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Discussion Forum

OSB Nightmare

sebastian | Posted in General Discussion on May 25, 2006 04:35am

 I just completed replacing the OSB sheathing on the gable end of a 15 year old house in northeastern Mass.

The sheathing was soaking wet and rotted. In places it was like wet cardboard. The siding was cedar clapboard with Typar wrap.The windows had flashband under the pine trim. The exposure was northeast and the rest of the house was ok. I wish I had a photo, you wouldn’t believe the mess. The frame and siding were done according to best practice. The damage was most extensive around the chimney and windows.

I have been in this business for over 30 years and have never seen a problem like this without an obvious cause.The water penetration was through the Typar.

The only flaw I could find with the previous work was that the joints were not caulked where the clapboard met the trim, but how did the water penetrate the Typar.

I don’t think the damage would have been as extensive with plywood sheathing. the OSB acted like a sponge holding the water.

Has anyone ever experienced a similar problem.

 

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Replies

  1. andy_engel | May 25, 2006 04:41am | #1

    Not caulking the joints isn't bad practice - Quite the opposite in fact. It's the recommended practice according to the Western Red Cedar Lumber Association and the USDA's Forest Products Lab. Seems that caulk does a better job keeping water in than keeping it out.

    I've seen deteriorated housewrap before. There can be several causes, including leaving it exposed to the sun for too long before installing the clapboards.

    Were the claps backprimed?

    Andy

    "Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein

    "Get off your dead #### and on your dying feet." Mom

    1. sebastian | May 25, 2006 04:47am | #2

      No The siding was not primed both sides. there was no rot on the siding and the insulation was dry indicating a moisture problem from the interior was not the cause. the interior of the studs was covered with poly and the insulation was unfaced.

      Edited 5/24/2006 9:53 pm ET by sebastian

      1. andy_engel | May 25, 2006 06:12am | #3

        Very interesting. The whole gable was cheesecake? Not centered around the window? Is there a decent overhang? Any chance of pictures? How far up and down did the trouble go?Andy

        "Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein

        "Get off your dead #### and on your dying feet." Mom

        1. rez | May 25, 2006 09:50am | #6

          heh heh

          Andy's walking pretty light.

           

          being careful

          half of good living is staying out of bad situations

          1. andy_engel | May 26, 2006 03:23am | #8

            I don't know about walking light, but I've occasionally jumped to a conclusion when the known facts dovetailed with my prejudices. Sometimes, I've been proven wrong when other facts came to light. Just looking for as much info as I can get.Andy

            "Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein

            "Get off your dead #### and on your dying feet." Mom

          2. rez | May 26, 2006 03:55am | #10

            I was recalling a thread a year or so back dealing with cedar tannins/tyvex discussions that got a bit controversial.

            be history

            half of good living is staying out of bad situations

        2. sebastian | May 26, 2006 03:56am | #11

          Andy,

          No overhang. the most extensive damage seemed to be around the windows,but it was not confined exclusively to those areas.the house is two stories with an attick.a couple of sheets at the top were salvageable.

      2. GUNN308 | May 25, 2006 07:26am | #5

        there's your problem poly VB, I have replaced windows in 2 structures one residential housing for the elderly 11 yrs old, one house 8 yrs old both had poly VB and cedar claps both had rotted osb sheathing and framing, double 2x6 sills completely gone, elderly job was slab on frost wall 16" above grade with crips and wall plate gone only pt sill plate was usable. This will probably open a can of worms but my theory, the only escape for interior moisture is through the window openings or your chimney where there is no VB.Both structures had properly sealed windows with aluminum caps and Typar.

        1. sebastian | May 26, 2006 04:00am | #12

          It seems plausible. I cant figure anything, But it is my feeling the problem lies with the OSB.The side of the chimney facing  NE( the predominant weather direction) the sheathing could be removed with a finger, but on the sheltered side it had to be cut with a sawsall.

          Edited 5/25/2006 9:14 pm ET by sebastian

  2. BillBrennen | May 25, 2006 07:19am | #4

    Sebastian,

    Maybe Typar is similar to Tyvek, which can be destroyed by the leachate from red cedar. Tar paper is immune to this problem. Maybe don't use Typar for the replacement?

    Bill

    1. sebastian | May 26, 2006 05:39am | #16

      It is similar to Tyvec. Does Tyvec provide a disclaimer regarding its use under cedar siding? Most cedar siding applied in Eastern Mass.is applied over Tyvec.

      1. andy_engel | May 26, 2006 03:02pm | #19

        Tyvek provides no such disclaimer.

        But we're talking Typar here.

        For more info, go to http://www.jlconline and click on research. Search keywords like "housewrap" and "tannins" or "extractives".

        In a nutshell, IIRC, Paul Fissette from UMass conducted experiments wherein he made a tea of cedar and water. He then filled bottles with the tea, covered the tops with various housewraps and with felt, and upended the bottles. He timed how long it took for them to leak. Felt faired best, Tyvek second, and so forth.

        The theory is that the extractives in cedar act like surfactants (detergent and soap are both surfactants - they reduce water's surface tension and help it to more easily wet other surfaces). Now, if that's true, doesn't it make you wonder what other surfactants might do? For example, I understand that all OSB manufacturing entails the use of sodium hydroxide - lye. Soap is fat and lye. What about pressure washing with a detergent solution? Heck, even latex paint contains surfactants.

        I don't know of collaborating reasearch, or if Fissette has taken this further. I do know that his results fit some anecdotal evidence.Andy

        "Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein

        "Get off your dead #### and on your dying feet." Mom

        1. sebastian | May 26, 2006 03:39pm | #20

          Thanks for the well worded technical reply. It makes more sense than anything I can come up with. something allowed the water to penetrate the house wrap letting the water reach the OSB sheathing. If this occurence is any indication, there is big potential problem out there.

          If this situation was not discovered for another year or so, the entire frame on that side of the house would have needed replacement.

          1. experienced | May 26, 2006 06:33pm | #21

            If this occurence is any indication, there is big potential problem out there.

            Yep!! People have to re-learn that these homes they are building to look like the homes of the late 1800's do not even come close to being the same house behind the exterior skin. We are using caulking to replace water shedding design and flashing. The houses are not loose to air leakage and heat loss that used to help dry leakage at the exterior sheathing and trim. These old houses used to get wet at window trim, cornerboards, etc as they didn't have caulking to seal the siding/trim gap. They dried due air/heat leakage; not a good situation today.

            Contractors should be running to any seminars dealing with energy efficiency, rainscreens, indoor air quality, ERV's/HRV's, heating system design and heat loss calculations, new products. Don't wait for a customer to ask for a new product and then have to learn about it- the manufacturer's rep won't be there to answer all questions.

          2. andy_engel | May 27, 2006 12:34am | #22

            Don't forget that they had far better wood back in the day, too. Old growth lumber of pretty much any species is more rot resistant than the plantation grown stuff we get today. Tighter growth rings, less summer wood, and less taper to the grain all contribute to wood's rot resistance. About the only old growth still in regular supply is western red cedar.

            Sebastion - Be careful about leaping to conclusions based on the little I posted. That's one possibility, but don't let that stop you from continuing to ponder the causes. The housewrap manufacturers, as far as I know, all deny that scenario. Presumably they've done some reasearch on the topic. As long as the siding is backprimed, I'd be OK with using housewrap instead of felt.

            When you re-do the gable, please take the time to flash the window correctly, and prime all six sides of every board that goes up. I do the end grain twice.Andy

            "Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein

            "Get off your dead #### and on your dying feet." Mom

    2. DanH | May 27, 2006 02:25pm | #25

      Typar is inherently much more water-permeable (that's wet water, not vapor) than Tyvek. Should not be relied on as a secondary water barrier.
      If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison

  3. Snowmon | May 25, 2006 07:02pm | #7

    Just curious.

    When you started this project, was it during the heating season?

     

    1. sebastian | May 26, 2006 04:05am | #13

      The project was started on monday as a replacement of a few clapboards and some rotted trim. when the claps were removed the extent of the problem was discovered.we recently had two weeks of very rainy weather,but this has been a problen which has developed over probably several years.

  4. curley | May 26, 2006 03:35am | #9

    FHB had an article on this topic. Basically delt with putting fur strips underneath the clapboard allowing air to circulate underneath and up to the soffit, drying clapboard.

    Would this have helped????

    I only ask because I was going to use this idea on my addition. Seems like alot of extra work

    1. sebastian | May 26, 2006 04:08am | #14

      Probably,but I have never seen this done and a lot of prep would have to be done extending the casings, corner boards,ect. I would a lot cheaper tto just use fir plywood.

      1. Westcoast | May 26, 2006 05:29am | #15

        If you subject plywood to a major ongoing water problem it will still delaminate.

        The water is the problem, not the sheathing.

        1. sebastian | May 26, 2006 05:45am | #17

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

           

          It doesn't hold the water like OSB. In this case you could take a piec of deterioated osb and wring water out of it like you would a sponge. It doesn't seem prudent to me to build a $750,000 high end house and cut corners by saving a couple of thousand using Osb board instead of plywood.

           

           

           

           

           

           

           

          1. User avater
            Soultrain | May 26, 2006 06:28am | #18

            I've seen plywood delaminate after just one rain storm.  I like Advantech for everything.

  5. mike4244 | May 27, 2006 04:34am | #23

    It's the typar not the osb. A friend of mine specializes in cedar siding,30 lb felt is all he will use. He says if the siding has typex,typar etc , he will remove it and go with the felt . He has seen this problem before, plywood will fare no better than osb according to him.

    mike

    1. toolpouchguy | May 27, 2006 02:23pm | #24

      have had the same prob with typar letting water in .don't use the stuff any more if it is exposed to the sun for a couple of days it not work as it should

      felt is the tried tested and holds up better than anything .i always strap and stain all surfaces of cedar siding i find typar will let water in but not out

      and use a air screen behind cedar shingle with felt. sheathing makes not diffence it could be ten test it is not to keep water out it is all the other layers after it.  

       just my thoughts on the matter

      if plywood is much better why shingle a roof .

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