C33 Caulking, Patching, and Surface Repair

Question 1

Which type of caulk should NOT be painted over with latex paint?

Accepted Answer

100% silicone caulk

Answer

100% silicone caulk has a non-stick surface that repels latex paint, causing it to bead and peel. Acrylic latex, siliconized acrylic, and polyurethane caulks all accept latex paint once dry.

Question 2

What is the primary purpose of installing a backer rod in a wide joint before caulking?

Accepted Answer

To control caulk depth and achieve the correct two-point adhesion profile

Answer

A backer rod limits how deep the caulk sinks, ensuring the bead bonds only to the two joint faces (not the back wall). This 'two-point adhesion' allows the caulk to flex with joint movement without tearing. Three-point adhesion causes premature cracking.

Question 3

When patching a hole in drywall before painting, how should the final coat of joint compound be finished?

Accepted Answer

Feathered out several inches beyond the repair and sanded smooth when fully dry

Answer

Feathering the compound out well beyond the repair and sanding it flush when dry eliminates any visible edge or ridge after painting. Leaving it raised or wet-priming traps moisture and creates bumps; shellac is used to seal stains, not compound coats.

Question 4

Before caulking an exterior joint between wood trim and stucco, the most critical preparation step is to:

Accepted Answer

Ensure both surfaces are clean, dry, and free of old caulk and loose material

Answer

Caulk adhesion depends entirely on clean, dry, sound substrates. Old caulk residue, dust, oil, or moisture will prevent the new caulk from bonding to either surface. Primers are sometimes used but are secondary to cleanliness; dampening stucco and adding weep screeds are not caulking preparation steps.

Question 5

Which patching material is best suited for filling small nail holes and minor surface dents in interior drywall prior to painting?

Accepted Answer

Lightweight spackling compound

Answer

Lightweight spackling compound dries quickly, sands easily, and shrinks minimally — ideal for small surface repairs on drywall. Hydraulic cement is for wet masonry repairs, epoxy filler is for structural or exterior repairs, and roofing mastic is a waterproofing sealant not meant for drywall.

C33 - C-33 California Painting Contractor License Practice Test

C33 - C-33 California Painting Contractor License Practice Test

C33 Caulking, Patching, and Surface Repair