Why do fixings pull out of old soft brick?
What makes Victorian and handmade brick different, why expansion plugs crush it, and the fixings and depths that hold in it.
- Difficulty
- intermediate
- Time
- 30 min
- Read
- 3 min
Short answer
Soft brick cannot resist the sideways pressure an expansion plug applies, so the plug crushes its own hole. Drill with hammer off, go deeper than you would in modern brick, and use a long plug, a nylon frame fixing or, for anything of weight, resin.
Handmade and early machine-made bricks were fired at lower temperatures and are far softer than modern engineering or facing brick. They also weather, so the outer few millimetres of a face brick can be soft even when the core is sound.
What you'll need
- resin anchor or long nylon fixings
- drill with hammer selectable
- dust brush and blower
Step by step
- Check what you are dealing with.Soft brick drills quickly with hammer off, produces powdery rather than gritty dust, and can be scratched with a coin or a screwdriver tip.
- Drill with hammer action off.Percussion in soft brick shatters the material rather than cutting it. You end up with a ragged crater instead of a hole.
- Go deeper.Depth substitutes for the grip you cannot get near the surface. Aim for a fixing embedment of at least twice what you would use in modern brick.
- Get past the weathered face.The outer skin of an old external brick may be soft and friable. The sound material is behind it, so the fixing must reach well past it.
- Choose a long-bodied fixing.A long nylon frame fixing or a long spiral plug spreads its expansion over a much greater area, so the pressure on any part of the hole wall stays low.
- Use resin for anything of weight.Chemical anchoring bonds along the whole hole wall and applies no outward pressure at all, which is exactly what soft brick needs.
- Never fix into the mortar joint on an old wall.Lime mortar in a Victorian wall is deliberately weaker than the brick. A fixing in it has very little to hold onto.
- Clean the hole obsessively.Soft brick produces a great deal of fine dust which lines the hole. Brush, blow, brush again — with resin in particular, dust is the difference between full strength and none.
- Spread the load.More fixings at lower individual loads. Soft brick fails locally, so halving the load per fixing more than halves the risk.
Tips
- Hammer off is the counter-intuitive step that makes the biggest difference in old brick.
- If a hole crumbles as you drill, stop and move — a crumbled hole never recovers with a bigger plug.
- Resin with a mesh sleeve is designed exactly for hollow and friable substrates and is worth the cost on anything you would not want to fall.
Common mistakes
- Using hammer action because it is masonry — Percussion is for hard dense material. In soft brick it fractures the surrounding brick and produces a hole far larger and weaker than the bit.
- Fixing into the mortar joint — Old lime mortar is intentionally soft and sacrificial. It offers a fraction of the grip of even soft brick, and a fixing in it works loose quickly.
If it doesn't work
Plug spins in the hole
Cause: Hole crushed oversize — Fix: Move at least 100mm to fresh brick, drill with hammer off, and use resin or a long frame fixing.
Cone of brick pulls out with the fixing
Cause: Expansion pressure exceeded what the brick could take — Fix: Fill with a repair mortar or resin, cure, and refix deeper with a chemical anchor.
Face of the brick has spalled around the hole
Cause: Weathered soft face plus expansion pressure — Fix: Drill past the weathered layer and set a resin anchor deeper into sound material.
Fixing held initially then loosened over months
Cause: Slow crushing under cyclic load — Fix: Replace with a resin anchor, which does not rely on sustained outward pressure.
Questions people ask
Is this the same as fixing into aerated block?
The principle is the same — avoid expansion, prefer depth and resin — but the materials differ. Aerated block is uniformly soft, whereas old brick is often sound in the core and soft at the face.
Can I hang a gate on an old brick wall?
Yes, but with resin anchors through into sound brick, and preferably through a plate that spreads the load across several bricks rather than concentrating it on one.
How do I tell soft brick from a soft mortar joint?
By colour and position. Joints are 8 to 12mm bands in a regular pattern; the brick is everything else. If your bit suddenly speeds up, you have wandered into a joint.