Making a Custom Tractor Tire Skylight

by ziggy on July 30, 2009 -- 5 comments -- Follow

skylight-whoa

You may remember reading about how I stumbled upon a perfectly sized tractor tire that I decided to use for the frame of my skylight atop my reciprocal roof. Well, I finally installed the actual skylight to the tractor tire frame a couple of weeks ago with the help of my friend Tamar. Read ahead for all the details!

The first step in installing the skylight for my reciprocal roof was cutting the EPDM that was stretched over the tire. I started with a smaller hole than I thought I would need, cutting conservatively just in case the EPDM was more taut than I thought. Once I realized that was not the case, I cut the EPDM to be about flush with the diameter of the hole of the tractor tire.

skylight-down

Now there was a hole in the roof!

Tractor tire skylight specs

The piece of material I decided to use for my actual skylight is a 1/4″ thick piece of 60″x60″ clear polycarbonate, a rather expensive piece of plastic. (In fact, the polycarbonate was the second most expensive piece of material for the whole house – $400!). Next time, I’ll be careful to make the skylight smaller so that I do not have to find/buy such a large piece of suitable material. I decided on the polycarbonate because I knew that it would ultimately be more durable than something like tempered glass, especially since my skylight is pretty much flat. (Hailstorms are a concern out here.)

Installing the polycarbonate

Next we took pieces of pipe insulation (which in this case would serve as a kind of gasket) and did a test, laying them on top of the tractor tire and under the polycarbonate.

skylight-test

(The polycarbonate overhangs the tractor tire to help prevent rainwater from coming near the seal.)

skylight-tape

After tying the pipe foam together, we laid it down in a circle, and began using silicone caulk to seal it against the EPDM. Next, we used masking tape to prevent the foam from shifting while we added a bead of caulk on top of the foam.

skylight-caulk

With three pairs of hands, we verrrry carefully lowered the polycarbonate onto the caulked pipe insulation. The polycarbonate does not actually rest totally evenly on the tire, since the tire is not perfectly plane. Thankfully, polycarbonate has enough flex to negate this issue.

We then proceeded to bolt the polycarbote into the tire, using a drill to go through the material and into the tire. With someone working outside and another on a ladder on the interior, we threaded the nuts and a small rubber gasket (cut from scrap EPDM) to a bolt, caulking the bolt to make sure it was sealed as best as possible. Now the skylight was firmly affixed to the tractor tire.

skylight-final

(It’s not the prettiest thing when viewed from above, but it works…!)

How does the skylight perform?

I’m in love with the skylight. It doesn’t seem to make the house any significantly warmer, other than inside of the spotlight that passes across the back of the house interior throughout the day (which is actually really cool to see… you can pretty much tell the time based on where the spotlight is.)

It has rained several times since the skylight has been installed, and there haven’t been any leaks. I’m not confident that will be the case if/when we get a gigantic and windy thunderstorm, but I plan on watching the skylight carefully to gauge what I can do to prevent that. It could be a matter of more caulk, or some kind of (nasty) foam sealant. The overhang of the polycarbonate definitely helps to prevent water getting close to the seal.

So far so good.

On a random note… that spotlight sure does make for some very nifty photo opportunities inside the house!

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  • Terri

    Well done! I’ve looked forward to seeing how your tractor tire skylight would work. Please keep us posted on its success. Also, is your living roof still keeping you green and dry?

  • Joe

    Very cool. You should do some mosaic on the back wall in the form of a clock/calendar as you watch the seasons travel across the wall. Something like spring/fall lunch or summer breakfast or whatever… I love your house.

  • Jacques

    Why not put a dot on the glass and then you could mark the wall for approximate time of day ?

  • CK

    Hi Zig!
    Thanks so much for this blog and the ideas you’ve shared. I’m working on my own cob cottage (though I’m still a long way from having to commit to a roof idea just yet) and I like your reciprocal/plexi skylight/living roof concept. I plan to be electric-free so I might really appreciate the additional light it brings to the space. What are your thoughts/recommendations regarding your roof and how it functions?

  • The roof is great. It’s not that insulative, from what I can tell. Depending on where you live, that might not be an issue. It’s not impossible to insulate it, though.

    The skylight works beautifully with one exception: condensation! Since the panel is a single pane, the thing collects huge amounts of condensation in the winter. For a couple months this winter, I put a clear plastic tarp over the exterior of the polycarbonate to act as a buffer against cold, and it helped, but I still had to wipe down the skylight (with a towel on a long pole) regularly. It does not condense in warmer weather.

    I plan on getting another pane of material to help insulate. But anyway, I haven’t had any leaks around the skylight either, which has been great. It’s held up to pretty intense wind without a hitch.

    Another thing about the roof: it’s really hard to gutter. I still haven’t figured out how exactly to best do it.

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