Box Flashing - The Correct Way to Hang a Gutter on a Trim Board
Box Flashing
What is is it and why might I need it?
Trim Piece or Shadow Board
20% of houses that Fox’s Flowrite Gutters installs gutters on have a trim piece on the fascia. This trim piece, sometimes referred to as a shadow board, creates an uneven fascia. Some builders or homeowners choose to put this trim piece on their fascia mostly for looks. The trim piece creates a shadow line on the fascia, which gives the fascia some added depth and character. In some cases, the trim will add support to the shingles.
The Issue
A trim piece at the top of the fascia creates a few problems when installing gutters. Mounting on this trim piece means that there will be a gap between the bottom backside of the gutter and the fascia board. This gap can cause the bottom of the gutter to tip in and potentially pull its screws out, causing the gutter to fall off. This gap is also a great place for bees to build nests all around your house.
The second issue with mounting a gutter on a trim piece is that it limits the amount of pitch that can be put on a gutter; Especially if the gutter is pitching a great distance in just one direction. For example, if the trim piece is a 1x2 at the top of the fascia, then the gutter cannot be pitched more than two inches because it will be falling below the trim piece. After two inches of pitch, the gutter will not have any support along the back of the gutter. Without box flashing, the gutter cannot be properly pitched. Hanging the gutter below the trim board makes properly flashing the gutter more difficult and reduces the amount of pitch that is able to be put on a gutter.
What Box Flashing Looks Like on a House
Box flashing is installed with the same color material as the gutter. It is pitched with the gutter so you cannot see it from the front. It is the best and cleanest way to remedy a house with a trim piece when the board cannot be taken off.
Summary of Box Flashing
Box flashing provides a clean and permanent solution for hanging a gutter on a fascia with a trim board or freeze board. Formed from the same color material as the gutter and pitched to match its slope, it blends into the system and remains hidden from the front for a polished and professional appearance that also improves functionality. It is especially valuable on homes with trim pieces that cannot be removed.
Box flashing fills in the awkward void in a clean and effective way when trim boards are present.