CTE & TRADES · POSTSECONDARY CTE, APPRENTICESHIP, COLLEGE · 60 MINUTES
The Pre-Pour Walk: Under-Slab Rough-In Verification lesson plan
Apprentices and construction-management students check every plumbing and conduit stub-out against the plan, from two gridlines, before the concrete makes a mistake permanent.
On this page: Teach it in 5 steps · Learner card · Printable
At a glance
Time: 60 minutes
Level: Postsecondary CTE, apprenticeship, college
Subject: CTE & trades: Under-Slab Rough-In Verification
Grouping: Teams of 2-3: one reads the plan, two pull tapes.
Space: A 16 ft x 20 ft clear floor area.
Included: Teacher script, scenario sheet, learner sheet, exit ticket and answer key with every number worked
Open the printable lesson: script, scenario, learner sheet and answer key (PDF) →
Teach it in 5 steps
The whole lesson on one screen. Details for each step are further down.
Before class: Tape the 16 ft x 20 ft slab outline (or roll out the print).
Hook (0-5 min): Show the slab outline. "Tomorrow at 7 a.m. this is about 4 yards of concrete. What do we check tonight?"
Model one item (5-12 min): Measure P3 from gridline A (x) and gridline 1 (y) with two tapes held square.
Main work (12-55 min): Work through the procedure below: Teams check P1-P6 → Code check → Hold list.
Check (55-60 min): Exit ticket: Name the two references you measure a stub-out from on a slab.
Learner card
Read this with your crew, or print it for each team.
Your challenge
The concrete truck is booked for tomorrow morning. Find every stub-out that is in the wrong place, or missing, while moving it still costs a shovel and not a jackhammer.
By the end, I can:
measure a point from two gridlines and compare it with the plan
apply a stated tolerance and decide pass or fail
write a pre-pour hold list a superintendent can act on
Who uses this
plumbing and electrical apprentices, concrete foremen, superintendents and construction managers, who sign off rough-ins before a pour.
Essential question
What has to be true before you let concrete cover the work, and how do you prove it?
What learners learn and show
The big idea: Under-slab rough-ins are located from fixed references (gridlines or slab edges), checked against a tolerance, and fixed or documented before the pour, because afterwards a move means cutting concrete.
Show it: a completed check sheet for six items with offsets and pass/fail, one code check on the water closet, and a hold list with the action for each failure.
Objectives
Measure each stub-out from gridline A and gridline 1 to the nearest 1/8 in.
Compare as-placed and plan positions against the stated tolerance.
Check the water closet against its back and side clearances.
Write a hold list that names the item, the error and the fix.
Materials and prep
A 1:1 print of the slab plan, or the 16 ft x 20 ft outline taped on the floor
Two 25-ft tape measures per team, chalk or painter's tape
Six markers for the stub-outs (cups, cones or tape crosses), placed by the teacher from the scenario sheet
The printable: scenario sheet and check sheet
Prep
Tape the 16 ft x 20 ft slab outline (or roll out the print). Mark gridline A on the west edge and gridline 1 on the south edge.
Place the stub-out markers at the AS-PLACED positions on the teacher scenario sheet (not the plan positions). Leave P4 out on purpose.
Print one check sheet per team.
Space: A 16 ft x 20 ft clear floor area.
Grouping: Teams of 2-3: one reads the plan, two pull tapes.
Lesson procedure
0-5 min, Hook: Show the slab outline. "Tomorrow at 7 a.m. this is about 4 yards of concrete. What do we check tonight?" Ask: What gets buried in a slab? Listen for: Drains, water lines, conduit, sleeves.
5-12 min, Model one item: Measure P3 from gridline A (x) and gridline 1 (y) with two tapes held square. Read to 1/8 in. Compare with the plan: 120 in and 96 in. Ask: Why two references and not one? Listen for: One measurement fixes a line; two fix a point.
12-35 min, Teams check P1-P6: Teams measure every item, record the offsets, and mark OK, FAIL or MISSING against the tolerance: plumbing within 1/2 in, conduit within 1 in. Ask: Which items failed, and by how much? Listen for: P1 1 1/2 in short in y, E1 2 1/2 in long in x, P4 missing.
35-45 min, Code check: For the water closet, measure from the finished-wall lines (4 in inside the slab edges) to the drain center. Ask: Will a standard 12-in rough-in toilet fit? Is the side clearance at least 15 in? Listen for: Back 10 1/2 in: too tight for a 12-in rough-in. Side 18 in: passes 15 in.
45-55 min, Hold list: Teams write the hold list: item, error, fix, who. Ask: Do we pour tomorrow? Listen for: Not until P1 and E1 are moved and P4 is installed and re-checked.
55-60 min, Exit ticket: Individual exit ticket.
Checks for understanding
Ask: Why measure from gridlines instead of from the nearest stub-out? Look for: Gridlines do not move; measuring stub to stub carries one error into the next.
Ask: A conduit is 3/4 in off and the tolerance is 1 in. Pass? Look for: Yes, it is within tolerance; record it anyway.
Ask: Why is a 1 1/2-in error on a toilet drain worse than on a floor drain in an open room? Look for: The toilet must fit between a finished wall and its rough-in; the floor drain only needs to sit in the sloped area.
Exit ticket
Name the two references you measure a stub-out from on a slab. Answer: Two fixed, perpendicular references: gridlines or established slab edges.
P1 sits 1 1/2 in toward the back wall. What two things does that break? Answer: It is outside the 1/2-in tolerance, and the 12-in rough-in no longer fits (10 1/2 in to the finished wall).
Write one hold-list line for the missing cleanout. Answer: P4 cleanout missing at 200 in / 60 in: plumber to install and re-check before pour.
Scoring: Item 1: 1 point. Item 2: 2 points (tolerance and fit). Item 3: 2 points (item, location, action). 4 or more = secure.
Common misconceptions
Learners may think: If it is within an inch it is fine. Address it: Tolerances differ by trade and fixture; a toilet rough-in has almost no room. Use the stated tolerance for each item.
Learners may think: We can fix it after the pour. Address it: After the pour, a move means saw-cutting, trenching and patching. The walk is the cheapest moment to catch it.
Supports and extensions
Pre-mark the gridlines with large letters and numbers; give the tape-reading card (eighths of an inch) to anyone who wants it.
Multilingual learners: label each marker with its ID and a picture of the fixture.
Mobility: one teammate can read tapes seated at the gridline while another holds the far end.
Transfer task: Walk a real slab, or photos of one, with the plumber's rough-in plan and write the same hold list.
Ready to teach it?
The printable has the teacher script, the scenario sheet, the learner sheet and the answer key. Open the printable lesson →
Need the floor plan itself? Get a 1:1 print quote.
Paying for the print? Use a grant
Many teachers fund the 1:1 print with Perkins V career and technical education funds. Start from From Drawing to Takeoff: a construction-trades pathway on life-size plans, our grades 9-12 CTE grant packet, and add this lesson to its timetable. The packet has a project description, measurable objectives, a lesson timetable, an evaluation plan, a budget and a principal letter, written to the questions funders ask.
Download the grant packet (PDF) · Editable Word version · All funding options
Why at full scale
The whole lesson happens on the floor: the slab outline at full size is the inspection surface, so the measurements are the same ones a foreman takes.
Codes, standards and frameworks
Perkins V (CTE): postsecondary and secondary CTE program context
IRC R307.1 / IPC 405.3.1: water closet side clearance of at least 15 in from the centerline (check the edition your jurisdiction adopted)
Codes and standards change and are adopted locally. This lesson teaches the method; use the edition your jurisdiction or program has adopted.
Related lessons
The Plumbing Wall · Wet Walls, Supply & Drain Runs, Grades 9-12, CTE
The Circuit Walk · Electrical Layout & Working Clearance, Grades 9-12, CTE
Code Walk · Construction Trades, Grades 11-12
More in the College & Trades track: The MacLeamy Curve · The Slab Takeoff · Square the Layout · Receptacle Layout to Code · Measure It Like an Appraiser