Tag Archives: fiber cement

Siding and Rainscreen Details

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I thought I would take a few moments to share a few of the details for the siding installation, as most of the fiber cement has now been installed.  We were stepping slightly outside the normal bounds of siding installation (especially for the builder) and I wanted to share how we are achieving the results.  We wanted a simple pallet of materials that still allowed for an interesting end result.

The primary exterior cladding for the home is fiber cement.  However, we did not simply want to install fiber cement lap siding in a traditional fashion.  We wanted a vertically oriented pattern, to contrast with the horizontal nature of other features of the home (overhang, cedar rainscreen, etc) but did not want to simply do this through the addition of a batten on top of 4×8 fiber cement sheets.  As a result, we decided to reorient lap siding vertically.  We took 12″ lap siding and ran it vertically.

Further, we know the value of a rainscreen system for cladding a home and wanted to incorporate this design element into the house.  The basic concept of a rainscreen is to allow for an airspace behind the cladding material, allowing the cladding to breathe.  If water penetrates the outer cladding layer (which it almost always does at some point), the air space behind the cladding allows for the water to exit the system and to also dry out faster because of the movement of air within this cavity.

FIBER CEMENT CORNER DETAIL

We have achieved the air space behind the fiber cement lap siding by running fiber cement furring strips vertically at every joint, spaced 12″ apart.  We then chose to leave a 1/4″ reveal between each of the 12″ vertically oriented lap siding pieces to express the joint and to create a subtle shadow line.  We noted the use of caulk at the joint between the lap siding and the furring strip to ease the worries of the contractor, though we believe this is overkill as the system is designed to breathe and dry out.  You can essentially think of the design as a reverse board and batten system, with the batten beneath the seam instead of on top of the seam.

Fiber Cement Parapet Detail

Fiber Cement Horizontal Joint

I have to say, it has been quite a challenge convincing the builder of the feasibility of the design and also the merits of it.  In the end, though, I hope he understands the value of the system, both aesthetically and also fucntionally speaking.

*Will post some pictures of the actual installation soon.

Rainscreen

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The largest portion of the exterior is clad in fiber cement.

We are using a 12″ lap siding by CertainTeed but using it in a slightly unconventional manner.

We are planning to run the lap boards vertically as opposed to the traditional horizontal manner.  Further, the joints will not be lapped but will be open with a very small reveal between each of the boards.

The complete system is designed in the fashion of a vented rainscreen.  Essentially what this means is there is a small gap between the exterior siding material and the sheathing behind.  This gaps serves a couple functions but the key function is the ability for water to move through this opening.  In a traditional siding application, the material is fastened directly to the sheathing, with no gap.  If water reaches this point, it has no where to go and simply sits on the surface.  While there is a weather barrier in place, you can still imagine that this is not good for the system.  In a rainscreen application, the water has a way out.  It no longer sits on the surface, but is allowed to move down the length of the wall and out the base.  The rainscreen increases the life of both the exterior cladding and its subsurface.

To achieve this small gap, we are running furring strips a 12″ on center at each joint of the vertical fiber cement boards.  We are using a metal product called Furring Master. These are 22 gauge galvanized steel which ensures they will not warp or degrade over time.  Further, they are designed with an almost u-shaped profile, creating a hollow channel, allowing for water to escape in the rare event that it would actually get behind the furring strip itself.

Again, thanks to the folks at Postgreen for all the great posts details much of the process they went through.  While I have been familiar with rainscreen systems for some time, they have used the Furring Master product in the past with great results.  Here is an image of their Skinny Project with the furring strips installed: