Never use nylon wall plugs or plasterboard anchors for safety-critical fixings. Handrails, stair rails, banisters, balustrades, gates, ladders, climbing or play equipment, overhead fixings, and anything else whose failure could cause a fall or injury need a fixing designed and rated for that purpose — typically a through-bolt, a mechanical anchor or a resin-bonded anchor with a published load rating (and, for structural use, a European Technical Assessment). If you are not certain the wall and the fixing are up to the job, get advice from a builder or structural engineer.
Solid masonry walls — brick, concrete block, stone, and poured concrete — offer the best holding power of any wall type. A correctly installed fixing in solid brick can support surprisingly heavy loads, making masonry the ideal surface for TV mounts, heavy shelves, boiler brackets, and structural supports.
This guide covers everything you need to know about fixing into masonry walls: which wall plugs to use, the correct drill bits, how to drill properly, and how to handle tricky situations like crumbly mortar, engineering brick, and lightweight block.
Standard Nylon Wall Plugs for Masonry
The standard colour-coded nylon wall plug is the backbone of masonry fixing in the UK. These expansion plugs work by gripping the inside of a drilled hole when a screw is driven into them — the plug expands outward against the masonry, creating a strong friction fit.
| Plug Colour | Diameter | Drill Bit | Screw Gauge | Typical use (indicative — not a load rating) | Best For |
|---|---|---|---|---|---|
| Yellow | 5mm | 5mm | No. 4–8 | Light | Light fixings: picture hooks, cable clips, thermostats |
| Red | 6mm | 6mm | No. 6–10 | Medium | General purpose: shelves, curtain poles, towel rails |
| Brown | 7mm | 7mm | No. 8–14 | Heavier | TV mounts, heavy shelves, radiator brackets |
| Blue | 10mm | 10mm | No. 14–18 | Heaviest of the nylon plug range | Large TV brackets and heavy wall units. Not for handrails, balustrades, gates or any fixing whose failure could cause a fall or injury — use an anchor with a published load rating instead |
Recommended Wall Plugs & Fixings
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How much weight will a wall plug actually hold?
There is no single answer per colour, and any site that gives you one is guessing. A plug’s capacity is set by the product, the wall it goes into, and how well it is installed — not by the colour of the plastic. The same nominal 6 mm plug is rated very differently by different manufacturers, and the same plug loses most of its capacity in perforated brick.
The table below is fischer’s own published figures for its SX range. These are recommended loads for a single anchor with the required safety factors already applied — fischer’s wording, not ours — and they are valid for tensile, shear and oblique load at any angle.
| Base material | SX 5 (5 mm) | SX 6 (6 mm) | SX 8 (8 mm) | SX 10 (10 mm) | SX 12 (12 mm) |
|---|---|---|---|---|---|
| Concrete ≥ C20/25 | 31 kg | 71 kg | 122 kg | 173 kg | 204 kg |
| Solid clay brick ≥ Mz 12 | 25 kg | 61 kg | 66 kg | 71 kg | 82 kg |
| Solid sand-lime brick ≥ KS 12 | 31 kg | 61 kg | 122 kg | 173 kg | 204 kg |
| Vertically perforated brick ≥ Hlz 12 | 7 kg | 17 kg | 17 kg | 27 kg | 41 kg |
| Aerated concrete / aircrete ≥ AAC 4 | 9 kg | 14 kg | 31 kg | 46 kg | 51 kg |
Source: fischer SX load table (fischer publishes these as recommended loads for a single anchor, safety factors considered).
How to read it
- If you don’t know what your wall is made of, work to the perforated-brick row. Vertically perforated brick and aircrete are both common in UK housing, and they cut a nylon plug’s capacity by roughly 60–85% compared with solid brick. Drilling gives you a clue: solid brick throws out dense red or grey dust and resists steadily; perforated brick and blockwork suddenly go soft as the bit breaks into a void.
- These figures are for the fischer SX. Other brands publish different numbers for the same nominal diameter — Rawlplug’s figures for its UNO range are considerably higher, because they are stated on a different basis. Always work from the datasheet for the plug you actually bought.
- There is no 7 mm figure here because fischer does not make an SX 7. For a brown 7 mm plug, check Rawlplug’s UNO datasheet.
- Colour is not a standard. On Rawlplug’s UNO range blue is 8 mm and grey is 10 mm; the older merchant convention puts blue at 10 mm. fischer’s SX plugs are grey in every size. Go by the printed diameter, not the colour.
- Installation decides the real number. The right drill diameter, full embedment depth, a clean dust-free hole, the correct screw, and adequate edge and spacing distances all have to be right. A hole drilled 1 mm oversize, or one left full of dust, will not reach these figures.
- Spread the load. These are per-anchor figures, and plastic plugs are approved on the assumption that several fixings share the load (see below). Use at least two fixings on anything that matters, and more on brackets that create a lever effect.
Never use a plastic plug for a safety-critical fixing
Nylon and plastic expansion plugs are assessed under EAD 330284-00-0604, “Plastic anchors for redundant non-structural systems in concrete and masonry”. That approval assumes at least three or four fixing points sharing the load, so that if one slips the others take over, and it explicitly excludes structural and safety-critical use.
That means plastic plugs are the wrong fixing — whatever their rated load — for:
- Grab rails and handrails
- Balustrades and guarding
- Wall-hung WCs, basins and cisterns
- Gates and external ironwork
- Anything overhead, and anything whose failure could cause a fall or an injury
These need an ETA-approved metal or resin anchor, selected for the actual base material and installed in line with BS 8539:2012+A1:2021, the UK code of practice for post-installed anchors in concrete and masonry. Using an anchor in a substrate it was not assessed for can cut its performance by up to 80%, so the substrate has to be identified before the anchor is chosen. In plasterboard, no cavity fixing is adequate for a safety-critical load: the rail must be fixed to solid backing — a timber noggin or plywood pattress screwed to the studs. If you are not sure, this is the point to bring in a professional.
Get the free Drill Bit & Wall-Plug Size Chart (PDF)
Every drill size, wall-plug colour & tap size on one printable sheet.
For the full size chart with screw lengths and detailed specifications, see our Wall Plug Size Chart.
Fischer vs Rawlplug vs Unbranded — Does Brand Matter?
The three most common wall plug brands in the UK are Fischer, Rawlplug, and various own-brand/unbranded options from Screwfix, Toolstation, and B&Q. Here’s what you need to know:
- Fischer: German-engineered, widely regarded as the gold standard. Their UX and SX ranges have aggressive expansion ribs that grip exceptionally well, even in softer masonry. Slightly more expensive but worth it for critical fixings. Fischer SX plug kit — check price on Amazon
- Rawlplug: The original wall plug inventor. Their Uno range is excellent — a single plug design that works in solid and hollow materials. Good all-round performance. Rawlplug Uno assortment — check price on Amazon
- Unbranded / own-brand: Perfectly adequate for standard household fixings in solid brick. For heavy or safety-critical fixings (TV mounts, handrails, overhead fixings), spend the extra pennies on Fischer or Rawlplug.
How to Drill into Masonry — Step by Step
What You’ll Need
- Combi drill with hammer action, or SDS rotary hammer for larger holes
- Masonry drill bit (TCT tip) in the correct size
- Wall plugs and screws
- Pencil, spirit level, and tape measure
- Pipe and cable detector
- Vacuum cleaner
Step-by-Step Process
- Scan the wall: Use a pipe and cable detector to check for hidden services. Pay special attention to areas above and below sockets, switches, and radiator pipes. Bosch stud/pipe detector — check price on Amazon
- Mark the fixing positions: Use a pencil and spirit level to mark exactly where each hole needs to go. For brackets, hold the bracket in position and mark through the screw holes.
- Set the drill depth: Wrap masking tape around the drill bit to mark the required depth — the plug length plus 5–10mm extra for dust clearance.
- Drill the hole: Set your drill to hammer mode. Start slowly to establish the hole, then increase speed. Apply firm, steady pressure — let the hammer action do the work. Don’t force the bit sideways or you’ll widen the hole.
- Clear the dust: Withdraw the bit periodically to clear debris. Once drilled to depth, vacuum the hole to remove dust. This is important — packed dust reduces the plug’s expansion.
- Insert the plug: Push the wall plug into the hole. It should be a firm push fit — tap gently with a hammer if needed. The plug should sit flush with or just below the wall surface.
- Drive the screw: Insert the screw through your bracket/fitting and into the plug. Tighten until snug — don’t over-tighten. The plug should grip firmly without spinning in the hole.
Masonry Types and Their Holding Power
Not all masonry is equal. The wall plug load ratings above assume solid facing brick or dense concrete block. Here’s how different masonry types compare:
| Masonry Type | Relative Strength | Drilling Notes | Fixing Notes |
|---|---|---|---|
| Engineering brick | Excellent | Very hard — may need SDS drill. Bits dull quickly. | Highest holding power. Plugs grip extremely well. |
| Solid facing brick | Very good | Standard hammer drill works well. | Standard plug ratings apply. |
| Dense concrete block | Very good | Standard hammer drill. Watch for aggregate. | Standard plug ratings apply. |
| Poured concrete | Good to excellent | Can be very hard. SDS recommended for 10mm+. | May hit rebar — stop and reposition if so. |
| Breeze block | Moderate | Easy to drill. No hammer action needed. | Reduced holding power — consider longer plugs or frame fixings. |
| Thermalite / aircrete | Low | Very easy to drill — almost like wood. | Standard plugs may pull out. Use specialist fixings or chemical anchors. |
| Natural stone | Variable | Can be extremely hard (granite) or soft (sandstone). | Hard stone — excellent grip. Soft stone — consider resin anchors. |
Frame Fixings for Masonry
For applications where you’re fixing timber or plastic frames to masonry — such as door frames, window frames, battens, and timber cladding — frame fixings (also called hammer fixings or nylon frame anchors) are faster than plugs and screws.
A frame fixing is a long nylon plug with a pre-assembled screw. You drill through the frame and into the masonry in one operation, push the fixing through, and hammer or screw it tight. They’re available in 8mm and 10mm diameters and various lengths from 60mm to 180mm.
Fischer frame fixings assortment — check price on Amazon
Chemical Anchors (Resin Fixings) for Masonry
When standard expansion plugs aren’t enough — in crumbly masonry, oversized holes, or for very heavy loads — chemical anchors provide a permanent, ultra-strong solution. A chemical anchor uses a two-part resin that bonds a threaded stud into the drilled hole, creating a fixing far stronger than any plastic plug. Resin anchors are the appropriate choice where the load is high or the fixing is safety-critical — work to the published figures in the anchor European Technical Assessment for your substrate rather than to a generic number.
Common uses include: satellite dish brackets, large TV mounts on questionable masonry, handrail posts, Juliet balconies, and structural steelwork connections.
Fischer chemical resin anchor kit — check price on Amazon
Common Mistakes When Fixing to Masonry
- Drilling into mortar joints: Always drill into the brick or block, never the mortar between them. Mortar has far less holding power and can crumble around the plug.
- Using the wrong drill mode: Hammer action is essential for brick and concrete. Without it, the bit just spins against the surface and overheats. Exception: thermalite and lightweight blocks — use drill mode only, as hammer action shatters them.
- Not clearing dust from the hole: Packed dust prevents the plug from sitting at full depth and reduces its expansion grip. Always vacuum or blow out the hole before inserting the plug.
- Using screws that are too short: The screw must engage the full length of the plug. If the screw only reaches halfway, you’re getting half the holding power at best.
- Over-tightening: This is the most common cause of a spinning plug. Once the bracket is secure and doesn’t move, stop. Over-driving the screw strips the grip out of the plug.
Watch: Video Guide
Frequently Asked Questions
Can I drill into brick without a hammer drill?
You can try, but it’s very slow and wears out bits quickly. A standard drill in rotation-only mode will struggle with most brick. For the occasional hole, a sharp masonry bit with firm pressure may work in softer brick. For anything more than a couple of holes, a hammer drill or combi drill with hammer setting is essential.
Should I drill into the brick or the mortar?
Always drill into the brick, not the mortar. Mortar joints have significantly lower compressive strength than brick and wall plugs can pull out more easily. The only exception is if you’re trying to avoid cracking a decorative or thin brick — in that case, use longer plugs in the mortar and expect significantly reduced load capacity, and never use mortar fixings for heavy or safety-critical loads.
What if the plug spins in the hole?
This means the hole is oversized or the masonry has crumbled around it. Options: (1) Try the next size up plug in the same hole, (2) pack the hole with a small amount of filler, let it set, then re-drill, or (3) use a chemical anchor which fills the gap with resin and provides an even stronger fixing.
Related Guides
- Wall Plug & Fixing Compatibility Guide
- Wall Plug Size Chart
- Plasterboard Fixings Guide
- Cavity Wall Fixings Guide
- What Fixings for a TV Mount?
- What Fixings for Heavy Shelves?
Recommended Masonry Fixings & Tools
Quality fixings make all the difference in masonry. Fischer products are widely regarded as the trade standard.
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How we compile this guide
We cross-reference compatibility details against manufacturer specifications where available, official tool manuals, and the physical standards that govern fitment (bore sizes, arbor diameters, voltage platforms, connector types). We prioritise primary sources over retailer listings, flag anything we can’t confirm, and re-verify the data on a regular cycle. Where we give a buying recommendation, we tell you the reasoning — not just the link. More on our method →
