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  1. #1
    Join Date
    Aug 2013
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    5

    Default Venting bathroom without attic access in flat roofed house

    Just got a 1923-ish house, doing some work on it, and trying to figure out the best way to vent the bathrooms. Neither has any venting at all, and there's no access to the attic space. It's only about 18-24" tall, so I guess it's more of an attic crawl space? Either way, not sure how to go about running any duct short of installing an access hatch and crawling on in.

    We have those old spanish-style terracotta attic vents - could I finagle a 4" vent into that from within the house without having to climb up? I'm in LA, and it's a stucco house with a flat roof, so moisture isn't as much of a concern as it ordinarily would be.

  2. #2
    Join Date
    Jul 2010
    Location
    SoCal
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    Default Re: Venting bathroom without attic access in flat roofed house

    Those terracotta vents are most likely sewer vents, and you may not connect your bathroom vent into them.

    Better, try to vent through the roof. Simply remove some of the roofing materials above the location of the venting unit, drop a vent down and connect to the unit at the ceiling and make sure it extends about a foot above the roof. From the unit to the rigid vent (maybe a foot or two long) use a flex vent.

    You also need electric power to the unit and a wall switch.

    Finish the job by finishing the roof.

  3. #3
    Join Date
    Aug 2013
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    5

    Default Re: Venting bathroom without attic access in flat roofed house

    The terracotta pipes are definitely not sewer vents - they just open straight into the attic crawlspace. (We have the ceiling open for unrelated reno right now and you can see straight outside if you look up through them.) I'm hoping to avoid doing any penetration to the roof, for the usual reasons, but it's certainly an option if there's no alternative. I was hoping I could push a rigid vent assembly up through the attic, then pull it into the terracotta from exterior. This may be pie in the sky though!

  4. #4
    Join Date
    Jul 2010
    Location
    SoCal
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    5,443

    Default Re: Venting bathroom without attic access in flat roofed house

    What diameter are those terracotta vents and how many vents do you have of this kind?

  5. #5
    Join Date
    Dec 2010
    Location
    Houston Texas
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    2,509

    Default Re: Venting bathroom without attic access in flat roofed house

    A Broan or Panasonic vent will give you a smallish but usable space to work with to get a vent up through the roof. These vents require ~ a 12 x 12 hole. Combining that with the roof access, you can make it happen.

    Flashing is critical

  6. #6
    Join Date
    Jan 2008
    Posts
    1,337

    Default Re: Venting bathroom without attic access in flat roofed house

    It seems the existing vents you refer to are for under-roof ventilation. So long as you have enough ventilation with them after the bath vent is snaked in, then all you have to worry about is weatherproofing the bath vent. You may need someone familiar with terra-cotta roofs in your area to determine whether the venting is adequate.

    Being in LA, I'm sure you are supposed to have some kind of permit to do the work you are planning and currently doing- all big cities are like that. Whether you wish to get one is your choice but if it were me I'd just tell the roofer to give me a roof venting assessment from the outside and leave the rest unspoken of. If he said it was substandard or marginal I might see if I could vent through a wall instead. And while you can get to it, insulate- in SoCal's heat you need all the help you can get!

    Phil

  7. #7
    Join Date
    Aug 2013
    Posts
    5

    Default Re: Venting bathroom without attic access in flat roofed house

    Just an update, mostly for those who come after me. We put in attic access ourselves - took a good hour or two to get through the plaster+lath in the closet, but once I was able to get up and look around it all made a lot of sense. The terra cotta pipes are, indeed, just open to the inside of the attic crawlspace. So for now, we installed a broan combo light/fan that does 70 CFM, and ran 4" flex vent out to the terra cotta pipe. Climbed up the outside of the house and tugged it in a few inches. Some day I'll go up and throw some sealant around it, but for now, it's certainly better than no vent at all, and didn't need to add any new holes to the envelope.

    And in case someone else finds themselves in a similar place - the pipes were about 5.5" on the outside diameter, 3.75" on the inside. Crimped flex vent was able to snuggle fit a few inches into it.

    Thanks all!

  8. #8
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,509

    Default Re: Venting bathroom without attic access in flat roofed house

    Thanks for the update

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