Can I fix into the mortar joint instead of the brick?
Sometimes it is the right answer and usually it is not — how to judge which by the mortar, the load and whether the fixing will ever come out.
- Difficulty
- beginner
- Time
- 12 min
- Read
- 3 min
Short answer
For light fixings, mortar is acceptable and much easier to make good afterwards. For anything heavy, fix into the brick — modern cement mortar is weaker than brick and old lime mortar is far weaker again. The two exceptions are perforated brick, where the joint may be the only solid material, and soft historic brick, where drilling the joint protects the face.
The general rule taught in every fixing guide is to drill the brick rather than the joint, and it is the right default. But it is a default, not a law, and there are three common situations where the joint is genuinely the better choice. Knowing which situation you are in matters more than remembering the rule.
Step by step
- Identify what the mortar is.Modern cement mortar is hard, grey and drills with resistance. Lime mortar is softer, often buff or sandy, crumbles under a key, and can frequently be scraped out with a screwdriver. The two are not comparable as fixing substrates.
- Judge the load honestly.A cable clip, a small bracket, a trellis, a light batten: mortar is fine and easily repaired later. A shelf, a rail, a gate, a TV, a radiator: fix into the brick or use resin.
- Prefer the brick where the wall is modern and solid.A sound facing brick is considerably stronger than the joint around it and gives a plug far better material to expand against.
- Prefer the joint on perforated brick.Where the bricks are half void, the mortar bed is continuous and solid. This inverts the usual advice — check by drilling and see which gives you real material.
- Prefer the joint on soft historic brick.Old handmade brick has a hard fired face and a soft core. Drilling the face damages the most durable part of the wall and blows out easily. Fixing into the joint is more repairable and, in conservation terms, far more acceptable.
- Never fix into a joint that has been raked, weathered back or is failing.If the pointing is recessed, hollow or falls out as you drill, there is nothing there to hold anything. Repoint first, or move to sound material.
- Use resin in a joint for anything above a light load.Resin does not need the joint to resist expansion pressure, which is exactly what a mortar joint is worst at. It bonds along the length of the hole instead.
- Think about making good.A hole in a joint is repointed and disappears. A hole in the face of a brick is visible forever and a plug cut flush and filled is always slightly obvious. On a front elevation that is a real consideration.
Tips
- Perpends — the vertical joints — are usually less well filled than the horizontal beds, and are the worst place of all to fix. If you are using a joint, use a bed joint.
- On a listed or historic building, drilling the joint rather than the brick is the conservation-standard approach precisely because it is reversible.
- A fixing that goes into a joint and immediately feels soft is telling you the mortar is perished for some depth. Stop and reassess the wall rather than the fixing.
Common mistakes
- Fixing a heavy bracket into a lime mortar joint — Lime mortar is deliberately weak so that movement goes through the joints. It has very little compressive or tensile strength and will not hold an expanding plug under load.
- Assuming a hard-looking joint is cement — Repointed historic walls often have a thin cement skin over soft lime behind. Drill a test hole and look at what comes out.