Skylight Install: How to Retrofit New Asphalt Paper?

amakarevic

The instructions that came with Velux call for a 38" x 62" rectangular workspace around the skylight curb.

Q1: Should I set the asphalt paper before installing the curb, i.e. set the curb on top of the paper so that the paper is sandwiched between the curb and the roof sheathing or should i first install the curb and then simply have the paper go butt the curb?

Q2: I understand the new paper should be tucked into the old paper on top and lap the old paper in the bottom, for water drainage. However, it is unclear to me how I should integrate the old and new paper on the sides, just butt them or lap them and in the case of latter in which direction and by how much? Please see the exhibit.

Thanks

Attached Thumbnails

 

tinner666

Mount the curb, run the felt up it's sides couple of inches. Bend it in tightly because the felt makes it hard to keep the step flashing tight.
Lap the old felt 6" to the sides, 3" bottom, and under 3" at the top.

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Frank

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tinner666

Oh, I put Permanant Sealer -gutter sealer on the undersie and top side of the hemmed together seams of the rear pan, just in case water gets into them. If moisture gets there and freezes, it could cause splits and leaks.

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Frank

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rossfingal

Use "Ice and Water Shield" -
up the sides of the curb -
against the roof.
Felt is better than nothing, though!!
"RF"

amakarevic

Thanks, however, no one really answered the 2nd question. The lap vs. butt pertains to the outside perimeter of the new felt (patch) where it meets the old one. On the exhibit, it is where the gray area meets the red, which is shingle, actually more like the old felt under that shingle.

Tom Struble

tinner answered that




Velux has their own s.a. in the flashing kit and they accept no substitute...i know,i know but it's in the instructions

skylightguy

After mounting your curb, use the VELUX provided ice and water shield (assuming that you purchased the VELUX flashing kit) The ice and water shield goes to the top of the curb and out to the side of the curb and it is placed directly on the sheathing. You can then install new underlayment over the ice and water shield and then terminate it under the old underlayment. Do not use any kind of sealant/tar with the ice and water shield or the VELUX flashing system as you can void the warranty. The VELUX skylights come with a ten year no leak warranty as long as you follow the installation instructions.

amakarevic

i am sorry, i didn't see this post when i said that no one answered the 2nd question. does it matter whether i lap new over old or tuck new under old ?

tinner666

No. Not on the sides.

BTW, I hope you didn't misconstrue their instructions to mean that you cut that exact work area out in a straight line! You have to remove nails from the shingles and keep them intact for reinstallation. The shingle joints do not line up like the area drawn. Your exact work area will be determined by those joints!

The felt is primarily to keep water out while the job is open. After the shingles are back on, it's purpose will be to provide a barrier between the flashing and the inside air to prevent any condensation. It will not do any waterproofing.


OH, A tip! If the step-flashings are bent square, or slightly oversquare, flex them a bit to about 80-85 degrees. Force them against the skylight for a tight fit and then nail them. Failure to do so can create vertical gaps where the contact each other and rain can be blown in. That will cause leaks no matter what product is used under the shingles.

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Frank

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tinner666

I'm glad to see Velux is now covering roof installation issues too. They used to only warranty the skylights. Nice.

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Frank

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amakarevic

what does that mean? should i NOT lap them on the sides? that means butt them one against the other on the sides (kind of like you would do two sheets of drywall)?

got that. thanks

tinner666

It means that is does NOT matter whther the new or the old is on top of the laps to the sides. Generally, it just goes on top of the old.

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Frank

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