Drylining walls

Drylining walls

Drylining walls

If you convert your garage, basement or a loft, the walls needs to be plastered in order to achieve a nice smooth finish.An easy way to plaster the walls if you dont want to spend extra time and money on undercoat plaster (bonding) is to dry line the walls. Alternatively, you can call a Plastering Company to do the job.

Drylining with fibreboard pads

Pads are arranged to cover a wall vertically at 450mm centres, starting either at an opening such as a window or door, or from a corner (fig. A). The vertical separation between pads should not exceed lm, and additional pads are required for window reveals wider than 450mm. For reveals narrower than this, plasterboard can normally be fixed simply by generous dabs of adhesive or plaster.

Start the fixing sequence by marking the walls, ceiling and floor at the various 450mm centres. Afterwards, locate and mark the high spot. You can use dabs of bonding coat (Carlite), finish plaster (Thistleboard) or a suitable multi-purpose adhesive (Gyproc) for fixing the pads in position. Setting time varies from one hour for the first to two hours for the others. Bear this in mind should you be able to complete the pad fixing quickly the pads must be allowed time to bond to the wall before the boards are fixed in place. Fix the first pad in position on the high spot using a minimum amount of plaster or adhesive. Its distance from the wall is used straight away to determine the setting of the three or more pads on the same fixing line.

Apply a dab of plaster or adhesive to a point about 250mm from the ceiling, and along the fixing line. Apply another, 100mm from the floor, and a third at an intermediate position (or two more if the separation is greater than lm). Push a fibreboard pad into each dab, at this stage hard enough only to hold them in place. Next, using the timber straightedge in conjunction with a spirit level and a plumbline, plumb vertically and sideways from the high spot pad to the ceiling pad in the fixing line. Push this into the fixative until it is exactly level with the high spot pad. If necessary, remove the pad and add more plaster or adhesive to build up additional support.

Then plumb downwards and sideways to set the floor pad in the fixing line. When this is level with the high spot pad, carefully push home the intermediate pad using the straightedge until it is level with the rest. You must take care not to disturb any of the pads in the process, as they are now used to align all the remaining fixings on that particular wall. With the pads in position, carefully hold the straightedge against them and mark off its leading edge at both the ceiling and the floor. From these two marks draw guidelines across the ceiling and floor to coincide with each of the vertical fixing lines.

Choose a fairly distant fixing line (a separation of three lines, 1800mm, would be ideal) so that alignment errors are minimized, and then proceed to fix the pads of this line in position, applying dabs of fixative and pads at top, middle and bottom as before. Hold the straightedge against the fixing line so that its leading edge coincides with the guidelines you have just marked, and at the same time use it to push the three pads level with each other. If you have taken care in the marking of the guidelines, these three pads should be level with the three original pads. These two sets of ceiling, middle and base pads can then be used to level the pads of the fixing lines in between. Apply plaster and pads to all the fixing points.

Run the straightedge horizontally between the ceiling pads of the first and second fixing lines and, without disturbing these, carefully push the intermediate pads until they are level. Do exactly the same for the horizontal lines oi middle and base pads. This completes the pad fixing for a panel of wall board 1800mm wide. The pads of the second fixing line can be used to originate a new panel by producing a further fixing line 1800mm (or as far as possible) away from them.

Any remaining fixing lines are then levelled in exactly the same way as the other intermediate fixing lines. Accuracy of the levelling procedure on the new panel can be checked as you go by observing the relationship of the straightedge to the pads which have already been levelled in the first panel.

Fixing the plasterboard

When the pads are firmly bonded to the wall, you can proceed to fix the wallboard in position using the same plaster or adhesive. Apply large, vertical dabs between the pads and cover an area sufficient for one board fixing at a time, always starting at a corner or opening. The depth of the plaster or adhesive dabs must exceed that of the pads, but their width need not exceed 50-70mm.

To avoid bridging joints, try to keep the dabs clear of the eventual board edge. When the dabs for one board have been applied, carefully offer up the wallboard. This should be cut about 12mm short of the actual wall height, and apertures for fixtures and fittings made beforehand. On the presumption that a skirtingboard will be fitted, arrange for the cut edge to be floormost. Edge the first board into position against the dabs of fixative with the aid of a footlift, and then use the straightedge to tap the board firmly against the pads themselves. Providing you spread the load along the straightedge— and hence across the board— considerable pressure can be applied without risk of damage.

Once all the boards are in place you can use standard plasterboard jointing methods to hide the gaps and the screw fixing holes The plaster or adhesive dabs are thus forced flat against the rear of the board, and this adhesion is normally strong enough to keep the board in position. As you apply the final pressure, use the footlift to raise the board tightly against the ceiling and to see that the edges remain plumb and central to the line of vertical pads. Permanent or temporary secondary fixings are then made to prevent the board slipping during the two hour drying period.

Special double-headed nails can be obtained for temporary fixings; permanent fixing nails are carefully indented so that the nail heads may be spotted later. Be careful not to break the paper surface of the board when nailing. Second and subsequent boards are treated individually, each being carefully butted to the edge of the previous one.

Fit the facing boards below and above a window last. External and internal angles are treated as described above. Should you decide to use thermal board instead of standard wallboard, follow the same procedure but employ 600mm fixing centres (boards are 1200mm wide) and secondary fixings— the latter to reduce fire risk.

Using metal furring

Drylining walls

The metal furring system uses two types of component: channelling for the vertical fixing centres (every 60mm for 1200mm board); and stops, which are used horizontally to support the board ends top and bottom. Multi-purpose adhesive (Gyproc) with a drying time of two hours is used to bond the channelling and stops securely to the wall. First of all establish the high spot and mark continuous lines on the ceiling and the floor corresponding to the leading edge of your straightedge. The vertical channelling is set at 600mm centres in plain walling, but because board edges need support, internal and external corners must be carefully considered when marking up the position of the centres.

Channelling should be brought as close as possible to the edge of the board in either instance. There is a slight complication with external corners in that the facing board must always be wide enough to take in the depth of the reveal board, its furring, and the adhesive. For this reason, you should work from the corners to determine the setting out of the board fixing centres, and mark these on the floor and ceiling as well as on the wall.

Apply dabs of adhesive along the vertical lines. These need not be continuous—you can allow gaps of as much as 500mm between dabs of about 250mm length—but they must be deep enough to fill out the perforated rear of the channelling or the bond with the wall will not be strong enough. Bear in mind also that the distance between the deepest part of the wall and the back of the channelling must not exceed 25mm. When a line of adhesive is complete, cut the furring to length (it is available in lengths of 2260mm) and push it into position on the dabs of plaster, taking care not to take its leading edge past the lines you have marked on the ceiling and floor. Use a spirit level to ensure that it remains perfectly vertical at all times.

If channelling has to cross wiring or pipework, simply cut the length into as many pieces as is necessary to complete the vertical run. But take particular care to ensure that you know where the junctions fall and that you do not accidently screw or drill through the services when you come to fix the boards. When all the channels have been fixed into position, apply dabs of adhesive to fix the stops. These should be located 25mm-30mm from the ceiling and floor. Use a straightedge to tap them level with the vertical furring. Then use a straightedge, line and spirit level to check the overall alignment, breaking down and repeating any part of the system that is out of line. Leave the channelling to bond to the wall before attempting to fit the wallboard over the top with the screws provided in the metal furring kit.

Fixing the wallboards

Wallboard is fixed to the metal furring by special drywall screws (available in various lengths), which are both self-drilling and tapping. The 2mm size is suitable for 12.7mm board. Start by accurately aligning the edge of the first board with the centre of the furring. The board does in fact cover three furrings if your system has worked out correctly, so each board has three vertical fixing lines.

Fix the boards at 300mm centres, but take care not to come any closer than 10mm to the edges or you may damage them irreparably. Cut the board to length and use a footlift and offcuts of wood to wedge it tight against the channelling and firmly against the ceiling. End the fixing of each board by screwing it to the stop at the top and the bottom. All screws should be driven very slightly below the paper surface of the board to enable you to spot them later. The next board is lightly butted in place and its edge carefully aligned to the centre of the metal furring. If necessary, correct small vertical alignment errors by leaving a gap between the boards.

Use wedges and offcuts to hold the board in the desired position while the fixings are made. Subsequent boards are then added in order. Window reveals and soffits normally require only narrow sections of board, and it is usual to mount these directly on pads of adhesive rather than on small sections of furring. Once the boards have been mounted, normal methods of jointing and spotting can be used to complete the dry lining.


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