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Discussion Forum

sill seal … acoustic caulk ????

xtal_01 | Posted in General Discussion on March 19, 2021 04:31pm

Here I go again ….

So, concrete pad … getting ready to put down the mud sill … pressure treated 2 x 6

Cement is “relatively” smooth.

I will use a foam sill seal (both Dow and Dupont say theirs are polyethylene)

From what I read, I should also be using an acoustic caulk.

My understanding is that this should be some type of mastic that takes up the small gaps where the concrete may dip or mud sill may warp up.

Problems …

1) everything I see is latex based …. will this not just harden to some kind of seal .. not really be mastic ?

2) if it is latex … sandwiched between the seal and cement or seal and pressure treat .. will it dry? Cement is moist and PT is fairly wet?

3) do I use it on both sides of he seal or just one?

Finally …. I never got a firm answer … a sill seal just between the concrete pad and mud sill or a second between the mud sill and the wall also?

I got two answers … one said the mud sill may hold water and rot if it can’t dry upward into the wall. Another said it would be great as it would isolate the mud sill and the wall so no wicking takes place.

30 deg here in VT today but 50 for the next 5 days … and sun!!!!!!!!! I plan to get started on this shop … sill by next week … wall the week after!

Thanks …. Mike

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Replies

  1. user-6759690 | Mar 19, 2021 07:34pm | #1

    Hi Mike, I’m a builder with almost 40 yrs. experience. I’ve spent a lot of time researching this subject for my own home. My wife has a severe mold allergy so I have to get the details right. In my own home I would apply acoustical sealant or mastic generously first. Then the foam sill seal and finally your pressure treated sill plate. That’s all. Build on top of that.
    RDP3

    1. xtal_01 | Mar 19, 2021 08:35pm | #2

      Awesome!

      Any particular type of acoustical sealant or mastic?

      I used sill seal on the house ... then went on the outside with cans of foam ... then the inside with caulk. I am hoping I can do it in one step this time!

      Thanks!

      1. user-6759690 | Mar 19, 2021 09:38pm | #3

        Mike, I would use brand of acoustical sealant or mastic that is not water based. The brand that’s available here in Nova Scotia is PL brand. It’s really messy but stays flexible. Make sure the concrete is very clean. Doesn’t have to be dry, just clean. If you do use any spray foam, don’t use window and door type as it will absorb water and hold it(open cell).
        RDP3

        1. xtal_01 | Mar 19, 2021 10:09pm | #4

          Thanks so very much for the advice !!!!!!!!

          Side note ..... my brother went out to NS a couple years back (he lives just outside of Niagara Falls ... I was born and raised there). He said it was the friendliest place he has ever been!

          It took me 7 years to built the house ... hoping the shop will only take one or two. My wife says she is ready to travel again. NS is one of the places on our list.

          Thanks again ... Mike

  2. spb2015 | Mar 22, 2021 11:12am | #5

    Hi Mike,

    My wife and I are building a home, and our builder talked with Tremco about which product to use for the sill plate. Tremco recommended their Dymonic 100 which is a polyurethane based sealant in conjunction with a seal siller that is extremely flexible with +-50% movement capability. The other bonus is that the Dymonic 100 can be applied to green concrete and in unfavorable weather conditions.

    https://www.tremcosealants.com/fileshare/DataSheets_Hyland/Dymonic_100_DS.pdf

    Tremco recommended not using their acoustical sealant as a sill sealer since that's not what the product is designed for and they cannot guarantee its performance long term. I do know a lot of builders use an acoustical style sealant, and so far it seems to work extremely well as a sill sealer.

    Another interesting statement the Tremco technical staff stated was that in terms of performance, 100% silicone sealants are the best if applicable to the substrate applied and conditions applied in (most expensive), followed by polyurethane sealants which tend to be very forgiving in terms of conditions it can be applied in. Any acrylic or latex style sealant while cheap has pretty bad performance long term.

    1. xtal_01 | Mar 29, 2021 12:18pm | #7

      Thanks again!

      Just got 14 tubes of Dymonic 100 ordered .. should be in on Thursday.

      Just a dusting of snow this morning ... already melting.

      Calling for a sunny but cold day on Friday ... I will get the materials.

      By Saturday it will be in the 40's and I can start putting down the sill ... walls next week with some luck.

      Thanks again!

  3. xtal_01 | Mar 22, 2021 11:23am | #6

    Fantastic!

    Thanks so much for the advice.

    I had some old paint on the pad ... long story .. taking a hand grinder and getting it off where the wall is going (I will rent a large grinder and get the rest off later).

    Just going out to get the rest off today.

    I want to start the sill later this week or early next depending on the weather.

    Thanks again !!!!

    Mike

  4. ericpollard | Jun 15, 2023 08:29pm | #8

    Any sealant would do as they would all perform the same as an acoustical sealant. The only difference is really that one is acoustically rated and others are not. Chemically they are the same otherwise. Something flexible like this one can be a great solution: https://isostore.com/case-of-noiseproofing-sealant-acoustical-caulk.html

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