Do I need plasterboarding before plastering?

Plasterboarding and plastering often go hand in hand, but not every job needs new boards. Whether you need them depends on what's there now, what state it's in and what you're trying to achieve. Boarding a wall that only needs a fresh surface adds cost you don't need, while skimming over failing plaster stores up problems. Here's how to work out which route makes sense for your walls and ceilings.

Can you plaster straight over existing walls?

Often, yes. If your existing walls are sound, reasonably flat and not blown, a skim coat is usually the simplest and most cost-effective route to a great finish. Tap the wall to check: a solid, dull sound means the plaster is bonded, while a hollow sound means it's come away. Painted walls can be skimmed with the right preparation, and small damaged areas can be patched first. There's no need to board over a wall that only needs a fresh surface.

Artex walls and ceilings are a common grey area. In many cases they can be sealed and skimmed rather than boarded. Older artex, roughly anything applied before 2000, may contain asbestos, so it should be tested before anyone sands or scrapes it. If the texture is very heavy, or the ceiling is also cracked and uneven, over-boarding and skimming can be the neater option.

When should you board out instead?

Boarding out makes sense when:

• The existing plaster is failing, blown or crumbling over large areas
• You've got bare brick or block after hacking off, or in an extension
• You've removed walls or knocked through and need to make good
• You're building new stud walls or partitions
• A ceiling is badly cracked or uneven and over-boarding is better than pulling it down
• Walls are too far out of line to straighten easily with plaster alone

Boarding can also be quicker to dry than a traditional backing coat, because you're only waiting for the skim rather than a thick wet layer underneath. That can make a real difference if you're working towards a kitchen fit or a move-in date.

What is dot and dab plasterboard?

There are two main ways to fix plasterboard. Dot and dab means sticking boards to a solid wall with blobs of adhesive, then tapping them into line. It's quick, works well on sound masonry walls and can take out a fair bit of unevenness. It isn't suited to damp walls or surfaces the adhesive won't grip. Screw-fixing means fixing boards to a timber or metal frame, such as stud walls, battens or ceiling joists. Ceilings should always be screw-fixed rather than stuck. Each method has its place, and Darren will recommend whichever fits the job and your budget.

Which type of plasterboard should you use?

Standard plasterboard suits most rooms, but there are alternatives for specific situations:

• Moisture-resistant board for bathrooms and other humid areas
• Fire-rated board where building regulations call for it, such as some ceilings and walls next to integral garages
• Acoustic board to reduce noise between rooms
• Insulated board for cold external walls

Board choice can affect building regulations on some jobs, so it's worth checking early rather than finding out afterwards. For areas that will be tiled in a shower or wet room, a dedicated tile backer board is often a better choice than plasterboard.

Do you need to skim new plasterboard?

In most cases, yes. Plasterboard gives you a flat, true surface, but it isn't a finish on its own. The joints are covered with scrim tape, external corners are protected with angle beads, and then the whole surface is skimmed to give a hard, smooth finish ready for paint. The alternative is taping and jointing, where tapered-edge boards are used and only the joints are filled and sanded. That's more common in new-builds, while a full skim gives a harder, more consistent surface.

What goes wrong with badly fitted plasterboard?

Done well, boarding gives you a perfectly flat, true surface ready for a skim. Done badly, it leaves lumps, visible joints and cracks along the board edges. Common faults include boards that aren't fixed securely, joints left untaped, boards not staggered, and dot and dab adhesive spaced too far apart, which leaves boards that flex when you press them. All of these show up sooner or later through the finish. It's worth doing properly the first time.

If you're renovating in Leeds or elsewhere in Yorkshire and aren't sure whether to skim or board, Darren can look at the walls and give you a clear recommendation along with a free quote.