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Community and Q&A

Detailing a Mud Sill

gatter | Posted in Energy Efficiency and Durability on

I’m designing a house for Zone 5A. I’ve been reading a lot of articles in GBA and have found it a great source for information about energy efficient houses.  So first off, thanks!   I’m trying to do a ‘pretty good house’  but I’d like to get the air sealing to near Passive House standards.

In regards to the mud sill, the builder would like to use an ice and water membrane over the concrete foundation at the sill plate. In looking at the Vycor recommended details, it looks like they still want some type of sill seal over the membrane.

Is it overkill to have an EPDM gasket over this membrane? How important is it to overlap this membrane over the under slab Stego wrap?

If you go with just the EPDM gasket, do you still need something over the top of the foundation wall that will prevent moisture from wicking into the cellulose?

I don’t mind redundancy, I just don’t want to put a lot of effort in where it may not be necessary. Thanks!

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  1. user-2310254 | | #1


    I can't answer your question about whether it is overkill. I will note that GCP has two drawings for this situation ( and Both show a sill seal installed above the Vycor Plus. It's my understanding that sill seal is usually a ribbed polyethylene foam, so I would guess you could use that rather than EPDM.

    Matt Risinger has a video here ( where he recommends installing standard sill sealer in combination with acoustic caulk, which is probably a lot cheaper than Vycor plus EPDM.

    Maybe one of the building experts will chime in with some real-world perspective.

  2. Expert Member
    ARMANDO COBO | | #2

    I agree with Steve. I specify on my plans to use ProtectoWrap, which is a better sill sealer than the regular thin stuff, specially when the foundation is neither smooth or level, and then a double line of tub-sealer on top and bottom of the Sill sealer. It's the best way to airseal and bug-proof your wall.
    If you still want more protection, the ProtectoWrap Triple Guard has a strong adhesive to apply it on top the concrete. I really love their line of products. You can check uot their website:

  3. gatter | | #3

    Thanks Steve. That Risinger video is certainly up to date (posted yesterday!)

  4. gatter | | #4

    Thanks Armando, I will definitely check that out!

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