Lean-To Roof Flashing

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Old 09-04-19, 05:41 PM
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Lean-To Roof Flashing

I am building a lean-to against the side of my shed. The exterior of the shed wall is T1-11 siding. I will be using a corrugated metal roof. How do I properly flash where the metal roof ties into the wood siding? Thanks in advance for your help.
 
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Old 09-04-19, 06:06 PM
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Generally you want a wall flashing that goes under the siding. You would want to make a horizontal cut in the siding about 3 1/2" above where your ledger will be, and another cut where the top of the ledger will be. Remove that section of siding above where the ledger will be sitting to make room for the flashing. (The ledger itself can be installed on top of the siding.)

The flashing should be about 4x8... (you may want the flashing to be 8" long on the roof side if the pitch is going to be shallow... such as if it's a 1:12 or 2:12 but as the pitch gets more steep, that 8" leg can be shorter)... bend that flashing to match the angle of the roof slope. You would slip that flashing under the siding first... before you even put the ledger up. Slide it as high as it will go and just tack each piece with a single nail so it stays put during construction... you will remove those nails later.

Why 3 1/2" above the ledger? Generally when framing a roof for a lean to, you put up a ledger, with rafters that will be installed flush with the top of the ledger. Then across the rafters you place purlins (horizontal 2x4 nailers on 24" - 32" centers for your steel roofing to screw into.) So once the top purlin is on, you are left with 2". Your steel roofing will be about 1"... so now you are left with 1".

After the roof is complete, you will want to get "foam top closure" that matches the profile of your steel roofing. You place that on top of the roof panels where the flashing will cover it. Then pull the temporary nails out of the flashing and slide it down so it sits right on top of the closure. Then nail the cut edge of the siding (and flashing) to each stud. You should have about 1" of clearance left between the flashing and the siding so that you can still paint the bottom cut edge of the siding.

And you get "foam bottom closure" to go under each panel of steel roofing at the bottom of the roof. These are installed on top of your metal roof edging one at a time as you put each roofing panel on.
 
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Old 09-04-19, 06:32 PM
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Sorry but I am new to DIY construction and don’t understand completely what you are saying. The lean-to will be 12’ x 20’ with a 1:12 pitch metal roof. I planned on bolting a 2 x 8 ledger board through the T1-11 siding and into the vertical 2 x 4 studs behind the wall. Are you saying I make a horizontal cut completely through the siding 3 1/2” above the ledger board the entire length of my wall? What do you mean by remove the section of siding where the ledger will be sitting? Does that mean cut out the siding where the 2x8 will be bolted, leaving a 7 1/2” x 20’ rectangular hole in my wall where the 2x8 will sit about 1/2” recessed? I still don’t understand about the cut 3 1/2“ above that. I’m sure I got this all wrong. Thanks for your patience.
 
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Old 09-04-19, 06:37 PM
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What do you mean by remove the section of siding where the ledger will be sitting?
Remove the 3 1/2" section of siding ABOVE where the ledger will be sitting. This allows you to slip your flashing all the way up under the siding and then drop it down on top of the roofing later.

just reread it until it makes sense. It may take a while for it to click.
 
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