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UK Anchor Bolt & Wall Plug Sizes
Wall plugs, rawlbolts, sleeve anchors and chemical anchors with drill hole sizes, load ratings and colour codes for UK fixings.
Standard Wall Plug Sizes (Colour Coded)
| Colour | Drill Size (mm) | Screw Gauge | Screw Size (mm) | Typical Use |
|---|---|---|---|---|
| Yellow | 5 | No.4–8 | 3.0–4.0 | Light shelves, pictures, switch plates |
| Red | 5.5 | No.6–10 | 3.5–5.0 | Curtain poles, brackets, towel rails |
| Brown | 7 | No.8–14 | 4.0–6.0 | Heavy shelving, TV brackets, radiators |
| Blue | 10 | No.14–18 | 6.0–8.0 | Heavy-duty, boilers, large brackets |
Rawlbolts (Expanding Anchors)
Mechanical expanding anchors for solid masonry and concrete. The bolt tightens a cone which expands a shield against the hole walls.
| Bolt Size | Drill Hole (mm) | Min. Hole Depth (mm) | Safe Load — Concrete (kg) |
|---|---|---|---|
| M6 | 10 | 45 | ~120 |
| M8 | 12 | 55 | ~200 |
| M10 | 14 | 65 | ~340 |
| M12 | 16 | 75 | ~520 |
| M16 | 22 | 95 | ~900 |
Safe loads are indicative for C20/25 concrete. Always check manufacturer data for your specific substrate.
Sleeve Anchors
Suitable for solid and hollow masonry. The sleeve expands along its full length for better load distribution in weaker substrates.
| Bolt Size | Drill Hole (mm) | Lengths Available (mm) | Typical Use |
|---|---|---|---|
| M6 | 8 | 40–100 | Light steelwork, cable trays |
| M8 | 10 | 50–130 | Racking, handrails, brackets |
| M10 | 12 | 60–160 | Steelwork, joist hangers, gates |
| M12 | 14 | 75–200 | Heavy structural connections |
Chemical (Resin) Anchors
Two-part resin injected into a drilled hole with a threaded stud. Ideal for hollow blocks, aerated concrete and close-to-edge fixings.
| Stud Size | Drill Hole (mm) | Embedment (mm) | Resin Type |
|---|---|---|---|
| M8 | 10 | 80 | Polyester / vinylester / epoxy |
| M10 | 12 | 90 | Polyester / vinylester / epoxy |
| M12 | 14 | 110 | Polyester / vinylester / epoxy |
| M16 | 18 | 125 | Vinylester / epoxy (structural) |
Use perforated sleeves (mesh sleeves) when fixing into hollow blocks with chemical anchors. Cure times vary by temperature — typically 20-45 minutes at 20°C.
Related Calculators
See the Fixings Guide by Wall Type for choosing fixings by substrate, or the UK Screw Sizes reference for screw gauges. See also the Resin Anchor Calculator.
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Frequently Asked Questions
Wall plug colours indicate the size: yellow fits 5 mm holes (No.4–8 screws), red fits 5.5 mm holes (No.6–10 screws), brown fits 7 mm holes (No.8–14 screws), and blue fits 10 mm holes (No.14–18 screws). These colours are standardised across most UK manufacturers including Rawlplug, Fischer and Plugit.
Chemical anchors (resin anchors) are preferred in hollow or perforated blocks, aerated concrete (Thermalite/Celcon), close to edges where expansion forces could crack the substrate, and for heavy-duty structural fixings. They distribute load over a larger area than mechanical anchors and do not create expansion stress in the masonry.
Minimum embedment depth varies by anchor type and substrate. As a general rule: mechanical anchors need at least 4-6 times the bolt diameter embedded in solid masonry. For an M10 bolt, that is 40-60 mm minimum. Always check manufacturer data for the specific anchor and substrate combination — aerated blocks require deeper embedment than dense concrete.
No. Standard wall plugs are designed for masonry and will pull straight out of plasterboard. For plasterboard fixings, use spring toggles (heaviest loads, up to 25 kg+), gravity toggles, metal self-drill fixings (up to 15 kg), or hollow wall anchors (up to 20 kg). Always check the manufacturer rated load for your specific fixing.
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Last updated: April 2026
Verified against UK standards · estimates only, confirm with your supplier.