CSLB C-33 Painting & DecoratingSurface PreparationHard
A painting contractor is preparing an interior wall for painting. After cleaning, they notice a small area where the drywall paper has torn, exposing the gypsum core, and some loose fibers are present. What is the most appropriate repair step before priming?
- AApply a thin layer of regular joint compound.
- BSeal the torn paper and loose fibers with a shellac-based primer.
- CCut out the torn section and replace it with a new piece of drywall.
- DCover the damaged area with fiberglass mesh tape.
Show answer & explanationAnswer & explanation
Correct answer: B. Seal the torn paper and loose fibers with a shellac-based primer.
Torn drywall paper, especially when the gypsum core is exposed, needs to be sealed. The paper fibers and gypsum are absorbent and can swell or blister if directly covered with water-based compounds or paints. A shellac-based primer effectively seals these areas, preventing moisture absorption and creating a stable surface for subsequent repairs.
Why the other options are wrong
- A. Applying joint compound directly over unsealed torn paper can cause the paper to swell, bubble, or absorb moisture unevenly.
- C. Cutting out and replacing is excessive for a small torn paper area; sealing and patching is more appropriate.
- D. Fiberglass mesh tape is for bridging cracks or seams, not for sealing torn paper that needs to be stabilized against moisture.
Torn Drywall Paper Repair
The process of stabilizing and repairing areas where drywall paper has torn, exposing the gypsum core, before applying finishes.
- Essential to seal exposed paper/gypsum to prevent moisture issues.
- Shellac or oil-based primers are effective sealers.
- Prevents bubbling and uneven absorption of subsequent coats.
Memory trick: Torn paper, seal it first, or your paint will burst.