Choosing Between Plasterboard and the Boards That Replace It

Plasterboard is a set gypsum core cast between paper liners, and it relies on those liners for much of its bending strength. Gypsum fibreboard mixes gypsum with cellulose fibre and presses it into a homogeneous sheet with no paper at all. Calcium silicate board is a mineral sheet cured under steam pressure so the binder forms throughout it. Cement bonded particle board binds wood particles in Portland cement, which is the reverse of the usual arrangement in a wood panel.

Those differences are not trivia. They determine everything the following sections describe, because a board with no paper face cannot be jointed like one that has a recessed paper edge, and a board that is homogeneous through its thickness behaves differently at a cut edge.

A paper-faced board is scored and snapped, which is fast, quiet and clean. A homogeneous gypsum fibre panel is usually sawn, gives gypsum dust rather than a clean snap, and takes longer. A mineral board cuts, drills and profiles cleanly but generates mineral dust that needs extraction. A cement-bound panel blunts ordinary tooling and generally requires pre-drilling for fixings.

That changes programme, site protection and who can do the work. A team that knows only paper-faced board practice will treat every other board the same way, which is where a great deal of the trouble in this family starts.

A denser board asks more of whatever supports it, and the difference is felt first on ceilings and on stairs. Where the additional weight matters to handling, to the ceiling framing or to the structure is a matter for others to confirm, and a cement-bound panel in particular is heavy, awkward work rather than a routine lift.

Weight also feeds back into the framing decision. A framework arranged for one board is not automatically arranged for a heavier one, and that is a design question rather than something to resolve while the boards are being lifted.

Plasterboard joints are formed by taping over recessed paper edges, and the resulting wall is either skimmed or taped and filled, which look different under grazing light. A board with no paper has no such edge, so its joints are formed by a documented method instead, and treating it as though it were plasterboard is precisely what goes wrong.

The same applies to repairs. There is no paper face to feather a patch into on a paperless board, so patching depends on the manufacturer's documented filler and technique, and a repair on a mineral board shows unless the jointing and coating match what was used originally.

Some boards take a fixing directly into their body because they are homogeneous through the thickness; others depend almost entirely on what sits behind them. That distinction is often the reason a particular board was chosen, and it is the fact most likely to go unrecorded.

In every case, fixing capacity is a property of the board, its backing and the specific fixing together, and it is confirmed rather than assumed from the fact that a board feels dense in the hand.

A gypsum core and paper liners are not intended to sit wet. A board wetted before fixing is not simply dried out again. A mineral board may tolerate humid interior air better than a paper-faced sheet, and tolerating humidity is not the same thing as suitability for wetting. A magnesium-bound board's binder is formed from salts that stay in the sheet, which makes dry service conditions the first question rather than a detail.

None of that makes any board a wet-area product. Wet-area use depends on the complete waterproofing strategy for the room, which is designed by a qualified professional rather than chosen from a board.

Where a board is named in a specified arrangement, only the documented components for that arrangement may be used, and swapping one produces a different assembly from the one that was designed. That is true even where the substitute is denser, heavier or in some general sense better.

Provenance matters more than usual for some of these products. Formulations vary widely between makers of magnesium-bound board, and calcium silicate and fibre cement boards are stocked side by side and routinely swapped by mistake.