Certification Practice Exam 100

Thermoplastic Roofing Installer Certification Practice Exam 100 Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

1. A thermoplastic single-ply roof membrane is best described as:

• A bitumen-based sheet that cannot be reheated
• A rubber membrane that permanently vulcanizes after installation
• A polymer sheet that softens when heated and hardens when

cooled repeatedly

• A built-up roofing system made of multiple asphalt plies

Answer: C. A polymer sheet that softens when heated and hardens when

cooled repeatedly

Rationale: Thermoplastic membranes (such as TPO and PVC) can be

repeatedly softened by heat and re-hardened on cooling, which is why their seams can be hot-air welded multiple times if needed. 1 / 4

• The two most common thermoplastic single-ply membranes used in

commercial roofing are:

• EPDM and CSPE
• TPO and PVC
• BUR and modified bitumen
• APP and SBS

Answer: B. TPO and PVC

Rationale: Modern thermoplastic single-ply roofing is dominated by

thermoplastic polyolefin (TPO) and polyvinyl chloride (PVC) membranes.

3. “Hot-air welding” in thermoplastic roofing is primarily used for:

• Adhering insulation boards to the deck
• Fusing membrane seams and flashings
• Fastening edge metal mechanically
• Applying primer to the substrate

Answer: B. Fusing membrane seams and flashings

Rationale: In thermoplastic systems, hot-air welding is the standard

method to join membrane sheets and create monolithic, watertight seams and flashings.

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• When hot-air welding TPO seams, the most important combination of

variables for a quality weld is:

• Roller speed and membrane color
• Ambient temperature and roof slope
• Nozzle temperature, travel speed, and contact pressure
• Type of insulation and fastener length

Answer: C. Nozzle temperature, travel speed, and contact pressure

Rationale: Proper welding requires controlling heat (nozzle temperature),

how fast the welder is moved (travel speed), and the force used with the roller (contact pressure) to achieve full fusion without scorching.

• A properly welded thermoplastic lap seam should show which

characteristic when probed:

• The probe easily slips into the lap along the full length
• The probe cannot penetrate the lap and the weld feels solid
• The lap is brittle and cracks when probed
• The lap separates easily when lightly lifted

Answer: B. The probe cannot penetrate the lap and the weld feels solid

Rationale: A good weld is continuous, fully fused, and resists penetration

by a seam probe, indicating a strong, watertight bond.

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6. The main function of a seam probe in thermoplastic roofing is to:

• Measure membrane thickness
• Remove debris from seams
• Test weld integrity and detect voids or skips
• Mark layout lines

Answer: C. Test weld integrity and detect voids or skips

Rationale: A seam probe is used after welding to inspect seams by gently

attempting to insert the probe into the lap, identifying any unbonded or weak areas.

7. Before welding thermoplastic seams, the installer should first:

• Apply solvent-based seam adhesive
• Remove release film only at the ends of rolls
• Clean the seam area of dirt, dust, and moisture
• Coat the seam with asphalt primer

Answer: C. Clean the seam area of dirt, dust, and moisture

Rationale: Contamination at the seam (dust, dirt, moisture, or talc)

prevents proper fusion; cleaning the seam area is a critical preparation step.

8. Excessive heat during hot-air welding can cause:

• Insufficient fusion at the lap
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