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Materials & Specificationsaka: step flashingaka: counter flashingaka: through-wall flashing

Flashing

In Plain English

Thin metal strips installed at joints and transitions in the building envelope to prevent water from getting in.

Definition

Flashing is thin sheet metal or other waterproof material installed at joints, transitions, and penetrations in the building envelope to prevent water infiltration. It is used at roof-to-wall intersections, around windows, at copings, and at any point where two different materials meet. Improper flashing is the leading cause of building envelope leaks and moisture damage.

Why It Matters in Bidding

Flashing is a small-dollar scope with outsized risk: because faulty flashing is a leading source of envelope leaks, omitting or under-detailing it in a bid can lead to costly callbacks and warranty claims long after award. Estimators must capture flashing at every transition during takeoff or the line vanishes into someone else's scope, creating gaps at the bid table.

Example

Reviewing wall sections during takeoff, an estimator quantifies linear feet of through-wall flashing at every roof-to-parapet intersection so the masonry and roofing bids do not each assume the other carries it.

Related Terms

Waterproofing MembraneMembraneCladdingSheathing

Frequently Asked Questions

Flashing often straddles trades, appearing in roofing, masonry, window, and sheet-metal scopes. Without a clear scope assignment, each subcontractor may exclude it, leaving the GC exposed. Smart estimators issue scope letters or pre-bid clarifications naming who flashes each transition to close these recurring coverage gaps.
Flashing is typically quantified in linear feet by location and type, such as base, step, counter, through-wall, and cap flashing. Estimators read wall sections and details to capture every penetration and transition, then apply material and labor unit costs that vary by metal gauge and complexity of the bends.
Because flashing sits at the boundary between trades and is detailed across many drawings, it is frequently overlooked or double-excluded. When leaks appear, owners pursue the GC, who then sorts out which sub owned the detail. Clear pre-bid scope definition prevents these back-charge fights.

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