Roof end blocking #2

This is the promised part 2. Part 1 described the roof end blocking for the insulation at the lower roof edge, which was covered by the roofing system (the base sheet and the torch down membrane).

The new blocking was in the same location, and again providing a containment edge. This time for the insulated pavers and additional ballast pavers. For part 2, we did not need to worry about chamfers and cant strips, but had to pay attention to waterproofing and the integration of the drainage layer. Let’s start with the latter.

We didn’t want to terminate the drainage layer behind (on the upstream side of) the roof end blocking and have water pooling behind it. The drainage mat measured 1/4 inch in height. We needed to elevate the blocking about the same distance to allow for water to drain off the roof.

I took scraps of the torch down membrane and cut it into two by six inch pieces to fabricate spacers. For a spacer to measure over 1/4 inch, we stacked four membrane pieces atop each other. We rolled the drainage layer out of the way, and welded the spacers to the roof edge about every 20 inches, like studs that will hold a top plate.

We then rolled the drainage layer back into place and cut out slots so that it fit around the freshly installed spacers.

We used a pressure treated two by six joist for the roof blocking edge. When set on the spacers, we had the needed gap to assure proper roof drainage.

And this is where we had to pay attention to waterproofing.

We needed to attach the two by six with screws to the roof blocking under the roofing system. That means we had to contend with eight roof penetrations, one at every spacer. Our solution was to pre-drill through the two by six and the spacers, and fill the drill holes in the spacers and the two by six with sealant. We now had the screw anchor encased in sealant, which should give us a waterproof connection.

The last step was to attach a second two by six to the first so that the roof end blocking about matches the height of the surface behind it.

And why are we doing all this again? Oh yes, it’s in preparation for the solar array installation. Well then, let’s get on with it!

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About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

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