Category Archives: general construction

Parapet coping

It is time to finish our never ending roof project with the crowning of the parapet. This coronation did not involve gemstones or precious metals, just a simple steel coping.

I had the coping manufactured by a local roofing supply company to fit the dimensions of our parapet. The one thing I had not manufactured were the turns or corners. Those I fit myself on-site.

I slipped each piece of coping over the cleats on the outside of the parapet while placing it, and made sure that the ends of each coping butt up against each other. On the inside of the parapet, I fastened the coping to the nailer about every 24 inches.

That was the easy part. The tedious part was to cover the seams between each coping section.

The roofing supply company supplied me with connectors that have the same profile as the coping itself, but are just a fraction larger. That way I could fit the connector over each seam. I first cleaned the coping and connector with rubbing alcohol. I then laid down a layer of high end silicone sealant around the seam, placed the connector on top, and carefully caulked it in on both ends.

Taking a look at the whole parapet assembly, we have the coping cleats on the outside, which hold the steel coping. On the inside we have the coping nailer, to which we fastened the coping, and the insulation and the cladding, to protect the roofing system.

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Parapet cladding

Roofing system (or roofing membrane) degradation is largely driven by physical impact (foot traffic, hail, etc.), solar radiation, and extreme temperature fluctuations. The longevity of a roofing system can be increased by protecting it from these elements.

Our roofing system is protected from the elements by the drainage layer and the insulated roof pavers, except along the parapet. Our solution was to cover the parapet with XPS insulation (or pink board). Because XPS insulation will degrade when exposed to sunlight, I cladded the whole parapet in aluminum.

It is a similar principle to the insulated pavers, with the XPS insulation at the bottom, which in turn is protected by the thinset layer atop.

The XPS insulation along the parapet is basically an extension of the coping nailer. The aluminum cladding is fastened to the coping nailer, and riveted together at the seams. The cladding is installed from the bottom of the roof to the top so that the overlap at each seam is pointing downstream.

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Parapet coping cleats

The steel parapet coping will be attached to coping nailers on the inside of the parapet, and coping cleats on the outside. Because the steel coping will be held by the coping cleats, there will be no visible fasteners on the outside of the parapet.

I fit the coping cleats to the various sections of the parapet edge, and anchored them into the parapet top with masonry anchors. In the process, I kept checking the distance between the outer edge of the nailer and the cleat to make sure that it fit the width of the steel coping I had ordered.

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Coping nailers

Even though we had the photovoltaic roof array installed, I had a couple of items left on the roof project to do list:

The roof was waterproof since we installed the membranes and flashing. The same cannot be said for the parapet, which still needed a coping. We originally had clay tile coping on the parapet…

…but I opted for steel coping this time round to reduce maintenance and water infiltration issues.

The steel coping is secured by a cleat on the outside of the parapet, and as such has no visible fasteners. On the inside of the parapet, it needs to be fastened to a nailer that is anchored along the top edge of the parapet.

We used a pressure treated stud for the nailer, cut it to length, clamped it to the top edge of the parapet, and anchored it about every 24 inches.

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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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