冰和水下或滴水边缘？
在问这个问题之前，我进行了一些搜索，以为
*必须*过去已经出现，但没有找到任何连贯的东西。
We’re having this bit of disagreement between a GC and a roofer as
to whether ice & water shield over decking should flash over or
在与筋膜连接的连接处的滴角边缘下面。这
屋顶工声称将滴灌金属放在I＆W上
isn’t a reverse flash because water in an ice-dam situation would
flow upward, and the GC [who I’m tending to agree with] points out
小屋顶泄漏[或者，不可避免的凝结径流
在金属屋顶面板下]将撞到I＆W并安全地下来
over the drip-edge and be ejected instead of soaking into the
胶合板下面。
*Note*: this is a situation where the ice&water was trimmed to
stop just shy of the edge of the deck, leaving a little lip of
甲板和/或耙子上的影子板暴露在外。这个
甲板是屋顶和墙壁上的过度屋顶结构，Polyiso改造，
where everyone seems to assume the taped foam underneath is yet
另一个水控制层。[提示：不是，因为胶带铺设
仓促的方式有许多鱼嘴。] GC的家伙
must have wanted to leave a “clean slate” of nailable wood for the
屋顶工，但我个人认为不留下一英寸的襟翼
of I&W *over* the edge was crazy — especially when it took another
屋顶工可以到达现场的月份，只留下完整的包装
of I&W on the deck *as* my roof in the interim [with occasional water
leaking into the soffit space, I might add, which didn’t seem to
太关心他们]。终于来的问题出现了
time to finish off these details and git ‘er done.
It seems to me that you’d want some way to flash against *both*
potential scenarios, which we kinda wound up doing by putting the
在I＆W上滴边，但然后推出Triflex滑动表
under the [metal] roofing that lapped over the drip-edge piece.
But Triflex or even generic roofing felt isn’t really supposed
据我所知，要成为水障。因为不是
self-adhesive at all and gets *stapled* down.
_H*
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
答复
霍比特人，
I answered this question on the Letters page of issue #226 ofFine Homebuildingmagazine:
“恩,冰和水盾的制造商,广告vises that its peel-and-stick membrane should be installed before the drip edge. There are several reasons for this. If ice ever backs up from a clogged gutter, the ice can get under the drip edge and reach the plywood. If the Ice & Water Shield goes down first, the plywood is better protected. Also, if the galvanized drip edge ever rusts, it is easier to replace when reroofing if it is installed on top of the Ice & Water Shield. When it comes to synthetic roofing underlayments in warm climates, the same rule applies, but for different reasons. Water can wick uphill on top of the drip edge, so it's better to have the drip edge on top of the underlayment."
最近，我参加了W.R.Grace举行的培训课程。主持人同意马丁上面所说的话，但也说他们也建议在滴利皮上放一条膜，如下所示：http://www.na.graceconstruction.com/template.cfm?page=/underlayments/dd_iws102.html&did=8。
标准安装在这里：http://www.na.graceconstruction.com/template.cfm?page=/underlayments/dd_iws101.html&did=8。
还有其他好的信息在这里：http://www.na.graceconstruction.com/template.cfm?page=/underlayments/frofing_faqs.html&did=8#frofdrip。
我喜欢这两个层的细节，这似乎是正确的一般
答案，因为可以想象的水来自两种不同
directions. I'll note that the "alternate" detail sends at least one
layer of Grace over the edge of the deck, protecting the plywood
from water arriving from above. Unfortunately that wasn't the
case with my reno, as the builders inexplicably cut the IWS back
在甲板和subfascia的边缘上略微 *上方 *
水到达层的边缘并在筋膜后面下来
metal trim itself. Any ideas on why they would have done that??
_H*
Are you sure it was cut back, and not just installed a bit high? If it was cut, it could be that the bottom edge got gummed up on itself, or had puckers, or they overhung the roll and were sloppy about cutting it back. Installing I&WS properly is a real art that many carpenters and roofers have not learned.
虽然这与原始问题有所不同，但似乎
适合澄清情况。因为这是一个
原始屋顶和墙壁的外部有泡沫，
an over-roof nailing plane was built up over the foam with fairly
大悬垂。整个顶部胶合板表面都得到了尊重，但是
for the most part matching the lower edges as it was rolled out.
In spots where it overhung the plywood, it was actually trimmed
离开以匹配subfascia和Rake Ladder表面
it. I watched as they took a cordless skilsaw and did the same
all along both eaves, too. Hopefully I can post valid links to
图片 - 这显示了一个这样的修剪织物：
http://techno-fandom.org/~hobbit/hse/log/oGeWNzGx/ren/1249trimrakeply.jpg
这个one shows the IWS on a return detail. The IWS, plywood, and
shadow board attached to the fascia basically all end at the same
point:
http://techno-fandom.org/~hobbit/hse/log/ogewnzgx/ren/1286lkick-ret1.jpg
As the white trim metal got placed onto that same detail, it created
水可以下来地情况d drop right behind
装饰金属 - 在这里看着家伙的右手上方：
http://techno-fandom.org/~hobbit/hse/log/ogewnzgx/ren/1288lkick-cornfail.jpg
Basically, all the edges of the over-roof deck sat like that for a
*月*屋顶工最终到达并开始滴水之前
edge. Water would get down behind the metal, run onto the perforated
soffit pieces *on top*, travel toward the house, and get into the
"rainscreen" space under the siding that was eventually applied over
所有垂直绑带的顶部。由于胶带面条实际上是
*不是*一定是水密或闪烁到外部的，这可能
[and I think did once or twice] bring water in toward the structure.
具有讽刺意味的是，在第三张照片中，这个家伙试图做得这么小
我张贴了大约几个
months ago -- this is about the point where he gave up trying to make
90度的角落工作，回到了常规的L弯。即使
不会有帮助，因为水落后于金属可以跳跃
到达该点之前，请在穿孔的塑料片上。
Does this strike anybody else as poor technique, aka a massive reverse
flash even if they thought it was going to get handled later?? It would
have been so simple to leave an inch or two of IWS hanging over this
整个混乱，即使还有一些释放纸仍然附着，所以屋顶工
以后可以选择如何处理，但要保护结构
同时。甚至半英寸的I＆W悬挂在金属上，
then all that buried under the drip-edge would have been far better.
_H*