# Tyvek



## Rider Rick (Mar 1, 2016)

Have you ever seen Tyvek used on the inside of exterior walls?


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## cda (Mar 1, 2016)

Should DuPont Tyvek® HomeWrap® be placed over or under the sheathing?

DuPont Tyvek® HomeWrap® can be used either over or under sheathing. When DuPont Tyvek® HomeWrap® is used under sheathing, it functions only as an air barrier and does not protect the sheathing as a secondary water barrier. DuPont Tyvek® HomeWrap® has been used directly over studs where there is no sheathing, although use of sheathing is a highly recommended building practice.

https://www.diyhomecenter.com/dupont/tyvek/faq.aspx

use a Tyvek® weather barrier in combination with a vapor barrier?

Using a Tyvek® weather barrier in combination with a vapor barrier depends on how the rest of the wall system is constructed, and the climate the building is in. If the majority of the year is spent heating the home, where the inside temperature is greater than the outside, it is generally good to use a vapor retarder behind the interior drywall. In hot, humid climates, vapor barriers should not be used.

http://www.dupont.com/products-and-services/construction-materials/building-envelope-systems/faqs/wb-faq.html


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## tmurray (Mar 1, 2016)

Nope. I guess the question is why are they installing it inside?


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## conarb (Mar 1, 2016)

In my estimation this has been the biggest failure or both contractors and building inspectors in cases I've been involved in, I'm glad to see that DuPont is finally making it clear that Tyvek is not a WRB.

The history is that DuPont tried and failed to get Tyvek approved as a WRB because it could not pass the "Boat Test" (or "water holdout test"), in what I consider an unethical move they got the ICBO to approve it as an air barrier and not a WRB (there was no air barrier requirement in the code), many CBOs approved it under the alternative materials and methods section of the code, I advised a few over 20 years ago that they were crazy and should be held accountable, the ICBO Report on the material clearly stated that ti was approved as an air barrier and not a water barrier.  Eventually DuPont changed course and attacked the boat test and got the ASTM to approve a new test, the 'Hydrostatic pressure Test",  a test with different parameters that Tyvek could pass, so for several years we had two tests for a WRB, the boat test and the hydrostatic pressure test.  When the ICC took over from the ICBO (and other code writing agencies)  the old approvals were supposedly retained as "Legacy Reports", at some point I went to the Legacy Reports to copy the original Tyvek approval and it had disappeared, I contacted the ICC and they disclaimed any knowledge of what had happened with some kind of weak excuse about all they were doing was republishing the ICBO reports as Legacy Reports.


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## Mark K (Mar 1, 2016)

My understanding is that in some climates it makes sense to put the membrane on the inside, but you need to know what you are doing.  You need to be talking to somebody who is an expert in building science.

Forget the evaluation reports.  What does the building code say about these membranes and whether the products comply with the code requirements.  One must keep in mind that ICC_ES takes money from manufacturers to product these reports and ICC-ES does not independently perform any tests.


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## conarb (Mar 1, 2016)

I haven't looked it up in years so I just did:



			
				\ said:
			
		

> *R703.2 Water-resistive barrier.* One layer of No. 15 asphaltfelt, free from holes and breaks, complying with ASTM D
> 
> 226 for Type 1 felt or other approved water-resistive barrier
> 
> ...


I am very surprised to see a change here from the last code I looked it up under, in the past there was also an exception allowing for an approved alternative, in the past CBO's who allowed Tyvek did it under the approved alternative exception and as far as I have ever seen required documentation in the form of an ICBO or ICC Report.  In the 2013 Code I see no exception allowing Tyvek or any other plastic wrap at all.  In the past allowing it was misfeasance, allowing it now is malfeasance.


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## msmrphy (Mar 2, 2016)

My $0.02

Conarb, you might also want to mention that special conditions apply if the finish is stucco and the sheathing is plywood.  My understanding is that plywood substrates require (2) WRB's under stucco.  I've seen too many failures in poorly applied stucco systems that used a  house-wrap only, without a backer paper.  You're simply inviting a soggy plywood sheet, and where I live that means termite infestation.  Perhaps I'm old school, but 15 # felts still do it for me as a WRB.  Air barriers are a different animal, of course, and permeance is key when deciding where to place it in the wall assembly.  My $0.02


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## conarb (Mar 2, 2016)

There is strange language in the code stating that the WRB can be omitted: . 3) Under paperbacked stucco lath when the paper, Paperbacked stucco lath is two layers of Grade D paper so it is an approved water-resistive barrier. Because of the problem you reference I go to great lengths and expense to eliminate the plywood sheathing, including getting the engineer to approve putting the diaphragm plywood on the interior rather than the exterior and it some cases installing a full steel frame.  The last home I built I installed a full steel frame because in our seismic zone the engineers require so much steel that it really isn't a larger expense.  In a prior house I had $30,000 worth of Simpson  metal which probably cost me $60,000 to install and there were still $30,000 worth of steel moment frames, on the last house I did a full steel framed for $120,000 with probably $10,000 worth of Simpson and labor.  Most affluent owners will pay the extra cost to get a better building.  I then use old fashioned line-wire and 4 coat stucco so there is no sheathing to rot out and seal up the walls.

The fact is that walls have to breathe to dry out from the inevitable moisture that is eventually going to get in, plywood seals the exterior and sheetrock seals the interior, if you use plywood sheathing you are creating a dual barrier sealing moisture in.  In the old days before plywood we used 1x8 boards for sheathing, and that is still in the prescriptive code, we used low grade 1x8 full of knots and green, when the knots fell out and the boards dried out there was plenty of room for the moisture to dry out the exterior.


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## JBI (Mar 2, 2016)

Diagonal board sheathing is a prescriptive bracing method as well.


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## conarb (Mar 2, 2016)

> Diagonal board sheathing is a prescriptive bracing method as well.


You know I considered that on a house but the mills, at least here in California, don't mill it any more, my yard offered to run 2x8s through their resaw machine to make them for me.  Too bad, we actually wanted very low quality material so plenty of air could flow through it.  Back in the 40s and 50s the first thing I did when starting a house was ordering units of 16' 2x4s and 16' 1x8s, we used the 2x4s for walers and the 1x8s to line the forms, after we stripped we had a laborer clean them up so we could reuse the 2x4s in the framing and the 1x8s as diagonal subfloor and wall sheathing if we were building a stucco house, we never sheathed a house getting redwood siding so the redwood could breathe, by the mid 50s we eliminated wall sheathing altogether and used line-wire behind stucco so it could breathe


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## ICE (Mar 2, 2016)

> Have you ever seen Tyvek used on the inside of exterior walls?


I have seen Tyvek end up in a pile on the top of the bottom plate.  There is another product called Barricade that is much more durable.  I don't know if it rots like Tyvek.


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## steveray (Mar 3, 2016)

Barricade is more plastic than Tyvek, so in theory it would rot less. I believe it is made by Berry Plastics with offices in Massachusetts and they will put any name you want on it for a price...

http://icc-es.cyberregs.com/data/ES/reports/ESR-1197.pdf


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## ADAguy (Oct 3, 2016)

Conarb, bet you used button board for interior lath too (smiling). Built my mom's house that way and it road through Sylmar and Northridge fine.


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## my250r11 (Oct 3, 2016)

It can be used as Grade D paper which means 2 layers for stucco. Here is the link to the ESR report.

http://www.dupont.com/content/dam/a...- DuPont Tyvek Water - Resistive Barriers.pdf


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## Pcinspector1 (Oct 3, 2016)

Rider Rick said:


> Have you ever seen Tyvek used on the inside of exterior walls?



No!


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## Pcinspector1 (Oct 3, 2016)

I once meet the guy from the Federal Government that said he prescribed polyethylene on the ceiling of government backed loans on residential homes. He was out promoting cellulose blow-in insulation after he'd worked for the Feds. 

He said Quote: "Don't do that!" 

He kinda looked like Jerry Clower!


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## conarb (Oct 3, 2016)

My250:

With conventional stucco 3 layers are required, on high quality work we are now doing 4 layers, that ES Report is confusing in that the one report covers several products, my interpretation is that it only applies to EIFS and one-coat stucco, not conventional stucco. 


> 5.0.5.3
> When  DuPont™  Tyvek®  StuccoWrap® –Style  1062X,  DuPont™  Tyvek®  DrainWrap™–Style 1063X or  DuPont™  Tyvek®  CommercialWrap®  D-Style  1083  are  used  in  an  EIFS  wall  covering assembly  with drainage or a one-coat stucco assembly as described in  Section  4.4,  the  assembly must  be  specifically recognized  in  the  evaluation  report  on  the  EIFS  or one-coat stucco.


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## my250r11 (Oct 3, 2016)

They have to use the correct style but the report says they comply with type D paper.
Cali. might require more but here just the min. above and beyond is great but don't get it much.


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## ICE (Oct 3, 2016)

Conarb,
Please enlighten me on steps, materials and methods that you employ to avoid cracks in stucco plaster.

Thanks


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## conarb (Oct 3, 2016)

my250r11 said:


> View attachment 2409
> 
> 
> They have to use the correct style but the report says they comply with type D paper.
> Cali. might require more but here just the min. above and beyond is great but don't get it much.


How do you know as a plan checker which "style" complies? 

The biggest problem with any plastic WRB is they all disintegrate when in contact with a surfactant, cement,*tanins*  in redwood and cedar are all surfactants.  About 30 years ago a Stanford electrical engineering professor asked me to bid his house, he specified Tyvek under redwood siding, I refused to build the house with Tyvek, he insisted on it because fo it's air blocking qualities, the house was on a hill top overlooking the Pacific Ocean on the west and Silicon Valley on the east, the house was/is subject to over 100 MPH winds.  A few years ago he called to say that I was right, all the Tyvek had literally disappeared leaving nothing but a few white plastic shards at the bottom of walls, he had ripped the redwood off a couple of leaking walls. He wanted me to replace the redwood with Grace's new liquid Therm-A-Barrier and the Hardie Artisan siding, again I refused.  You can go to Building Science Corp's site and find all kinds of information on Tyvek and tannins. 

Tiger:


			
				Tiger said:
			
		

> Please enlighten me on steps, materials and methods that you employ to avoid cracks in stucco plaster.



I do not sheathe behind stucco, if I have to I use diagonal 1x8 but prefer to get the engineer's approval of interior sheathing, or brace with a steel frame.  The best way to explain is a picture fo one of my walls, house braced with a steel frame, two-layers of Grade D over line-wire, one scratch coat of stucco, one brown coat of stucco, two color coats of
	

		
			
		

		
	



	

		
			
		

		
	
 stucco.


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## Pcinspector1 (Dec 14, 2016)

conarb, your opinion of Zip wall systems, or do I all ready know?


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## conarb (Dec 14, 2016)

Pcinspector1 said:


> conarb, your opinion of Zip wall systems, or do I all ready know?


You know, you can't have a dual barrier, somewhere sometime water is going to get inside the wall and needs to dry in or dry out, put sheetrock or plaster on the inside and it has to dry out, Zipwall seals it in.


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## mfichter80 (Jan 10, 2017)

conarb said:


> You know, you can't have a dual barrier, somewhere sometime water is going to get inside the wall and needs to dry in or dry out, put sheetrock or plaster on the inside and it has to dry out, Zipwall seals it in.



I have no skin in this game, just looking for different perspectives on this.  But my understanding is that tyvek, tar paper, and I assume the zip system do not (or are not intended to) completely seal moisture in.  The perforations in tyvek are supposed to allow moisture to evaporate out, but keep water from leaking in.  I always thought tar paper made more sense though, and would hold together a lot better.

I would think the only time something similar to tyvek is actually on the inside of a wall would be on the inside of masonry or concrete foundations and crawls, when there are no studs on the wall.

And I have never heard of putting sheathing over tyvek... I guess that would be similar to putting the tyvek around the outside of the studs and putting t-111 over that?

Anyway there is a difference between the "puffy jacket" thing of completely sealing a house with a membrane, foam insulation, etc. vs. just having something like tyvek as a vapor barrier, where it should be able to dry out.  In addition to the potential for water damage, for how freaked out everyone is about mold, and considering the real dangers related to radon, I have always thought making a house completely water and air tight is absurd... but for some reason people are doing it, and it's not cheap either.


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## Rick18071 (Jan 10, 2017)

If tyvek is a "Water-Resistive" barrier which is different than a "Vapor Retarder" that is required under slabs.
What's the difference?


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## JBI (Jan 11, 2017)

Rick18071 said:


> If tyvek is a "Water-Resistive" barrier which is different than a "Vapor Retarder" that is required under slabs.
> What's the difference?


Water resistive barrier prevents liquid water from penetrating into the assembly but is vapor permeable allowing water vapor to escape, a vapor retarder impedes water vapor from passing into the assembly.


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## tmurray (Jan 11, 2017)

Rick18071 said:


> If tyvek is a "Water-Resistive" barrier which is different than a "Vapor Retarder" that is required under slabs.
> What's the difference?


 Water resistive barriers do not allow the passage of liquid phase water. Vapour retarders slow the passage of gas phase water (vapour). Important to note that the poly underneath a slab is not there for vapour resistive purposes, but as a capillary break. The slab itself may be considered a vapour barrier. Keep in mind that just because a building material absorbs water, doesn't meant it can't be a vapour barrier. Stud wood is another good example of a material that absorbs water, but is also a vapour barrier.


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## mfichter80 (Jan 11, 2017)

Rick18071 said:


> If tyvek is a "Water-Resistive" barrier which is different than a "Vapor Retarder" that is required under slabs.
> What's the difference?



I don't know the actual definitions of these terms, it's just like mobile home, manufactured home, industrialized building, trailer, tiny home... other than "industrialized building", all the other terms can mean different things depending on who you are talking to or what you are talking about.  But the bottom line is that that tyvek has holes in it, and what you put under your slab doesn't.  The holes in tyvek are supposed to be small enough to keep out drops of water, but big enough to allow vapor to evaporate out from behind it, because vapor particles are smaller than water droplets.  As far as I can tell tar paper does the same thing, so I don't know why tyvek is supposed to be better.

Usually what goes under a slab is solid plastic.  Around foundations and under slabs you want to block water out of any kind, because if water drains under the slab, basement wall, or foundation, it evaporates up onto the floor, or into the crawl or basement.  It rises up into the area you are trying to protect.

Under a building, depending on the grade and density of the ground, gravity and dirt will keep water from draining or evaporating away from a structure, but in a wall it's not as hard to direct the vapor away from the structure.


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## tmurray (Jan 11, 2017)

mfichter80 said:


> I don't know the actual definitions of these terms, it's just like mobile home, manufactured home, industrialized building, trailer, tiny home... other than "industrialized building", all the other terms can mean different things depending on who you are talking to or what you are talking about.  But the bottom line is that that tyvek has holes in it, and what you put under your slab doesn't.  The holes in tyvek are supposed to be small enough to keep out drops of water, but big enough to allow vapor to evaporate out from behind it, because vapor particles are smaller than water droplets.  As far as I can tell tar paper does the same thing, so I don't know why tyvek is supposed to be better.



Just to be clear, Tyvek (and other WRBs) allow vapour to pass in both directions. This is an issue along coastal regions where capillary moisture between the WRB and the siding is pushed into the building envelope when that wall surface gets exposed to the sun.

Tyvek is better because their marketing says so. Tar paper has an advantage in that the permeability rate varies with the amount of moisture, while WRBs mostly have a static permeability rating. Really, neither is better than the other, it all depends on how you design your enclosure. Just different tools for different jobs.


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## Rick18071 (Jan 11, 2017)

Cool, so Tyvek is like Gore-Tex boots.


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## Paul Sweet (Jan 11, 2017)

I think the only advantage for Tyvek (or equal) is the width of the roll which allows it to go on quicker - $$$.


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## Yikes (Jan 26, 2017)

tmurray said:


> Water resistive barriers do not allow the passage of liquid phase water. Vapour retarders slow the passage of gas phase water (vapour). Important to note that the poly underneath a slab is not there for vapour resistive purposes, but as a capillary break. The slab itself may be considered a vapour barrier. .



The technical support reps at Stego Wrap say that the air gaps between aggregate underneath the poly is the capillary break, and the poly is the vapor barrier, and concrete has tiny pores that can make it act like a sponge.
 With our buildings being sealed so efficiently these days, you can actually get a water vapor pressure differential via your HVAC system.  Turn on your air conditioner, and the room is dehumidified.  Meanwhile, the soil under the foundation has moisture in it, and in vapor form it eventually gets sucked up into the slab towards the "low pressure weather system" that is your room interior.  If you have VCT, some of that water lingers on the underside of the tiles, and today's water-based glues can't stick when the slab stays moist.  The next thing you know the building owner is yelling at the contractor that their building tiles are popping up.  I've seen this happen in buildings in the Arizona desert in summer!

To prevent this:
1.  Use aggregate, not dirt or sand, below the slab to create a robust capillary air break.
2.  Put the poly vapor barrier right on top of the aggregate.  (This where are reinforced barrier will help prevent tears.)  Seal all edges and penetrations; they make special tapes and adhesives for this.
3.  Put the floor rebar system on top of the barrier.  Do not add a layer of protective sand (explanation to follow below*).  A good reinforced vapor barrier will help prevent punctures during construction.
4.  Pour the concrete.  Keep only as moist as necessary, but don't over-water (e.g. don't run a sprinkler 24/7 on top of the slab).

*The reason you don't want a protective sand layer on top of a well-sealed vapor barrier is that during the concrete pour, the sand will hold a lot of moisture form the concrete mix, but it can't drain downward (because congratulations, you did such a good job of sealing the barrier).  It is too easy to over-water the slab during its curing period.  If the sand gets soaked in that situation, it may take 12-18 months to dry out enough to glue down flooring.


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## tmurray (Jan 27, 2017)

Yikes said:


> The technical support reps at Stego Wrap say that the air gaps between aggregate underneath the poly is the capillary break, and the poly is the vapor barrier, and concrete has tiny pores that can make it act like a sponge.
> With our buildings being sealed so efficiently these days, you can actually get a water vapor pressure differential via your HVAC system.  Turn on your air conditioner, and the room is dehumidified.  Meanwhile, the soil under the foundation has moisture in it, and in vapor form it eventually gets sucked up into the slab towards the "low pressure weather system" that is your room interior.  If you have VCT, some of that water lingers on the underside of the tiles, and today's water-based glues can't stick when the slab stays moist.  The next thing you know the building owner is yelling at the contractor that their building tiles are popping up.  I've seen this happen in buildings in the Arizona desert in summer!
> 
> To prevent this:
> ...



Be careful not to confuse moisture moving through assemblies in different phases. Just because a product prevents the passage of moisture doesn't mean it won't absorb water. concrete and lumber both have permeability rates less than 1 perm (60ng/(s*Pa*m^2) in Canada, man I wish I could measure permeability like you folks), but both are hygroscopic and will readily absorb water. This makes a concrete foundation ideal to prevent soil gas infiltration into most buildings, but a capillary break is required below the concrete. The major issue is that most contractors do not use a capillary break beneath the footing, so unless unless there is another capillary break, say between the footing and the wall and slab, you've just created a capillary bridge. Water will travel about 10 kilometers high in concrete, so it can travel quite a distance.


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## Clem Kadiddlehopper (Feb 23, 2020)

Any pictures of the walls where all the Tyvek had literally disappeared leaving nothing but a few white plastic shards at the bottom of walls?


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## ICE (Feb 23, 2020)

Clem Kadiddlehopper said:


> Any pictures of the walls where all the Tyvek had literally disappeared leaving nothing but a few white plastic shards at the bottom of walls?



Sorry but no.  I have seen that one time and that was thirty-five years ago.


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## jwilly3879 (Feb 23, 2020)

I have seen tyvek used on the back of attic kneewalls as an air barrier.


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## ADAguy (Feb 25, 2020)

conarb said:


> There is strange language in the code stating that the WRB can be omitted: . 3) Under paperbacked stucco lath when the paper, Paperbacked stucco lath is two layers of Grade D paper so it is an approved water-resistive barrier. Because of the problem you reference I go to great lengths and expense to eliminate the plywood sheathing, including getting the engineer to approve putting the diaphragm plywood on the interior rather than the exterior and it some cases installing a full steel frame.  The last home I built I installed a full steel frame because in our seismic zone the engineers require so much steel that it really isn't a larger expense.  In a prior house I had $30,000 worth of Simpson  metal which probably cost me $60,000 to install and there were still $30,000 worth of steel moment frames, on the last house I did a full steel framed for $120,000 with probably $10,000 worth of Simpson and labor.  Most affluent owners will pay the extra cost to get a better building.  I then use old fashioned line-wire and 4 coat stucco so there is no sheathing to rot out and seal up the walls.
> 
> The fact is that walls have to breathe to dry out from the inevitable moisture that is eventually going to get in, plywood seals the exterior and sheetrock seals the interior, if you use plywood sheathing you are creating a dual barrier sealing moisture in.  In the old days before plywood we used 1x8 boards for sheathing, and that is still in the prescriptive code, we used low grade 1x8 full of knots and green, when the knots fell out and the boards dried out there was plenty of room for the moisture to dry out the exterior.



Thank you for reminding me how "old" I am as I know of what you speak. So much is unknown/forgotten by old and young tradesmen alike. Something to be said for institutional memory loss/retention. You are appreciated for this (smiling).


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