Jointing and Finishing

Module 6: Jointing and Finishing

Applying Scrim Tape to Joints

Scrim tape reinforces plasterboard joints to prevent cracking and ensures a seamless finish.

Process:
✔ Use Self-Adhesive Fiberglass Tape – Sticks directly to joints.
✔ Apply Over Wet Filler – For non-adhesive tape, embed into a thin layer of joint compound.
✔ Center on Joints – Covers tapered edges completely.
✔ Smooth Out Bubbles – Use a drywall knife to eliminate air pockets.

Pro Tip:

• For butt joints (non-tapered edges), apply a wider coat of filler first.

Filling and Sanding Techniques

A smooth finish requires proper filling and sanding.

1. Filling (3-Coat System)
✔ 1st Coat (Bedding Coat) –

• Fill joints with joint compound using a 150mm knife.

• Feather edges outward to blend with the board.
  ✔ 2nd Coat (Butterfly Coat) –

• Apply a wider layer (200-250mm) after the first coat dries.

• Smooth ridges for an even surface.
  ✔ 3rd Coat (Skim Coat) –

• Thin final layer with a 300mm knife for ultra-smooth blending.

2. Sanding
✔ Use 120-150 Grit Sandpaper – For light smoothing between coats.
✔ Final Sand with 180 Grit – For a paint-ready finish.
✔ Dust Control – Vacuum or damp-cloth sanding reduces airborne particles.

Pro Tip:

• Sand in circular motions to avoid grooves.

Beading for External Corners

Metal or plastic corner beads protect edges and create sharp corners.

Types:
✔ Metal Corner Bead – Nailed/screwed into place, then coated with joint compound.
✔ Flexible Plastic Bead – Self-adhesive; ideal for curved walls.

Installation Steps:

1. Cut Bead to Length – Snip with tin snips for metal, scissors for plastic.

2. Secure in Place –

• For metal: Fasten with drywall nails or screws every 200mm.

• For plastic: Press into wet joint compound.

3. Apply Joint Compound – Cover fully with 2-3 coats, feathering outward.

Pro Tip:

• Use corner trowels for crisp, clean angles.

Achieving a Smooth Finish Ready for Decoration

Final checks before painting/wallpapering:

✔ Inspect Under Side Lighting – Highlights imperfections.
✔ Fill Minor Blemishes – Use lightweight filler for pin holes.
✔ Prime the Surface – Ensures even paint adhesion.

Common Mistakes to Avoid:
❌ Over-sanding (can expose tape).
❌ Applying filler too thickly (causes cracking).
❌ Skipping primer (leads to uneven paint absorption).

Summary Table: Jointing & Finishing Steps

Final Advice:

• For ultra-smooth walls, consider a polished skim coat over the entire surface.

• Always mask off areas before sanding to contain dust.