Installation : Day 1!
One of the tribulations of researching the construction of green roofs is that the YouTube videos are a little skimpy on some of the details. The examples always seem pretty straight forward. And they fit into a 3 minute video clip.
So, one of the purposes of this blog is to provide a little more detail so people who wish to save the installation costs by doing-it-themselves will have a better idea of some of the pitfalls.
You may or may not be an engineer, as I am. You might have the time and the inclination. You might have the same tools in your garage. At least readers will get a better heads-up than I had.
Or you might elect to pay a crew to do it for you. Your choice.
Commercial Declaration = Suppliers / Vendors
At the end of all the navel gazing, researching, "googling", budgeting, scheming, gleaning and toing-and-froing I elected to buy most of the materials from the XEROFLOR company here in Toronto. Their staff are extremely helpful, particularly through the approvals phase - getting the building permit, as previously blogged
We are going to use sedum mats as our "living layer" rather than planting individual plants and waiting a season or two. We may (later on) over-plant some of the areas with taller plants (sedges, grasses) as energy and horticultural desires permit.
We are basically using the XEROFLOR "XF300 +XT" design, with different thicknesses of growing medium as the roof strength permits. However, we will also be using 2 layers of fleece to provide water storage, so you might describe it at "XF300 XT + 2FL".
Here is the link : XF300 +XT
The exception is the the sedum mats for the kitchen roof are coming from SedumMaster in Princeton, Ontario, because of a different and more colourful mix of species just outside my office window.
Growing Medium Thicknesses
This commodity is light-weight, relative to soil and has a higher mineral content. I will put a layer 1 inch thick on the kitchen roof, 4" thick on the main roof, and 6" thick on the walk-out roof. These numbers are all developed from the load carrying capacity of the roofs, which is based on joist dimensions, spacing and spans. [Table 6 on the Ontario Building Code was crucial part of the design process as it mandates the permutations and combination of dead / snow loads, joists and spans.]
We have 8 yards of growing medium to put into place - 2 cu ft at a time in mid-size recycling containers - up 1, 2 or 3 flights of stairs / ladders - about 120 trips all going smoothly.
Day Zero : In the beginning..
Flat roof, DUROLAST D50 TPO roof membrane, three years old. This is the same roof all over our home, and will be "Day Zero" everywhere. The drainage is via scuppers, shown here in the middle of the left hand end.
Day One - Installation
The first layer to be installed was the DUROLAST WalkTRAK III protection layer, as mandated by DUROLAST, the manufacturer of our DUROLAST D50 [TPO] roof membrane. This layer was needed to maintain our 15 year roof warranty.
It comes in 5' by 5' sheets and can be easily cut with a box-cutter, having measured twice!!
Layer 2 - Root Barrier
The second layer is a thick polyethylene (LDPS) layer just to stop root penetration of the roof membrane. This is made from plastic 0.5 mm thick (0.020") and is delivered in a roll. It folds out to be 4 m wide by 25 m long, per roll. Cuts with a pair of scissors. The product is called XEROFLOR XF112.
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The timber in the picture is just temporary ballast so it doesn't blow away overnight.
NB: the plywood frames in the background of many of the pictures are the new houses being built next door.
The only gotcha with the root barrier material is that there is a substantial crease where the material is folded. The crease does not pull out easily. I have re-rolled the piece perpendicular to the crease in an overnight effort to straighten it out a bit. Tomorrow and a few hours of sunlight will tell.
Layer 3 - Perimeter Railing
The 3rd "layer" is a perimeter railing to contain the whole installation neatly and prevent it from collapsing sideways and flowing away down the drain. It is an aluminium extrusion from XEROFLOR (XF510) and comes in many heights and 10 ft lengths. We will be using the 4", 7" and 9" versions. On the Kitchen Roof, the installation will be boxed in by the 4" high railing.
The railing material is aluminium, 1.6 mm (0.63") thick. It can be cut with (tin) snips and a hacksaw, but have a good breakfast because cutting it by hand is grunty work. Measure at least 3 times .....
XEROFLOR has a corner product, but I have elected to build my own. When the sedum mats are growing well no one is going to notice who built the corners. Not from the ground, anyway. Beside, many of my corners (around the scuppers) are 135 degrees, and would need to be handcrafted anyway. Besides twice, their corners look like mine, at a distance.
All the corners are braced with 3/4" aluminium straps pop riveted with the smooth side "down" towards the root barrier - penetration prevention. I use aluminium rivets so they could be drilled out quickly and there should not be any osmotic corrosion.
As an aside, the reason for the shaping around the scuppers is simple. Each winter I put 1/2 a bag of rock salt (water softener salt chunks) just in front of the scupper. It prevents it from freezing past the point of blockage and causing flooding. The shaping of the railing will keep the living components of the green roof away from the salty component.
The first winter we were in the home was the infamous 2012/2013 Toronto Ice Storm. We had well over 4" of ice on the roof, plus melt water. All the 3" scuppers were frozen, blocked and flooded. We discovered one small leak on the walk-out roof, but that is another story. Rock salt is easier than kettles of hot water or heating cables. I checked with Durolast and they told me that the TPO membrane will not be affected by the seasonal salt.
The fabrication of the railing takes time. Measuring twice, then back up to the roof to remeasure up there as well.
It also helps if you have both left and right handed snips. Thank heaven Home Depot is only a 5 minute drive away.
Thus ends Day 1. Railing is not finished on the kitchen roof. Have only had to drill out 5 rivets so far. Need more measuring and prefabrication on jigs at ground level, before I lug pieces up the ladder to find them 2" too long... The time consuming part is the succession of 135 degree corners around the scupper.
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