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Proper drip edge installing for shed roof?

GreyWolf92 | Posted in General Questions on

I will be installing my roof underlayment and drip edges this weekend on my shed roof. I know the drip edge at the low slope eave goes underneath the underlayment and the drip edges at the rake go above the underlayment. But how about the drip edge at the upper slope of the roof? I am planning on installing this last (which would go over the underlayment AND over the rake drip edge). Is this correct?

Additionally, is it adequate to use the same drip edge for edges of the roof? Or will I need a different angle for the top of the roof?

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  1. Expert Member

    Grey Wolf,
    Sorry, I've forgotten - is it a standing seam snap-lock roof?

  2. GBA Editor
    Martin Holladay | | #2

    Grey Wolf,
    Malcolm's question is obviously relevant. We need to know what type of roofing you intend to install to give you advice.

    Just so you understand the relevant vocabulary: drip-edge flashing is used for eaves and rakes. At the ridge (upper edge) of a shed roof, in most cases a ridge cap, not drip-edge, would be installed.

  3. GreyWolf92 | | #3

    Hi Malcolm and Martin,

    The roof will be 16" snap lock on 24 OC (roof company said this is ok). I attached a picture of what my shed style roof will look like.

    Would trim serve the same purpose? I have only seen ridge caps on gable style roofs. Do you happen to have any online resources/pictures I can look at?


  4. GreyWolf92 | | #4

    Also wanted to note that I will be using Ed dorado roof battens underneath the metal roof (to allow for horizontal air flow). Would it be foolish to install rake edge trim, because this would block the horizontal air flow?

  5. GBA Editor
    Martin Holladay | | #5

    Grey Wolf,
    Most steel roofing manufacturers also sell different types of flashing. The first step is to contact the manufacturer of your roofing to ask them about the trim and flashing options that the company offers. (If you are installing painted metal roofing, you probably want to order flashing that matches the color of your roofing.)

  6. GreyWolf92 | | #6

    Hey Martin, yep I did and have everything ordered already. They didn't mention anything about a ridge cap. I got matching color trim and drip edge.

    Here is what they included in my order. I was originally planning on a drip edge at the ridge. I am picking it up today and will ask them about that again.

  7. GBA Editor
    Martin Holladay | | #7

    Grey Wolf,
    In the Fabral catalog (just one example of a steel roofing manufacturer), the type of flashing you are looking for is called "Monoslope ridge flashing." I'll post an image below.


  8. GreyWolf92 | | #8

    Great, This helps a lot!

    Looks like it allows airflow as well

    Also, I did email ASC roofing sales and their answer was "Drip edge flashing is installed at the leading edge of your panels top and bottom on shed type roof generally is a 1”x 3” or 1”x 2” piece of metal flashing slipped under the roofing material and over the top of the paper felting underneath the roofing panels or shingles" so I suppose either would work.

  9. Expert Member

    Grey Wolf,
    The only place you may want drip edge is at the eaves.

    Here is a link to a good installation guide which shows the details for the three conditions you have on your roof:

    If you look about half way down the link you will see a detail called Fascia/Eaves Trim detail showing how to deal with what you are calling the drip edge.

    Just below it is the Gable Trim detail for the two sides of your roof. Note that they show the gable trim covering one of the ribs of your snap-lock panels. If the end of the roof doesn't fall on a rib you should turn up the edge of your panel the same height as a rib to create a dam.

    About three quarters down is the ridge or Peak Cap detail showing a flashing similar to that posted by Martin.

    As to venting the horizontal battens: I don't how much air flow you will get, but shimming out the gable trim or installing it on pieces of for-a-vent would allow some movement.

  10. GreyWolf92 | | #10

    Thanks Malcolm I'll look over this weekend. I do an to install the same drip edge on the rake edge as well. This was reccomended by asc.

    A few other last questions I'm looking to have answered.

    1) should I be using a different style drip edge for the rake edge (than what I'm using for the bottom edge eave)?
    2) I assumed that the metal roof needs to be screwed into the rafters, but the roofing company assured me this is not the case. Considering my tiny house will be on the road against higher winds, I would think this is more important than normal houses. What do you think? It would be nice to screw into some rafters but with the measurement of my eave overhang, my 16" snaplock won't line up on 24oc rafters. We may hit a few if we are lucky. Do you have any reccomendations to Add additional holding strength Than just screwed into plywood sheathing?

  11. Expert Member
    MALCOLM TAYLOR | | #11

    "Do you have any reccomendations to Add additional holding strength Than just screwed into plywood sheathing?"

    More screws. Most snap lock panels come with slots every 12", and the installation manuals often only recommend fasteners in every second one. Fill alls the slots, or even screw at 6" oc. for peace of mind - and remember to start your panels at the back of the house so that the overlap will not be working against the wind when the trailer is moved.

  12. GreyWolf92 | | #12

    Thanks Malcolm. Good advice and I will do that.

    "start your panels at the back of the house so that the overlap will not be working against the wind when the trailer is moved."

    In that case, wouldn't at make sense to start at the front of the house so the panels are layered over each other front to back (since wind is coming from front mostly)?

  13. Expert Member
    MALCOLM TAYLOR | | #13

    Grey Wolf,
    The "lock' on the panels layers over the smaller screwed rib, but the vulnerable seam is oriented back towards the panel you have already installed, so layering from back to front gives you the right orientation.

  14. GreyWolf92 | | #14

    Thanks for the clarification!

  15. jackofalltrades777 | | #15

    I also have a snap-lock roof and it sits on steel battens to provide an air channel for the SIP roof and to provide a thermal break from the steel roof.

  16. GreyWolf92 | | #16

    Hi guys,

    A few more questions came up that I want to make sure about.

    1) Should me metal roof edge go flush with the rake edge or overhang? Note, I will be installing a drip edge on the rake, and then will be installing trim over that. See attached picture (but this doesn't show a drip edge).

    2) We missed the step of cutting and bending the eave drip edge on the corner of the rake (see attached picture).. Is this essential? What can I do to aim for the same effect without having to pull off the eave drip edge and start over (the rake edge has not been installed yet).

    Also, Malcolm - I was looking at your link and seemed to be missing the guide you were talking about. What is it titles in the link you provided?

    Thanks guys.

  17. GBA Editor
    Martin Holladay | | #17

    I'm not sure why you are installing drip edge on the rake, if you intend to entirely cover the drip edge flashing with a different kind of flashing (the trim piece shown in your photo).

    Whether or not to extend the steel roof beyond the rake depends on your trim details. The type of metal trim you have chosen looks like it needs to be supported by a rake board -- so the vertical leg can't just flop in the air. That determines the way you terminate the roofing at the rake.

    If you want, you can pack out the rake trim with a 1x4 (or some similar dimension of lumber) so that the drip edge of the rake trim is proud of the rake board. This 1x4 can be visible or invisible, depending on its width. The decision is mostly aesthetic, although there are water-management implications to every decision.

    If you forgot to fold the little corner on the drip edge at the eave, there is no reason to lose any sleep. Forget about it.

  18. GreyWolf92 | | #18

    Hey Martin,

    As you know, I lean towards the cautious side when doing something for the first time to try and avoid failure. I do see rake drip edges quite often. Is that only if there is no trim at the rake? Is there any downsides of having the drip edge under the trim (besides extra time)?

    For my rake trim, the roof company provided me with gable trim (see pictures). And my roof is 16" Snaplock from ASC. I'm going to have to read over their directions closely but by main concern for the rake overhang would be water management. I assume it's only necessary to overhang if there in NO rake trim?

  19. GBA Editor
    Martin Holladay | | #19

    There are many styles of buildings that have steel roofing. When I install steel roofing on a garage or barn, I don't typically include rake trim. If there is no rake trim, drip-edge on the rake is usually a good idea.

    Rake trim looks good to some eyes -- not so good to others. It's an aesthetic decision.

    On a simple building, I'll sometimes install a nice clean rake board, followed by a clean 1x3 or 1x4 at the top of the rake board to pack out the rake. The steel roofing can extend an inch or two beyond the rake board without much fear of drooping, and the extended roofing helps keep everything dry.

    If you install the rake trim, the trim sits against the rake board.

  20. Expert Member
    MALCOLM TAYLOR | | #20

    Grey Wolf,

    Martin has given you good advice.

    Sorry, the Westman website must be having difficulties. I can't access their metal roofing installation guide either. Here is a smaller one which shows the common flashing details you need.

  21. Tommy87 | | #21

    I just did a similar install although my house is not going on the highway. This was my first time installing a metal roof as well. Definitely agree with Malcolm to start from the back since you will be driving it.

  22. GreyWolf92 | | #22

    Thanks Malcolm. That will help doing the trim this weekend. End up getting the roof installed yesterday and went up great.

    Tommy, We screwed 7 out of the 11 holes on each panel because this is the amount of furring strips we had enough for.

    Do either of you have any ideas how to add extra holding strength once screwed down? We used the 1" screws it came with but those only gave us 3/8" holding (into plywood sheathing) because my corravent roof furring strips were 5/8". We did not hit any studs either. I would think this is plenty secure for a foundation house but have no experience with moving a house down the highway..

  23. Expert Member
    MALCOLM TAYLOR | | #23

    Grey Wolf,

    All the specs I've seen for fastener penetration want them to leave 1/2" to 3/4" showing through the underside of the sheathing. You need to take the panels off and use longer screws. 3/8" into the plywood won't do.

  24. GreyWolf92 | | #24

    Malcolm, so the screws are supposed to actually go through the plywood even if it doesn't hit the stud? That's unfortunate I'll have to start over but hopefully the snaplock panels are easy enough to remove Without damaging. I suppose I will use 1 1/2" screws.

    Also, do you maybe have a link that states this just so I can read over it further?

  25. Expert Member
  26. Expert Member
    MALCOLM TAYLOR | | #26

    The 1" screws typically supplied are assumed to be adequate for 1/2" to 3/4" sheathing or solid wood. The idea behind it is that the whole depth of the sheathing will be held by the threaded shank of the fastener, not the tapered tip. If you have added a 5/8" spacer you should use at least an 1 1/2" screw.

  27. GreyWolf92 | | #27


  28. GreyWolf92 | | #28

    Thank you. Just to make sure I am understanding what it says correctly, it says minimum of 3/4" through plywood. My plywood is only 1/2" so does that mean it should stick out 1/4" through the underside or 3/4"?

  29. GreyWolf92 | | #29

    Makes sense. Just to be clear though, the corravent strips have no holding strength. It's corrugated plastic. So even by going with 1 1/2" screws I will only get 1/8" more through the plywood (because it is already 3/8" in). So what your saying is that it will be stronger having a screw stick out the underside than running the screw to the bottom of the plywood?

    I suppose I could run some 1/2" thick purlins/strips on the underside of the sheathing if that would add holding strength.

    Are snaplock panels easy to remove without damaging them?

  30. GreyWolf92 | | #30

    I'm also thinking of just keeping the snaplock panels and screwing in several dozen 1 1/2" rubber roofing screws all around so I don't have to take off the panels.

    My slope is only 2:12. Think that would be an ok solution?

  31. Expert Member
    MALCOLM TAYLOR | | #31

    Grey Wolf,
    There are two ways to remove the panels. You can slide them off the bottom holding them with padded vice-grips or fold them over so the rib unlocks.

    It makes no sense to try and remediate things with gasketted fasteners when that will only lock down the perimeter not the field. You have repeatedly spoken about wanting a belt and suspenders approach to this roof. What you would end up with would be inadequate for any roof, never mind one designed to move. Unfortunately you have messed up. Problems happen, they need to be corrected.

    How do you end up with only having an additional 1/8" penetration by increasing the screws by 1/2"? Regardless, you want screws that will leave 1/2" to 3/4" exposed on the underside. Whatever that works out to is what you need to use.

  32. GreyWolf92 | | #32


    I was saying only an additional 1/8" because the screw is already 3/8" through the plywood so there is only 1/8" more plywood to drill through before poking out the bottom. But I understand what you mean now, to have the screws poking out the bottom by more than 1/2".

    I was just brainstorming with my builder who is helping me..and since the last three panels have not been installed yet we were taking about using 1 1/2" screws on every single hole (for these three) plus use 1 1/2" screws along all edges over the roof because the trim will cover these. Since the snap system goes from back to front, the panels in the front are the most important. Important to note I'm trying to avoid any penetration in my weldano underlayment.

    Do you think this would be strong enough? If not, I'll just rip then all off.

    I attached a picture to show my situation

  33. Expert Member
    MALCOLM TAYLOR | | #33

    Grey Wolf,
    I don't want to appear short with you, but it seems everything I suggest I get push back against. It's your roof, you can do whatever you want. if you want to properly fasten three panels and leave the rest inadequately secured that's your choice. I don't like to see people do that when they are building because invariably sometime in the future it becomes someone else's problem, but that's just me.

    I was a bit surprised to read you have a builder helping you. Has he not been able to give you sound advice on the pretty routine questions you have had? Did he not know that fasteners need to penetrate sheathing?

  34. GreyWolf92 | | #34

    Sorry if I made you feel that way. Im asking on here for a reason because I am asking help for solutions. I tried to take the panels off but no matter which way they tried they got all bent up. These things are fastened in here like none other.

    Yes he did but was thinking 3/8" penetration into the sheathing was enough.

    I totally with you on that. I don't want it to be my problem or someone else's. May just have to buy all new panels at this point :/

    Thank you so much for your kind advice.

  35. Expert Member
    MALCOLM TAYLOR | | #35

    Grey Wolf,
    The fault is all mine. For someone in construction watching an owner build their house can be a bit like watching someone play a video game for the first time. There are moments of elation, satisfaction - and also "oh no!" moments when things go wrong. It's easy to get a bit too involved in the outcome. I hope I can be of some help with any further questions that crop up..

  36. GreyWolf92 | | #36

    Thanks Malcolm. It definitely Is a roller coaster. Sometimes I wish I wasn't so involved. I sure will be happy when it's all finished though!

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