MT381 Unit 2 Construction Work Breakdown Structure Example

Eleven Branches, Sixty-One Activities: An MT381 Unit 2 Work Breakdown Structure for a Three-Story Medical Office Building

[Student Name]

Purdue University Global

MT381: Construction Planning and Scheduling

Unit 2 Work Breakdown Structure

[Instructor Name]

[Date]

The building, quantities and subcontractor assignments are composite; the standards and sources cited are real.

The Project

The building is a three-story medical office building of 14,200 square feet per floor, 42,600 square feet in all, on a suburban lot. It has a structural steel frame on spread footings, composite metal deck with concrete fill at levels 2 and 3, exterior walls of brick veneer and aluminum curtain wall over light-gauge framing and an air barrier, a TPO roof carrying three rooftop units, and two hydraulic elevators. Notice to proceed is planned for March 1, 2027, and the contract completion date is December 27, 2027.

How the Top Level Divides the Job

A work breakdown structure breaks the whole scope into smaller and smaller pieces until each one can be planned and assigned, and every piece of scope should appear in it exactly once (Project Management Institute [PMI], 2019). There is more than one valid way to divide a building at the top level. One common approach follows the project manual, division by division. This structure instead follows the way the site will be run: the building comes out of the ground, goes up, gets closed in and is then finished floor by floor.

The eleven branches are procurement, sitework, substructure, superstructure, envelope, level 1 interiors, level 2 interiors, level 3 interiors, vertical transportation, permanent power, and commissioning with closeout. Three milestones sit outside the branches because they are moments rather than work: notice to proceed, dry-in and substantial completion.

What Each Branch Holds

Sitework holds five activities: mobilization and erosion control, excavation and grading, underground utilities, and, at the end of the job, paving with curbs and landscaping. Substructure holds four: footings, the footing inspection, foundation walls and piers, and the slab on grade. Superstructure holds four: steel erection, metal deck, and concrete on the level 2 and level 3 decks. The envelope holds six: exterior framing and sheathing, air barrier, curtain wall, brick veneer, TPO roofing and setting the rooftop units. Vertical transportation holds elevator installation; permanent power holds setting and terminating the switchgear and energizing the service; commissioning and closeout holds test and balance, final inspections and the punch list. With twelve procurement lines and twenty-four interior activities, the total is sixty-one.

Interiors by Level

Interiors fill three branches, one per floor, and each holds the same eight activities in the same order: overhead rough-in, wall framing, in-wall rough-in, cover inspection, drywall hang, tape and finish, paint, and ceilings with flooring and trim-out. Splitting by level matters because the drywall, paint and ceiling crews will move from floor to floor, and the schedule must show that movement. A single interiors branch with one drywall activity for the whole building would hide the fact that level 3 cannot be hung until the crew finishes level 2. Identical lists on each floor also make the links between floors easy to draw in Unit 4.

The Crew-and-Quantity Test

Every field activity had to pass two questions before it stayed in the tree. Can one crew, or one subcontractor, be held responsible for it? And does it have a quantity that can be measured and turned into a duration? Steel erection passes: one erector, about 410 tons. Footings pass: one concrete subcontractor, 236 cubic yards. An activity called building envelope fails, because it combines four trades and has no single quantity; it was split into exterior framing, air barrier, curtain wall and brick veneer. Mubarak (2015) notes that activities defined too broadly cannot be controlled and those defined too narrowly cannot be maintained, and the test is a practical way to find the middle.

An activity stays in the tree only if one crew can own it and someone can count how much of it there is.

Inspections as Activities

Footing and cover inspections appear as activities with durations of their own, one day each. They are short, but they are real constraints: concrete cannot be placed until the footing inspection passes, and drywall cannot hide the rough-in until the cover inspection on that level passes. Leaving them out would make the schedule assume inspectors arrive the moment they are called.

Three Codes on Every Field Activity

Each field activity carries three codes: its level or area, its responsible subcontractor, and its MasterFormat division (Construction Specifications Institute, 2020). One list can then be sorted by trade for a coordination meeting, by floor for a site walk or by division for cost reports. Level 2 in-wall rough-in, for example, is coded L2, electrical and mechanical subcontractors, and Divisions 22, 23 and 26.

The Longest Field Activities

Field durations run from one day to thirty-two, and the longest are defended in the dictionary. Brick veneer, at 32 working days, keeps a single six-mason crew circling the building, and splitting it by face would only create four activities that the same crew performs one after another. Steel erection, at 30 days, belongs to one erector with one crane. Elevator installation, at 30 days, belongs to one installer working both cars. Each is long because one crew does it, not because the activity is vague.

Procurement as a Branch

Procurement forms its own branch of twelve lines covering submittals, reviews, and fabrication with delivery for structural steel, curtain wall, switchgear, elevators and rooftop units. It stands apart because fabrication consumes calendar time while nobody occupies the site. The switchgear line, at 140 working days of fabrication and delivery, is longer than most of the field work combined, and a schedule without it would show the electrical gear arriving whenever the electrician needs it.

The Dictionary

A WBS dictionary follows the tree and gives each of the 61 activities its code, responsible crew or supplier, quantity, unit and planned duration. Durations are carried forward from the Unit 3 worksheet, so the dictionary and the network will always agree.

How the Structure Will Be Used

The structure is the skeleton for every later unit. Unit 3 gives each field activity a duration from its quantity. Unit 4 ties the activities together, and the identical interior lists make the floor-to-floor links easy to see. The codes let the Unit 9 look-ahead split activities into zones without losing track of where each zone rolls back up. A structure that changed every week would undermine all of that, so changes after the baseline are made only through the update process and recorded.

What the Structure Leaves Out

General conditions, such as supervision, temporary facilities and insurance, are not activities in this structure, because they run for the whole job and have no logic of their own. They appear in the cost estimate, not the schedule.

References

Construction Specifications Institute. (2020). MasterFormat. Construction Specifications Institute.

Mubarak, S. (2015). Construction project scheduling and control (3rd ed.). Wiley.

Project Management Institute. (2019). Practice standard for work breakdown structures (3rd ed.). Project Management Institute.