Cutting Plasterboard to size

Types of, uses and fixing sheets of Gyproc Plasterboard

After you have framed the wall or ceiling you can start cutting plasterboard to size and fixing it in place, ready for the plasterers.

cutting plasterboard

Gyproc sheets either get flushed (tape & jointed) or skimmed with a thin layer of finish plaster. For flushing special boards with tapered edges are used. The taper allows a space for the tape and jointing compound to sit into ready for sanding, hence the term 'flushing'.

The joints in between boards need to fit together tightly, more important if being flushed than skimmed. Provided all the studs are set out to the correct centers for the size of the boards you are using and all the noggins are in place you should be able to board the wall really quickly.

Once one side is done, sound insulation like Rockwool can be fitted in between the studs before boarding up the other side.

Cutting plasterboard and the tools required

It's rarely the case in carpentry but for cutting plasterboard you don't need any expensive tools. If it's a one off or you are not going to be cutting plasterboard a lot, then all you need is an old handsaw (or plasterboard one), Stanley knife and a straight edge.

Plasterboard is cut to length by first marking then scoring a line on the face side of the board with a straight edge and Stanley knife. Then, lift the sheet off the floor and snap the board along the score line. Finally you run the knife down the other side of the cut to sever the paper on the back. I cut loads of plasterboard so I've got a Plasterboard T-Square too. Using this tool means rather than measuring across the board twice and marking two lines to join up with a straight edge, you only have to mark the board once when cutting to length. Place the square up to the line and you can score it perfectly across the board. It saves loads of set out time and means I get perfectly square cuts every time.

Fixing sheets of plasterboard

The pictures below are of a wall that is being plastered. If the joints are only being taped and jointed the boards are better installed vertically (one board from floor to ceiling) so there are only vertical joints to finish.

You can screw plasterboard to the studs with a drywall screw-gun, normal battery drill/driver or an auto-feed screw-gun. The auto-feed screwdriver

I haven't drawn a door frame in the picture, but when a board is installed it should be tight up against a door lining or other wall but half lap onto a stud and noggin where boards join, like below. Don't screw too close to the edge of the boards and no boards edge should be without timber behind it to fix to.

When fixing 1200mm wide boards (4ft), I put 5 screws (or tacks) across the width and screw into the bottom plate and noggin in between the studs too. So the screws should be no more than 250-300mm apart.

fixing plasterboard

When installing the next board stagger the joints for strength wherever possible. Sometimes like above a doorway a notch needs to be cut so that the sheets all land half on a stud.

fixing plasterboard

If you are cutting plasterboard in an L shape, or need to cut a corner out of a board you will need to first cut one line (I normally do the shortest) with a handsaw and the other you can scribe with a knife and snap like before. Rather than buying a saw, I just use an old hand saw. Cutting plasterboard with your best hand saw will dull the teeth really quickly and you'll soon need another one.

cutting plasterboard

How to cut holes in plasterboard

For perfectly round holes in plasterboard for things like spotlights and soil/waste pipes I use a plasterboard circle cutter. Alternatively you can use a jab-saw (sometimes called a pad-saw) which is also good for cutting holes for electrical cables etc. that need to be brought forward too.

Trimming the cut for a better fit

If you need to shave a bit of the board off, when scribing to an irregular shape for example instead of cutting plasterboard with a saw or knife you can use a Surform, otherwise known as a Rasp. This tool works like a plane but has a replaceable blade that looks a bit like a cheese grater.

How to fix plasterboard

Plaster-boarding used to be called 'tacking', because boards were nailed to the studs or joists with tacks. These would often 'pop' the plaster off themselves if they weren't fixed tight to the ceiling joists or studs and the board then moved. Instead, boards are now screwed with drywall screws that almost eliminate this problem - provided they are not wound in too far. The screw heads need to finish just under flush with the surface of the board. If they are proud, not only are they not doing the job but the plasterer will catch and dent his trowel on them (then he'll probably moan like f#@k).

You can buy auto-feed screw-guns and collated screws to fix plasterboard, special drywall screw guns or just use an ordinary cordless drill with a plasterboard bit that has a depth stop that means you can quickly screw to the right depth each time.

Special drywall hammers are available for fixing plasterboard too. They have a large milled face for extra grip on the nail heads and also have a sharp flat claw that can be used like an axe for quickly and accurately cutting plasterboard for electrical boxes and cables etc. Click here for loads more info on hammers.

Tiling on plasterboard

Plasterboard is also a good sheet material to tile onto because it doesn't expand and contract like plywood. Whenever I build pipe boxing's that are going to be tiled in a kitchen or bathroom for example I use 12.5mm plasterboard to cover them. If the boxing needs more strength I'll ply it first then fix plasterboard onto that for the tiler.

Sizes available

There are varying thicknesses and specifications of boards available ranging from 6-25mm (1/4in to 1inch thick). The most commonly used boards on site are 2400x1200(8x4) and 1800x900(6x3) but longer boards (6m) are available for commercial projects. The 1800x900/600 boards are perfect for loft conversions because they can easily fit through Velux windows.

Types of boards

Boards with loads of different properties are available, from acoustic to fire retardant. Some wall board systems can offer up to 4 hours worth of protection from a fire (hopefully you'd be long gone by then..). 'Aqua boards' are also available that are mould resistant and can withstand high levels of moisture/ humidity, great for bathroom walls and ceilings etc.

Have a question or comment about cutting plasterboard?