What is horizontal work?

Why horizontal work is the most predictable surprise in delivery

Its load is not driven by its own schedule but by everyone else's. Three streams that were planned independently all reach their security gate in the same fortnight, and the reviewer who was allocated a comfortable ten per cent across the quarter is now the constraint on three commitments at once. Nothing went wrong in any individual plan; the collision was created by planning them separately.

Averaging hides it. A horizontal sized as a quarterly percentage looks harmless on every plan it appears in, and the peak — the only number that matters — appears on none of them.

How to plan horizontal work

Size it by gate, not by rate: which streams need this concern, at what point in each, and what the review actually costs when it happens. Then look across the streams for the fortnights where two or three gates land together, because that is where the delay will come from.

Treat a horizontal as a dependency with an owner rather than a task inside someone else's stream. It has its own capacity, its own queue and its own ability to say not yet — and a plan that does not name who owns it has quietly assumed the answer will always be yes.

Related terms

• Vertical work — A delivery stream owned by a single team or discipline that produces end-to-end value within its own lane — frontend, backend, data, mobile, platform.
• Readiness (three-state) — A planning dimension has three states, not two: not assessed, assessed and nothing found, and assessed with items.
• Time-boxed discovery — A deliberate learning step taken instead of a decision: a goal, optionally the questions to answer, a time-box, and a target date on which it must conclude with recorded findings and an explicit decision.