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rigid foam as a vapour barrier

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  • #46

    Re: rigid foam as a vapour barrier

    Originally posted by dave_k View Post

    Tentest is a fiberboard that is commonly used in flat roofing, pinboards and retail / office displays. It was really popular in the 70's and 80's wrapped in fabric and used for tack boards.

    There was an asphalt impregnated sheathing product with a tentest core sold in the 70's through to the early 1990s that is referred to as "tentest" by some people .... "buffalo board" to others. I believe it was made by BP and I forget what the real trade name of it was, you would just call it "tentest sheathing" or "buffalo board" when you ordered it. It has no racking strength, You needed to include let in sway bracing to use it in construction. The selling point was that you didn't need to include a layer of tarpaper.

    It was meant for masonry buy allowable under siding up until the early 1990's however it wouldn't hold a nail and over the years it would start to bulge between the studs so you would get these wavy walls. We used to fasten it with 1 1/4" roofing nails .... miss the nail and your hammer would go through the wall.
    Dave just a question or two and hopefully we are on the same page. I believe we are.

    The product I describe and quoted in a post above was absolutely called Tentest in the GTA and southern Ontario for certain. The quote calls it structural sheathing as do several other quotes you could easily find on Google. It certainly could have been called something different in the maritimes, so if that's where you have always lived I could understand your input totally. I have ordered it by the tractor trailer load by the way. Buffalo Board is a totally different product. It was not impregnated with anything and was basically an interior product. Beaver Board was a similar interior product but with a much smoother surface. Both were used for walls and ceilings in low cost housing, cottages and cabins.

    A much smoother version of Buffalo Board was used in the aluminum siding business. It was purchased in bundles of 6 foot long by 8 or 10 inch wide sheets that were placed individually behind the siding as a stiffener and an increased insulation source. You are right about a hammer being able to go through it but the same could be said of drywall or Gypsum lathe under plaster. It absolutely does have racking strength and the question I would like to ask and hope you will answer is "Where did you guys install what you describe as sway bracing?" If your sway bracing was a length of construction grade lumber "Let In" to an interior wall on a 45 degree angle from floor to ceiling than I understand that to be what we called a wind wall. I have never ever installed such bracing on an exterior wall. I am not saying you or anyone else in the maritimes or elsewhere outside of B.C. Alberta and Ontario did not brace an exterior wall, just that I did not and nor did anyone I worked with or for. I would love to see pics of the position of your sway bracing if you have any.

    When you consider a structure in general where you might have a 20 foot long wall that you did not want to fall over, you certainly could brace it temporarily, or if you built another three 10 foot long walls, and placed one at each end and one in the middle, all of which were perpendicular to the long wall, do you think that long wall would fall over? Of course not! Again speaking generally, a floor plan of walls going perpendicular to each other will create a strong web of support structure that on it's own, is very strong. All it is in reality is a great big torsion box. Think about it for a second. Why would it even need bracing on the exterior?
    "Do it Right!"

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    • #47

      Re: rigid foam as a vapour barrier

      Originally posted by Brian @ Muir View Post
      John... I don't think the name " black joe " would win you many friends these days, lol

      Brian
      I agree, the name would be problematic these days, but ..... in the context of those times, I don't think we ever even considered that there might be a racial or ethnic aspect to it. it certainly wasn't intended.

      Anyway ... that's what it was called then.

      cheers

      John

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      • #48

        Re: rigid foam as a vapour barrier

        Going back to the OP's subject. If he wants to remove the tenets he needs to replace it with something. IN my opinion he could use steel strapping or steel bar of some sort placed diagonally on the corners of the house much like today's hurricane straps used in the lower states and midwestern USA, "Tornado alley!". I am a firm believer that if you negate something in a structure you need to replace it with something better and stronger.
        "Do it Right!"

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        • #49

          Re: rigid foam as a vapour barrier

          Rusty,

          Aren't hurricane straps used to hold the trusses to the walls (so to hold the roof to the house)?
          Frank
          SPCHT

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          • #50

            Re: rigid foam as a vapour barrier

            Man did this get way off track on the subject and suitability of Tentest which had little to do with my initial question. And yes Rusty, I had intended to put some bracing, likely metal, even though there is no clear agreement that tentest is in fact a suitable structural component. I seems that the only insulation board that is not a vapour barrier is the expanded or white stuff, with or without an air barrier attached. Still going to check with our local inspector though.

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            • #51

              Re: rigid foam as a vapour barrier

              Originally posted by billyt View Post
              Man did this get way off track on the subject and suitability of Tentest which had little to do with my initial question. And yes Rusty, I had intended to put some bracing, likely metal, even though there is no clear agreement that tentest is in fact a suitable structural component. I seems that the only insulation board that is not a vapour barrier is the expanded or white stuff, with or without an air barrier attached. Still going to check with our local inspector though.
              In what way did this thread go ''way off track''?

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              • #52

                Re: rigid foam as a vapour barrier

                Originally posted by Frank D. View Post
                Rusty,

                Aren't hurricane straps used to hold the trusses to the walls (so to hold the roof to the house)?
                Yes Frank they are but also to hold the walls to the foundation and my comparison is a suggestion only in terms of the metal products used and also to differentiate from a wood brace to a metal brace.
                "Do it Right!"

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                • #53

                  Re: rigid foam as a vapour barrier

                  Originally posted by billyt View Post
                  Man did this get way off track on the subject and suitability of Tentest which had little to do with my initial question. And yes Rusty, I had intended to put some bracing, likely metal, even though there is no clear agreement that tentest is in fact a suitable structural component. I seems that the only insulation board that is not a vapour barrier is the expanded or white stuff, with or without an air barrier attached. Still going to check with our local inspector though.
                  I really don't think it's that far off track Billy. You mentioned removal of the product and I have worries for your success so I thought getting input from this group might be helpful. Unfortunate that some guys don't believe what uses and what strength it does provide. The fact is it is not as strong as Plywood or osb or steel but no one ever said it was. Some guys get running around trying to prove something that really doesn't matter in this context.

                  The foam boards that will work on your project are not as favourable in terms of R values when compared to other foams but that's a trade off you will have to make and nor are they as ridgid as TENTEST or have the same nail holding capacities.
                  "Do it Right!"

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                  • #54

                    Re: rigid foam as a vapour barrier

                    Originally posted by billyt View Post
                    Man did this get way off track on the subject and suitability of Tentest which had little to do with my initial question. And yes Rusty, I had intended to put some bracing, likely metal, even though there is no clear agreement that tentest is in fact a suitable structural component. I seems that the only insulation board that is not a vapour barrier is the expanded or white stuff, with or without an air barrier attached. Still going to check with our local inspector though.
                    If the house was built after the mid sixties and was built with permits and inspection it will most likely have lateral bracing. You will likely be able to see it with a FLIR camera if you know someone who has one or can rent one. I have a little one that works with my phone ..... cost a couple of hundred bucks and is great for looking in walls and sussing out insulation or water problems.

                    Like I said in an earlier post you can use foam boardstock as a weather barrier (tyvek replacement) as long as you tape the joints wit VB tape. This will affect the performance of the wall wall assembly in that it foam boardstock is an air/vapour barrier and it MAY affect the passage of warm moist air into the wall assembly in that it can cause water vapour to condense in the building envelope.

                    If you have a good air / vapour on the warm side of the wall this may not be a problem. When the house was built should give you a clue as to what the building practices were at the time of construction. Houses built prior to 1990 have no air / vapour barriers or poorly detailed one. The former can result in water collecting at the base of the foam board sheathing and rotting out the belt. The latter can have the same result or rot out windows prematurely. The 1990 OBC rectified these problems by requiring properly detailed air/vapour barriers and mechanical ventilation.

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                    • #55

                      Re: rigid foam as a vapour barrier

                      Most likely Billy the reason some people don't answer direct questions is they have no answers. All the work I did in Ontario in the 60's and 70's must have been a bad dream and the building inspectors I dealt with were all tooth fairies apparently.
                      "Do it Right!"

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