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What's the "house wrap" obsession all about?

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tagal4

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I'm starting to get my ducks in a row for re-shingling the outside walls of my house with cedar shingles like what was on it originally and I'm having a hard time understanding what this business of "house wrap" that seems to be all the rage nowadays is about, when for probably over a century tar paper (some would call it building felt or felt underlayment) was used to cover every house's sheathing and it worked just fine. The spiel seems to be house wrap offers wind and moisture resistance, but isn't that the main reason why we put siding on our houses? If house wrap is so great why isn't it commonly used on the roof also because the roof is just as susceptible to moisture and wind infiltration. I'm thinking if people are putting house wrap under their siding for wind and moisture resistance they must not have a lot of confidence in their siding, and they are being suckered into using an expensive material unnecessarily. To me it seems like the most important thing would be to get whatever underlayment you use on the side of you house covered up in a timely manner and not expecting it to BE your siding indefinitely. I could understand plastic siding not offering much in the way of protection for a house's exterior walls, but several layers of cedar shingles (the way shingles are typically installed) with properly staggered joints seems like it would be impervious to about anything mother nature could dish out.
 

kok328

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well nowadays, the have synthetic roof underlayment. seems pretty much to be house wrap. very much desired if you have only vinyl siding. my house was built in 1997, finished with vinyl siding and much to my surprise, it does NOT have any wrap underneath. on windy days, you can just feel the heat leaving the home. :mad:
 

Snoonyb

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As in all phases of life, evolution will out last us all.

The dwelling, "conditioned space," that we occupy, has a demand, yet adjustable, comfort level, which is "engineered" to be within certain boundaries, which "evolution" has deemed the use of systems and practices, a step toward optimization.

Walls, ceilings and floors, didn't need to be insulated, cedar shakes were acceptable, as was asbestos siding.
 

Flyover

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I don't know much about siding or housewrap in particular but I'd guess it's a similar pattern as where you could say "What's this 'asphalt shingles' obsession all about? Thatched straw worked just fine!" or "What's this 'electric/gas stove' obsession all about? Wood-burning stoves worked just fine!" or "What's this 'car' obsession all about? Horse-drawn carriages worked just fine!" Being somewhat of a Luddite I am definitely sympathetic to these sentiments.

@Snoonyb alluded to the "evolution" of systems and practices, but I don't think that term should construe linear progression. To quote the sci-fi author Neal Stephenson, "every adoption is an amputation". We perceive new technologies as being a step forward, and when we abandon the old technologies we call them "obsolete" as if the entirety of their value has been nullified. But in just about ever case that isn't really true. My old eggbeater drill still has some advantages over my electric one, even if by the most obvious metric (effort-to-work ratio) it is inferior. New technologies tend to optimize some aspects of the relevant system or practice, while other aspects are ignored or even made worse. You'll hear many people on this forum complain, for example, about newer energy efficient washing machines.

So, I'd guess maybe the relationship between housewrap and tar paper is the same: housewrap is better in some way that lots of people now consider important, but doesn't substantially improve on tar paper in other ways or may even be inferior. If those other ways are equally important to you, then housewrap will seem like a big fuss over nothing.
 

oldognewtrick

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Roofing felt/tar paper will degrade over the years after exposure to heat cycles. When you penetrate the membrane with a fastener it's like sticking a pencil through a newspaper, it leaves a jagged hole. Some of the newer synthetics will have an effect like a nail in your tire, it will seal around the nail to an extetent. The purpose is to minimize wind drift through the wall. Sealing around doors, windows and any wall penetration is equally important for weatherization.
On a roof, you want any moisture that migrants into the attic to have the ability to evacuate the attic through exhaust vents. Synthetic roof underlayments have been used in roofing for years, it's a more durable underlayments and allows for UV expose during new construction.
 

bud16415

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Interesting discussion.



My take is in today’s world efficiency is the relative driver that and simplicity. When constructing a building the time on labor cost many times outweighs the material cost. There was a time where it was cost efficient to have someone cut logs into sections and then hand split out shingles then another worker would hand nail overlapping shingles over rough sawed sheathing on the outside and on the inside nailed up lath covered by 3 layers of plaster fortified with pig or horse hair. Those days were a time of cheap and abundant labor and skilled people that didn’t mind working.



Today we have automation of all building products starting with cutting trees to pumping oil out of the ground hardly anything is touched by human hands.



House wrap is likely cheaper to make and with the efficiency of installing can be sold for more than older tech. So win/win greater profits all around.



All things are market driven within capitalism. Like it or not.

Being a thrifty DIYer I sometimes have to make my DIY capitalism apply using personal factors. No professional builder is going to tear down an old structure and build a new one from it because it would be cost prohibitive over using new materials. The same is true (maybe) for DIY home wrap. It might just be better or cheaper or easier for a single guy doing a vapor wrap job to use felt paper still.
 

Sparky617

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If you're replacing cedar shakes, you'll want to look at the mesh underlayment on top of the house wrap that will allow the shingles to dry out better after a rain storm. House wraps also keep any moisture that gets through the siding material to drain outside without soaking the sheathing. Some siding materials are better than others at keeping water out and away from the sheathing.
 

tagal4

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As far as tar paper degrading over time goes the 80 year old tar paper under my shingles looks as good as new tar paper except for the dirt and nail holes, and it also looks like it did a good job keeping the moisture off of my sheathing. I don't buy the argument that house wrap seals around nails any better than tar paper does. Also around where I live in central Kansas all the roofs I see being replaced have tar paper put down first, not some new fangled synthetic material.

The reason I want to replace my underlayment before shingling is because of all the nail holes and the large holes left behind by the guys who blew insulation in my walls in it . They used ill-fitting plastic plugs in their holes afterwards so I had to order some of the tapered wood plugs in the appropriate diameter and I've been gluing them in the holes my house' solid wood sheathing since I'm pretty obsessed about making sure the cellulose insulation that is now in my walls stays dry, although the cold weather here has put the kibosh on that project.

I was wondering about the mesh under shingles. I'm not doing shakes but smooth cedar shingles, and I plan to stain them ahead of time on all sides before nailing them on so I was wondering if the mesh is necessary then. Seems like the mesh is mainly for raw wood shingles so they can dry out, or raw wood shingles that are only going to be finished on the outside after they are installed. If all sides of the shingles are sealed fairly well I can't see much point in using the mesh.

The only benefit I can see in "house wrap" is it is lighter and easier to work with than tar paper, especially if you don't have a helper to help install it. Also, they have house wrap that is 9' wide so you can do a house in a short amount of time with fewer overlaps to waste material.
 

oldognewtrick

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Huge difference in tar paper of 80 years ago and asphalt impregnated roofing felt of today.
 

bud16415

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My old place I bought a few years back on short sale came with a nice new vinyl siding job. In remodeling the house I moved and added a couple windows and put in a door. When I started into the walls they are horsehair plaster inside over lath. On the outside there is 1” rough saw sheathing and over that wood clapboard siding over that asbestos siding over that .5 fan fold foam all taped and over that the new vinyl. I often wonder how my vapor barrier and R number is. It gets super cold here and it’s a good size 2 story house and the gas bill is like 130 bucks last month. I’m not about to rework any of it. It was a bit of a pain extending the framing out and the jambs in.



I wanted a cheap way to cover my workshop outside and I used rolled roofing hung vertically and battens made from ripped PT 5/4 decking. That asphalt rolled roofing is more like the old tar paper only with stone dust added.
 

tagal4

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My old place I bought a few years back on short sale came with a nice new vinyl siding job. In remodeling the house I moved and added a couple windows and put in a door. When I started into the walls they are horsehair plaster inside over lath. On the outside there is 1” rough saw sheathing and over that wood clapboard siding over that asbestos siding over that .5 fan fold foam all taped and over that the new vinyl. I often wonder how my vapor barrier and R number is. It gets super cold here and it’s a good size 2 story house and the gas bill is like 130 bucks last month. I’m not about to rework any of it. It was a bit of a pain extending the framing out and the jambs in.



I wanted a cheap way to cover my workshop outside and I used rolled roofing hung vertically and battens made from ripped PT 5/4 decking. That asphalt rolled roofing is more like the old tar paper only with stone dust added.
Yea, those plastic siding folks will put their cheap crap over anything. I have actually seen the plastic siding extend further out than the roof (on houses with no roof overhang) that had it installed on it was over so many layers of existing siding.

In regard to asbestos siding (actually it was asbestos impregnated cement siding according to my research): I believe this was the "no maintenance" siding of the mid-20th century and was installed much like plastic siding is today - right over whatever was already on the house. This is why you often find good wood siding underneath it if you take it off. Some new houses built during the era probably got installed as the only siding however.
 

AskToddMiller

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Much has changed over the years in how we construct and use our homes. Our homes are built to be much more airtight than in the past, especially in regards to doors and windows. At the same time, we create much more moisture inside our homes than ever before from bathing, laundry, cooking, dishwashers, houseplants, ventless gas stoves, etc. That moisture is always trying to drive to drier places. It used to go out through leaky doors and windows but it can no longer do that. So, housewraps are designed to be breathable -- sore of like Gore-Tex. They help let that moisture vapor pass from the inside to the outside through the walls. Much of that moisture though still migrates to the attic, carried by convective air forces with warm air. That moisture, in the attic, will condense if it stays there and hits a cool surface, usually the back of the roof deck. So, we vent our attics normally with intake and exhaust vents to get the moisture safely outside. Most synthetic roof underlayments do NOT breathe except through their seams, expecting that moisture to be carried out by ventilation. I agree that, on your walls, a combination of a breathable house wrap plus the entangled mesh product such as Vent3 or Cedar Breather to create a drainage plane behind the wood shakes is wise. This way, moisture that drives out through the housewrap will have a drainage plane rather than get trapped and condense in the wood shingles, causing them to rot from the back side. I hope this helps.
 
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