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Labour and productivity

Finding where crews wait: a one-day observation

By Review.LivePublished 3 min readHow we write

The masonry foreman is sure his crew works flat out, yet the block walls on level 3 fall further behind every week. At the Wednesday meeting he blames the hoist, and the superintendent blames the crew. Neither of them has counted anything.

Reclaimed concrete paving blocks are stacked on a wooden pallet beside a brick wall.
Photo: Kolforn (Wikimedia) on Wikimedia Commons · -2021-01-09 Reclaimed concrete paving blocks, Trimingham, Norfolk (2) · CC BY-SA 4.0 · Cropped, resized, colour adjusted and sharpened.

Walk the area at random times through one shift and note what each worker is doing the moment you first see them. At the end of the day, each activity's share of the observations estimates its share of the crew's time, including waiting, walking and fetching. This is work sampling: random observations taken while touring the site, each sorted into set categories such as direct work, support work and delays. The Construction Industry Institute's activity analysis uses it to measure and improve the time craft workers spend on actual construction. It finds what timesheets miss, because lost time comes in pieces of a few minutes that nobody records.

Running the observation

  1. Tell the crew first: you are measuring the system (hoist, material, information), not rating people, and no names go on the sheet.
  2. Set the categories: working, preparing, carrying material, waiting, walking and other, noting what each wait is for.
  3. Choose random round times across the whole shift, for example 40 of the shift's five-minute slots drawn by lot, and walk the same route each round.
  4. Mark each worker at the first instant you see them, not what they do a moment later.
  5. Count that evening: each category's share of the marks, times the crew's hours. More rounds give steadier shares.
  6. Take the biggest non-working category to the crew, find its cause and agree one change with a name and a date, using a one-page problem-solving sheet.
  7. Observe again on a similar day after the change.

Common mistakes

  • Choosing the times yourself, which catches the moments you expected.
  • Recording what a worker does after noticing you.
  • Using the marks to blame people, so the next count shows a crew that works only when watched.
  • Treating one day as the job's rate instead of a pointer to a cause.

Checklist

Your one-day observation

  • Crew told why; no names on the sheet
  • Categories set, with what each wait was for
  • Random rounds across the whole shift
  • One mark per worker, at the first instant
  • Shares and hours counted that evening
  • One change for the biggest cause
  • A second observation after it

Check your understanding

Walking is 10 per cent of the marks, and the foreman says walking is part of the job. How do you decide whether to act on it?

Show the answer
Look at where the walking goes. Moving between wall runs as the work advances is part of the job; walking back to the gang box for parts or looking for the foreman is time that staging and better planning can recover. Act first on the largest non-working category with a cause you can remove.

Sources

  1. Guide to Activity Analysis (IR252-2a, 2010): publication pageConstruction Industry Institute · accessed
  2. Lecture 10: Work samplingNational Programme on Technology Enhanced Learning (NPTEL) · accessed

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