We did that with various bits of scrap wood, cut to size. They would also act as the backing for the numerous screws used to hold everything together. It's important that the "lip" around the new skylight plexiglass (or Lexan in my case) doesn't get bent too far. It could crack under the vibration and heating/cooling cycles of an RV roof. Flatter is better. I also wanted to eliminate a low spot at the front left corner that would pool water after a big rain. I added a fraction more height to that side so water would drain off the roof properly.
After all the wood was added and triple-checked, next was filling in the gaps with an expanding foam product. This would have several effects.
1. It would lock the wood in place before the screws were in place.
2. It would seal any large gaps or cracks around the shower stall.
3. It would add insulation and support to the skin of the roof.
4. It would add to the "water-tightness" of the repair.
All good things!
Using expanding foam can be a bit difficult. It's really easy to use too much and end up with gobs of it expanding out, and over everything you are working on. Trust me I know. It's also hard to clean up and sticks to EVERYTHING. Used sparingly, it's a great thing indeed.
After the foam fully expands and is dried all the way through, you can cut/pinch it to the level you need all the way around the opening. I tried to keep it as neat as possible, but it will always have a "lumpy" look. Don't worry it's all hidden anyway.
|Bottom Of Skylight Before Test Fitting|
Cut the aluminum so it evenly surrounds the lip of the skylight with no gaps.
|Aluminum Strips With Counter Sunk Screw Holes|
First, I purchased a drill bit set that let me drill countersunk holes so the screws would sit flush with the aluminum. To put it all together, I used flat head stainless steel screws to prevent rust and each one was coated in sealant to further seal them and make sure we'd have very little contact between the aluminum and the stainless steel. (It is possible to have dissimilar metal corrosion over time) I spaced the screws evenly around the edges making sure each corner had its' own screw. I left most of the protective covering on the new skylight, just in case. I have been known to damage things in my haste to get things done.
|See The Slight Oozing Of The Sealant!|
Once everything was test fit, I used a caulking gun and lots of the sealant to lay thick beads all the way around the fiberglass under the skylight. Gently placed the new skylight over the hole. To be honest I was in the shower stall holding and positioning it while a friend actually held it above the still wet sealant. Once placed, we added a light bead of sealant on top and placed the pre-drilled (and test fit!) aluminum strips all around the edges. Then the holes were filled with sealant and inserted one screw for each hole (DUH!). Gently tightening down each one until it was snug, but not tight. Working from the flattest corner we tightened one screw at at a time until all of them were snug. Watch carefully for sealant being pressed out from the edge. You should have that happen all the way around.
Clean it up with a paper towel or rag (NOT DYED!!) spreading the excess around the edge to create an additional sealing surface.
|Plastic Roller For Bonding Tape|
After that dries, I used 4" Eternabond tape all the way around (4 Strips) to further seal the assembly and hide the nasty outside edges. Use a hard roller to press down each flat section of the tape so the "micro-bubbles" burst and mix to create the bonding adhesive. When done properly, you should be able to see the shapes underneath. (Think "Wet T-shirt" contest...Or don't, if it will get you into trouble!)
Make sure all the sides are air bubble free. It takes a fair amount of pressure and patience, but it's very important.
Lastly, remove the protective coating on the new skylight and check inside and out, making sure the seal is visually good.
I let mine cure for 48 Hours before water testing. Actually, it rained, HARD, two days later so it was a bit nerve wracking. So far I can detect no leaks! Amazing, I know.
The "milk" color of the new skylight looks much better than the dingy, dirty old one. It's also got less cracks and chunks missing from it!
The lighting in the shower is much more natural and pleasing to the eye than it was before. Likely, when it was new it was pretty close to this, but time and the killer UV from the sun had taken its' toll on the old plastic.
This just goes to show you, "if I can do this, you can too!" No job is too big if you divide it into smaller stages and have a plan of action. It also helps to make sure you have all the supplies and tools needed. Close at hand. "Work Smarter, Not Harder!"
Be Seeing You, Down The Road...
Rich "The Wanderman"