There are several layers within a proper roofing job that are necessary to provide the most protection against water damage. Of all of them, the first line of defense is to install drip edge flashing. Unfortunately, many contractors tend to neglect this step.
The elimination of this installation can end up being your future nightmare. So, if you are re-roofing your house, be sure to demand a drip edge. If your roof is already finished (sans drip edge), you can still do a drip edge retrofit installation.
What Is Drip Edge Flashing?
Drip edging is a strip of flashing that is applied to the edge of roofing prior to the installation of other items. It is designed to protect the roof’s sheathing from water damage caused by rain, snow, or ice being blown or rolling back beneath the edge of the shingles.
When placed on the eaves side of a roof, the drip edge will prevent capillary action water damage caused by surface tension. When placed on the rakes’ side, it protects the sheathing from wind driven (or forced) rain blowing back into the sheathing.
Why You Need a Roof Drip Edge
Without the installation of a drip edge, water can wick into the edges of the roof sheathing and cause the roof to develop rot and/or mold. In worse cases, a leak will develop in the ceiling or along the walls.
Although it is not the intention, drip edge flashing will also provide protection for the fascia board. Because the drip edge directs the water directly down and into the gutters, the back of the fascia is protected from excessive moisture. This helps to extend the life of the wood.
Another benefit that wasn’t intended but has been a useful outcome from installing a drip edge is that it prevents rodents, squirrels, and birds from being able to access the attic space via the builder’s gap. If you have ever had a family of squirrels living in your attic, you can appreciate this extra bonus.
Why Doesn’t My Roof Have a Drip Edge?
If your house is like many, you may find that you do not have drip edge flashing installed. Often the common practice is to leave out the drip edge and compensate by installing asphalt roof shingles so that they hang over the edge by an inch or two.
This has been a common practice that is becoming less and less popular. It is now more frequently understood that a roof needs this extra protection. In 2012 the Internation Code Council changed things to reflect the requirement of drip edging on all asphalt roofs.
Parts of Roof Drip Edge Flashing
How to Install Drip Edge Flashing to a New Roof
To install a drip edge on a newly constructed roof or on a re-roofing job, attach the drip edge along the roof’s eaves first. The roof leg should extend a minimum of 2” back onto the roof sheathing. While the vertical leg should be placed 1/4” – 1/2” away from the fascia.
Omitting the spacing between the fascia and the drip edge is a common mistake that contractors often make. It is not uncommon for them to place the drip edge right against the fascia.
Doing this will cause surface tension water to roll back onto the fascia. The end result is quickly deteriorating wood. So, make sure you have that gap.
Next, roll out and install the underlayment or felt. The proper layering is for the membrane to be installed over the drip edge at the eaves and under the drip edge for the rakes.
Video demonstrating water run-off without drip edge and with proper placements vs incorrect placement.
Corners and Joints:
All joints should overlap by about 2 inches including joints made at or near the corners.
Outside Corner Cuts
To make the outside corner turns, place a straight cut through the roof leg. Make sure that you are wrapping a minimum of two inches. For Florida residents, the requirements call for 4” overlaps.
Bend on the vertical leg and make sure the flap on the roof leg is on top of the roof leg of the eaves.
Inside Corner Cuts
To make the inside corner turns, you will need to create an overlap that meets at the interior of the corner. That means that you will make cuts at the ends of two sections of drip edging and overlap the two at the juncture.
A common mistake made by contractors is to place a straight cut down the roof leg (same as shown for the outer corner) and then bend the section into the corner. However, doing it this way leaves an exposed square of sheathing right in the center of the valley.
Although this section will be covered with membrane, the valleys are one of the most vulnerable spots for water damage. Water run-off is very heavy in these locations and it is best to make cuts that prevent any exposure.
To make proper cuts and bends for the inner corners, place a cut line at the location where the roof leg meets the vertical leg.
Cuts for the Rake Side
After the membrane is installed, attach the drip edge to the rakes making sure to start at the bottom and work your way towards the peak. This ensures that a step effect is achieved which will allow the water run-off to move correctly.
There are a few recommendations out there for making the bends and the cuts at the peak of the rake side. I have experimented with several but found my method to be far easier and just as effective.
To do the rakes, I align my drip edge piece up with the peak and make a cut straight up through the vertical leg. Then, I make the bend on the roof leg over the peak.
Next, I place a line down the other side of the vertical leg, again using the the peak seam as a guide. Then, I snip off the kick-out that crosses over that line. This allows the overlap section to fit flush beneath the front drip edge piece.
Finally, I slip the overlap beneath the first cut and apply a thin bead of 100% silicone along the seam for extra assurance.
Types of nails to use:
For most applications, the use of galvanized roofing nails is the best practice. Always use the appropriate nails and/or adhesive that is required by your local code.
Where to place nails:
Nails should be placed along two separate rows in a staggered “W” pattern. The maximum spacing is 12” on center. However, 10” on center is a better spacing and will give a better performance.
If you live in an area where high winds are an issue (i.e Florida), the recommended spacing is 4” on center. This spacing varies from one location to another. So, be sure to check your local code requirements.
Install Drip Edge Flashing to Old Roof
When installing drip edge to a finished roof, the process is the same with one not-so-tiny addition. Ideally, you want to be able to nail the drip edge in place without doing any damage to the roof shingles.
This often means that the lower run (starter shingles and 1st course) have to be removed or loosened enough to allow access for tools. Removal will provide the easiest install for the drip edge.
If removal of the roof shingles is not an option, you can still get some good protection by doing a cement attachment. Doing this is a subpar installation method to using the above method, and does not meet the standards set by the International Code Council of using mechanical attachments, but is still better than having no drip edge at all.
To use this method, you will need to loosen the lower run of shingles with a putty knife. Then, slip the roof drip edge under the shingles (and the tar paper on the eaves). Place a bead of roofing cement along the top edge of the drip edging and press down on the loose shingles.
To prevent causing damage to the roof shingles, it is better to do this when the temperatures are warm enough to make the shingles pliable. In cold temps, the roof shingles become stiff and brittle and will break very easily.
In addition, the warmer temps will allow the loosened shingles to reseal themselves in a quicker fashion. If you have to wait out the cold weather for the seal to retake, you run the risk of wind damage in the interim.
So, try to time all repair work that requires lifting or moving roof shingles to coincide with temps around 70 degrees. This includes shingle repairs and/or installing gutter guards.
How Many Wrong Things Do You See?
I wanted to include examples of some mistakes that you want to avoid and explain why these will cause issues. In the image above, the handyman is doing several things incorrectly.
First of all, the drip edge that he is using has a vertical leg that is way too short to fit inside the gutter. This, in and of itself, isn’t necessarily wrong, but it is a combination of mistakes that make it a bad install.
The whole point of installing drip edges is to direct the water into the gutters and away from the fascia and house foundation. To correct this situation, make sure to purchase drip edge flashing with a long enough vertical leg to reach the gutter. If the gutters have been installed too low, they may need to be raised and corrected.
If you find yourself in a situation where you are using drip edging that can not reach your gutters, you can still increase your protection by using the proper drip edge to fascia distance. Unfortunately, this is the next mistake that he is making.
He is placing the drip edge right against the fascia. If spaced properly, the drip edge would still provide some protection despite the gutter issue. But installed this way is going to result in surface tension water running down the face of the fascia board and behind the gutter.
To correct this mistake, the drip edge should be pulled forward by 1/2”. This will help keep the run-off from reaching the fascia board and will allow it to drip down into the gutter.
Although this is not as good as having the drip edge inside the gutter, it is far better than the way he is doing it. However, it still exposes the fascia to windblown rain which will also run down behind the gutter.
The next thing that just jumps out to me is that he is not creating the proper overlap at the corners. You can see that he is snipping the corner flush with the eaves side and is doing the same with the rakes’ side.
What is going to happen in this situation is the rain is going to run down the corner and wick back between the space where these two sections meet. You should never, never, never butt two seams up against each other when doing any type of flashing.
To correct this situation, make sure there is at least 2” of drip edge available to wrap around the corners. (more if your situation or code merits it). Learn how to do the proper cuts to make the wraps. Practice on some scraps if needed.
Situations You May Face:
In a perfect world, the drip edge would be installed prior to roofing shingles. The vertical leg would extend down into the gutters and not have any face nails or screws. It would be spaced 1/2” away from the fascia board and be supported by 1/2” furring strips.
In an imperfect world, you are likely to find that retrofitting drip edging presents you with some questionable situations. For instance, how do you install drip edge flashing around gutter clips that are in the way?
Some may tell you to make two relief cuts around the gutter clips and fold the tab up. I don’t like that method because it interrupts the continuous barrier desired. There is no way to overlap these cuts and water can work its way behind the exposed edges.
Instead, I prefer to place the clip screws through both the gutter and the drip edge. I always swap out the old screw with a fresh one (roofing screws with sealing washers) and then apply a dollop of 100% silicone over the screw for extra security.
Things to Remember
The drip edge should always be installed with the flashing under the felt on the eaves side and over felt on the rakes unless local code dictates otherwise. A few places (Florida) may require an alternative way of drip edge installation.
Generally, they want it installed so that the drip edge must go over the underlayment and then be cemented to the shingle’s starter course and/or tar paper.
The best practice is to always install the drip edge so that it is inside the gutter. The whole purpose is to direct the water into the gutters. It should never be installed outside the gutter (i.e against the fascia board).
For proper water drainage, the drip edge on the rakes should always overlap the drip edge on the eaves. This works out correctly if you do the eaves first. Then, finish by installing the drip edge flashing on the rakes.
Use the nail spacing and pattern dictated by your code and/or location. Avoid placing nails within 1 1/2” of the roof edge. Always set the nails back close to the edge of the roof leg.
In some locations, it is acceptable for the roof shingles to line up with the drip edge. However, when permitted it is best to have the roof shingles hang over the drip edge by a minimum of 1/4” and a maximum of 3/4”. When combined with the drip edge spacing, the shingles will clear the fascia by 3/4″ – 1 1/4″ total.
Remember that every region, city, or local may have slightly different requirements. It is best to double check these instruction against your local code.
Regardless of the type of drip edge that you use, or whether you are installing drip edge on a new roof or are retrofitting an old roof, you should always follow your local code requirements. In addition, you should follow the shingle manufacturer’s instructions for installation.
Keep in mind that going outside of the shingle manufacturer’s requirements can void your warranty. You want to weigh any situational adjustments against that risk.
Did I miss something? Drop a question or comment below and I’ll answer or respond.