Engineering a Custom Gutter

Water collection is a main premise for our design, therefore the gutter was specially designed to move water from the butterfly roofs, across the structure, to the water cistern on the south-end.  We decided to orient seating and storage underneath the gutter to create a clean, organized space.  We started to call this “Clutter in the Gutter” after having a conversation with Reggie Gibson about the project.

In this project the gutter creates the “spine” of the structure, running down the middle and connecting the two butterfly roofs.  We decided to space the two roofs 3′ apart to fit the seating and storage below creating a clean composition.  In order to shed water, the gutter needed to slope at least 1/4″ per linear foot.  The slope could be created several ways, one way involved designing a rail or  ledge for the material to rest on.  Then the rail would create the slope by having one end higher than the other.  Another option was to slope the beams that carry the rafters, but this ended up complicating the roof structure.  The last option, which we chose to pursue, was to shape the material in such a way that would create the slope.  Throughout this process we looked at several materials: culverts, slides, giant PVC, and sheet metal.  Sheet metal offered the most customization, affordability, and a straight forward process.

So then begs the question, “how do you make it slope”.  If you unroll a paper cone, you would see that the shape of the cone tapers from one end to the other.  Keeping this in mind, we knew the sheet metal would have to taper from one end to the other, generating a slope when hung between two beams, see drawing below.  In order to find out how wide the sheet needed to be from one end to the other was a matter of drawing in 2D and modeling in 3D.  I knew that the beams ran 3′ apart on center, and I knew that for every linear foot I needed 1/4 slope.  Since these sheets had a max length of 10′ I determined we would have a difference of 2.5″ from front to back.

Drawing two parallel lines 2.5″ apart, I could find the bottom most point of the gutter from one end to the other.  From here I measured the two arc lengths, in this picture they are 4′ – 1 9/16″ and 4′ – 6 5/8″.  From these dimensions I was able to draw the trapezoidal shapes, and viola! Self-sloping gutter.  After figuring the process out we were able to manipulate the form, for instance, we decided we could add a 3/4″ drop between each 10′ section to great light gaps, allowing more light in the middle of the structure without compromising water collection.  Looking forward to seeing this constructed.

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