Butt joints are where two non-tapered edges of the plasterboard meet. They are difficult to hide because the tape protrudes above the surface of the plasterboard.
You can avoid butt joints by using long sheets of plasterboard to span the walls and ceilings, but you will still end up with a few.
The key to hiding a butt joint is to keep the tape coat thin. Build up a layer of compound over the tape that’s thin and wide enough to blend into the surrounding surface.
TIP Mix the joint compound by adding the dry powder to the water, according to the instructions, then mix until it forms a smooth and creamy consistency.
Once the plasterboard is secured to the studs, use a sharp utility knife to trim the edges of each sheet at an angle to remove loose or torn paper and create a shallow recess for the compound.
Fill the recess with a 100mm wide, 2mm thick coat of compound using a broad knife. Roll out the tape, then lightly press along it with the blade, so 1mm of compound is left underneath.
Apply a thin second coat of compound 200-300mm wide over the tape. Allow to dry, then apply a third coat, tapering out the edges 300-500mm to conceal the bump left by the tape.