L Flashing
A simple L-shaped piece of bent metal used at various roof-to-wall transitions, window and door head details, and other locations requiring a basic angled water diverter.
Specifications
| Profile | Single 90-degree bend creating two equal or unequal legs |
| Common Leg Sizes | 2x2, 3x3, 4x4, and 4x6 inches |
| Materials | Galvanized steel, aluminum, copper, PVC (for non-structural applications) |
| Standard Lengths | 10-foot sections |
Common issues
- Leg dimensions too small for the application, providing insufficient coverage
- Improper orientation with the wrong leg against the wall or roof surface
- Joints between sections not overlapped or sealed, allowing water at the seams
- Used as a substitute for step flashing at sidewalls where individual pieces are required
Insurance relevance
L flashing is a basic component used in many roof and wall details. In insurance claims, the specific application determines the line item. L flashing used as drip cap above a window is a different scope item than L flashing used at a headwall. Adjusters should note where the L flashing is installed and what function it serves rather than generically listing L flashing, since Xactimate has specific line items for each application. Damage to L flashing from wind or impact is straightforward to document with linear footage measurements.
What Is L Flashing
L flashing is one of the simplest and most widely used flashing profiles in residential construction. It consists of a single piece of sheet metal bent at a 90-degree angle to create two legs of equal or unequal length. This basic geometry makes it suitable for any location where an angled water diverter is needed at the intersection of a horizontal and vertical surface. L flashing is used at headwall roof-to-wall junctions (as apron flashing), above windows and doors (as drip cap), at the base of walls where they meet paved surfaces or decks, and in various other weatherproofing applications. Standard sizes range from 2x2 inches for light-duty trim applications to 4x6 inches or larger for roof flashing. It is available in galvanized steel, aluminum, copper, and PVC, with galvanized steel being the most common for roofing applications.
Common Applications in Roofing
In roofing, L flashing serves several distinct functions. At headwall junctions, a 4x4 or larger L piece functions as the apron flashing, with one leg under the shingles and the other leg up behind the siding. At window and door heads below a roof line, a smaller L piece acts as a drip cap that prevents water from running behind the trim and into the frame. On non-masonry walls, an L piece can function as counter flashing when installed over step flashing with the wall leg extending up behind the cladding. At rake edges on some roof types, an L piece provides a simple edge trim. The versatility of the L profile means that a roofer with a hand brake and flat stock can fabricate any size needed on site, which is faster and less expensive than sourcing specialized pre-formed flashing for every detail.
Installation and Sizing
L flashing installation follows the same water-shedding principles as all roof flashing. The upslope piece overlaps the downslope piece at joints. The leg under horizontal surfaces (roof deck, shingles) is secured with fasteners that are covered by the overlapping material above. The leg against vertical surfaces (walls, trim) extends behind the cladding. Sections are overlapped by at least 2 inches at joints and sealed with butyl tape or polyurethane sealant at the lap. Sizing is determined by the application. Roof headwall flashing requires a minimum 4-inch leg on each side to meet code and manufacturer requirements. Window drip caps typically use 2-inch or 3-inch legs. Undersized L flashing is a common installation error that reduces the effective water barrier, particularly at roof-to-wall junctions where the wall leg must be tall enough to prevent wind-driven rain from getting behind the metal.
L Flashing in Insurance Estimates
When L flashing appears in an insurance claim, the specific application determines how it is scoped. L flashing functioning as headwall apron flashing is a roof flashing line item in Xactimate. L flashing above a window is an exterior trim item. The distinction matters because the trade category, labor rate, and material cost differ by application. Adjusters should identify the function of each L flashing piece rather than listing generic L flashing. Damage is typically caused by wind displacing the flashing, hail denting the metal surface, or debris impact. Documentation should include the application, material, leg dimensions, and linear footage for accurate Xactimate line items.
Frequently asked questions
L flashing is a versatile piece used wherever a simple angled water diverter is needed. Common uses include headwall apron flashing at roof-to-wall junctions, drip caps above windows and doors, kick-out pieces at the base of wall-to-roof transitions, counter flashing on non-masonry walls, and edge trim at roof perimeters. The two-leg design allows one leg to lie flat against a horizontal surface and the other to turn up (or down) against a vertical surface, creating a basic water barrier at the intersection.
The required size depends on the application. For headwall apron flashing, a minimum 4x4 inch L is standard, with 5x5 or 4x6 common for added protection. For window and door drip caps, a 2x2 or 3x3 inch L is typical. For counter flashing on wood or vinyl walls, a 4x4 inch L provides adequate coverage. The general rule is that each leg should extend far enough to cover the vulnerable joint and be overlapped by the adjacent material (shingles, siding, or trim) by at least 2 inches.
L flashing and drip edge are related but not identical. A basic Type C drip edge is essentially an L-shaped piece, making it a form of L flashing. However, Type D drip edge has an additional lower kick-out flange that distinguishes it from a simple L shape. In practice, the term L flashing refers to a generic angled piece used in multiple applications, while drip edge specifically refers to the flashing installed along the eave and rake edges of a roof. Using a generic L flashing as drip edge may not meet code if the local jurisdiction requires a Type D profile.
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