Rooftop Skylight Installation

[Rokrover]

Just finished the skylight installation over the 14x14 void left by the recently departed air conditioner that now rests in our city’s refuse transfer station. The saga of A/C removal is in my “Rooftop A/C Stopped Cooling” under the Electrical / Electronics section.

To recap, the existing rooftop hole is the standard 14” x 14’ square. The skylight I chose is in 2mm thick ‘smoke’ tinted lexan from SR Speciality Recreation. The OD flange is 18.5” x 18.5” with a dome size of 14" x 14” (naturally) a 4” height and 24 screw holes around the perimeter. The kit came with a tube of SR140 flexible butyl rubber sealant but no screws. The screws I selected are #8 metal screws with a length of 3/4” that is plenty as there is little stress on them. Since the dome is thin plastic I used fender washers under each screw as you will see in the pictures.

As with every job, the devil is in the details, so I proceeded cautiously with time on my hands now the storm passed through our region. First and most tedious step was cleanup of the old gasket and silicon sealant residue from the A/C. Silicon is a pain to strip as it resists most solvents and I didn’t want to get to aggressive on the fiberglass. Finally a stiff putty knife, plenty of elbow grease and mop up with mineral spirits prepped the surface nicely.

Next I centered the skylight and marked each screw hole with a felt pen. Naturally the perimeter holes are not symmetrical so I was sure to put a reference mark on the front of the skylight as well. Past experience has taught me well that any fitting coated in tacky sealant has one shot for seating and any reorientation causes a horrible mess.

Drilling the holes was straightforward BUT the drill bit size is critical. The web told me to use a 1/8” bit for #8 screws and this turned out too small for the fiberglass skin that fractures and delaminates trying to force a #8 through. I ended up with a 5/32” pilot hole just through the skin and 1/8” underneath was OK. Naturally I tested every screw hole lined up first to be sure as these end up hidden by the butyl sealant at final installation. Putty tape would be a mistake.

Now for the point of no return - I applied a continuous bead of the SR140 sealant under the flange of the skylight and a second bead on the roof surface over the screw holes. I let the sealant set a bit then it was “dome on” time.

I snugged the screws down in series, much like the pan on an automatic transmission and just finger tight was enough without forcing dimpling. The skylight has to “float” a bit to relieve stress under thermal expansion, especially under an Arizona sun.

I’ll let the pictures do the talking: #1 shows the finished job from topside and #2 the view through from the Captain’s cabin.

Next to deal with those pesky wires as Blue~Go suggested. Finally I think I’ll use a flat plate of clear polycarbonate inside on the ceiling to insulate the space. We shall see after I get used to the new interior ambience.....

[Blue~Go]

Nice! Do you feel lighter and sleeker? I know I did

I like the domed top. I wonder if I could get one of those in clear...

One note: Maybe the smoked top would make the difference, but I wouldn't put a permanent clear sheet on the inside of my rig under the skylight. Reason is hot sun coming through the (in my case) clear skylight wouldn't have anyplace to go and I think it would get too hot in there and maybe deform things. Again, maybe the smoked top would prevent that.

I used a "garnish" (inside trim piece) from a Fantastic Vent to trim out the opening in mine. They come really "tall" and then you just use a utility knife or whatever to cut them to depth. So it covers up the entire inside "side wall" (i.e. roof sandwich). I also got a piece of grey-patterned foam board and cut that so that it covered the dented carpeting from the Air-con and velcroed it up. Then cut a square hole in the middle of it and the garnish fits into that. This way it all looks tidy and fairly spiffy. If you use four snap studs instead of the four corner screws to hold the garnish up, then you can make a snap on inner cover for those trips to Alaska when the sun never sets, or sleeping under the "never setting" lights at a Wal-Mart

I had (have?) planned to use a marine type hatch, as I like those and am familiar with them from boating. I like that it would be one big slab of view, like my skylight, but also openable, so less heat gain. However there is only one model I've found that would fit the 14" x 14" hole, and I'd still have to make a fiberglass plate for the roof because it has radiused corners not square ones. Not a big deal but then too it's $375 and has to be special ordered. Also on those you have to remove the screen to reach the opener handles. (No bugs to speak of if you are far enough from shore.)

An RV roof vent blocks off a lot of view, they're kind of cheesy, and.... I already have two. Upshot was I slapped a piece of Acrylic up there "temporarily," and I've liked it so much I haven't changed it. I suppose a marine hatch would be my next choice. But the domed skylight would be nice if it were clear (I like to stargaze through it). My flat one has the disadvantage that after it rains I need to wipe off water/dust spots. Maybe they'd just drain off a dome. I'll have to check out the dome you got to see if I can get a clear one.

PS: What I can see of your wiring/placement looks *just* like mine did.

[Blue~Go]

By the way, if anyone now (or in future) is intrigued by the idea of a skylight, I made a similar thread back when I did mine. (Not to hijack your thread, but just that I know when I'm contemplating a project I like to see how various people tackled the concept.) Scott also posted some info about installing his skylight in the same thread:

viewtopic.php?f=4&t=300&hilit=skylight

BG

PS: I looked up the skylight you used on SR and they come in smoke or white.... no clear (waaaah).