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  1. #1
    Join Date
    Apr 2007
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    66

    Default Ext. trim - where does the flashing go?

    I'm planning to install a 3/4 x 9-1/4" MiraTec "skirtboard" and top it off with a piece of PVC drip cap. Siding will be Hardi. Should I install some sort of flashing (like Z-flashing) under the drip cap or should I just caulk between the skirtboard and drip cap during installation? Same scenario over the windows, except the top piece will be 5/4 x 6" MiraTec.
    I don't want to overkill it just for the sake of overkill and can't really see where flashing would do much, if any, good in this situation. Any thoughts.

  2. #2
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    Mar 2006
    Location
    Seattle, WA
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    11,339

    Default Re: Ext. trim - where does the flashing go?

    Quote Originally Posted by Tom Anderson View Post
    I'm planning to install a 3/4 x 9-1/4" MiraTec "skirtboard" and top it off with a piece of PVC drip cap. Siding will be Hardi. Should I install some sort of flashing (like Z-flashing) under the drip cap or should I just caulk between the skirtboard and drip cap during installation? Same scenario over the windows, except the top piece will be 5/4 x 6" MiraTec.
    I don't want to overkill it just for the sake of overkill and can't really see where flashing would do much, if any, good in this situation. Any thoughts.
    What sort of drip cap?

    If you're doing what I would call a water table: a trim piece that's coming over the skirt at an angle with a drip-edge cut into the bottom, it shouldn't need the joint between the skirt & drip cap to be caulked, because water shouldn't be able to make it back up there. You can caulk it if you want...

    Bigger question is how you're going to flash the drip cap. I've attached a picture of the one I make below- I have flashing made up that covers over the upper part & turns down a little. Covers the nail or screw holes.
    http://www.lavrans.com

    "He uses statistics as a drunken man uses lamp posts; for support rather than illumination." -Andrew Lang

  3. #3
    Join Date
    Apr 2007
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    66

    Default Re: Ext. trim - where does the flashing go?

    Lavrans,
    Yes, I think the correct term may be "water table". The drip cap I'm talking about is the kind that you can purchase most anywhere - they are about 1-1/2" wide with a slope to them and a kerf cut underneath near the edge to cause the water to drip off.

    I wasn't able to see a picture. ???

  4. #4
    Join Date
    Mar 2005
    Location
    Kansas the land of oz!
    Posts
    757

    Default Re: Ext. trim - where does the flashing go?

    IRC

    R613.5.1 Anchoring requirements. Window and glass
    door assemblies shall be anchored in accordance with the
    published manufacturer.s recommendations to achieve the
    design pressure specified. Substitute anchoring systems
    used for substrates not specified by the fenestration
    manufacturer shall provide equal or greater anchoring per-
    formance asdemonstrated by accepted engineering practice.

    R703.1 General. Exterior walls shall provide the building
    with a weather-resistant exterior wall envelope. The exterior
    wall envelope shall include flashing as described in Section
    R703.8. The exterior wall envelope shall be designed and
    constructed in such a manner as to prevent the accumulation
    of water within the wall assembly by providing a water-resis-
    tive barrier behind the exterior veneer as required by Section
    R703.2.

    R703.2 Weather-resistant sheathing paper. Asphalt-satu-
    rated felt free from holes and breaks,weighing not less than 14
    pounds per 100 square feet (0.683 kg/m2) and complyingwith
    ASTM D 226 or other approved weather-resistant material
    shall be applied over studs or sheathing of all exterior walls as
    required by Table R703.4. Such felt or material shall be ap-
    plied horizontally, with the upper layer lapped over the lower
    layer not less than 2 inches (51 mm). Where joints occur, felt
    shall be lapped not less than 6 inches (152 mm).
    Exception: Such felt or material is permitted to be omitted
    in the following situations:
    1. In detached accessory buildings.
    2. Under panel siding with shiplap joints or battens.
    3. Under exterior wall finish materials as permitted in
    Table R703.4.
    4. Under paperbacked stucco lath.

    R703.8 Flashing.Approved corrosion-resistive flashing shall
    be provided in the exterior wall envelope in such a manner as
    to prevent entry of water into the wall cavity or penetration of
    water to the building structural framing components. The
    flashing shall extend to the surface of the exterior wall finish
    and shall be installed to prevent water from reentering the ex-
    terior wall envelope. Approved corrosion-resistant flashings
    shall be installed at all of the following locations:
    1. At top of all exterior window and door openings in such
    a manner as to be leakproof, except that self-flashing
    windows having a continuous lap of not less than11/8
    inches (28 mm) over the sheathing material around the
    perimeter of the opening, including corners, do not re-
    quire additional flashing; jamb flashing may also be
    omitted when specifically approved by the building of-
    ficial.
    2. At the intersection of chimneys or other masonry
    constructionwith frameor stuccowalls,with projecting
    lips on both sides under stucco copings.
    3. Under and at the ends of masonry, wood or metal cop-
    ings and sills.
    4. Continuously above all projecting wood trim.
    5. Where exterior porches, decks or stairs attach to a wall
    or floor assembly of wood-frame construction.
    6. At wall and roof intersections.
    7. At built-in gutters.
    Last edited by Bill Robinson; 10-04-2007 at 06:39 AM.

  5. #5
    Join Date
    Apr 2007
    Posts
    66

    Default Re: Ext. trim - where does the flashing go?

    Bill,
    That's nice and all, but I've never seen an inspector pay any attention to how trim is flashed. Unfortunately, it's the poor flashing and lack of attention to water intrusion that does the most damage - at least from what I've seen.
    I have to remind myself that the Codes are written mainly to project someone from getting injured...they don't care if the house isn't level and plumb and leaks water 2 weeks after a cert. of occupancy is issued.

    So, if I have a piece of wood trim that is covered by a piece of PVC drip cap, does #4 apply?
    Last edited by Tom Anderson; 10-04-2007 at 10:04 AM.

  6. #6
    Join Date
    Jul 2004
    Location
    NOLA
    Posts
    4,018

    Default Re: Ext. trim - where does the flashing go?

    It would be simpler to see the detail drawn.

    However I would be inclined to put a piece of rigid flashing first over the skirt board, flashed to the wrb and then apply the drip edge and then the siding.

    Over the window I would put the rigid flashing over the trim.

    You are right, most code officials do not check if the flashing is correct, the evidence is everywhere that they do not.

    Rigid flashing would be metal, or PVC bent in an "L" shape with a "drip".
    Drip cap is a fuller profile made of PVC, wood or composite.
    All of this should have a slight positive slope to the outside.

    Bill R

  7. #7
    Join Date
    Mar 2006
    Location
    Seattle, WA
    Posts
    11,339

    Default Re: Ext. trim - where does the flashing go?

    Quote Originally Posted by Tom Anderson View Post
    Lavrans,
    Yes, I think the correct term may be "water table". The drip cap I'm talking about is the kind that you can purchase most anywhere - they are about 1-1/2" wide with a slope to them and a kerf cut underneath near the edge to cause the water to drip off.

    I wasn't able to see a picture. ???
    sorry, maybe it'll work this time.
    Last edited by Lavrans; 10-23-2008 at 03:20 PM.
    http://www.lavrans.com

    "He uses statistics as a drunken man uses lamp posts; for support rather than illumination." -Andrew Lang

  8. #8
    Join Date
    Apr 2007
    Posts
    66

    Default Re: Ext. trim - where does the flashing go?

    Lavrans,
    Well, I see a link, but can't find any software that will open a file with a .skp extension. Can you provide a .jpg or .bmp file, please.

  9. #9
    Join Date
    Sep 2004
    Location
    down the shore
    Posts
    2,176

    Default Re: Ext. trim - where does the flashing go?

    .skp is a file created by Google Sketch Up - a 3D drwing program. THe basic program is free (do a seach for "google sketch up). If you don't have it, get it. It has made a big difference for a lot of us - likely fo you also.

    And .skp files can be converted to .jpg files. I do this when emailing drawings to my clients.

  10. #10
    Join Date
    Mar 2006
    Location
    Seattle, WA
    Posts
    11,339

    Default Re: Ext. trim - where does the flashing go?

    Sorry, I can convert to .jpg, but I'll wait until you say you don't want to use Sketchup first. I thought everyone had it by now... living in a bubble I guess.
    http://www.lavrans.com

    "He uses statistics as a drunken man uses lamp posts; for support rather than illumination." -Andrew Lang

  11. #11
    Join Date
    Jun 2004
    Location
    Caldwell, NJ
    Posts
    3,153

    Default Re: Ext. trim - where does the flashing go?

    Quote Originally Posted by Lavrans View Post
    Sorry, I can convert to .jpg, but I'll wait until you say you don't want to use Sketchup first. I thought everyone had it by now... living in a bubble I guess.
    Lavrans,

    I saved it for you in 2d graphic so that you can see it.
    Attached Images Attached Images
    Joe Carola

  12. #12
    Join Date
    Sep 2007
    Location
    Middletown, Ohio
    Posts
    765

    Default Re: Ext. trim - where does the flashing go?

    Holy over kill bat man!

    We don't flash that much here in the snow belt and before you say it, some of these original skirt details still survive sometimes 150 yrs or more.

    As far as I've ever known, you should never caulk under cap flashing. Provided that the drip is far enough ahead of the trim and has the proper angle for watershead. You should only need to flash from behind the botttom coarse of siding and onto the cap or sill above the skirt. That is were the water needs to be diverted. The flashing under the cap is overdoing it in my opion. The drip rip under the cap in the previous drawing should take care of any back travel from the heavy rain loads.
    Last edited by No faux zone; 10-06-2007 at 06:30 PM. Reason: The flashing under the cap is overdoing it in my opion.
    Jason E. Whipple
    Historic House Restoration
    Cincinnati, Ohio
    http://www.facebook.com/RestoreOhio

  13. #13
    Join Date
    Jan 2007
    Location
    Louisville, KY
    Posts
    3,753

    Default Re: Ext. trim - where does the flashing go?

    I do it like Joe posted. The water table might break down in 10 years but your aluminum flashing will stay forever. It doesn't take much time or cost to run the flashing so why not.
    Louisville Exteriors
    Professional Installers of:
    Siding | Replacement Windows | Roofing | Hand Rails | Gutters | And More!

  14. #14
    Join Date
    Mar 2006
    Location
    Seattle, WA
    Posts
    11,339

    Default Re: Ext. trim - where does the flashing go?

    Quote Originally Posted by No faux zone View Post
    Holy over kill bat man!

    We don't flash that much here in the snow belt and before you say it, some of these original skirt details still survive sometimes 150 yrs or more.
    I do the flashing above the water table, not the one over the skirt- that one was put in as an illustration of what stuccoman quoted, although it's overkill.

    I didn't put in the little z that I put in under the skirtboard if it's a bellyband & will have siding underneath (rather than if it's a skirt over the foundation- in which case the skirt should lap over the foundation).

    Hey, Joe- do you have any idea why I couldn't upload the jpg to JLC? I tried saving it, even reduced the size, but the JLC page would just go blank when I tried uploading it.
    http://www.lavrans.com

    "He uses statistics as a drunken man uses lamp posts; for support rather than illumination." -Andrew Lang

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