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Dryer Vent in Wall with Hardie Board Siding

washxhouse | Posted in General Questions on

I have a dryer vent cover and bathroom vent cover installed behind Hardie siding – neither of them have any functioning backdraft protection, so they’re just holes in my wall.

I want to replace them with covers that air-seal well and got a pair of these Seiho guys as recommended by a thread on this very forum:

Of course, when I went to replace the existing covers I realized they’re two-part, where the backplate is mounted behind the Hardie siding and the front is a simple hood snapping into the keystone-shaped assembly on top of the siding.

I spoke with a siding guy who said you need to use Hardie brand vent covers – that doesn’t sound right to me … my simplest question is – is there a way to use the Seiho covers I bought? Perhaps with a Sturdimount as recommended by the Hardie manual?

I understand the issue is detailing this in so that water doesn’t make its way into the building. I just don’t know what the method is. TIA!

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  1. oliver999 | | #1

    Sounds like the vents are going through the wall. So water really should not be able to get inside, unless the cap and sealant is missing or broken.

    I did have an issue with backdrafts in one of my vents. No water though.

    An inline, spring-loaded damper was installed that solved that problem nicely.

  2. oliver999 | | #2

    Also, your siding contractor should be able to remove the existing vent, pop off the existing siding, pop in the new one and re-install the siding to fit around the new vent.

    But maybe an inline damper is easier. Do you have an actual leak or water intrusion?

    1. washxhouse | | #5

      No leak, nope. This was my thinking too ... since I'm already holding these cover I'm gonna go ahead with trying to install them.

  3. Expert Member


    With almost every cladding it's easier to use mounting blocks - either homemade or something like the sturdimount.

    1. washxhouse | | #6

      Copy that I'll give it a shot.

  4. monkeyman9 | | #4

    I use a multi tool to cut a square out of the siding and use a piece of PVC trim cut so there will be about a 3/16" gap all around it. Screw it down, caulk it and put the vent over it. In the case of yours, maybe the first vent part under and cover over. If your careful cutting with the multi tool you can slide some tape in with a putty knife over any tears on the house wrap. As for the drip edge above, you can usually put tape on it and slide it up, pushing the tape down with a small flat bar. Better to pull the siding but this is the best I've managed without that.

    Pic as an example, this is older and in cedar, as my vents are up high.

    1. washxhouse | | #7

      Thanks for that. One of my locations is pretty difficult to access and since this is cement fiber board I'll probably leave it to a pro to make this cut / remove the courses for me, but this gives me an idea of what I'm looking at. Appreciate it!

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