Drylining means cladding a wall or ceiling with a prefabricated building board called plasterboard which consists of a layer of aerated gypsum plaster sandwiched between two sheets of heavy-duty paper. Plasterboard comes in several different forms suitable for a variety of cladding tasks, and is used in many forms of modern building and renovation in place of plastered finishes.
Plasterboard is quickly and easily fixed into place and, when properly jointed and finished, equals the smooth and appealing looks of a plastered finish. By comparison, plastering requires considerable practice and skill, and is probably the most difficult of the trade skills the handyman is ever likely to attempt. A further significant advantage of drylining walls is that almost no drying-out time is necessary—which means you can decorate almost as soon as jointing is complete.
Plasterboard is available in different forms, the most common being wall-board, a general-purpose gypsum plasterboard suitable for building partitions and for drylining walls and ceilings. It is suitable only for internal use and in situations that are not subjected to continuously damp or humid conditions—such as a badly-ventilated bathroom or washroom.
Wallboard is manufactured with three different types of long edge. Tapered-edged board leaves a small recess at the contact region of two boards; this is filled and smoothed . for a seamless joint which then needs only light decoration or painting for final finishing. Square-edged board for cover strip jointing, and bevelled-edge board which is V-jointed, are normally used when it is almost certain that wallpapering is to be used for decoration. The surface is primed before wallpapering.
The taper is, in fact, very slight and hardly noticeable. This makes tapered-edge board suitable for general purpose use even when the plasterboard construction employs exposed butt-joints, such as at corners.
Wallboard for drylining has an ivory-coloured surface on one side, and this requires the minimum amount of preparation for most forms of decoration. The reverse side, normally mounted inwards against the wall, is grey. Mounted outwards, this surface is used when a skim coat of finish plaster is to be used for decoration, a typical situation being to match an unusual plasterwork pattern in the remainder of the room. Light designs can be moulded or brushed in relief on the skim coat while this is still in the plastic state.
Wallboard is usually available in sheet widths of 600i.im and 1200mm, thicknesses of 9.5mm or 12.7mm, and lengths normally between 1800mm and 3000mm. You may have to place a special order for the larger board sizes.
Insulating wallboard is the first of several variations on the standard board and differs only in having a veneer of aluminium foil on one surface, which is mounted towards the cavity to reduce both cold penetration and room heat loss. A far superior form is thermal wallboard consisting of standard plasterboard bonded to a backing of expanded polystyrene, available with or without a vapour check paper membrane sandwiched between the two, and in various thicknesses. It is used to line external walls and roofs where thermal insulation is the main requirement of lining. It has one distinct advantage over the others in that it can be fixed directly to a flat wall, a much-employed method of providing low-cost insulation to a masonry wall.
A useful board for drylining external walls and roofspace ceilings is vapour check wallboard which consists of standard plasterboard with a backing of polyethylene film.
Although standard plasterboard has good fire safety characteristics, some situations call for better fire resistance. A special wallboard, consisting of a core of aerated gypsum plaster incorporating glass fibre and vermic-ulite is available for such cases.
Two other types of board can be useful for some work: plank and baseboard. Plank simply describes an especially thick form of plasterboard. Because of its thickness, plank is especially useful in certain laminated partition systems. Baseboard is, as suggested by its name and its two grey surfaces, designed specifically as a base for further plastering. Lath is a thin-width form of baseboard. Tapered-edge wallboard and thermal insulating wallboard are considered adequate for most do-it-yourself work, and you may have difficulty in obtaining other than these from your local supplier.
Drylining with timber battening
There are several methods of drylining a wall with plasterboard. Wallboard is normally mounted onto some form of timber framework—for example, the studs of a timber-framed wall. On masonry walls timber battens can be used; an alternative, covered later, is metal furring or a system of support pads.
Timber battening is the most popular method with the home handyman on account of its relatively low cost, but alignment problems caused by skewing framework can be a particular problem unless special care is taken when dealing with walls which are of less than perfect trueness. Good quality, properly seasoned timber must be used, in conjunction with sound, dry walls.
For old walls, start work by stripping all the old plaster from the walls unless this is perfectly sound. Remove all surface fixtures, marking the nearby wall or ceiling with their position so they can be replaced after the drylining.
Concealed pipework and electrical cables or conduits must be arranged before framework is fixed, with chasing of the wall if the cavity depth is insufficient. Bear in mind the total thickness of the wallboard and timber battening when accounting for new fixtures and wiring lengths.
Carefully plan out the framework arrangement that best suits the room features, bearing in mind that the wallboard sheets you use have to be supported at centres not exceeding 450mm or 600mm. Wallboard is usually fixed vertically, and the board width must correspond with the spacing of the vertical support framework while at the same time observing these recommended maximums. Plan on starting work from one particular end of the wall in order to transverse the wall in complete sheet widths, if necessary ending with a cut edge which can be disguised by the butt joint of an internal corner.
Timber battening—good quality 50 mm x 25mm must be used for wall dry-lining—spaced at 600mm centres vertically would be sufficient for 12.7mm wallboard. Provide additional supports around window and door frames.
Heavy items like sinks and cupboards must be mounted through the drylining and fixed securely to some form of inlaid timber support. If the fixing centres for these cannot be arranged to co-incide with the drylining support framework, you must consider providing further noggins and struts.
Methods of construction around corners and frames may also influence the precise framework de- sign, and should be borne in mind.
You will find that a sketch of your proposed design will be very useful in subsequent stages.
Very few walls are truly even, and to lay battening on these without further ado is asking for trouble when it comes to fixing plasterboard on top.
Setting out is the procedure for making corrections to the effective lie of the wall so that one common level is adopted across the whole area, regardless of all the minor imperfections that may or may not exist beneath what is then taken to be the high point of the wall.
Start by marking the wall at points which by plans and measurement corresponds with the board widths you have chosen to use. Also mark the positions of intermediate battening and any other support timbers you have included as part of the overall framework. If these are door or window openings, work from these.
The next stage is slightly tricky in that you have to find the high point of the wall. This is perhaps easiest done by running a suitable straightedge vertically along the length of the wall. Use a spirit level to keep this straightedge in true plumb, noting at what points—and by how much—protrusions force the straightedge away from the wall. Make sure to cover all the areas where battens are to be fixed.
When you have established the high point, mark the corresponding positions at ceiling and floor. Substitute a particularly straight length of battening for the straightedge you have used and, keeping it perfectly plumb with the help of a spirit level, mark the ceiling and floor again to establish the face plane of this and all other battening of the framework.
Individually transfer these reference marks to all other batten positions by using careful measurement and ruling.
Making the frame
Start making the frame by fixing a floor batten along the length of the wall, about 25mm above floor level.Use plugs and screws for fixing the batten at 600mm centres, ensuring at all times that its facing surface is quite true to the setting out marks. Use wood packing where necessary.
Then fix the ceiling batten in a similar fashion, checking that it, too, is true with the setting out marks of the high point batten, and also that its face is in perfect alignment with the batten near the floor.
The two horizontal battens are then used for correct alignment checks on all the vertical battens as these are individually fixed, with support padding being provided where necessary. The physical appearance of the framework is not important, but do pay particular attention to see that the facing surface is straight and true.
Adopt the same procedures if further support timbers are to be added. Later, when fixing short board lengths or widths, it may become necessary to add noggins or struts at points where the cut sheet edges do not coincide with the main components of the support frame. All edges must be supported, and fixed, to prevent local- ized weak spots which may lead to board fracture, holes or edge chipping. Plasterboard continued into the reveal, soffit and head of a window must be supported also.
If you have planned to use wallboards in the normal, vertical mode, buy sheets the length of which either just exceeds the wall height, or that are between a third and two-thirds longer again than your wall height. In this way, wastage is minimized: the near-size board can be trimmed to size ar/3 the waste simply discarded; the over-long boards will still yield easily usable offcuts.
Trim the sheets at their base, about 25mm shorter than the full floor to ceiling height of the wall—the gap will be concealed by skirting. Use a fme-bladed handsaw or, much easier, a handyman’s knife for the job; with the latter, score the ivory side, break the board over a suitable straightedge, then finally cut through the backing paper on the reverse side. Use a combination of bradawl and pad-saw to make the necessary apertures for switches, sockets, through pipes and other fittings at this stage. Smooth the frayed paper edges with fine sandpaper.
Carefully edge the first sheet into position;—ivory side outwards—at the starting point at one end of the wall. Use a foot-lift to raise the board hard against the ceiling while you push the sheet carefully but firmly home against the first part of the framework so preventing a loose, uneven fixing. Using assistance if you have it, maintain this position while the board is fixed to the support battening.
Use 30mm or 40mm galvanized or sherardized plasterboard nails at approximately 150mm centres, no less than 12mm from the board edges, to fix the sheet into place at all support points. Start at the middle and work radially outwards. In order to simplify later ‘nail spotting’, drive the nail heads down as far as possible without fracturing the bonding paper.
A special drywall hammer for nailing plasterboard nails can be purchased. The rounded head of this does not break the paper but drives the nail below the surrounding level while at the same time forming a checkered pattern which acts as a key for the minute amount of plaster or filler used to conceal the nail during spotting. A ball-pein hammer can be just as effective if used with care.
Offer up the next sheet in a similar manner, lightly butting this against the fixed wallboard. Avoid tight butting—leaving a 3mm gap between adjacent boards—as forcing a board into place results in bowing which may in turn lead to misalignment and unsatisfactory fixing.
Continue fixing this and other sheets in order until you come to the frame of a doorway or window—or any other obstruction which requires the board to be cut to something other than length. With planning, it is possible to arrange for the untrimmed board edge to form the new line of the reveal of the window , but trimming is likely, if only for the sill.
Plasterboard for the reveals—cut perhaps from short-length offcuts— should protrude to a point level with the battening face so that the edge of the adjoining wallboard can be trimmed to face this off. As this trimming is better done from direct measurement of an existing arrangement , finish the wallboarding of the window and door reveals before you cut the main sheets to fit the window or door frame area.
At the later finishing stage, the joint areas are bound with tape and concealed prior to decoration. This aspect is covered in the next plasterboard section.
Lining a ceiling
Wallboard can also be used in a variety of ways to clad a ceiling, often to repair a section of lath and plaster which has been damaged. However, it can only be fixed directly to joists if these are perfectly true and level. In many cases, it is easier to remove the entire damaged ceiling in order to expose the joists or rafters rather than attempt a patch.
Wallboard is easily mounted if sheet sizes can be arranged to match ceiling joists. But edges, cut or otherwise, must always be supported and this means providing cross noggins to complete the framework.
The joist separation and the best pattern of laying the wallboard across the ceiling are two important factors to consider when choosing the most suitable size and thickness of board. You cannot use 9.5mm board if the joists are further apart than 450mm, or 12.7mm board if the separation exceeds 600mm, unless you install many additional cross noggins to reauce the effective fixing centres to within these limits.
When you have established a suitable framework, based on laying sheets in ‘brick bond’ pattern , mark the position of the joists to aid subsequent nailing of the boards to them. It is important that the boards are fixed in this staggered pattern to reduce the strain along a line of joints.
Board is then laid, ivory face down, with the papered-covered long edge at right-angles to the joist and supported by the cross noggins. You will need assistance—or the aid of a lazy man—ceiling prop—to support the board while it is being fixed into correct position.
Use 40mm plasterboard nails and work from the middle outwards, nailing at 150mm spacings along the joist and noggin supports. Use previously-made wall marks—and later, the visible lines of nails—to guide you. Force the heads below surface to simplify nail spotting later.
The second and subsequent sheets should be lightly butted together, if possible leaving a very slight gap. Where necessary, cut the board to shape and length as you would normally, making sure the ends are staggered and that they co-incide with a joist or cross noggin.
For widely separated joints plasterboard plank can be used. At least five 60mm plasterboard nails must be used across the width of the board at every support to ensure adequate fixing.
But if the joists are not level and true, you have to consider using alternative fixing forms , or resort to the traditional methods of lath and plastering.