Plasterboarding

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Contents

General plasterboarding information, tips and tricks

See also

Thickness

  • Common thicknesses are 9.5mm and 12.5mm.
  • 9mm is a good choice for ceilings, where extra weight would make the job harder
  • 9 is not very robust for wall use, 12 is a good deal tougher for very little more cost, and its better acoustically.
  • 2 layers of PB can be used for extra robustness, better acoustics and longer fire resistance. Sticking the 2 layers together makes them even tougher.
  • Thicker sizes, eg 15mm or 18mm exist as well as thinner, eg 6mm.

Sheet Size

  • Sheet sizes are commonly 2.4 x 1.2m (aka 8ft by 4ft, most usual size), and 1.8m x 0.9m (6x3) (for easier handling, especially on ceilings). Trying to use whole 8x4s for ceilings isn't recommended, they're too heavy and big to handle easily.

Also available are:

  • 4' x 3' (1220mm x 900mm)
  • 9' x 4' and 10' x 4' boards, very handy with high ceilings.

Types

  • Plain - paper both sides. Usually beige or grey in colour. Most PB is this type
  • Vapour barrier or vapour check - usually with a metallised plastic film (which may degrade radio signals such as cordless telephones or Wifi).
  • Fire check - usually pink in colour
  • Moisture shield - for areas of high humidity, usually green.
  • Sound block or acoustic plasterboard - usually blue.
  • Various combinations of the above properties, dependant on manufacturer.

Note: some older types of board had one side designed for painting and one designed for skimming. The approach seems to be less common these days (2009), with one side only designated as the face side. Fit the board the right way around for best results. The facing side has no paper joins or edges, the back has, and often has information printed on it. Its no biggie to use the board the wrong way, it just means more chance of paper peeling and a slightly less consistently finished surface.

Edge shapes

  • Taper - for filling prior to painting direct.
  • Recessed edge - also for filling with no skim coat
  • Square edge - used when a skim coat of plaster is going to be applied.

Permutations

Not every permutation of edge, type, size and thickness are available so you should check with your local supplier before committing to a particular design.

Building regulations

For certain applications, you may need to meet certain levels of fire resistance or acoustic performance. For now, this is an area too involved to cover here, so please seek the advice of your local Building Control department at your Borough/District Council if you have any doubts.

Sometimes you may be asked to fit two overlapping layers of plasterboard with staggered joints to allow longer fire resistance times.

Otherwise, use 9.5mm for ceilings and 12.5mm for walls as a sensible default, in whatever sheet sizes are most convenient.

Cables & pipes

Screwing into them is less than ideal. Photographing the studwork before you put the boards on gives you a record of pipe & cable runs.

Steel plates are cheaply available to protect pipes & wires where they pass through uprights. It takes little effort to fit them before boarding.

Tools

Useful tools include...

  • Utility knife & blades, or wallpaper knives
  • You can't have too many tape measures.
  • as long-as-possible metal ruler, ideally 1-2m - but a large spirit level or even a straight piece of timber can substitute
  • big tee square (or a hardboard offcut will do)
  • pointy shaped saw, eg padsaw
  • Cordless drill or similar for screwdriving
  • Dead man prop for plasterboarding ceilings
  • Plasterboard screwdriving bit can help if you're not good at setting screw depth correctly.

Also nice:

  • The Gyproc bladerunner gets a big thumbs up for making board cutting much faster & more accurate.
  • plasterboard rasps with guides
  • Fein Multimaster type tool excellent for doing quick, precise cutouts for sockets.
  • Board-lifter handles, and skates/trolleys are useful to manoeuvre boards easier. Both are easily homemade.
  • Laser guide if working on a bigger scale
  • A decent collated screwgun speeds things up enormously
  • For curved cuts, a metal-cutting blade in a jigsaw works well.


Logistics

Plasterboard sheets are large, but the corners are very weak. Watch it when you move them, its very easy to bump them into things and crush the corners. Don't scrape them across anything when putting them down. If you have to leave them horizontally overnight for some reason, lining the corners up properly much reduces the risk of damage.

Getting the plasterboard sheets to the right place is a sizeable part of the physical work when they need to go upstairs. If you're doing a large job, moving the plasterboard can be demanding, and its worth doing all you can to make this operation easier. For a large job this can include: use board lifting handles, skates/trolleys, remove doors, move everything possible out of the path, add protection at scrape points, maybe construct temporary ramps etc. Plan it fully.


Cutting plasterboard

There are three basic types of cut most commonly needed:

Straight cut across full board

  • Used all the time when boarding large areas
  • Very easy and clean to do.
  1. Place board across a couple of supports (eg sawhorses, workmates or even lumps of timber or bricks if nothing else to hand). Be sure the board is well supported near the new cut and stable.
  2. Mark the cut line
  3. Score through the paper layer on one side of the board with a sharp stanley type knife. A couple of lighter strokes are better (and safer) than applying serious pressure. Always work the knife away from your body and hands - it's very easy for the knife to slip.

    Scoring-plasterboard.jpg

  4. Position the board so that one of the supports runs parallel and just behind the score line.
  5. Put the knife away(!)
  6. Using both hands (better two people, if the cut is long, eg 2.4m board), rotate the board edge downwards. (Whacking it down also works.) The board should snap cleanly along the scored line.
  7. The cut section of the board will continue to hang on the layer of cardboard on the back. Do not attempt to rip by tearing the cut section off - it will make a mess.

    Snapping-scored-plasterboard.jpg

  8. Retrieve the knife and whilst supporting the cut section at 45-90 degrees, simply cut through the remaining paper. The result should be a clean straight edge, mostly square with almost no dust.
  9. If desired the edge may be cleaned up with sandpaper, a coarse file, a coarse hand stone (this bit makes some mess) or a knife.

Alternative method requiring less space and handling

(Copied with edits, with thanks to the original author)

  1. Have the board vertical, leaning against a wall.
  2. Use a metal straight edge (long level typically), mark two points and align the level holding the bottom of it with your foot, and the top with one hand, then score with the other.
  3. Snap the board by hitting it in the middle of the back of the cut, and separate.

All in all it takes less space, and less handling of the board. You also are less likely to damage a board getting in and out of cutting positions.

Fiddly cuts

  • You'll need a narrow bladed saw, such as a padsaw, or a knife. A hacksaw blade in a holder will suffice for small works.
  • For extended work or cutting square holes for lightswitches, proper plasterboard saws are available which have pointy ends for piercing the board and coarse teeth.

Removing a rectangular section from a corner or edge can be done with a combination of sawing and scoring for the final cut, or with a knife.

Fixing plasterboard

To wood (eg ceilings and wooden studwork)

  • The sheets may be screwed (best) or nailed (old fashioned method, not so good as nails can loosen) directly to the studwork or ceiling rafters.
  • For nailing, plasterboard nails are needed, though the consensus on uk.d-i-y is that they are nowhere near as good as using screws.
  • For screwing, use purpose made drywall screws. These have a continuous thread, bugle head (designed not to tear the paper which weakens the fixing), a very sharp point for self drilling, a thin shank for easy pilotless insertion, and are not liable to corrode. On the end of a small cordless electric screwdriver, these generally go in single handed, quickly and securely. The heads become "lost" in the surface of the plasterboard. Non-PB screws make a mess of the plasterboard, and create a weaker fixing
  • Purpose made driver bits are available that help to prevent the screw going in too deep.

Plasterboard-driver-and-screws.jpg Plasterboard-driver-bit.jpg

  • Be aware if you are screwing or nailing over an area with low support (eg a hole in the previous plasterboard that you are covering. The screws can crack small sections of your new board especially near the edge.
  • Put enough screws or nails in to support the board so it feels firm all over. Every 9-12" is a reasonable spacing for 12mm on walls, or 6-9" for 9mm on ceilings (opinions vary a bit). You want to avoid any board edges being able to flex if you are going to skim it). Obviously, rafter or studwork puts limits on screw spacings in one direction.

Ceiling work

1.8 x 0.9m x 9mm board is easily handled by two people without additional props. One person should have the screwdriver at the ready with plenty of screws and be in a position to rest the board on their head periodically whilst reaching for the next screw. Once a couple of well spaced screws are in supporting the whole board, both people can let go and concentrate on getting the rest of the screws in.

Working single handedly is also possible using a prop. A variety of tools are available or can be made:

  • Plasterboard lifters Google search. Expensive and generally used by contractors on large projects, but also hireable.
  • Plasterboard prop. Cheaper ready made solution.
  • DIY prop or dead man: quickly made from a length of wood
  • A less common method is to nail a length of rope between a spread of joists, hanging down a little below ceiling level. You can then lift the board overhead, and slide one end into the rope loop. That will then take the weight of one end while you fix the other.

To brickwork and old plaster

Board is often fixed using blobs of drywall adhesive Google search at regular intervals.

D&D (Dot and Dab) is used on newbuild as well as old plaster and brickwork, certainly on 'thermalite' type blocks, the lightweight insulative ones are only really fit to have D&D as most other plasters won't adhere - even dry lining adhesive (DLA) will only stick to it once it's been damped down, indeed, all surfaces to have D&D should be damped down but thermalite thoroughly due to the high suction.

Mixing DLA is similar to mixing other plaster, except it's more sticky obviously and it should be mixed slightly thicker if you are going over very uneven surfaces, so that you can use huge blobs to get the board out to the desired level, if you mix it too wet, you can't build it out thick enough. Working time is normally 45mins, but it can last longer.

Make sure the wall to be lined is free from nails, screws and other protusions and any old plaster is sound. Flaky or loose plaster should be removed, as should any old wallpaper, and painted surfaces should be scored with a blade or scrabbler to form a key, and a coat of dilute (1:1) PVA and water applied prior to work commencing - it doesn't matter if this is wet or left to dry, brick or blockwork just requires wetting with plain water as mentioned above.

Some people apply the DLA to the wall and others apply it to the back of the board, personally I prefer to apply it to the wall because a board can get very heavy with two dozen blobs of DLA on the back of it so I will describe this method.

Only apply the DLA to the part of the wall which is to be covered by one board (you may need to measure) and using a gauger or small trowel apply snowball sized blobs to the wall about every 12ins, try to keep the blobs even because large ones will cause a bulge, while very small ones will probably not touch the back of the board.

Once all the blobs are in place, offer the board to the wall, but remember that if you are working on a bare wall, you will need some pieces of scrap timber as spacers at the bottom so that the board is not in contact with the floor, an inch or two is sufficient, this is assuming there is no skirting board already in place. Once the board is in contact with the DLA, use a spirit level (about 3 ft long if you have one) in all directions to make sure the board is not bulging anywhere and then proceed with the blobs for the next board, bearing in mind that on large walls, the joints should be staggered in a similar way to brickwork, this is to avoid long straight joints which are prone to cracking, even though you will still get a long straight joint in one direction, there's no need for two!

This link has some very good pictures: Ultimate Handyman

Curved Plasterboard

There are 2 ways to fit plasterboard to curves.

  1. Wet the board to soften it, fix into place and let it dry
  2. For greater flexibility use a flexible plasterboard intended for the job


Plastering

A gap of about 3-5 mm should be left between boards when fitting. This enables the plaster to squish through to the rear, holding it in place more firmly and reducing cracking and stopping plaster falling out.

Board joints not supported all along by woodwork are inevitable, but should be minimised. These are by far the weakest part of any plastered wall or ceiling, and most likely to crack.

Plasterboard joint tape is put over the joint before the plaster or filler is applied. This is an open mesh tape of plastic or fibreglass, and it reinforces the plaster joint to prevent cracking or pieces falling out.

There are 2 plastering options:

  1. full skim coat covering the whole area. Excellent result, but significant work & skill
  2. Fill the edge gaps only. Good result, much less work, less skill needed

When a joint fill only is used, wiping the filler/plaster on with a float makes for a fast job.

Its also an option to just stick paper tape over the joints, and no plaster, but this is only really suitable for locations like garages where a good finish is not required.


Noise reduction

There are various ways to reduce the sound transmission of timber frame walls. See Stud wall noise reduction


Disposal

There's always damage along the way, so you need to buy a bit extra, and there's always plasterboard left over. Disposal options include:

  • break it up & bin it
  • Use it in the garden as a soil amendment
  • dump offcuts in an internal timber frame wall cavity, where it'll reduce sound transmission slightly
  • break it up, stick bits randomly onto the interior side of the wall's PB for a little noise reduction.
  • Tips have a plasterboard skip, it gets recycled into new board.
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