Tag Archives: roofing

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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Solar PV installation

We had been actively preparing for this moment for a long time. The installation of the 8.58 kW photovoltaic roof array with its 26 modules is a massive step towards our goal of achieving net-zero-energy. So, let’s break down the installation process into digestible pieces.

In preparation for the roof solar array installation, we had to fix various items on and around the roof (see “The roof project” for more information). Elements that were directly related to the solar array were the solar blocking to anchor the array to the roof, and the solar posts installation that will support the array, which we carefully coordinated with Lisa Albrecht from All Bright Solar.

The morning of the installation a crate with our 26 solar modules was dropped off, which were carefully unpacked and hoisted onto the roof. It was not really much of a workout, as the modules themselves were rather light.

Up on the roof, the crew began to mount the railing system to the previously installed solar posts, and laid out the wiring of the array. Next the crew set the modules onto the rails, carefully lined them up and bolted them down. Once they were attached, the crew made the final wiring connections and cut off the rail ends to fit.

Now let’s talk about the hidden elements that went into this installation, such as building code requirements. If you look at the photovoltaic array layout, you may ask why we only had four modules in a row, while there would have been space for six modules.

Chicago building code requires a minimum of 36 inch clearance around the array. My understanding is that this is a fire safety provision, i.e. to make roof access to fire fighters easier.

How about the other direction? Why didn’t we space the rows closer together? Why didn’t we  increase the angle of the modules to get a better solar yield?

The answer is: 21. Like December 21st – or the winter solstice. To prevent the modules from casting shadows onto each other, the row spacing and angle of the modules was determined by the sun’s angle at winter solstice.

Are we ready yet to catch some photons? Well, hold your horses! For the photovoltaic array to actually work, we need an inverter, which will be the subject of the next post.

If you find any of the solar terminology confusing, you find answers in the previous blog post “Solar lingo”.

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