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Gene’s aborted discussion of the Vinyl/Housewrap lawsuit did raise the following question: “And is it still said by y’all that no paper or Tyvek under vinyl is plain stupid?” I’m sure I could find the answer to that if I did a search, but this area is not inundated with new threads, so here goes (just ignore it if you don’t want to reply).
Why is it now “conventional wisdom” to install housewrap under vinyl? From what I’ve seen around here, very few folks do it properly, which if I understand correctly is as much for flashing considerations as it is for stopping infiltration. But the flashing aspect is pretty much ignored. If it’s not done right, is it worth the effort/cost at all?
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Vinyl does not stop water infiltration. Period.
Between the expansion gaps where the plastic ends butt into trim (J-channel, corner boards, etc), the overlapping seams where plastic butt meets plastic butt, and the way the plastic panels snap together (mini-water trough after a rain storm) as you go up the wall, none of these areas are impervious to water penetration.
Standard plastic trim pieces (J-channel, corner boards, etc), in conjunction with plastic siding, are not to be relied upon to keep water on the siding from getting behind the siding. These same pieces will not provide a drainage plane that will allow water that gets behind the siding to shed off the structure before it penetrates the structure and possibly causes water damage to the structure.
A gentle rain? It may shed all of the water with minimal penetration. A summer storm with wind-blown rain? Fuggedaboudit. Certainly not all installation techniques are the same. Some installations may outperform others.
My opinion.
A cedar clap installation, with claps tightly snapped into place, with a piece of flashing behind the butt joints, and with an overlap between claps as you run them vertically, is far superior to vinyl in terms of shedding rain. Even horizontally, wind-driven rain. Yet I'd still feel that a cedar clap installation was inadequate if it was installed without some form of a drainage plane behind it.
On the plus side? There's a decent chance that if you install vinyl without paper/wrap behind it, you'll have to rip off the vinyl a few years down the road to repair any structural water damage. That will give you a chance to change the siding material/color when you reinstall.
There's always a silver lining...
*Capillary action and bulk water penetration makes plastic to wood connections dangerous ... period. Plastic prevents drying and therefore the wood is at risk. Vinal or any other material (eg, steel on roof deck) that keeps moisture prevailing on the surface of the sheathing material should be avoided. This can be done with strapping, purlins, firring strips; etc to create a space for convection, evaporation; etc, or some form of barrier can be used to keep the water off the sheathing. Performance and price-wise, Tyvek and its sisters do not prove to do the job. Tar paper, roofing felt, and building paper are better performers but only under certain conditions are they advisable. If moisture can arrive on the exterior wall (eg; no vapor diffusion retarder, insufficient insulation causing condensation on the sheathing because of temp differential across wall cavity to outside air), anything that stops water and evaporation will have the same problem -- mildew and rotting of the sheathing and bottom plates and sills.Tyvek et al are sold as if they perform like Gortex --bulk water will not penetrate and vapor will -- so claimed. The claim is that rain and wind driven water will not get on to the sheathing but condensation on the inside of the housewrap will evaporate and pass out through it. I don't believe this because I have purchased lots of outdoor equipment and the materials that work this way cost way more per sq ft than housewrap (I have bought it by the yard).But, even so, the other claim against Tyvek et al is that it contains or at least activates surfactants present naturally in wood. Surfactants are the stuff in laundry detergent that make water droplets breakdown and penetrate more deeply into the fabric. Well, if this is true, Tyvek et al will eventually be compromised, absorbing/passing/attracting exterior vapor and depositng it on the sheathing. Tyvek is made with a polyester fabric grid.I tested a 2' square piece of Tyvek by wrinkling it and crushing it into a ball, then I laid/stretched it over a bucket and held it on with an elastic. I figured the crushing would simulate folds, bends, corners and abrasion on buildings and during installation. I left a concave dip in the surface and filled it with water. It began to leak droplets within 3 hours and by morning, all the water was in the bucket.I would be the happiest guy if it worked as claimed since I could use it for rain gear at much lower price than my I pay now.As far as cedar clapboards go, the problem is even more serious when using Tyvek since the capillary action of water sandwiched between the cedar and the sheathing compromises both wood surfaces. The oils and natural surfactants in cedar will undoubtedly destroy the housewrap and certainly counter its intended purpose. Its DOW and the manufacturers and sellers of these wonder materials that shold be sued, not the smart builders that know a house is a system not an accumulation of individual building materials. Vinal siding is one of the worst plagues to have been invented. It has virtually no capacity for weather or moisture protection and turns into a brittle mess in when exposed to the sun. Between it and Tyvek, we have many horror stories to chew on in the next decade.
*Couple years ago my 2 boys were playing catch with a hardball at a family function. My younger son ran in saying "Jayme broke the house next door!". I thought, sh*t, he broke a window. I went out and saw big holes in the neighbors vinyl siding. You could push on it with your hand and break it. Vinyl is final, yeah right.Jayme is now 11 and has a hell of a fastball.
*The vinal side of a house in my neighbourhood lifted off from the top and rolled out across the lawn a few weeks ago in a thunder storm. The fastener holes all split open.
*OK, so you all hate vinyl and it's not worth putting on your house. Humor me a minute. What if you're building a house in a moderate climate, where it's nearly always humid, say in Arkansas near the delta (rice fields in every direction). I've been told my vapor barrier belongs on the outside. It's been suggested that I use 1" foil faced foam board on the outside (over the plywood sheathing) and tape the joints and nail lines. This is supposed to keep the humidity on the outside; since the inner wall will be fairly well insulated, the moisture from the inside is not supposed to condense. Certainly you'd still need flashing above the windows, doors, etc., but would there be any reason to "wrap" the outside.As for your vinyl "horror stories" there are those who used to install (still do?) vinyl over 1/2" insulation (with no sheathing except at the corners). Even with sheathing, ANY siding will come loose if the nails don't hit the studs as they're supposed to, especially with poor quality sheathing -- it's not the siding's fault. I see lots of vinyl that is 20 years old (we be poor in Arkansas) that's in good shape.As for the Tyvek "experiment" -- what does standing water on a horizontal surface of Tyvek prove? Is it supposed to be used that way? Why not take a five gallon bucket, cut out the ends, cover the ends with Tyvek (seal with tape) stand it out in the yard with the ends perpendicular (like it'd be on your house), put your sprinkler where the water would strike it from above, and inject a little steam into the bucket. Wait three hours and see what you have. That's closer to a real experiment -- what you did was prove a pre-assumed conclusion.
*How can you cut out the ends of a 5 gal bucket, cover them with tyvek, and have them oriented PERPENDICULAR?They will be parallel.Do you mean vertical?In your experiment, you are leaving out any pressure differential due to wind loading on the windward side of a structure. Gravity can be used to simulate that loading, which is what tedd was doing. Don't underestimate how this pressure can drive water through structures (up over drainage planes, etc)
*Tyvek is design to be an breathable moisture barrier for humity areas like the gulf coast. It is suppose to slow the moisture from entering the resident. But since it is $300 a roll, I,m using tar paper.
*johnnie... been usin that damn spell checker again , huh ?$125 a roll for the 9 foot big one...
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Gene's aborted discussion of the Vinyl/Housewrap lawsuit did raise the following question: "And is it still said by y'all that no paper or Tyvek under vinyl is plain stupid?" I'm sure I could find the answer to that if I did a search, but this area is not inundated with new threads, so here goes (just ignore it if you don't want to reply).
Why is it now "conventional wisdom" to install housewrap under vinyl? From what I've seen around here, very few folks do it properly, which if I understand correctly is as much for flashing considerations as it is for stopping infiltration. But the flashing aspect is pretty much ignored. If it's not done right, is it worth the effort/cost at all?