Fixing into plasterboard: plug, bit and screw
fischer rates its HM metal cavity fixing and its DuoPower plug in plasterboard, row by row for each board thickness. The tables below give each fixing's drill bit, screw and recommended load.
Plasterboard: what fischer rates
| Fixing | Drill bit | Screw | Recommended load per fixing |
|---|---|---|---|
| fischer HM metal cavity fixing 4 x 32 S | 8 mm | Screw M4 x 40, thread M4 | 0.15 kN (fischer does not give this in kg) |
| fischer HM metal cavity fixing 5 x 37 S | 10 mm | Screw M5 x 44, thread M5 | 0.15 kN (fischer does not give this in kg) |
| fischer HM metal cavity fixing 5 x 52 S | 10 mm | Screw M5 x 58, thread M5 | 0.15 kN (fischer does not give this in kg) |
| Fixing | Drill bit | Screw | Recommended load per fixing |
|---|---|---|---|
| fischer HM metal cavity fixing 4 x 32 S | 8 mm | Screw M4 x 40, thread M4 | 0.20 kN (fischer does not give this in kg) |
| fischer HM metal cavity fixing 5 x 37 S | 10 mm | Screw M5 x 44, thread M5 | 0.20 kN (fischer does not give this in kg) |
| fischer HM metal cavity fixing 5 x 52 S | 10 mm | Screw M5 x 58, thread M5 | 0.20 kN (fischer does not give this in kg) |
| fischer DuoPower 5 x 25 | 5 mm, at least 35 mm deep | 4.0 mm wood screw | 0.12 kN (fischer shows this as 12 kg) |
| fischer DuoPower 6 x 30 | 6 mm, at least 40 mm deep | 5.0 mm wood screw | 0.15 kN (fischer shows this as 15 kg) |
| fischer DuoPower 6 x 50 | 6 mm, at least 60 mm deep | 5.0 mm wood screw | 0.15 kN (fischer shows this as 15 kg) |
| fischer DuoPower 8 x 40 | 8 mm, at least 50 mm deep | 6.0 mm wood screw | 0.15 kN (fischer shows this as 15 kg) |
| fischer DuoPower 10 x 50 | 10 mm, at least 60 mm deep | 8.0 mm wood screw | 0.15 kN (fischer shows this as 15 kg) |
| Fixing | Drill bit | Screw | Recommended load per fixing |
|---|---|---|---|
| fischer DuoPower 5 x 25 | 5 mm, at least 35 mm deep | 4.0 mm wood screw | 0.13 kN (13 kg by fischer's own conversion) |
| fischer DuoPower 6 x 30 | 6 mm, at least 40 mm deep | 5.0 mm wood screw | 0.15 kN (15 kg by fischer's own conversion) |
| fischer DuoPower 6 x 50 | 6 mm, at least 60 mm deep | 5.0 mm wood screw | 0.24 kN (24 kg by fischer's own conversion) |
| fischer DuoPower 8 x 40 | 8 mm, at least 50 mm deep | 6.0 mm wood screw | 0.20 kN (20 kg by fischer's own conversion) |
| fischer DuoPower 8 x 65 | 8 mm, at least 75 mm deep | 6.0 mm wood screw | 0.32 kN (32 kg by fischer's own conversion) |
| fischer DuoPower 10 x 50 | 10 mm, at least 60 mm deep | 8.0 mm wood screw | 0.30 kN (30 kg by fischer's own conversion) |
Sources: fischer, Loads, Metal cavity fixing HM, recommended loads for a single anchor. Checked ; fischer, fischer Metal cavity fixing HM product page. Checked ; fischer, Loads, DuoPower, recommended loads for a single anchor. Checked ; fischer, fischer DuoPower product page. Checked .
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It never changes the answer above.
- fischer DuoPower 5 x 25fischer's recommended load in Gypsum plasterboard 12.5 mm: 0.12 kN (fischer shows this as 12 kg).fischer's recommended load in Gypsum plasterboard 2 x 12.5 mm: 0.13 kN (13 kg by fischer's own conversion).
- fischer DuoPower 6 x 30fischer's recommended load in Gypsum plasterboard 12.5 mm: 0.15 kN (fischer shows this as 15 kg).fischer's recommended load in Gypsum plasterboard 2 x 12.5 mm: 0.15 kN (15 kg by fischer's own conversion).
- fischer DuoPower 6 x 50fischer's recommended load in Gypsum plasterboard 12.5 mm: 0.15 kN (fischer shows this as 15 kg).fischer's recommended load in Gypsum plasterboard 2 x 12.5 mm: 0.24 kN (24 kg by fischer's own conversion).
- fischer DuoPower 8 x 40fischer's recommended load in Gypsum plasterboard 12.5 mm: 0.15 kN (fischer shows this as 15 kg).fischer's recommended load in Gypsum plasterboard 2 x 12.5 mm: 0.20 kN (20 kg by fischer's own conversion).
- fischer DuoPower 8 x 65fischer's recommended load in Gypsum plasterboard 2 x 12.5 mm: 0.32 kN (32 kg by fischer's own conversion).
Sources: fischer, Loads, DuoPower, recommended loads for a single anchor. Checked ; fischer, fischer DuoPower product page. Checked .
How much weight can plasterboard hold?
Per fixing, no more than fischer's recommended load in the table for your board. fischer prints its tables in kilonewtons (kN); beside each figure we show fischer's own kg where its page gives one, otherwise the kg at fischer's own rate of a hundred kilograms for each kN, or we say that fischer does not give it in kg. Both of fischer's plasterboard tables say “Required safety factors are considered”. For the DuoPower, fischer's table adds: “Valid for installation and use in dry base material for temperatures in the substrate up to +24 °C (resp. short term up to +40 °C)”.
What's my wall? shares your weight between your fixings and compares it with these figures exactly, with no margin of our own. For a shelf on brackets, or anything else that sticks out from the wall, we do not compare your weight with a figure per fixing: the bracket maker's own rating is then a limit too, and the lower of the two applies.
Wickes puts plasterboard in plain terms: Plasterboard: This is one of the weaker wall types, so wouldn’t be the best choice for a particularly heavy shelf.
Sources: fischer, Loads, Metal cavity fixing HM, recommended loads for a single anchor. Checked ; fischer, Loads, DuoPower, recommended loads for a single anchor. Checked ; Wickes, Where to start with putting up a shelf. Checked .
How thick is my plasterboard?
Usually a single board. Vogel's says Normally, 12 mm plasterboard is used for a single wall.
fischer's tables give separate rows for Gypsum plasterboard 9.5 mm, Gypsum plasterboard 12.5 mm and Gypsum plasterboard 2 x 12.5 mm, and the fixing has to suit the board. fischer says of its HM: The fixing should be selected based on the thickness of the board building material, to allow the very best expansion in the cavity.
Plasplugs adds that the finish counts as well: Plasterboard walls vary in thickness because boards come in different gauges and wall coverings, like tiles, also make walls deeper.
If you cannot tell which board you have, our checker gives no fixing rather than guess one.
Sources: Vogel's, How to mount a TV on a plasterboard or hollow wall. Checked ; fischer, Loads, Metal cavity fixing HM, recommended loads for a single anchor. Checked ; fischer, Loads, DuoPower, recommended loads for a single anchor. Checked ; fischer, fischer Metal cavity fixing HM product page. Checked ; Plasplugs, Plasplugs Wall Fixings brochure, 2024/5 edition. Checked .
How do I know if my wall is plasterboard?
By the sound when you knock (Wickes' words are with the knock drawing below), and by the dust from a small test hole.
A test hole is drilling, so it comes after the checks on Before you drill. Plasplugs says Use a HSS drill bit for hollow walls
, and reads the dust like this:
Fine white dust and paper shreds on the drill bit shows you have plasterboard
Grey sandy dust (and possibly sawdust if you hit a lath) shows you have lath and plaster walls and ceilings
Plasplugs also notes that Hollow walls and ceilings may be surfaced with lath and plaster (pre-1920's houses) or plasterboard
. We give no fixing for lath and plaster, because no fixing maker we read publishes a load for it.
Source: Plasplugs, Plasplugs Wall Fixings brochure, 2024/5 edition. Checked to .
Can you screw into plasterboard without a plug?
Only where a timber stud is behind the board. B&Q says If you're drilling into a plasterboard wall, you can also check where the timber studs are. If you find a timber stud where you want to drill, you won't need to use a wall plug.
Everywhere else it says Wall plugs are required for hollow walls like plasterboard, and solid walls such as brick or concrete. In general, screws can be inserted directly into wood without the use of plugs.
Wickes gives a reason to aim for the frame: It’s advisable to screw your fixings into this frame as it will better support weight.
To find the studs, knock along the wall as Wickes and Vogel's describe with the drawing.
In Wickes' and Vogel's words:
- Wickes:
You can tell if you've got a plasterboard wall if it sounds hollow when you knock on it, but these walls are generally supported by a frame so there will be vertical and horizontal sections that feel a little more solid.
- Vogel's:
For wooden profiles, you check this by knocking on the wall until you find a place that sounds less hollow.
- Vogel's:
Mark this point and then check whether the next upright is placed at 450 mm or 600 mm.
- Wickes:
To know exactly where the solid sections are, you can use a stud detector.
- Vogel's:
For metal stud profiles, you use a pipe finder, which allows you to detect the metal profiles.
Sources: Wickes, Where do I start putting up a shelf?. Checked to ; Vogel's, How to mount a TV on a plasterboard or hollow wall. Checked to .
Before you drill, check for cables Cables, pipes and studs: check first
Sources: B&Q, How to fit wall plugs. Checked to ; Wickes, Where to start with putting up a shelf. Checked .
How do you fit a plug in plasterboard?
After the checks on Before you drill, B&Q's steps for a wall plug in plain words, with its depth step in its own words, and the drill bit and hole depth from fischer's table:
- Put a strip of tape on the drill bit as a guide to how deep to drill.
You'll need to drill into the wall slightly deeper than the length of the plug, so hold the wall plug up to your drill bit and mark its length with the tape.
- Drill the hole with the right bit, to the depth the tape shows, keeping the drill square to the wall and steady.
- Push the plug in with your fingers: it should be a tight fit. Tap it lightly with a hammer if it needs levelling with the wall.
- Drive the screw into the plug with the drill.
Source: B&Q, How to fit wall plugs. Checked .
fischer describes what the DuoPower does as the screw goes in: The fischer DuoPower adjusts itself automatically to the building material and transfers the highest loads through the three product functions of folding, expanding and knotting.
For the screw length, fischer's rule is The required screw length is given by the plug length + fixture thickness + 1x the screw diameter.
Source: fischer, fischer DuoPower product page. Checked to .
How do you fit a metal cavity fixing?
Drill the hole with the bit size in fischer's table, after the checks on Before you drill. fischer describes setting its HM fixing like this:
The plug is set in the pre-positioned installation using the installation pliers fischer HM-Z 1.
The plug is pulled against the panel building materials using the pliers. The expanding arms swing open and press onto the reverse side of the board.
Alternatively, installation is also possible with a screwdriver or cordless screwdriver.
The drawing below shows the screwdriver method, with fischer's words beside it.
Setting a metal cavity fixing with a screwdriver, in fischer's words for its HM:
If using a battery operated screwdriver or screwdriver for installation, the pre-assembled screws must be removed first.
When screwing in and expanding the fixing, the attachment, or a max. 6 mm plate, needs to be used as a turning stop.
During installation, the expanding arms swing open and press onto the reverse side of the board.
fischer adds: The claws around the edge of the fixing penetrate the board building material, preventing the fixing from rotating, thus ensuring a secure installation.
Source: fischer, fischer Metal cavity fixing HM product page. Checked .
fischer's own list of uses for it: The fischer metal cavity fixing HM is suitable for fixing lighting, pictures and light shelves indoors.
Source: fischer, fischer Metal cavity fixing HM product page. Checked .
What if the plasterboard is fixed over a brick wall?
Then the gap behind the board decides whether a cavity fixing can open. Plasplugs' steps, for drilling after the checks on Before you drill:
On external walls with hollow dry lining, drill through the plaster or plasterboard lining until you hit solid masonry
Withdraw the drill and measure off the cavity depth.
Plasplugs warns: Some hollow wall fixings will not work if the cavity is less than about 25mm deep
No maker we read gives a cavity depth for each fixing size, so we cannot match a fixing to your gap.
Source: Plasplugs, Plasplugs Wall Fixings brochure, 2024/5 edition. Checked to .
Questions
What drill bit do I need for plasterboard?
B&Q and Plasplugs name different bits. B&Q says If you're drilling into a plasterboard wall, a multi-surface drill bit is recommended. For brick walls, always use a masonry drill bit.
Plasplugs says Use a HSS drill bit for hollow walls
. Either way, the size is the one in fischer's table for your fixing.
Can I hang a TV on plasterboard?
Yes, on the studs behind it, with the mount its maker allows. Vogel's, which makes TV mounts, says You can use a flat TV wall mount (for example, the COMFORT Fixed, suitable for a 450 or 600 mm frame) that bridges the space between the two wooden uprights.
For metal studs it says If you want to mount your TV on a metal stud wall, the wall must be reinforced with an extra back plate of sufficient thickness (underlayment).
For a full-motion mount and Vogel's stud adapter, see Put up a TV without drilling.
Sources: B&Q, How to fit wall plugs. Checked ; Plasplugs, Plasplugs Wall Fixings brochure, 2024/5 edition. Checked ; Vogel's, How to mount a TV on a plasterboard or hollow wall. Checked to .