Dry lining by direct bond – overview In recent years, dry lining has developed more than any other form of plastering. Most new buildings, especially houses, contain some form of dry lining. Direct bond is a dry method of producing a flat wall surface. Sheets of plasterboard are secured to the background surface, leaving air space between the board and background. Because it’s a better insulator than solid plaster, it will result in a warmer house. Construction is speedy and it dries out quickly, which means decoration can take place sooner. Quick construction = quick financial return for house builders.

Tools for installing direct bond system Hawk and trowel for applying adhesive dabs Tape measure Pad saw Chalk line Spirit level Square for fixing returns Straight edge Foot lifter Broad saw Internal corner trowel Taping Applicator Hand sander and universal sander Jointing sponge

Equipment for installing direct bond system Hand-held electric mixer (110 volts) – for mixing adhesives Whisk or paddle – for use with electric mixer Plastic mixing drum – for mixing smaller quantities of adhesives Different sizes of buckets or containers for different quantities of adhesives Spot board and stand Cement pan for keeping jointing material in – used with the taping knife Access equipment if required

Materials Types of board Tapered-edged plasterboard 9.5 or 12.5 mm thickness 900 or 1200 mm width Tapered-edge plasterboard is thinner at the edges than the rest of board

Jointing materials Jointing materials Mixing of jointing materials Setting materials Air-drying material Part setting + part air-drying Mixing of jointing materials Some materials are in powder form. Some materials come pre-mixed. Powder materials should be mixed to a smooth paste with no lumps or hard particles.

Joint reinforcement Reinforcement is needed to help prevent the joints between the boards from moving and cracking. This comes in the following forms: paper joint tape self-adhesive glass fibre mesh reinforced corner tape drywall metal beads drywall plastic beads. Note: glass fibre tape is not recommended by manufacturers.

Background Preparation of background Quality of background and how will it affect the method of direct bond Thickness of ‘dabs’ What is a ‘tacker or boarder’? When is a building ready for dry lining? What should happen to services before dry lining?

Setting out a plain wall Find the high spot of wall. Transfer high spot to ceiling. Add 10 mm on high spot for thickness of dab. Snap chalk lines. Transfer lines down to floor. Set out boards from internal angle Set out end of boards and centre of boards Method of transferring high spot to ceiling Setting out plasterboard for direct bond

Attached piers Face of attached pier should run parallel with back wall when pier is in the centre of a wall. An attached internal angle pier is within the corner of a room. Attached piers should be plumb and square. Squaring in an attached pier

Window opening Set out window wall as for a plain wall. Set out boards from a window reveal towards the internal angle. Board at window external angle should overhang to allow for a neat angle when the window reveal board is bedded on. Gap under window may not be same size as a full plasterboard sheet so will need to be trimmed accordingly. A continuous strip of adhesive is placed on the background at curtain rail height.

Fixing plasterboard Cut board to height and fix one board at a time. Apply continuous strip of adhesive around perimeter of the wall, services and openings. Apply adhesive dabs 250 mm long, 50-75 mm wide and no nearer than 25 mm to board edge lines. Offer grey side of plasterboard to dabs and lift up to ceiling with foot lifter. Tap boards back to dabs to line up with chalk lines. Wedge board in place. Repeat making sure edge of board is lightly butted against the last board. Run a straight edge across face horizontally and diagonally to check for flatness.

Separating walls Add a parge coat to the background before applying direct bond to help with sound insulation. It is applied at 6 mm thickness and not scratched. For insulating boards a special type of nail called a ‘nailable plug’ is fixed through the dab when the adhesive dab has set. This will prevent insulation board from falling off the wall if in a fire.

Hand taping and jointing The suggested order for applying joints is: 1. internal angles 2. tapered-edged joints 3. cut board edge joints 4. external angles. Method of forming joints Cut tapes. Apply band of jointing material into depression. Press tape into filler. Cover tape with joint filler flush with board. Feather out jointing material with sponge. Apply a further two coats after each coat has dried and feather out with sponge. When first learning to tape slightly damp plasterboard either side of joint

Methods of forming external angles Apply adhesive 50 mm each side of joint. Bend tape to 90°. Use thumb and forefinger to press tape into adhesive. Slight pinch action is used to raise nosing of tape. Finish off as for taping straight joints.

Sealing the boards All joints should be lightly sanded down. Remove dust. Apply sealer by brush or roller. Why should the boards be sealed?

Name three tools used for fixing plasterboard for direct bond.? Foot lifter Broad saw Internal corner trowel Taping Applicator Hand sander and universal sander Jointing sponge Hawk and trowel for applying adhesive dabs Tape measure Pad saw Chalk line Spirit level Square for fixing returns Straight edge

List two thicknesses and widths of plasterboard used in direct bond . thickness: 9.5 mm and 12.5 mm, width: 900 mm and 1200 mm

What type of plasterboard is best for direct bond? The best type of plasterboard for direct bond is tapered-edged plasterboard

Name two different types of jointing material. setting material, air-dry material

To produce the best results with jointing material what should you avoid within the material? Jointing material should be mixed to a smooth paste with no lumps or set hard pieces of jointing material.

Name two types of reinforcement used on plasterboard joints in direct bond. two types of joint tape: paper tape and self-adhesive glass fibre mesh  

Name two types of reinforcement used on external angles in direct bond. reinforced paper corner tape, drywall metal beads

The background for direct bond should be of what quality and why? The background for direct bond should be of good quality and level, because if the adhesive used to fix the boards is too thick it will not hold the boards securely back to the background.

Dabs of bonding adhesive for fixing plasterboard should be no thicker than: a 10 mm b 15 mm c 20 mm d 25 mm  

What should happen with electrical wires and pipes that are larger than the air gap behind the plasterboard? Pipes and electrical cables should be chased into the background if possible

What is the first thing that should be done when setting out for direct bond? The first thing to do when setting out for direct bond is find the high spot

After marking the width of the plasterboard from the internal angles what should be done next? After marking the width of plasterboard, mark the centre of the plasterboards.  

When dry lining a window wall, where should you start the setting out? The setting out of a window wall should start from the external angles of the window

What should be the length of the adhesive dabs? The length of a dab should be the length of the trowel – about 250 mm.  

Where on a plain flat wall should a continuous strip of adhesive be placed? A continuous strip of adhesive should be placed around the perimeter of the wall and around electrical power sockets and light switches

How many strips of vertical adhesive are required to secure a sheet of plasterboard for direct bond?

What is the purpose of a ‘parge coat’ on a separating wall? The parge coat acts as a sound barrier between separating walls.

When using an insulating board, what is used, besides the dabs, to secure the board? a nailable plug  

What is the head of a window called? The head of a window is the soffit or top of the window.

Name three tools used in hand taping. Any three of the following: trowel, filling knife, sponge, internal angle trowel  

Why is plasterboard sealed before decoration? Plasterboard is sealed before decoration because of the different suctions between the jointing material and the plasterboard face. If the boards are not sealed the joints will show through.

What should be done to the joints after completion but before sealing? Before sealing and after finishing of joints they should be lightly sanded.

When using a paper reinforcing tape for angles how is the nosing of the tape raised? The external reinforced paper tape is raised by running the thumb and forefinger in a slight pinching action down the tape which will raise the nosing.

For an exposed angle what type of reinforcement is best? For exposed external angles an external metal dry lining bead is best.

What should be done if a blister is found in the paper joint? If a blister is found it should be cut out and a new tape applied.