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Discussion Starter · #1 ·
I have the following situation:

Rectangle Font Parallel Slope Wood


I want to redo the low-slope roof on the left but I am trying to learn the best way to reconnect it to the high-pitch roof on the right. Do I just shove the top row of the underlayment of the low-slope roof under the underlayment of the roof on the right? Should I add a flashing over it? Should I put cement in between the connecting underlayments? Any details would help! Thank you!
 

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Id flash just under the higher roof and maybe throw in a sealant under the flashing. I have something similar with an aluminum porch cover and mine just tucked under the drip edge. I have shingles though. Been there for 15 yrs ish. I did caulk the edge so any water doesn’t squeak by where the cover connects with the roof rim thingy.
 

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Is it around 20 feet long? Metal roof shop will bend you a custom transition piece to fit the angle...like 158 degrees. I have a similar roof transition. Or make one from valley flashing that is around 3 feet wide.
 

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Product Rectangle Slope Font Parallel


Not roofer. Above image shows conventional way. That is finish roofing that is under the shingles. In theory, rain will flow down but there is wind blown rain too. For you, tiles would be difficult and you can't transition with flashing or underlayment since potential leaks will flow under the roofing. There is no drip edge either. Second what oggy bleacher says. Slip a trowel or such under tile underlayment and make sure there is no nail obstruction. If nail, you need to cut through them with oscillating saw. If you can slip a sheetmetal as much as you can:
1. Low slope roof first
2. sheetmetal flashing over the low slope roof with roof cement.
Like above, any potential leak drains over flashing and to day light. Sheetmetal flashing must be under the tile underlayment without tears.
 

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Discussion Starter · #5 ·
Id flash just under the higher roof and maybe throw in a sealant under the flashing. I have something similar with an aluminum porch cover and mine just tucked under the drip edge. I have shingles though. Been there for 15 yrs ish. I did caulk the edge so any water doesn’t squeak by where the cover connects with the roof rim thingy.
Can you please explain how you would flash under the higher roof? I don't have a drip edge on the higher roof. How would I attach the flash to the flat roof? Details are appreciated!
 

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Discussion Starter · #7 · (Edited)
View attachment 700985

Not roofer. Above image shows conventional way. That is finish roofing that is under the shingles. In theory, rain will flow down but there is wind blown rain too. For you, tiles would be difficult and you can't transition with flashing or underlayment since potential leaks will flow under the roofing. There is no drip edge either. Second what oggy bleacher says. Slip a trowel or such under tile underlayment and make sure there is no nail obstruction. If nail, you need to cut through them with oscillating saw. If you can slip a sheetmetal as much as you can:
1. Low slope roof first
2. sheetmetal flashing over the low slope roof with roof cement.
Like above, any potential leak drains over flashing and to day light. Sheetmetal flashing must be under the tile underlayment without tears.

If I slip the sheetmetal under the underlayment of the higher roof, its just going to be laying on top of the sheathing and not attached to it. How do i attach the flashing to the flat roof? Sheathing -> underlayment -> cement -> flashing -.cement -> cap sheet ?
 

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If I slip the sheetmetal under the underlayment of the higher roof, its just going to be laying on top of the sheathing and not attached to it. How do i attach the flashing to the flat roof? Sheathing -> underlayment -> cement -> flashing -.cement -> cap sheet ?
Is this new construction addition?
 

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I think two courses of the clay tile will have to be taken off to attach the flashing. If that cant happen the wide flashing will only be attached to the bottom section...and slipped loose under the tile...which will probably work but is risky.
I thought the redo applied to both roofs...but you are just redoing the lower roof.
Is there drip edge at the bottom of the upper roof?
 

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Not, not new construction. Basically what is happening is the underlayment and capsheet is getting torn off on flat roof. High roof is already there and in good shape. If i strip the flat roof down to the sheathing and then relayer it, I need to re-transition it to the high roof.
What are the tile on the upper roof, can you remove some so you can do what ever up under them?
 

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Discussion Starter · #12 ·
I think two courses of the clay tile will have to be taken off to attach the flashing. If that cant happen the wide flashing will only be attached to the bottom section...and slipped loose under the tile...which will probably work but is risky.
I thought the redo applied to both roofs...but you are just redoing the lower roof.
Is there drip edge at the bottom of the upper roof?
Yeah, just the lower roof is being redone. There is no drip edge on the high roof, it just transitions into the flat roof.
 

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Yep. They are delicate and lower courses will be a problem.

So after finishing the lower roof you slip the transition flashing under the upper underlayment wrap and use roofing screws with gaskets to fix the flashing to the patio roof. What material is the bottom roof going to roofer with?
Are there walls to the patio?
 

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No. If you cement the flashing to underlayment then the cap sheet, and if that cement fails, water leaks under the cap sheet. I was thinking flashing should be cemented on top of the cap sheet. Even then try to caulk/cement the joint between flashing and underlayment above so wind driven rain will be in trickle.
I'm wondering if roof cement can be used to mimic built up roof. Cement - tarpaper -cement-tar paper-cement. Where physical flashing is difficult, I think layering will help.
There was a post in past about tile roof. I think it was flat concrete tile? The poster as well as other replies said such tiles were very leaky. I don't get how such tiles can be accepted but there it was. As such, I would not seal the end of the tiles you have. Whatever seal is used, it must be between the underlayment and cap sheet. Any potential leak must drain to day light. My opinion.
What was there before? Did it work for some time? Sometimes, monkey see monkey do is only answer. Maybe another option is flash under the underlayment (of the top roof) then flash again under the tiles if possible. My thinking is layering.
BTW, 2nd oggy bleacher's last post. Flashing can be nailed and the nails sealed. Nails are not necessarily holes that will leak. Nail heads can be sealed for long term. It works esp on low slope roof. Not where there is ponding.
 

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Property Slope Rectangle Wood Font

Sorry somehow didn't go to edit. Like image above. Above is wall to shingle but the concept is same. Flashing angle will be less. Flashing will be cemented/nailed to the cap sheet.

Another option may be remove first row of tiles above if possible then flash that area. Not sure. I guess it all depends on how the underlayment was installed under the tiles. Another problem may be if there is nailer strips under the tiles?
 
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