GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Taping with Siga Wigluv AND 3M 8067

Jonathan_C | Posted in General Questions on

Hello all!

I’ve got some questions on taping:

-My trailer build will have treated 2x4s (fasted directly to trailer frame) supporting 3/4″ treated plywood as my first piece of a site-built SIP. Should I include a butyl tape in between the treated 2x4s and treated plywood, in order to prevent rot/moisture in between?

-I plan on using Siga Wigluv to tape the seams of EPS foamboard. I will be using the 2.4″ tape for seams in between sheets; those are easy for me to think about. I will be using 3m 8067 to tape any seams in sheathing and house-wrap. I am using both house-wrap and the EPS as WRBs because I’ve given in to Murphy’s Law. As I understand it, my air-barrier is at the sheathing and then I’ve got housewrap WRB, 1×4 spacers for rainscreen, and then taped EPS for another WRB as well as insulation.

Do i need to tape the following EPS interfaces?

–EPS wall to soffit (roofline)
–EPS wall to EPS wall (corners)
–EPS walls to trailer (foundation, if you will allow the concept)
–EPS on roof to sheathing, at overhangs
–EPS on roof to trusses (down the centerline of the 20′ trailer)

Taping these EPS interfaces will require wider and more Siga Wigluv tape, which is an increase in time and cost. I am wondering whether I need to this.

Thanks all!

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. GBA Editor
    Brian Pontolilo | | #1


    First, it would be great to know your name.

    Second, I unfortunately am having a hard time following your description of the assembly. Are you talking about site-made SIPs for walls? Walls and roof? Do you have a section drawing? Or could you please simply list the layers of the assemblies from the inside out? That will be helpful to get some good answers to your questions.

  2. Jonathan_C | | #2

    Hi Brian!

    This is a link to my first Q&A, which has discussions on what the build is:

    Zone 5A (SE Michigan)

    The floor build is as follows: trailer frame | treated 2x4s | treated 3/4" plywood | 2" of EPS or polyiso| 3/4" T&G plywood. I will be taping the seams in between the treated plywood sheets with a caulk and 3m 8067. Seams between the rigid foam board sheets will also be taped with 3m 8067. I had not planned on taping the T&G seams.

    The walls build is as follows: 2x4 stud | 1/2" plywood | Tyvek Housewrap as WRB | 1x4 furring for rainscreen | 2" of EPS or polyiso | metal siding. Plywood sheet seams to be filled with caulk and 3m 8067. Housewrap seams and seams in between rigid foam board sheets to be taped with 3m 8067. Bug barrier along bottom of walls, in space created by 1x4 furring strips.

    Roof build is as follows: 3/8" un-treated plywood | 3.5" of R-15 Rockwool | 2x4 trusses | 1/2" or 3/4" un-treated plywood | 3, 2" layers of EPS or polyiso | 2x4 studs for venting | metal roofing. The interior and exterior plywood seams will be taped with 3m 8067. The 3 layers of foam will be staggered and taped. I am still scratching my head on whether to mechanically fasten the foam boards or glue them or both. The final layer of foam board sheets will have their seams taped with 3m 8067.

    My questions on taping are what I call "exterior" edges, in my head. I don't know if all these exterior edges need to be taped or should be left open. The housewrap taping will already include all of these "exterior" edges being taped. The question I am asking is if I need to then tape the rigid foam board to itself along wall to wall exterior edges, the rigid foam board to the soffit along the roof line perimeter, and the rigid foam board to the trailer.

    Thank you for your help!


    1. Expert Member
      Akos | | #4

      That is a bit too much taping, but it never hurts.

      You always tape across transitions from floor to wall, wall to wall and wall to roof. The air barrier needs to be continuous whichever cross section you draw the line along.

      For the walls your EPS goes under the rain screen:
      -2x4 stud | 1/2" plywood | Tyvek Housewrap as WRB | 2" of EPS or polyiso | 1x4 furring for rainscreen | metal siding.

      Despite what the manufacturers say, detailing house wrap as an air barrier is futile. Doesn't hurt, taping the sheathing underneath is what you need to get right.

  3. Jon_R | | #3

    Consider using fully adhered WRB. It should air and water seal better and reduce the amount of tape needed.

    > 1x4 furring for rainscreen | 2" of EPS or polyiso | metal siding

    I wouldn't use EPS (or tape) outboard of a rain screen.

  4. GBA Editor
    Brian Pontolilo | | #5

    Hey Jonathan,

    I think Akos and Jon gave you good advice. And I think you're overdoing with the tape, but that's an issue of expense and consumption; you're not going to cause any problems.

    Make sure your air barrier is continuous. That's the key. And as Jon noted, the exterior insulation on your walls should be against the sheathing, not on the furring strips.

    Also, I'd use some sort of underlayment with lapped seams on top of the roof sheathing to shed water in the even of leaks. Felt would be fine.

    Finally, to your original question about a membrane between the 2x4s and plywood in the flooring system. A lot of deck builders do this between joists and decking and think it might be a smart idea for your project. Even treated lumber rots when water is captured and left to sit.

    1. Jonathan_C | | #6


      Thank you for your comments and setting me right on the rainscreen.

      If I skip the housewrap, what is considered a fully adhered WRB, per Jon's comment?

      My plan for making a continuous air barrier is to tape all plywood seams. And then add the EPS on top, without additional taping at exterior EPS interfaces.



      1. Expert Member
        Akos | | #8

        Fully adhered WRB is mostly needed if you have board sheathing with lots of gaps or questionable architectural details such as a pop in window.

        Stick to standard housewrap, under foam getting a crinkly one adds extra drying capacity for a small extra cost.

  5. Stockwell | | #7

    Fully adhered examples---Henry Blueskin or Solitex Adhero

    Check with the tape manufacturers on using their tapes on pressure treated wood. Some require steps to be taken before use.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |