To prepare, ensure all screwheads are properly driven into plasterboard, then blend the jointing compound using a drill with a mixing paddle, until smooth.
1. Apply compound to the join between the boards with a five-inch filling knife, starting in one corner of the room, really forcing the compound in.When the join is filled, hold the knife at a 25 angle to the surface and smooth it out. Also make sure you fill in screw holes.
2. Unroll around three feet of jointing tape, centre it over the seam and gently press it into the fresh compound with fingers. At the end of the joint, cut tape with a knife.
3. Starting halfway along the joint, hold the knife, or a caulker, against the tape at a 25 angle. Pull it to one end of the joint in a single stroke, smoothing the tape and pressing it firmly into the compound.Wipe excess compound off blade before smoothing in opposite direction. REPEAT STEPS 1 TO 3 ON OTHER JOINS.
4. On inside corners, cover two inches either side with compound, then push the tape into the corner with blade; smooth out one side of the crease at a time. On outside corners, simply smear the sides of the corner beads with compound, taking care when smoothing to keep the surfaces even.
5. Leave compound to dry overnight, then sand the covered surfaces with with a medium-grit abrasive, using a pole sander. Use a sanding block for inside corners.
6. Apply second coat of compound, this time with a 10-inch caulker, to all joins and screw heads, then smooth. Sand the next day, then repeat.When third coat is dry, sand to finish and wipe surfaces with a damp cloth, ready for priming.