Saturday, January 17, 2009

Wrapping up the exterior cladding

We are just about finished with the installation of the fiber-cement panels (from Certainteed) the only thing left to do is caulk the joints. The other remaining tasks for the exterior are installing the sunshades and the continuous metal cap flashing at the parapet. You can see in the rear facade image to the left that we have already installed ledgers and metal straps above the windows which will support the weight of the sunshades.

The black plastic downspout at the right side of the image is a temporary solution that will soon be replaced by a smooth galvanized pipe that will empty into a rain barrel. Also, we are planning to paint the cover for the whole house fan (top right) either the same gray color as the fiber-cement siding or black to match the window frames. The sunshades, made of exterior grade FSC spruce, will be left with a natural wood finish.

In the end, we are very pleased with the way the panels look. There was a slight change in the fastening system relative to what was originally intended. We had planned on using nails to fasten the panels (as per manufacturer) but as our contractor began to install the panels, he realized that he was not getting the attachment strength that we needed. A few times the panels began to pull away from the sheathing. The problem was partly due to slight undulations in the surface of the sheathing and partly due to the large surface area of the panels which are 2' x 8' in size.

The fiber-cement panels are very rigid and offer little room for any flexing. They tend to want to flatten back out if the surface is not perfectly flat, eventually breaking the caulk seal. A couple of panels even ended up breaking at the beginning due to the bending stress in addition to the impact of the hammer. We found that attaching the panels with stainless steel screws (which is also approved by the manufacturer) using a hammer drill gave us a much more secure connection.

Due to budget constraints, we are not using a rain screen system (which would involve furring strips or vertical runners and therefore would eliminate the flex issue) but instead we are simply attaching the panels directly to the sheathing, caulking only the top and side joints, while allowing any moisture to find its way down and vent out the bottom of the panels. We're hoping to explore a true rain screen system in the next project, possibly using Vaproshield (opposed to Tyvek, which we used and is great product but is white in color and not great if at all visible) for the waterproof membrane and a recycled composite (like Trex) for the vertical channels.

The image to the left shows where the east wall at the third floor (the party wall) meets our metal mansard roof at the front.

The exposed fasteners are more pronounced than we originally envisioned (the nails would have been flush with the face of the panels), but we love the look of it. The evenly-spaced screw heads along with the softly textured, concrete-colored FC panels are reminiscent of poured-in-place concrete with snap-ties (similar to the image below). We realize the appearance might not appeal to everyone, but we feel it embodies the modern aesthetic of the 'new addition' portion of the house.

1 comment:

Justin said...

I am starting to like the back more than the front!!!! The panels look great and I love the comparison to initial reaction to the 'rear yard' photo was metal.