Questions & answers on the installation requirements for house wrap, air barriers & water barriers under siding:

Frequently-asked questions, and answers, about installing housewrap, air barriers, water barriers, "vapor barriers" on building walls.

This article series discusses of the need for external vapor barriers beneath vinyl, siding - building code requirements, interpretation, and home inspection concerns.

Housewrap FAQs: Water Barrier on Building Exterior Walls

These questions & answers were posted originally

at VAPOR BARRIERS & HOUSEWRAP.

Our photo shows an example of Typar housewrap being applied during new construction.

The 2003 International Building Code calls for a “waterresistive barrier behind the exterior veneer” consisting of flashings and a “weather-resistant sheathing paper” lapped at least 2 inches horizontally and 6 inches vertically.

On 2017-08-23 by (mod) - housewrap details around windows and doors

Bill,

In new construction the housewrap is wrapped into the rough opening, stapled, trimmed.

In retrofit construction the housewrap is brought over the window or door trim but trimmed short so it won't stick out (ugly) past the ultimate cap flashing or side or j flashing around the opening.

In both of those cases we rely on proper installation of flashing tape around the window or door to keep water out where it belongs.

See PEEL & STICK FLASHING MEMBRANES

On 2017-08-23 by Bill

Thanks again so much, that was an amazing amount of info. I think I understand that this is a product that does what it is designed to do and I should not be worried about it per say.

The more important part is the installation process. Right now they are overlapping anywhere from 2" to 2 feet held down with nails and orange "washer". they are not using chalk or and sealant and are not marrying the wrap all the way to the window edge.

Also, it has started to rain, pour really, and they have not finished so everything is now wet, concernS??

On 2017-08-23 by (mod) - Effectiveness of plastic housewrap and EverBilt housewrap - opinions

Thanks for the follow-up: I hadn't considered remarking on Everbilt house wrap itself.

Everbilt is a 4.8 mil thick house wrap made of a "woven fabric made of HDPE high density polyethylene [plastic], coated on both sides with UV-resistant treated LDPE low density polyethylene as a coating.

It's basically polyetyhlene, "a tough, light, flexible synthetic resin made by polymerizing ethylene, chiefly used for plastic bags, food containers, and other packaging."

This is the most-widely used plastic, probably, in the world. According to its Home Depot listing it

Meets Building Code requirements: ICC-ES report no.: 2955, 2009 International Building Code (IBC), 2009 International Residential Code (IRC)

Water resistive barrier

Exceptional water vapor transmission: allow moisture to escape without condensing in the wall cavities-preventing mold and mildew

(not to mention that there is no mildew in buildings, mildew only grows on living plants, but that's another gripe).

I don't have a perm rating yet but 6 mil polyethylene has a perm rating of about 0.06 - very low. That would explain why, if I guess right, the product is micro-perforated to let it breathe moisture vapor out while keeping actual water out.

OPINION: I prefer the non-plastic house wraps but can't support that with science. More important than the house wrap material is probably how it is installed.

Most of the leak problems I've seen in years of field research, including siding tear-off inspections, have been from improperly-installed wraps: overlapped the wrong way, cuts and tears, omissions, and worst: improper detailing, lapping, sealing, flashing around the wall penetrations for windows, doors, lights, etc.

If you use the page bottom CONTACT to get my email I can send you some data sheets and the certification report on this product.

On 2017-08-23 by Bill

Thanks very much. What about that product? I had a neighbor take a look and tell me that the Everbuilt was not good and should not be used. The builder is using Norandex Wrap on another part of the house, it looks like he ran out so he got the Everbuilt.

On 2017-08-23 by (mod) - ok to leave old felt building paper on walls

Bill

Leaving on the old felt paper under the new house-wrap should not be a problem.

On 2017-08-23 by Bill

I am having old fake stucco replaced with hardi board. The contractor has removed the stucco, left on the tar paper barrier and placed a vapor barrier (Everbuilt sold a Home Depot) on top of it, is this correct?

On 2017-01-26 by (mod) - housewrap on interior walls?

Why house wrap on the interior?

On 2017-01-26 by david

have a steel sided pole barn was goin to put up typar on from the inside (barn allready built) then blue fan fold to help and to make up the stud difference in size (old poles are 5.5in.newer wall stud are one eigth smaller ) then put insulation with VP between studs will that be ok?

On 2016-07-10 by (mod) - fungal stains on tar paper underlayment

Dale,

I don't know your situation, but basically if you're tearing off all of the siding, the cost to tear off and replace old moldy (really?) felt house wrap with modern housewrap would probably be much less than the cost of trying to clean an old material (the asphalt-impregnated felt or "tar paper"). Besides you'd be replacing the material with one that works better.

On 2016-07-10 by dale

I have fungus stains on tar paper underlayment where I am replacing the siding should I clean, treat or replace it?

On 2016-06-28 by (mod) - R-values of HouseWrap

https://inspectapedia.com/interiors/TUFF_R_Product_Lit.pdf has some R-value claims

https://inspectapedia.com/insulation/Insulation-Values-Table.php is our complete table of R-values

You won't find claims for any R-value of housewrap but innately there is one in the R-value of thin layers of air on building walls, given in the table above.

Blocking air leaks is by far the more-important role of housewrap in saving energy.

On 2016-06-28 by Anonymous

What if Any R Value Does Regular House Wrap Provide
Thanks

On 2016-01-04 by (mod) -

Don't take the foam off; it may be fine; if you can, make a sketch for me so that I understand the wall structure, layers, materials, and send it using the page bottom CONTACT link and we can discuss this further.

It was good to open old walls, evict the visitors and clean the wall cavities. that makes wiring easier too. We'll discuss some insulation options when I know more.

On 2016-01-03 by Greg

Thank you for your response. We live in Western NY 60 miles south of Buffalo. The inside walls are only 4" thick with drywall and we're planning on putting mostly wood on the walls.

It has (Pink Panther) insulation. My original intent was to stud inside (rooms were big enough) and run all electric,plumbing and so on.

However, in places that I had to tear out walls and floors, all we found were nests from squirrels possum (recenctly deceased) and assorted other critters! Glad we found them! Anyway, so with what's inside, there's the planks (not completely covered, has spaces)and then the 1/2 foam board.

My thoughts are to, cover with OSB and then wrap it, then side it.

Or wrap it and side it, or do it the way I think it should have been done which is, OSB, wrap foamboard and siding. If I am looking for more problems by not taking the foam board off and doing it right, then I guess I'll have to. Your advise it greatly appreicated.

On 2016-01-03 by (mod) - OK to install foam boards with OSB?

Greg:

I don' t think we have the full picture, as you don't describe the whole wall structure, omitting what's in the wall cavity, where the vapor or moisture barriers are inside and moisture or rain barriers outside, nor in what climate the home is located. In a cooling climate (such as Georgia) the moisture barrier may go on the outside of a wall that would have it on the inside in Missouri.

But in general we don't want to build a wall that traps moisture inside the structure - risking rot, mold, insect damage. So consider the whole wall's R-value, where in the wall the dew point may occur, and where to place the moisture barrier and air barrier.

On 2016-01-03 by Greg

We have an old farm house that all of the clapboard and felt paper has been removed. Then 1/2" foam insulation boards have been put on directly over the outer planks of the walls.

Can this now be covered with OSB and then housewrap and vinyl siding? I'm pretty sure that the OSB or plywood should have gone on first and then the wrap but, that really isn't much of an option now. My e-mail is gregk3449@hughes.net Thank you for your time and this is a very informative website!

Comment:

(May 31, 2011) DIMA said:
Very clever

Question: asphalt roofing paper atop Tyvek?

(Aug 26, 2012) ray said:
can asphat building paper be applyed over top of tyvek plastic wrap

Reply:

Can, yes. But why?

Question: siding and wall leak diagnosis needed

(Feb 15, 2014) andy said:
The wind is blowing rain through my out side wall to inside wall

Reply:

Andy, you'll need to inspect very carefully the head flashing at windows and doors, starting with the J-channel if your home has vinyl or aluminum siding installed.

Then you may have to pull off some siding when weather permits to see where water is entering - most likely there are flashing or housewrap errors.

Sometimes we can't see exactly where water is entering until we remove some of the siding from suspicious areas.

Question: using Typar under steel siding on a barn

(Feb 16, 2014) Ruth said:
i am wondering about using Typar under steel siding on a barn. Is it studs then Typar then strapping then steel siding or is it studs then strapping then Typar then the siding on it? I can see reasons for doing each way. Went through the Typar site and do not see this info...nor a contact address. Thanks!

Reply:

Ruth; starting by admitting I don't know, I still have an opinion: in normal wood frame construction the housewrap is installed on the exterior surface of the wall sheathing that has been nailed over studs - then we use flashing tape around windows and doors, then the siding is installed, then trim.

I take it that by strapping you refer to diagonal steel straps for wall rigidity since there is no sheathing being installed? If we were installing sheathing we'd do that, then install the house wrap, then the siding.

If there is no sheathing, just strapping, it'd probably be best to install the housewrap after the strapping - my OPINION - is that by doing so we avoid damaging or ripping the siding or punching unnecessary holes in it while installing strapping.

But as housewrap is normally stapled to wood sheathing, how are you fastening it to the structure? Tape?

So my final arm-waving is to suggest that you ask the building and siding manufacturer for advice. Depending on the type of exterior steel siding being installed, there may be no advantage at all to using any building wrap product.

(Feb 16, 2014) Ruth said:
hi - thanks for your comments - correct - no sheathing will be used. By strapping I mean wood strips put on the framing members...if using wood siding we would put the Typar on the 2x6 framing material and then put the strapping on which creates an airspace and then the wood siding. But as this is steel siding we are not sure if an airspace is needed. The strapping is used to have something to fasten to as the siding will be installed vertically.

We have two opinions if the siding is directly against the Typar....one is the screws (steel siding is installed with screws/washers could mess up the Typar as it goes through it into the strapping (I think this was from experience)...and the other view is the idea that the Typar would protect the wood strapping from water damage.

I think the siding company had no opinion...cannot find a Typar contact number or email but will ask retailer.

Reply:

Ruth you make some good points; If you put the housewrap on before the horizontal strapping (to which vertical siding will be fastened), followed by strapping, then siding, not only does the strapping protect against a possible (IMO unlikely) event of a screw binding and tearing the housewrap, you also obtain a (probably 3/4") air gap that may improve the wall energy performance and would certainly allow for condensate or water penetration down to the wall bottom.

I'm doubtful that the retailer will have more than an arm waving opinion (as ours) about this, but people who build steel buildings should have an opinion.

Here are a couple of interesting references

(While I don't always agree with him, Joe L. in my first citations is indeed an industry expert whose views should be considered)

• Lstiburek, Joseph. "Water-Managed Wall Systems." Journal of Light Construction (2003).
• Lstiburek, Joseph. "Moisture control for buildings." ASHRAE journal 44.2 (2002): 36-41.
• Kasal, Bo, and Pat Huelman. "Design of Residential Building Shells: Minneapolis and Atlanta." (2004).
• Carll, Charles. "Rainwater intrusion in light-frame building walls." Proceedings of the second annual conference on durability and disaster mitigation in wood-frame housing. Madison, WI: Forest Products Society. 2000.
• Charlson, Joseph A. "Composite insulated framing members and envelope extension system for buildings." U.S. Patent 6,125,608, issued October 3, 2000.
• Zatkulak, Tony D. "Method for reducing penetration of liquid through nonwoven film-fibril sheets pierced by fastening elements." U.S. Patent 5,497,596, issued March 12, 1996.

Question:

(May 4, 2014) fj said:
when do I install typar housewrap between osb sheathing and 1 inch rigid board insulation or after osb and rigid board insulation THANK-YOU

Reply:

FJ:

If you're using housewrap as recommended it's the outer-most covering before the final siding is installed.

Question: Use Typar or house wrap on a 30 year old cedar sided house before installing vinyl siding?

Dec 15, 2014) Anonymous said:
should installers use typar or other new house wrap on a 30 year old cedar sided house before installing vinyl siding

Reply:

Unclear; are you removing the old siding or leaving it in place? What's beneath the old siding and in what condition is it?

Question: condensation and frost or ice on interior side of house wrap

Richard said:
Part of our basement is below grade with concrete walls and part above with traditional framing, Tyvek wrap, and siding. In cold weather, the inside of the Tyvek behind the insulation on the framed walls is wet, sometime ice, even with the house humidifier turned off. Is this normal? Should I be concerned? Thank you,
Richard

Reply:

Richard

Certainly I'd want to know why you're getting condensation in an area that ultimately could be asking for a mold or insect damage problem. Look for missing insulation, air leaks, or leaks from outside (less likely from what you've described).

Question: information about Insultex® house wrap

(Mar 17, 2015) David Osina said:
Have you examined the house wrap "Insultex"?

Reply:

No. I can tell you this is an insulating house-wrap that can add R-3 (1.0 mm thickness) or R-6 (1.5mm thickness) insulation value to the house wall (according to the company). Whether or not you want to add insulation to the exterior of your wall sheathing may depend on the climate where you live. Here is contact information from the company who can provide more details.

• Innovative Designs, Inc. 124 Cherry St. Pittsburgh, PA, 15223 P: 412-799-0350 F: 412-782-5303 

More Information about Insultex® house wrap is at the company's website: http://www.insultexhousewrap.com/ from which we excerpt:

Insultex House Wrap ® is a closed-cell foam composite with superior drainage and R-Value. This certified product meets or exceeds the competition in air and water resistance moisture vapor permeability and durability.

Watch out: website: insultex.com was not working other than as an advertising page as of October 2015

Question: installing new siding over asbestos-cement siding

(Sept 7, 2015) Marc G. said:
Can insulated siding go over asbestos siding without housewrap?
Please advise.
thanks!

Reply:

Physically "can" - of course.

Should ? The risk of omitting the housewrap is that there may be future leaks into the wall structure and wall cavity. You'd think "not" considering that you're adding a layer of siding, but in fact every nail banged through furring strips or banged directly into the asbestos cement siding is going to both punch holes and often physically break or crack much of the material.

We don't know the condition of any water or vapor barrier behind the asbestos cement siding but typically what was used was red rosin paper or at best 15# roofing felt.

In sum your job will be more water resistant if you use a housewrap.

...

Continue reading at VAPOR BARRIERS & HOUSEWRAP or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see

VAPOR CONDENSATION & BUILDING SHEATHING

PERFORMANCE TABLE of HOUSEWRAPS - permeance ratings or "perm" ratings of types of housewrap materials & plywood & OSB

CAN the VAPOR BARRIER or HOUSEWRAP be OMITTED?

Suggested citation for this web page

VAPOR BARRIER & HOUSEWRAP INSTALLATION FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to EXTERIORS of BUILDINGS

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