Fixing into concrete and block: plug, bit and screw
fischer rates its DuoPower and SX Plus plugs in concrete and in aircrete, and the tables give each plug's bit, screw and load. For dense concrete block we give no load figure: fischer gives none.
Updated
Concrete: what fischer rates
| 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 | 0.40 kN (fischer shows this as 40 kg) |
| fischer DuoPower 6 x 30 | 6 mm, at least 40 mm deep | 5.0 mm wood screw | 0.95 kN (fischer shows this as 95 kg) |
| fischer DuoPower 6 x 50 | 6 mm, at least 60 mm deep | 5.0 mm wood screw | 1.65 kN (fischer shows this as 165 kg) |
| fischer DuoPower 8 x 40 | 8 mm, at least 50 mm deep | 6.0 mm wood screw | 1.10 kN (fischer shows this as 110 kg) |
| fischer DuoPower 8 x 65 | 8 mm, at least 75 mm deep | 6.0 mm wood screw | 2.30 kN (fischer shows this as 230 kg) |
| fischer DuoPower 10 x 50 | 10 mm, at least 60 mm deep | 8.0 mm wood screw | 2.15 kN (fischer shows this as 215 kg) |
| fischer SX Plus 4 x 20 | 4 mm, at least 30 mm deep | 3.0 mm wood screw | 0.20 kN (fischer does not give this in kg) |
| fischer SX Plus 5 x 25 | 5 mm, at least 35 mm deep | 4.0 mm wood screw | 0.35 kN (fischer does not give this in kg) |
| fischer SX Plus 6 x 30 | 6 mm, at least 40 mm deep | 5.0 mm wood screw | 0.65 kN (fischer does not give this in kg) |
| fischer SX Plus 6 x 50 | 6 mm, at least 60 mm deep | 5.0 mm wood screw | 1.30 kN (fischer does not give this in kg) |
| fischer SX Plus 8 x 40 | 8 mm, at least 50 mm deep | 6.0 mm wood screw | 0.75 kN (fischer does not give this in kg) |
| fischer SX Plus 8 x 65 | 8 mm, at least 75 mm deep | 6.0 mm wood screw | 1.50 kN (fischer does not give this in kg) |
| fischer SX Plus 10 x 50 | 10 mm, at least 70 mm deep | 8.0 mm wood screw | 1.40 kN (fischer does not give this in kg) |
| fischer SX Plus 12 x 60 | 12 mm, at least 80 mm deep | 10.0 mm wood screw | 2.40 kN (fischer does not give this in kg) |
Sources: fischer, Loads, DuoPower, recommended loads for a single anchor. Checked ; fischer, fischer DuoPower product page. Checked ; fischer, Loads, Expansion plug SX Plus, recommended loads for a single anchor. Checked ; fischer, fischer Expansion plug SX Plus product page. Checked .
Aircrete or thermal block: what fischer rates
| 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 | 0.05 kN (fischer shows this as 5 kg) |
| fischer DuoPower 6 x 30 | 6 mm, at least 40 mm deep | 5.0 mm wood screw | 0.10 kN (fischer shows this as 10 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 | 0.10 kN (fischer shows this as 10 kg) |
| fischer DuoPower 8 x 65 | 8 mm, at least 75 mm deep | 6.0 mm wood screw | 0.16 kN (fischer shows this as 16 kg) |
| fischer DuoPower 10 x 50 | 10 mm, at least 60 mm deep | 8.0 mm wood screw | 0.20 kN (fischer shows this as 20 kg) |
| fischer SX Plus 4 x 20 | 4 mm, at least 30 mm deep | 3.0 mm wood screw | 0.03 kN (fischer does not give this in kg) |
| fischer SX Plus 5 x 25 | 5 mm, at least 35 mm deep | 4.0 mm wood screw | 0.03 kN (fischer does not give this in kg) |
| fischer SX Plus 6 x 30 | 6 mm, at least 40 mm deep | 5.0 mm wood screw | 0.07 kN (fischer does not give this in kg) |
| fischer SX Plus 6 x 50 | 6 mm, at least 60 mm deep | 5.0 mm wood screw | 0.12 kN (fischer does not give this in kg) |
| fischer SX Plus 8 x 40 | 8 mm, at least 50 mm deep | 6.0 mm wood screw | 0.10 kN (fischer does not give this in kg) |
| fischer SX Plus 8 x 65 | 8 mm, at least 75 mm deep | 6.0 mm wood screw | 0.15 kN (fischer does not give this in kg) |
| fischer SX Plus 10 x 50 | 10 mm, at least 70 mm deep | 8.0 mm wood screw | 0.18 kN (fischer does not give this in kg) |
| fischer SX Plus 12 x 60 | 12 mm, at least 80 mm deep | 10.0 mm wood screw | 0.22 kN (fischer does not give this in kg) |
Sources: fischer, Loads, DuoPower, recommended loads for a single anchor. Checked ; fischer, fischer DuoPower product page. Checked ; fischer, Loads, Expansion plug SX Plus, recommended loads for a single anchor. Checked ; fischer, fischer Expansion plug SX Plus product page. Checked .
fischer gives higher figures for stronger aerated concrete, but the class cannot be told from the wall, so we use its lowest class, AAC 2.
Dense concrete block: no fischer load figure
fischer gives no load figure for dense block, so we give none, and we do not apply its concrete row to blocks. The plug, bit and screw are under Which plug for dense concrete block? below.
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It never changes the answer above.
- fischer SX Plus 4 x 20fischer's recommended load in Concrete ≥ C20/25: 0.20 kN (fischer does not give this in kg).fischer's recommended load in Aerated concrete ≥ AAC 2: 0.03 kN (fischer does not give this in kg).Dense concrete block: no fischer load figure.
- fischer DuoPower 5 x 25fischer's recommended load in Concrete ≥ C20/25: 0.40 kN (fischer shows this as 40 kg).fischer's recommended load in Aerated concrete ≥ AAC 2: 0.05 kN (fischer shows this as 5 kg).Dense concrete block: no fischer load figure.
- fischer SX Plus 5 x 25fischer's recommended load in Concrete ≥ C20/25: 0.35 kN (fischer does not give this in kg).fischer's recommended load in Aerated concrete ≥ AAC 2: 0.03 kN (fischer does not give this in kg).Dense concrete block: no fischer load figure.
- fischer DuoPower 6 x 30fischer's recommended load in Concrete ≥ C20/25: 0.95 kN (fischer shows this as 95 kg).fischer's recommended load in Aerated concrete ≥ AAC 2: 0.10 kN (fischer shows this as 10 kg).Dense concrete block: no fischer load figure.
- fischer DuoPower 6 x 50fischer's recommended load in Concrete ≥ C20/25: 1.65 kN (fischer shows this as 165 kg).fischer's recommended load in Aerated concrete ≥ AAC 2: 0.15 kN (fischer shows this as 15 kg).Dense concrete block: no fischer load figure.
Sources: fischer, Loads, Expansion plug SX Plus, recommended loads for a single anchor. Checked ; fischer, Loads, DuoPower, recommended loads for a single anchor. Checked ; fischer, fischer DuoPower product page. Checked .
Is my wall concrete, dense block or aircrete?
The knock points to masonry, and the dust from a test hole tells dense block from aircrete. Wickes: If you knock on it and get a very solid and inflexible feeling that doesn't sound hollow, it will most likely be a brick or concrete masonry wall.
Plasplugs: Solid wall may be built of brick, dense block or thermal (lightweight) block
A test hole is drilling, so it comes after the checks on Before you drill. Plasplugs: Identify which type you have by drilling a test hole and examining the drill dust
Dark grey dust (and slow drill progress) shows you have concrete block walls
Light grey dust (and easy drill progress) shows you have thermal block walls
Of thermal block, Plasplugs says: It is likely to be found in post 1960's buildings making up the inner skin of the walls.
None of the sources we use gives a dust sign for poured concrete, so we give none.
Sources: Wickes, Where do I start putting up a shelf?. Checked ; Plasplugs, Plasplugs Wall Fixings brochure, 2024/5 edition. Checked to .
Which plug for a concrete wall?
Any plug in fischer's concrete table above, within its figure. The rows are fischer's Concrete ≥ C20/25: its table rates concrete of class C20/25 or stronger, and we cannot tell your concrete's class from the wall. The figures are in kilonewtons (kN) as fischer prints them, with fischer's kg beside them where fischer gives one, and fischer's tables say of them: “Required safety factors are considered”.
fischer describes the SX Plus as made for this kind of wall: Thanks to its four-way expansion, the fischer SX Plus expansion plug is the specialist for solid building materials such as concrete, sand-lime brick and masonry.
For the bit, Bosch says A masonry or concrete drill bit is the preferred option for drilling very hard materials like concrete, natural stone or granite.
What's my wall? compares your weight 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, and the bracket maker's own rating is a limit too: the lower of the two applies.
Sources: fischer, Loads, DuoPower, recommended loads for a single anchor. Checked ; fischer, fischer Expansion plug SX Plus product page. Checked ; Bosch DIY, Drill bits and wall anchors guide. Checked .
Which plug for aircrete or thermal block?
One from fischer's aircrete table above, which uses the lowest class fischer gives. fischer rates aerated concrete by class: for a DuoPower 6 x 30 it gives 0.10 kN in Aerated concrete ≥ AAC 2 and 0.38 kN in Aerated concrete ≥ AAC 4. fischer gives higher figures for stronger aircrete, but the class cannot be told from the wall, so every aircrete answer uses the lowest row.
fischer's own note on its longer plugs: The fischer DuoPower 6 x 50, 8 x 65 and 10 x 80, because of the larger anchorage depth, are particularly suitable for fixings in hollow building materials, aerated concrete and for bridge plaster.
fischer also makes a plug for aircrete alone: The fischer aircrete anchor GB is a special anchor for different fixings in aerated concrete.
The GB, made from high-quality nylon, is hammered in after pre-drilling.
We name it without a load figure, because we have not yet matched its load table to our checker.
Plasplugs makes a thermal block plug as well, sold as Thermal Block Fixings Clip Pack x 40, includes Drill Bit and Driver
, and says This plug cuts its own thread in Thermal Block to give a superior grip within the "crumbly" material
. We show no load figure for it: the load comparison in our checker uses fischer's aircrete table only. Its steps, which use the bit and driver in that pack, for drilling after the checks on Before you drill:
Drill hole using 8mm drill bit provided
- Push the fixing all the way onto the Power-Driver and fit the Power-Driver into the drill.
Secure fixture with a No.10 (5mm) full threaded screw
Source: Plasplugs, Plasplugs Wall Fixings brochure, 2024/5 edition. Checked .
Sources: fischer, fischer DuoPower product page. Checked ; fischer, Loads, DuoPower, recommended loads for a single anchor. Checked to ; fischer, fischer aircrete anchor GB product page. Checked .
Which plug for dense concrete block?
A solid wall plug with a masonry bit, with no load figure from us. fischer gives no load figure for dense block, and we do not apply its concrete row to blocks.
Plasplugs says of its solid wall plugs For general work into solid walls, these fixings are just made for the job.
Its colour code, with each plug's drill bit and screw range, is on Fixing into brick.
For the bit, Plasplugs says Thermal Block can easily be drilled using a HSS drill bit, making it easy to distinguish from solid concrete black ("breeze block") which requires a masonry drill.
(Plasplugs' “black” means block.)
Source: Plasplugs, Plasplugs Wall Fixings brochure, 2024/5 edition. Checked to .
How do you drill concrete or block and fit a plug?
After the checks on Before you drill, the B&Q steps for any 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.
- Clean the dust out of the hole before the plug goes in.
- Push the plug in with your fingers: it should be a tight fit.
- Drive the screw into the plug with the drill.
Sources: B&Q, How to fit wall plugs. Checked ; Bosch DIY, Drill bits and wall anchors guide. Checked .
The cleaning step is Bosch's; the rest are B&Q's. Bosch also says If you're using wall anchors as well as screws, the drill bit and anchors should have the same diameter.
Questions
Why is there no load figure for dense concrete block?
Because fischer gives no load figure for dense block. Its tables rate Concrete ≥ C20/25 and Aerated concrete ≥ AAC 2, and we never borrow a figure from another material. How we check a fixing explains the rule.
Can I use a brick plug in concrete?
The same fischer plugs are rated in both walls, each with its own figure, so use the concrete row for concrete. fischer's tables rate the DuoPower and SX Plus in Solid brick ≥ Mz 12 and in Concrete ≥ C20/25. Brick figures and B&Q's steps for brick are on Fixing into brick.
Source: fischer, Loads, DuoPower, recommended loads for a single anchor. Checked .