What is dry lining?

Plasterboard is a sheet of gypsum sandwiched between paper facings, and dry lining uses it to create a new, flat inner face on a wall or ceiling. The boards are either stuck directly to the wall with adhesive or screwed to a framework of timber or metal, and the joints are then finished so the surface is ready to decorate. Because the boards arrive dry and only the finishing involves any water, the room can be decorated much sooner than after a full wet plaster job.

Dry lining is used in new builds, extensions, loft conversions and refurbishments, and it is a common way to add insulation to the inside of an outside wall. It is also the standard way to form new partition walls and to replace old ceilings. The method chosen depends mainly on the condition of the existing wall, whether insulation is wanted and whether pipes or cables need to run behind the boards.

Insulated plasterboard combines a standard plasterboard with a layer of rigid insulation bonded to the back, commonly polyisocyanurate (PIR) foam or expanded polystyrene. It is a popular way to insulate solid outside walls from the inside, because the insulation and the new wall surface go up in one operation. Many products include a vapour control layer to reduce the risk of warm, moist indoor air reaching the cold wall behind.

These boards can be fixed by dot and dab or to battens, but manufacturers normally require mechanical fixings in addition to adhesive so the boards stay in place if the adhesive fails, for example in a fire. Thicker boards insulate better but take more space and make reveals at windows and doors deeper, so there is a balance to strike in smaller rooms. The joints, edges and any service penetrations need careful sealing, otherwise moist air can bypass the vapour control and condense behind the board.

Dry lining is not a cure for damp, and covering a damp wall usually makes the problem worse by hiding it. Adhesive dabs on a wet wall can let moisture reach the board, leading to staining, mould and failed fixings, and gypsum products do not cope well with persistent moisture. Before any work, find and fix the cause of the damp, whether that is a leaking gutter, bridged damp proof course, failed pointing or condensation.

Period homes with solid brick or stone walls and lime mortar need extra thought. These walls were built to absorb and release moisture, and sealing the inside face with impermeable materials can trap water in the masonry. On such walls a battened system with a ventilated gap, breathable insulation such as wood fibre, or a lime plaster finish may be more appropriate, and it is worth taking specialist advice. If you are weighing up insulating inside against insulating outside, our guide to the pros and cons of external wall insulation sets out the trade-offs.

Once the boards are up, there are two main ways to finish them. A skim finish is a thin coat of finishing plaster, usually two to three millimetres, trowelled over the whole surface after the joints are taped with scrim. It hides joints and screw heads completely, gives a hard, smooth surface and is the usual choice in UK homes where plasterers do the work.

Tape and joint, sometimes called taping and filling, uses tapered-edge boards. The shallow recess along each joint is filled with jointing compound and paper or mesh tape, built up in thin layers, then sanded flush, so only the joints and fixings are treated rather than the whole wall. It produces less moisture and dust from mixing plaster, and the walls can be decorated soon after, but the surface is a little softer and a good result relies on careful sanding and a suitable primer. Ask your plasterer which they recommend for your rooms, as the board type needs to match the finish.