Should plasterboard go horizontally or vertically?

People argue about this and both answers are correct in different situations. The direction matters much less than the four rules that apply regardless, and most of the cracks that appear in a boarded wall six months later trace back to one of those rules rather than to the orientation.

Step by step

1. Measure the wall against the board length.If the floor-to-ceiling height is less than the board length, vertical boarding covers it in one piece with no horizontal joint. That is the deciding factor most of the time, and 2400mm board suits a great many British ceiling heights.
2. Board vertically on a short wall.Each 1200 wide board covers three stud bays at 400 centres or two at 600. Joints are full-height vertical lines, all landing on studs, and there are no horizontal joints anywhere. Quick, simple and structurally clean.
3. Board horizontally on a long wall.Boards run across four or more studs. On a wall wider than it is tall this produces fewer total metres of joint, and it puts the long tapered edges horizontally where they are easiest to tape and where the visible joint runs at a consistent height rather than in a series of vertical lines.
4. Land every board edge on framing.This is the rule that matters most. An unsupported board edge flexes, and a flexing joint cracks however well it was filled. Where a board edge falls between studs, add a noggin behind it before boarding.
5. Stagger butt joints from row to row.When boarding horizontally, offset the vertical butt joints between the upper and lower rows by at least one stud bay, so no joint runs continuously from ceiling to floor. A continuous joint is a crack waiting for a reason.
6. Never let a joint line up with the corner of an opening.The corners of doors and windows are where stress concentrates, and a board joint at that corner cracks reliably. Cut boards to an L or a U shape so they wrap round the opening, with the joint at least a couple of hundred millimetres clear of the corner.
7. Leave a small gap at the floor.Around 10mm, so the board is not standing on the floor and not carrying any load, and so it is not sitting in any water that ever reaches the floor. The skirting covers it.
8. Run ceiling boards across the joists, and board the ceiling first.On a ceiling, boards run at right angles to the joists so each board is supported by several, with joints staggered. Board the ceiling before the walls, so the wall boards support the ceiling boards' edges at the perimeter.

Tips

• Horizontal boarding puts the working joint at around waist height, which is far easier to tape and sand well than a full-height vertical joint you have to reach over your head for.
• Vertical boarding is much easier for one person, because you can walk a board into place on edge and tip it up rather than holding a heavy board horizontally against a wall.
• Whatever the direction, plan the layout on paper first and mark the stud centres on the floor and ceiling before boarding. Finding out that the last board edge lands 30mm off a stud, with three boards already up, is a bad way to spend an afternoon.
• Some fire-rated and acoustic specifications state the board orientation and the joint arrangement. Where a wall has a performance requirement, follow the system's specification rather than a general rule.

Common mistakes

• Letting a board joint run over a door or window corner — That corner concentrates stress from the whole opening, and a joint there cracks within a year almost regardless of how carefully it was filled. Cutting the board round the opening prevents it entirely.
• Continuous butt joints from floor to ceiling — A joint that runs the full height with no interruption is a hinge line, and it telegraphs through the finish. Staggering costs nothing but a little planning.
• Boarding walls before the ceiling — The ceiling board's perimeter edge then has nothing supporting it. Ceiling first, then walls tight up underneath, so the wall boards carry the edge of the ceiling boards.
• Leaving a board edge floating between studs — It is the single most common cause of cracked joints, and the fix — a noggin behind the joint — takes two minutes before boarding and is a great deal of work afterwards.

Questions people ask