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A dormer adds usable interior space and window light to a home, but from a construction standpoint it also multiplies the number of roof-to-wall and roof-to-roof transitions packed into a small area, each of which needs its own flashing detail done correctly. A typical gable dormer alone involves step flashing along both sidewalls, a small valley or cricket where the dormer roof meets the main roof plane, headwall flashing where the dormer roof meets the vertical wall of the main structure above it, and often window flashing integrated with the roof flashing at the base of the dormer windows.
The headwall condition, where the top of a dormer roof butts into a vertical wall, deserves particular attention because it combines several failure points at once. A continuous flashing piece, sometimes called an apron or headwall flashing, is installed so that its lower leg extends out over the dormer roof shingles and its upper leg runs up behind the wall cladding above, similar in principle to the base flashing used at the front of a chimney. Where this headwall flashing meets the step flashing coming down the dormer sidewalls, the pieces need to overlap correctly to keep water from finding a path behind the assembly at the corner, which is one of the more common points of leakage on older or poorly built dormers.
Window flashing at the base of dormer windows adds another layer of complexity where the dormer roof is short enough that the window sill sits close to the roofline. In that situation, the roof headwall flashing and the window’s own sill flashing or pan flashing need to work together, with water shed by the window directed onto the roof surface rather than trapped in the corner where the two systems meet, a detail that depends on the specific window product and the sequence followed during original construction.
Small dormers with limited roof area on either side sometimes have a miniature valley or a built-up cricket, a small sloped structure designed to divert water around the back of the dormer, rather than a full valley. Crickets are especially important on wider dormers or chimneys where the flat or nearly flat area behind the structure would otherwise collect standing water and snow. In Minnesota and similar cold climates, that standing snow and the ice it can form become a meaningful factor in how well a cricket or valley at a dormer performs over a full winter season.
Inspecting dormer flashing after a storm involves examining each of these transitions individually rather than assuming that condition or damage at one point applies to the whole assembly, since a dormer sidewall, headwall, and valley can each show entirely different wear, corrosion, or impact patterns depending on their exposure and pitch. Photographs taken close to each transition, along with notes on shingle cut lines, metal condition, and any visible gaps or prior sealant repairs, allow the parties involved to evaluate the physical facts at each location. Because dormers are architecturally varied, there is no single template for scope at this detail, and what is reasonable in a given case follows from what the inspection documents at that specific dormer.
This article is general education about how the appraisal process commonly works. It is not legal advice, and specific procedures can vary by state and policy.
Russ Lis is a working property insurance appraiser and umpire based in Minnesota, serving clients nationwide. Contact Appraisal Resolution.