The most common call we get is regarding water coming between the gutter and fascia.
Why does this happen? Capillary action is the culprit. The water is adhering to the shingle, drip edge and fascia as it travels off the edge of your roof.
This problem is common when shingles do not overhang the drip edge as suggested in the tech bulletins from the shingle manufacturers. Instead of water dripping off the edge away from your fascia, it is running down the fascia. This will occur whether you have gutters or not. It is also more likely to occur with lower pitch roofs.
When Seamless Gutters are installed, the goal is to slide the gutter behind the drip edge. This is not always possible due to the pitch, settling of a home, type of leaf guard system or how tight the drip edge is installed.
There is a company called DripStrip who makes a product that fills the gap between the drip edge and gutter. Their website has videos and a great explanation. www.dripstrip.net
Our installers will install DripStrip in situations they believe will be an issue as they fabricate your custom Seamless Gutter system. And even if it occurs after installation, we can retrofit DripStrip after install. In both situations it is usually invisible from the ground.