Replacing your RV skylight

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By Russ and Tiña De Maris

Need to replace your RV skylight? “Why would I ever need to do that?” you ask. You could be like somebody near and dear to our hearts, who, after carefully inching around the roof checking out roof sealant, accidentally rolled over on his skylight. The resulting noise from the stressed out skylight dome sounded akin to the breakup of polar ice.

Maybe the root of your replacement need isn’t as dramatic – perhaps it’s cracked, faded or just plain ugly from the elements. Regardless of the cause, replacing an RV skylight isn’t a difficult task, nor particularly time-consuming. It just needs to be done right. Here’s the skinny:

PREPARE
While you may be able to pick up a skylight at a local RV parts house, we found ours on the Internet on ebay, focusing on (not surprisingly) a strong skylight. The picture of the fellow standing on a skylight caught our fancy, and as the costs weren’t a great deal higher for the super-duper strength skylight, we ordered one. Took a few days to arrive. Of course, we had to know the size of the skylight to order. Yep, take your tape measure up topside and get the width and length, measuring along the outside edges of the skylight where it meets the roof.

While we were at it, we ordered sealant specifically designed for skylights. It’s a butyl-based compound that meets specifications for EPDM roofs, but also works with fiberglass and metal. Our pick, Surebond SB140 skylight sealant, set us back less than $15 and has proved leak-free. You’ll find it on Amazon.

You’ll also need the appropriate tools and other supplies. Battery-operated drill with bit to fit the existing screws for removal. A putty knife. A caulking gun is required if your sealant (like ours) comes in a tube like that. A can of mineral spirits and cloth cleaning rags. We used disposable gloves when dealing with the solvents and sealant. And don’t fool around with safety – make sure your ladder is in good shape and sturdy!

REMOVAL AND PREP
Taking the old skylight off and prepping is probably the most time-consuming part of the job. You’ll need to take your putty knife and carefully remove the sealant from around the tops of the existing mounting screws. Don’t slip if you’re working with an EPDM rubber roof – Don’t ask why. When all the screws are cleared, remove them. Can they be reused? Maybe, if they aren’t rusted. We went ahead and got all new hardware and had it on hand.

Now carefully slip your putty knife under the edge of the skylight, working around the margins of the skylight to loosen the existing sealant. It can be a bit frustrating, depending on the sealant used in the original install, but keep at it. With the old skylight removed, then you’ll need to use the scraper to carefully remove as much of the old sealant as you can. It’s nitpicky work, but pays dividends with reducing the chances of a leak.

Now clean up the area with mineral spirits. If you’re working with an EPDM roof, apply the mineral spirits to a cleaning rag, NOT directly to the rubber roof. EPDM is super-fussy, and if you dump solvents (or agents containing citrus) on the rubber, it can swell up and be damaged. Put the spirits on the rag, then work this over crud areas – use as little of the stuff as possible.

In our case, prepping also included a bit of repair work. If you slip with the putty knife and chop a slice in your EPDM roof, you’ll want to fix it. We applied EternaBond tape over a goof and, following directions, thoroughly rolled it to ensure good adhesion.

We’re discussing the replacement of the external skylight only here, and in our project didn’t remove the inner skylight dome. We did ensure that the inner skylight dome was clean while we had the old external dome off. You might want to do the same.

GOOP IT UP

We marked the outline of our skylight, as the size was slightly different from old to new.

Now’s the time to load the skylight sealant in the caulking gun. Assuming your new skylight is the same size as its predecessor, following the directions on the sealant container, run a bead around the roof covering the screw holes. Place the skylight down over the sealant and (using a terribly technical term here) moosh it down over the sealant. Skootch it around a bit to ensure the sealant is well-distributed. If your skylight size differs, before you lay the bead of goop down, mark out the outline on the roof so as to get the sealant in the right spot.

The number of screws required to install the new skylight may be more or less than the number you took out from the old. Indeed, the spacing on our new light was smaller, and it took more screws. Run the screws in snuggly, but DON’T torque them so tightly that you crack the skylight. The sealant will do an excellent job of holding the light down and keeping wet out, so over-tightening isn’t necessary, and certainly not desirable.

While a bit of sealant came out from under the edges all around our skylight, which told us we’d used the right amount, we still went ahead and ran a bead of sealant around the perimeter edges of the light. While each screw should have a dot of caulk over the top, it’s not necessary to run a bead from screw to screw – just make sure each screw is thoroughly covered.

CLEANUP

Cleanup is fairly straightforward. If you wear gloves (and change them out along the way), your hands should escape relatively unscathed, saving you from the potential adverse effects of dousing yourself in solvent. You’ll still need to clean up your tools, and we found that the mineral spirits and cleaning rags worked fine.

Our new skylight isn’t just tougher than the told one, the view upwards is much clearer now. Unseasonable rains have proved the job true, and we’re happy with the outcome.

All photos, R & T De Maris

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Joe Azzara
Joe Azzara

Is there a spray that can be applied to existing skylights to darken them to filter out light. Mine is viewable in my bedroom and sunrise always wakes me up, even if I want to sleep in. Help!

Dean Yoesting
Dean Yoesting

My skylight cracked over the shower. I repaired it a couple of times, but eventually the skylight had to be replaced.