu ft total. The compost I can get for free from the city but the coconut coir and perlite set me back $125. I weighed the mix to make sure it was within spec and a wet 4 inch layer weighs in at 6.3 lb/sq ft; well within range

EPDM degrades under UV so its important its covered in all places

Still don't have the wall sheathing 100% done but that's next up and it's then getting tar paper up and really getting this thing weather-proof


Cost total so far: $1,727.42