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Old 05-28-2009, 02:26 PM   #1
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Flashing skylight curbs with architectual shingles

I have a 4/12 roof that I am having reroofed with I&W shield and architectual shingles. I built curbs for the 3 Velux skylights that raised the skylights a minimum of 9" off the roof deck. The curbs are all about 36" across the top and are up to 6 feet long on the sides. The top of the curbs will use the ECB flashing kit, but what do I do with the bottom?

Perhaps I can use step flashing on the sides and custom make the top and bottom flashing? Would they be lead & would I solder it or just pound it into shape? What covers the curbs over the I&W? Use EPDM?

I was originally thinking of doing this roof with a membrane because of all the ice dams but it is cheaper and probably a better solution to rip out the cathedral ceilings and add another R20 to the R30 that is there already, fix the air leaks and increase the venting.



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Old 05-28-2009, 07:46 PM   #2
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not sure why

not sure what the curbs are for velux flashing kits don't need a curb
for either their standard or low pitch kits
as for the ice and snow run the bottom first cut on angle at sides and fold it back on the side then the sides run past the bottom cut at corner and fold onto the bottom run top long cut at corners and fold down the sides
then install flashing as per instructions
i think on some boxes of ice there diagrams of this application
don't cut the shingles to tight leave a 1/2" gap this will let the flow by and to stay clean
I have installed a lot velux sky lites and have never built a curb and as far as i know none of have ever leaked
if all else fails read the directions
as for the ice dams were at the eves is this case you need more insulation and better venting is there soffit vents and a ridge venting
there one more option could use spray foam insulation and leave the cathedral ceilings
would need more info were the daming is happening


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Old 05-28-2009, 10:27 PM   #3
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Thanks for your suggestions on how to install the I&W shield. I really think I need curbs on this roof. I got 2 feet of snow in 3 days last winter. The curbs get the joint to the skylights above the roof surface, which is prone to leaks.

It would be difficult for me to eliminate the curbs as there are curbs on these skylights already. Eliminating the curbs would require a lot of drywall and framing work inside.

The curbs that are there now do not have step flashing to the 3 tab shingles. They solely rely on I&W shield to seal the junction between the curb and the roof. Not the best way to do it if you ask me.

Unfortunately Velux stopped making the curbs and also stopped making the skylights that were there so I just built curbs according to Velux's plans. Velux does not specify a way to step flash the curbs to shingles.

It is actually cheaper to strip out the roof, add 4" of styrofoam insulation and reinstall the roof than adding high density spray foam insulation from the roof deck. High density would be the only thing that could give me R50 with 2 x 10s.
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Old 05-30-2009, 06:01 AM   #4
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Not sure why you need 9" high curbs for a curb mounted skylight.
Might look a little odd.
If you are using Ice & water shield in a layering fashion as well as flashings(Velux flashingings are not a requirement on curb mounts)
Then seal them down with a sealing strip or thermoplastic caulking there should never be a problem.
Part of the trick to any skylights is cutting & folding the flashings properly.
We do work in Whistler BC (as much as 20 ft of snow, ice damming galore)
Never had an issue.
We generaly get deck mounted Velux for new installs
Dale Chomechko
DC Roofing Inc
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