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newSchoolWorks.com › VoTechWorks › Building & Construction › Roofing › Capstone Project: Full-Scope Roof System Build and Defense › Lesson 2
BLD-ROOF12-07 · Lesson 2 · 20 clock hours · lab

Integrated Roof System Installation—Phase 1: Deck, Underlayment, and Flashing

Objective. Working in teams of two or three and following their approved work plan and fall-protection plan, students will install a structurally sound roof deck inspection, full synthetic underlayment, drip edge, step flashing, valley flashing, and all penetration flashings on the mock structure with zero critical installation deficiencies as defined by the NCCER Roofing task-list checklist.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed professional engineer or master tradesperson or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

Integrated Roof System Installation—Phase 1: Deck, Underlayment, and Flashing

This lab is the first working phase of your capstone project. By the end of it, your team will have a fully weatherproofed base system—deck inspection complete, synthetic underlayment installed, drip edge in place, and every flashing fabricated and set. The work must meet the NCCER Roofing task-list checklist with zero critical deficiencies before you move on.

Pre-Task Safety: Do This Before Anything Else

Fall protection is not optional and it is not a formality. On a roof structure of 4:12 pitch or steeper, OSHA regulations require fall protection for workers at heights of six feet or more above a lower level in construction. Before any team member sets foot on the deck, complete the documented pre-task safety check.

What to inspect:

If any component fails inspection, tag it out of service and replace it before climbing. This is the lockout/tagout principle applied to fall-protection equipment.

Deck Inspection

Before the first roll of underlayment is opened, walk the deck and inspect it. You are looking for soft spots (press with your foot along every joist line), delaminating plywood, protruding nail heads, and gaps wider than the manufacturer's underlayment specification allows. Mark defects with chalk. Do not proceed over a soft deck—report it to the instructor. A failed deck puts the whole system at risk and is a critical deficiency on the checklist.

Synthetic Underlayment: Shingle-Fashion Installation

Synthetic underlayment is your primary water-resistant barrier under the finish roofing. Install it in shingle fashion—each successive course laps over the top edge of the course below, so water running down the slope always travels onto the face of the next sheet, never behind it. Begin at the eave and work toward the ridge.

Follow the manufacturer's specified side-lap and end-lap dimensions. Most synthetic products require a minimum side lap and end lap; read the product data sheet because the dimensions vary by brand. Fasten with roofing nails or cap nails at spacings the manufacturer requires. In high-wind areas, closer fastening patterns apply—know your regional requirement.

At hips and ridges, carry the underlayment over and lap it from both sides, or use a separate cap strip per the manufacturer's instructions.

Drip Edge: Eave Before Rake

Drip edge controls where water drips off the roof edge and protects the fascia and deck edge from moisture. The installation sequence is critical and is commonly tested:

Remember: eave drip edge goes under underlayment; rake drip edge goes over underlayment. This is an installation standard requirement you must be able to explain verbally when the instructor pauses work.

Step Flashing at a Wall Tie-In

Step flashing is used wherever a sloped roof meets a vertical wall. Each piece of step flashing is an L-shaped metal unit that overlaps the one below it—like shingles, in shingle fashion. One leg of the L lies flat on the deck under the roofing; the other leg turns up against the wall at least the minimum height required by the installation standard. Each step flashing piece is offset to align with each course of shingles. Never rely on a single continuous piece of metal folded at the wall—step flashing provides redundancy so that if water penetrates one joint it cannot travel along the full length of the tie-in.

W-Valley Liner (Open Valley Metal)

A W-valley liner is formed metal installed in the valley—the internal angle where two roof slopes meet. The W-shaped profile creates a water channel and a raised center rib that separates water coming from each slope. Install the valley liner over the underlayment, centered in the valley, running continuously from eave to ridge with any joints lapped in the direction of water flow. The required overlap at joints and the minimum setback of finish roofing from the valley center are specified by the installation standard and the manufacturer.

Pipe-Boot Penetration Flashing

A pipe-boot (pipe flashing) seals around round penetrations such as plumbing vents. Slip the boot over the pipe, seal the base flange to the deck per the manufacturer's method, and weave the base under and over surrounding roofing courses so water cannot travel beneath the flange. Photograph each flashing immediately after installation with a tape measure in frame showing the required overlap dimension, then label and file the photo in your portfolio the same day.

Documentation and Portfolio

Every photograph must show: the tape measure confirming the overlap, the flashing component, and enough context to identify the location. Label each file with your team name, date, and component. Sloppy documentation is treated the same as a missing installation step during the final defense.

Checklist Walk-Through

Your instructor will conduct a mid-phase walk-through using the NCCER Roofing task-list checklist. Critical deficiencies stop work. Correct every item, then request the second walk-through. All items must be rated acceptable before your team proceeds to Phase 2.

Key terms10

Personal Fall-Arrest System (PFAS)A system consisting of an anchorage, connecting means (lanyard or self-retracting lifeline), and a full-body harness designed to stop a worker's fall before they strike a lower level.
Shingle-fashion overlapAn installation sequence in which each successive course of material laps over the top edge of the course below, so water always flows onto the face of the next piece rather than behind it.
Drip edgeA metal flashing installed along eave and rake edges that directs water off the deck edge and protects the fascia and deck substrate from moisture infiltration.
Step flashingIndividual L-shaped metal pieces installed in courses at the intersection of a sloped roof and a vertical wall, each piece overlapping the one below to create a redundant water barrier.
W-valley linerA formed metal flashing with a W-shaped cross-section installed in the valley between two converging roof slopes; the profile channels water and separates runoff from each slope.
Pipe-boot flashingA pre-formed or site-fabricated flashing unit that seals around a round roof penetration such as a plumbing vent pipe, with a base flange that integrates with the surrounding roofing.
Side lapThe horizontal distance one sheet of underlayment or roofing material overlaps the adjacent sheet on the same course, measured parallel to the eave.
Critical deficiencyAny installation error on the NCCER Roofing task-list checklist that compromises weatherproofing, structural integrity, or safety, and that must be corrected before work proceeds.
Anchor pointA secure point of attachment for a PFAS that is connected to structural framing and rated for the forces a fall arrest may generate.
Pre-task safety checkA documented inspection completed before work begins, covering fall-protection equipment, anchor points, and the work platform, with findings logged on a daily safety checklist.

Worked examples4

1. Your synthetic underlayment product requires a minimum 4-inch side lap. The roll is 48 inches wide. Starting the first course so its bottom edge is flush with the eave, at what height above the eave will the top edge of the first course sit, and where will you align the bottom edge of the second course to achieve exactly the minimum lap?
  1. Step 1: The roll is 48 inches wide, so the top edge of the first course sits 48 inches above the eave.
  2. Step 2: The second course must lap over the first by at least 4 inches, meaning the bottom edge of the second course must be placed no higher than 48 − 4 = 44 inches above the eave.
  3. Step 3: Snap a chalk line at 44 inches above the eave and align the bottom edge of the second course to that line.
Answer: The top of the first course is 48 inches above the eave. Align the bottom of the second course at 44 inches above the eave to achieve exactly the 4-inch minimum side lap.
2. You are installing W-valley liner in sections. The installation standard for your product requires a 12-inch end lap at any joint, with the upper piece overlapping the lower. The valley runs 18 feet from eave to ridge. Your valley liner comes in 10-foot lengths. How many pieces do you need, and what is the actual overlap on the second joint if you use full 10-foot pieces?
  1. Step 1: Convert the valley length to inches: 18 ft × 12 in/ft = 216 inches.
  2. Step 2: First piece covers 120 inches (10 ft). Remaining valley = 216 − 120 = 96 inches.
  3. Step 3: Second piece is 120 inches long. It must start at least 12 inches back from the top of the first piece (overlap). The second piece extends from 108 inches to 228 inches above the eave. The ridge is at 216 inches, so the second piece extends 228 − 216 = 12 inches past the ridge—trim it flush. Confirm the actual overlap: the second piece starts at 120 − 12 = 108 inches, so overlap = 120 − 108 = 12 inches, exactly meeting the minimum.
  4. Step 4: Two pieces are sufficient. The overlap is exactly 12 inches, meeting the minimum requirement.
Answer: Two 10-foot pieces of valley liner are needed. The end-lap overlap on the joint is exactly 12 inches, which meets the minimum requirement.
3. Each step-flashing unit must turn up the wall at least 4 inches and extend onto the deck at least 4 inches. You are cutting step-flashing blanks from flat sheet metal. What is the minimum flat width of blank you need to cut before bending, if the bend itself consumes no material?
  1. Step 1: Wall leg required = 4 inches minimum.
  2. Step 2: Deck leg required = 4 inches minimum.
  3. Step 3: Total flat blank width = wall leg + deck leg = 4 + 4 = 8 inches.
Answer: You need a minimum blank width of 8 inches before bending to produce a step flashing with a 4-inch wall leg and a 4-inch deck leg.
4. Your drip edge pieces at the rake are 10 feet 6 inches (126 inches) long, and the rake measures 22 feet 3 inches (267 inches) from eave to ridge. The manufacturer requires a 2-inch end lap at any joint. How many full pieces do you need, and how long is the final cut piece?
  1. Step 1: The first piece covers 126 inches. Remaining rake = 267 − 126 = 141 inches.
  2. Step 2: The second piece must lap 2 inches over the first, so it covers 126 inches of new rake from its leading edge. Remaining after second piece = 141 − (126 − 2) = 141 − 124 = 17 inches.
  3. Step 3: The third piece must lap 2 inches over the second and cover the remaining 17 inches of rake, so it must be 17 + 2 = 19 inches long.
  4. Step 4: Total pieces: two full 10 ft 6 in pieces plus one cut piece 19 inches long.
Answer: You need two full pieces and one cut piece 19 inches long, for a total of three pieces of rake drip edge.
In class: Before climbing, each team conducts a documented pre-task safety check: inspects the roof-bracket scaffold or guardrail system, checks each PFAS harness and lanyard for damage, confirms anchor-point load rating, and logs findings on the daily safety checklist sheet that will become a portfolio artifact—instructor observes and initials when the system is verified compliant. · Teams install synthetic underlayment in correct shingle-fashion overlap sequence from eave to ridge, then cut and nail drip edge at eave and rake edges in the code-required order; the instructor pauses work mid-installation and asks each team to explain why the drip edge sequence differs at eave versus rake, requiring a verbal answer citing the installation standard before work resumes. · Teams fabricate and install all required flashing components—step flashing at a simulated wall tie-in, a W-valley liner, and a pipe-boot penetration flashing—using pre-cut metal stock; each flashing is photographed by the student immediately after installation with a tape measure in frame showing the required overlap dimension, and the photo is labeled and filed in the project portfolio the same day.
Materials: Mock roof structure (plywood deck on wood framing, minimum 4:12 pitch, two slopes), synthetic underlayment rolls, galvanized drip edge stock, pre-cut step-flashing blanks, valley metal, pipe-boot flashings, roofing nails and pneumatic nailers, tape measures, chalk lines, tin snips, pry bars, fall-arrest harnesses and lanyards, roof-bracket scaffold or temporary guardrail system, daily safety checklist forms, cameras or smartphones for documentation, NCCER Roofing task-list checklist
Check: Instructor conducts a mid-phase walk-through using the NCCER Roofing task-list checklist; any critical deficiency (improper overlap, missing flashing, unprotected leading edge) stops work and must be corrected before the team advances—all items must be rated 'acceptable' with no critical deficiencies to proceed to Lesson 3; a second walk-through documents the corrected installation.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

NCCER Roofing—Underlayment and Flashing Installation
1. At the eave edge of a roof, what is the correct relationship between the drip edge and the synthetic underlayment?
NCCER Roofing—Flashing Installation
2. Why is step flashing installed in individual overlapping pieces rather than as a single continuous bent strip along a wall tie-in?
OSHA Fall Protection—Personal Fall-Arrest Systems
3. Before climbing onto the mock roof structure, a student finds that the webbing on one PFAS harness shows a visible cut through the outer sheath. What is the correct action?
NCCER Roofing—Underlayment Installation
4. Synthetic underlayment is described as being installed in 'shingle fashion.' What does this mean?
OSHA Fall Protection—Anchorage and System Setup
5. During the pre-task safety check, a student confirms the roof-bracket anchor bolt is fastened only to the roof sheathing and not to a rafter. What should the team do?
NCCER Roofing—Flashing Installation
6. When installing a W-valley liner in sections, which direction must the upper piece overlap the lower piece, and why?
NCCER Roofing—Documentation and Quality Control
7. After installing a pipe-boot flashing, a student is required to photograph it for the project portfolio. What must the photograph show to satisfy the documentation requirement?
NCCER Roofing—Quality Control and Inspection
8. During the mid-phase instructor walk-through, a team's step flashing at the wall tie-in is found to have the wall leg turned up only 2 inches rather than the required 4 inches. Under the checklist protocol, what happens next?
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