Replies

1. GBA Editor
   Martin Holladay | May 31, 2017 04:32am | #1

   Rocky12,
   As long as you remember to overhang your metal roofing at least an inch -- at the rakes as well as the eaves -- you don't need a drip edge.

   That said, many metal roofing manufacturers make metal trim for rakes. Some people think that this rake trim looks good, and makes for a neater installation. Ask your roofing materials supplier about rake trim.

   When it comes to "which is installed first, the drip edge or the asphalt felt?," there are defenders of both sides of this very old debate. With newer types of underlayment -- Grace Ice & Water Shield or synthetic roofing underlayment -- we aren't allowed to debate anymore. We have to follow manufacturers' instructions.

   The issue came up in a previous Q&A thread here at GBA, and here's what I wrote:

   "Grace, the manufacturer of Ice & Water Shield, advises 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."

2. 
   Rocky12 | Jun 01, 2017 12:44am | #2

   Thanks Martin. I actually spoke to the company who makes my roof underlayment. They recommended to cut a piece of that to install underneath the drip edge and then again over drip edge. So pretty much the same concept as ice and water shield.

   And I actually considering a vented drip edge for my soffit vent which may change things slightly. Have you ever done this? This would be a first for me and I'm trying to figure out the best installation technique. Directions seem to call for the roof sheathing to be a few inches short to allow airflow. Is there any reason why I wouldn't just trim a few inches off the top of the fascia board instead?

   I am just going by these images and can't really find any tutorials online.

   
3. GBA Editor
   Martin Holladay | Jun 01, 2017 05:56am | #3

   Rocky,
   I've never installed vented drip edge like that shown in your illustration. If I ever had to do it, though, I would follow the installation instructions provided by the drip edge manufacturer. If you can't find good installation instructions online, phone them up.

4. 
   SwitchgrassFarmer | Jun 01, 2017 07:53am | #4

   Rocky, I was very interested in this ventilated drip edge for the cold roof on our SIP home. Found my email comments why I ultimately decided against it:

   ***
   I read up on the ventilated drip edge product, and unfortunately I don't think it works for us. There are many online comments from roofers saying not to use it, and so I stopped at our local NJ roofing supply to chat. I got the same opinion from them, as well as our home roofer who happened to be standing at the counter.

   More digging finds that the National Roofing Contractors Association has this to say: "NRCA does not recommend the use of drip edge vents as intake vents in northern climates where there is a likelihood of ice damming." https://www.nrca.net/consumer/attic_ventilation/roof_vents.aspx
   ***

   We ended up going with a fascia vent using Cor-a-Vent.

5. 
   Rocky12 | Jun 01, 2017 04:03pm | #5

   Thanks Martin.

   Andrew, thanks for the info! I will be in a warm dry climate but hearing this I may avoid the vented drip edges as well.

   Any advantage using the corravent for fascia vent rather than bugscreen?