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Brick veneer soffit gap: block and drill weep holes?

BryanBL | Posted in Energy Efficiency and Durability on

Background:
Common scenario, but I searched the internet for hours and somehow couldn’t find this answer. I’m very slowly working on insulating and sealing our 40s brick veneer house, Cape 2.5 story with slate roof and no overhangs.

There is no dedicated soffit ventilation – what was there before was just rough gaps between the fascia board and the brick. There are gable vents. Existing insulation was R10 worth of black fiberglass between the rafters. There’s some discoloration but no frank mold/rot thankfully. Sheathing is planks with some sort of plastic/tar between them and the slates.

Gutters were destroyed by ice dams, so I’m having a roofer come and replace them, with new fascia boards that have dedicated vent spaces between them and the brick. The hope is that this ‘soffit ventilation’ will help keep things dry after installing thick insulation.

I tried to seal the attic floor and kneewalls but eventually gave up. On one side there’s a dropped ceiling for a shower, a utility chase to the basement, ducts (with asbestos wrap of course), and pipes. All the hits. So I’m doing a vented cathedral roof using mineral wool, Tyvek as wind washing/air sealing barrier, on the exterior, membrain on the interior (the mineral wool is furred out to R=60) and a little closed cell foam on the interior for sealing and at the eaves where space is at a premium.

Question:
It’s very difficult to access the gap between the wall sheathing and the top plate in the eaves (see picture). My understanding is this air leak is the #1 cause of ice dams, but I worry about closing off the ability of the brick to dry (inward solar drive issue). Conversely, I also worry about unsealed leaks in the exterior walls below entering this channel and contributing to warm, humid air hitting the roof sheathing.

If I bug the roofers, I could maybe get on the scaffold and do some work when the fascia board is off, but that’s asking a lot and the work is still tricky and prone to failure. What about blocking this off with foam board or garbage bags stuffed with insulation, foaming up to the baffle, and then drilling vent holes in the vertical mortar underneath the soffit? Is this a terrible plan?

PS there are currently no weep holes in the bricks near ground level. I’m considering making some but may defer to a mason.

Thank you!

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Replies

  1. BryanBL | | #1

    Forgot to clarify, and couldn't find a way to edit the post: the dark crack at the right, in focus, is what I definitely want to seal and the larger looming air gap in the center between the brick and the sheathing is the subject of the question.

  2. GBA Editor
    Martin Holladay | | #2

    Bryan,
    I'm having trouble understanding your description. I'll provide some information, and then perhaps you can clarify what's going on at your house.

    A brick veneer wall needs a ventilated air gap between the water-resistive barrier (asphalt felt or housewrap) and the brick veneer. The air intake occurs at the weep holes at the base of the wall, and the air outlet occurs at the top of the wall, below the soffit. The air outlet from the brick veneer wall is not supposed to be connected with your roof ventilation system, or with the air in your attic.

    For more information on brick veneer walls, see this article: "Flashing Brick Veneer."

    Your roof ventilation system shouldn't be connected to the rainscreen gap behind your brick veneer. The air inlet for your roof ventilation system is usually at the soffit vents. The air outlet is usually at the ridge vent.

    In a retrofit situation, achieving this ideal can be difficult. Nevertheless it's still good to understand the principles before beginning retrofit work.

    If there isn't any air outlet at the top of the brick veneer wall, you need to create one if possible. You don't want the air from the rainscreen gap to leak into the rafter bays.

    If there isn't any air inlet at the bottom of your roof ventilation system, you need to create one if possible. These air inlets shouldn't be connected to the rainscreen gap behind your bricks.

  3. BryanBL | | #3

    Martin,

    Thank you for your rapid reply. Sorry about the lack of clarity - here's hoping the attached diagram will help explain.

    Also here's a little video of what it looks like. You see what I see - the only way I can investigate is with a phone or scope.

    https://youtu.be/9GBrEqSlPcs

  4. GBA Editor
    Martin Holladay | | #4

    Bryan,
    I'm not sure whether the work is worth it. But if you have enough access, you should (working from the attic) get the nozzle of a spray foam gun into the top of the gap between the brick veneer and the sheathing. (You can attach flexible plastic hose to the end of the nozzle if needed.)

    Once this gap is sealed, you can drill some holes in the vertical mortar joints in the top course of bricks (or a course of bricks near the top) to provide exit holes for the ventilation channel behind the bricks (rainscreen gap).

    Finally, you can install ventilation baffles under the roof sheathing to direct the air entering near your eaves into the attic. For more information on ventilation baffles, see Site-Built Ventilation Baffles for Roofs.

  5. BryanBL | | #5

    And here's the plan of what I would like to accomplish

  6. BryanBL | | #6

    I see we were posting at the same time. I think I'm on the right track now. Thank you very much! This site is incredible.

    You say the work may not be worth it. What alternatives might you suggest? Should I just leave it as-is?

    Thanks!
    Bryan

  7. adivito | | #7

    Don't want to hijack a post but I have this same situation in a 1950s ranch home. I have no soffits on the house. Currently its just gable vents. I'll be doing some renovations shortly. What do you think is the best way to setup the attic ventilation?

  8. GBA Editor
    Martin Holladay | | #8

    Adivito,
    Your attic may not need soffit vents. Does your attic have any moisture or mold problems? If not, stop worrying. For more information on this issue, see "All About Attic Venting."

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