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Cross-market term

Cavity tray and through-wall flashing

A barrier built into a cavity above any obstruction, sloping upward from the outer leaf to the inner one, catching water running down the cavity and directing it back out through weep holes above the obstruction.
  • 4Markets
  • NoSame thing everywhere
  • 3Calculators

What it is called, by market

One concept, four markets. Where a name means something else locally, the card says so rather than leaving you to find out on site.

  • United Kingdom

    Close, not identical

    cavity tray

    also DPC tray, stepped cavity tray, preformed tray, stop end

    STOP ENDS at each end of the tray are part of the detail, not an accessory: without them the collected water runs off the end of the tray into the cavity again and appears somewhere unrelated.

  • Australia

    Close, not identical

    cavity flashing

    also cavity tray, flashing, damp course

    Cavity flashing is the common term with the same function, and it is required above every opening and at every cavity interruption in masonry veneer construction.

  • United Statesyours

    Same word, different thing

    through-wall flashing

    also cavity flashing, wall flashing, drip edge, end dam

    THROUGH-WALL sounds external and is not — it is inside the wall, running from the drainage plane to beyond the outer face. END DAM is the American name for a stop end and serves the same purpose.

  • Canada

    Same word, different thing

    through-wall flashing

    also cavity flashing, end dam, drip edge

    As the United States, with the flashing required to extend beyond the face of the veneer with a drip so the water leaves rather than tracking back.

The governing standard, by market

  • United Kingdom

    Approved Document C / BS 8215

    Resistance to moisture, and the design and installation of damp-proof courses in masonry including cavity trays.

  • United States

    TMS 402 Chapter 12 / ASTM E2112

    Anchored veneer flashing requirements, and the installation of exterior windows, doors and skylights including end dams.

Calculators for this

Each works in either measurement system, and the terminology on the page follows whichever market you have selected.

Cavity Wall Weep Hole Spacing Calculator →Window Opening Flashing Membrane Calculator →Brick Veneer Wall Tie Density Calculator →

Frequently asked questions

Where does a cavity tray have to go?
Above every point where something interrupts the cavity, and the list is longer than people expect: over every window and door lintel, at the junction where a lower roof abuts a wall, above an airbrick or a duct passing through, where a cavity is closed at a change of construction, and at the base of the cavity itself. The reasoning is mechanical rather than regulatory — water crossing the outer leaf runs down the inside of it, and anything that blocks the cavity becomes a shelf that water collects on. Without a tray it collects on the obstruction, saturates the masonry around it, and eventually bridges to the inner leaf. That is why damp caused by a missing tray appears at ONE CONSISTENT HEIGHT indoors, typically just above a window, rather than rising from the floor or coming from above.
Why do stop ends matter so much?
Because without them the tray does not drain, it diverts. A cavity tray collects water and slopes it toward the outer leaf, and weep holes above the obstruction let it out — but the tray is a shallow channel, and water runs along it to the lowest available exit. If the ends are open, the easiest exit is off the end of the tray and back into the cavity beyond the obstruction, where there are no weep holes and nothing to catch it. So an installation with a correctly fitted tray, correctly placed weeps and no stop ends delivers water into the cavity a metre from where it started, and the damp appears somewhere that makes no sense until somebody opens the wall. American practice names the same component END DAM, which describes what it does rather better.
Can one be retrofitted?
Yes, and it is disruptive enough that it is worth establishing the diagnosis first. Retrofitting means removing a course or two of the outer leaf along the length needed, cleaning the cavity out at that level, inserting the tray with its stop ends, forming the weep holes, and rebuilding — usually in short sections so the wall above is supported throughout. Proprietary systems exist for the common cases, particularly over an abutment. The reason to be sure first is that a missing tray, a bridged cavity from mortar droppings, and a failed lintel DPC all produce damp at a similar height, and only one of them is fixed by a tray. Opening a short length of wall to look is often cheaper than guessing.