MT381 Unit 4 CPM Network Logic Diagram Example

Course	MT381 Construction Planning and Scheduling
Unit	Unit 4
Paper type	Network logic diagram
Length	About 1,100 words, 6 pages double-spaced
Format	APA 7 student paper
School	Purdue University Global
Program	BS in Business Administration
Updated	October 2026

Free sample paper for MT381 Unit 4

Ninety-Six Ties, Each With a Reason: An MT381 Unit 4 Network Logic Diagram for a Medical Office Building

[Student Name]

Purdue University Global

MT381: Construction Planning and Scheduling

Unit 4 Network Logic Diagram

[Instructor Name]

[Date]

The building and its logic are composite; the scheduling sources cited are real.

What this part is doingClassifying ties before drawing them signals that the diagram's logic, not its layout, is the deliverable.

How the Diagram Is Drawn

The diagram uses activity-on-node format on four tabloid sheets. Each row is a building zone: procurement runs along the top, sitework and substructure below it, superstructure and envelope through the middle, and the three interior levels stacked beneath, with vertical transportation, permanent power and closeout at the bottom. Boxes carry an activity code, name and duration; arrows carry the relationship type and any lag. Kelley and Walker (1959), who introduced the critical path method, built it on exactly this idea: the network of dependencies, not the bar chart, is what lets a scheduler compute the consequences of a change.

The Register in Numbers

All 96 ties appear in one register: predecessor, successor, type, lag in working days, category and a one-line reason. Seventy-two are finish-to-start, eighteen are start-to-start and six are finish-to-finish. Thirty carry a lag, ranging from two to ten working days, and none is negative, because a lead would hide an overlap that should be shown as a start-to-start tie. Only notice to proceed holds a date; no other activity is constrained, so every date in the schedule comes from logic. Every activity except the first and last has at least one predecessor and one successor, which the register confirms with a count at its foot. A first draft left the slab on grade with no successor, an open end that made it appear to have 154 days of float; tying it to level 1 overhead rough-in closed the gap.

Three Categories of Logic

Logic is classified before it is drawn, because the three categories behave differently once the job starts.

Physical ties, 71 of them, follow from how a building is built. Concrete cannot be placed on deck that is not there, and a cover inspection must pass before drywall hides the rough-in. A physical tie survives any update.

Procurement ties, 17 of them, run from submittal to review to fabrication to delivery and then to installation: steel delivery ahead of erection, curtain wall delivery ahead of installation, switchgear delivery ahead of setting and terminating. A procurement tie ends once the material reaches the site.

Crew-flow ties, 8 of them, record decisions about how crews will move: the drywall, finishing and ceiling crews going from level 1 to level 2 to level 3, and the electricians starting each level's overhead rough-in ten days after the level below. They are marked preferential, so a later update can reorder them without pretending that physics changed.

A physical tie records what the building requires; a crew-flow tie records what someone decided, and the register says which is which.

What this part is doingSeparating required logic from chosen logic tells future updaters which ties they may change.

Pairs Instead of Single Lags

Overlapping trades use paired ties rather than one arbitrary lag. Steel erection to metal deck runs start-to-start plus ten days and finish-to-finish plus three. The start tie lets the deck crew begin once enough bays are erected; the finish tie stops the deck from finishing before the last bay of steel is plumbed and bolted. A start-to-start tie alone would let decking finish early, which cannot happen. Exterior framing to air barrier works the same way, start-to-start plus five and finish-to-finish plus three, so the barrier crew can neither overtake the framers nor finish before them. Drywall hang to tape and finish uses start-to-start plus four and finish-to-finish plus two on each level.

Cure and Bolt-Up Written as Lags

Some waits are physical but not activities. Level 1 overhead rough-in waits three days after the level 2 pour, so the slab can take hanger loads. Steel erection waits five days after the foundation walls and piers, for anchor bolt grout to cure. Each such lag is written on the tie and explained in the register, rather than hidden as extra duration on an activity.

Interiors Floor by Floor

Within each level, overhead rough-in leads wall framing by three days, wall framing leads in-wall rough-in by three days, and in-wall rough-in cannot start until overhead rough-in finishes. The cover inspection follows in-wall rough-in, and drywall hang waits for both the inspection and the building's dry-in milestone, since board cannot go up in an open building. Paint follows finishing and ceilings follow paint. Between floors, the crew-flow ties carry each crew upward. The result is a staircase on the diagram: each level's finishing sequence starts when the crew above it, in time, is free, which makes the floor-by-floor rhythm visible to anyone reading the sheets.

Checking the Logic Before Calculation

Three checks were run on the register before any dates were computed. The first looked for loops, chains of ties that return to an activity already in the chain, which would make a forward pass impossible; there are none. The second looked for redundant ties, such as a finish-to-start tie that another path already implies. Two were found and kept on purpose: drywall hang on each level is tied both to its cover inspection and to dry-in, and either could control depending on progress, so both stay. The third check confirmed that every lag is counted on the standard calendar, even where the activities it connects run on the exterior calendar, so a lag measures waiting time rather than workable weather days. Hinze (2012) recommends this kind of review because errors in logic are far harder to find once a schedule is printed with dates and everyone is arguing about the dates.

The Two Ties Trusted Least

The register ends with the two relationships the author trusted least. The first ties level 3 concrete to elevator installation with a ten-day lag, on the assumption that the installer needs the hoistway framed and the machine room slab cured. The installer has not confirmed the lag, and the tie is flagged for the Unit 9 constraint log. The second ties test and balance to level 3 ceilings with a start-to-start lag of six days, assuming the balancer can begin once most ceiling grid is in. If the balancer insists on complete ceilings, the tie becomes finish-to-start and the finish moves. Mubarak (2015) recommends documenting such assumptions so a schedule's weakest logic can be found quickly when dates are disputed.

What the Diagram Does Not Yet Show

The diagram shows logic and durations only. Dates, float and the critical path come from the Unit 5 calculation, and resource limits are tested in Unit 7.

What this part is doingEnding on what the diagram leaves to later units keeps its claims within what logic alone can show.

References

Hinze, J. W. (2012). Construction planning and scheduling (4th ed.). Pearson.

Kelley, J. E., & Walker, M. R. (1959). Critical-path planning and scheduling. Papers Presented at the Eastern Joint IRE-AIEE-ACM Computer Conference, 160-173. https://doi.org/10.1145/1460299.1460318

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

Reading the MT 381 Unit 4 instructions

Unit 4 asks students to connect the activities from earlier units into a logic network and document each relationship. The diagram is usually drawn activity-on-node, with relationship types and lags shown. Instructors expect a register listing every tie with its type, lag and reason. Students should explain why they used start-to-start or finish-to-finish ties where trades overlap, and why any lag exists. Negative lags and date constraints are generally discouraged, and their absence should be confirmed. Every activity except the first and last should have a predecessor and a successor. Classifying logic as physical or preferential helps later updates. Checks for loops and open ends are good practice, and the results should be reported rather than assumed.

How this MT381 Unit 4 example is built

The sample describes the diagram's layout by zone and cites Kelley and Walker. The register's totals come next, along with the open end found and fixed. Three categories of logic are explained with counts and examples, under a highlighted line separating required from chosen logic. Paired ties are justified for steel and deck, framing and air barrier, and hang and finish. Cure and bolt-up waits appear as lags. Interior logic within and between floors is described. A section on checking the logic covers loops, deliberately redundant ties and lag calendars, citing Hinze. The two least trusted ties are explained with what would change if they proved wrong, and one is carried to the look-ahead's constraint log.

Where the points sit in the MT381 Unit 4 rubric

Network diagrams are generally assessed on the soundness of the logic, the documentation of each relationship, the appropriate use of tie types and lags, and the absence of structural errors. Rubrics reward a register that gives every tie a reason a reader could challenge. Paired ties for overlapping work, explained, show understanding beyond basic finish-to-start logic. Classifying ties as physical or preferential demonstrates awareness of how logic will be updated. Confirming no open ends, no loops and no unnecessary constraints shows quality control. Naming the weakest logic shows honesty. Sources cited in APA 7 support the method, and counts in the text match the register line for line, which graders often check.

MT381 Unit 4 help: mistakes that cost points

Diagrams often use finish-to-start ties everywhere, which overstates the duration of overlapping work, or use single start-to-start ties that let a follower finish before its leader. Lags are frequently added without reasons, and leads appear where an overlap should have been modeled. Open ends are common and give activities false float. Date constraints are sometimes used to force a schedule to look right, which hides the logic that should be producing the dates. Before submitting, count each activity's predecessors and successors, and read every lag aloud with its reason. Any tie you cannot explain in one sentence, or any activity with no successor, needs attention before the network is calculated.

Get an MT381 Unit 4 example written to your instructions

Networks start from the activity list and durations built in earlier units, so attach those with the rubric and note whether this section wants a hand-drawn diagram, a precedence layout or a software file. A first network comes back free in 24-48h, every tie carrying its type, any lag, a category and the reason it exists. The paper above is an original model document written by our desk, not a submitted student paper and not an official Purdue University Global document.

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MT381 Unit 4 questions, answered

When should a construction network use start-to-start ties?

When a following trade can begin before the leading one finishes, as decking does behind steel erection or brick behind the air barrier. Pair the start-to-start with a finish-to-finish where the follower must also finish after the leader, and state the physical reason for each lag. Overlaps without reasons look like date-fitting to a grader.

What separates physical logic from preferential logic?

Physical logic reflects something that cannot be otherwise: concrete needs deck beneath it. Preferential logic reflects a choice, such as sending one drywall crew from floor to floor. Both belong in the network, but labeling them tells anyone updating the schedule which ties may be changed to recover time and which may not.

Are negative lags acceptable?

Many schedulers avoid them, because a lead lets a successor start before its predecessor finishes without saying what portion must be complete. A start-to-start tie with a positive lag usually expresses the same overlap more clearly. If your course or the specification permits leads, explain each one in the relationship register.

Where can I find a free MT381 Unit 4 sample paper?

This page has the complete MT381 Unit 4 network logic diagram and relationship register for a medical office building.

Why does the MT381 Unit 4 sample use paired ties for steel and deck?

A start-to-start tie lets decking begin once enough bays are erected, and a finish-to-finish tie stops it from finishing before the last bay is plumbed and bolted.