Carbide
Tipped masonry bit
3 to 20 mm
Render skin to get through
Hammer Off
Until you reach the brick
Slow Speed
Light, steady pressure
The Challenges of Drilling Render
What drill bit for rendered brick? A carbide tipped masonry bit. Start with the hammer action off and a slow speed to pass cleanly through the render, then switch the hammer on once the bit reaches the brick beneath. Match the bit size to the wall plug, not the screw.
The reason what drill bit for rendered brick is even a question comes down to this: render is not the wall. It is a coating of three to twenty millimetres bonded to the masonry behind it, and it behaves very differently to the brick it covers. Cement render is hard but brittle, whereas acrylic and polymer systems are thinner and more flexible. Either way, the layer has almost no tensile strength at an edge.
As a result, the damage always appears in the same place. For example, the bit skids across a smooth finish and scars it, or hammer action shatters the coating around the entry point and leaves a crater far wider than the hole. On a painted or coloured render, a repair to that crater will rarely match.
In addition, there is a second problem underneath. Where render sits over a lightweight substrate, a cavity or a hollow perp joint, the drill can break through into nothing and the plug will never grip. Feeling the change in resistance as you go is part of the job.
Almost every blown fixing we are asked to repair comes from hammer action starting too early, not from the wrong bit.
Recommended Masonry Drill Bits
In short, one bit type covers nearly all of this work. However, the shank and the tip quality still make a real difference on a hard cement render.
Carbide Tipped Masonry
Firstly, the standard round shank bit for a rotary or hammer drill. Right for light to medium fixings into rendered brick, and cheap enough to replace when it dulls.
SDS Plus Masonry
Secondly, a shanked bit for a rotary hammer. Faster and far more accurate in solid brick, although its power is exactly why the render layer needs the hammer off first.
Multi-Material Bit
Ground to cut render, brick and the occasional tile without changing bits. Useful over rendered walls with tiled returns, though slower than a dedicated masonry bit.
Match the bit diameter to the wall plug rather than the screw. For instance, red plugs take 6 mm, brown take 7 mm and blue take 10 mm. Also, drill ten millimetres deeper than the plug length so dust in the bottom of the hole does not stop it seating flush. Full render systems and substrates are covered on our rendering services page.
Hammer Versus Non-Hammer Drills
Choosing what drill bit for rendered brick to use is only half of it. The drill mode protects the finish just as much, and it is not one setting for the whole hole.
01
Rotary Only
Pure rotation, no impact. Therefore the setting to start in. It cuts the render cleanly without shock loading the coating around the bit.
02
Hammer Drill
Rotation plus a light percussive action. Switch to this once the bit is through the render and biting into the brick behind.
03
SDS Rotary Hammer
Far more impact energy. Excellent in brick, punishing on render. Keep it in rotary-only mode until you are past the coating.
04
Impact Driver
Not a drill for masonry at all. It drives fixings once the hole exists, and should never be used to make the hole.
Settings that spare the finish
- Start in rotary-only mode, whatever drill you are holding.
- Keep the speed low. High revs generate heat and glaze the render.
- Use light, steady pressure and let the carbide do the cutting.
- Switch the hammer on only once you feel the bit reach brick.
- Withdraw the bit periodically to clear dust from the flutes.
If your drill has a clutch, then set it low for the render layer. Similarly, if the bit stops advancing while the drill still sounds like it is working, stop and check. Most likely you have found a cavity or a hard aggregate, rather than a reason to push harder.
A Step by Step Guide
Finally, put together, this is the full method. Knowing what drill bit for rendered brick to reach for matters less than the order you work in.
Step by step
- Check what is behind the wall: Run a multi-detector over the area for cables and pipes. Avoid the vertical zones directly above and below switches and sockets.
- Mark and tape the point: Next, put a cross of masking tape over the mark. It stops the bit skidding on a smooth finish and also catches most of the dust.
- Start rotary only, slow: Then bring the drill up square to the wall and start slowly with no hammer action, letting the tip find its own centre.
- Feel for the brick: Resistance changes as the render ends. Only then should you switch the hammer on.
- Clear, plug and fix: Finally, withdraw and clear the dust, blow the hole out, seat the plug flush, and drive the fixing without over-tightening it.
However, if the render around a fixing has already blown, or the wall needs more than a patch, the repair is still straightforward for a plasterer and rarely means re-rendering the whole elevation. Our rendering services page covers the systems we apply, and the house rendering page sets out how whole-of-house projects run.
Frequently Asked Questions
Common questions about drilling into rendered brick, answered by our in-house team.
Will drilling crack the render?
Not if you go through the render layer with the hammer action switched off, at a slow speed and with light pressure. Most blown render around a fixing comes from hammering straight into a brittle coating rather than from the bit itself.
What size bit do I need for a wall plug?
Match the bit to the plug, not to the screw. A red plug takes a 6 mm bit, a brown plug takes 7 mm and a blue plug takes 10 mm. Drill deeper than the plug so dust at the bottom of the hole does not stop it seating.
Can I use a wood or metal bit on rendered brick?
No. HSS and wood bits will blunt almost immediately and will tear the render on the way in. Rendered brick needs a carbide tipped masonry bit, and for anything structural an SDS bit in a rotary hammer.
How do I avoid hitting a pipe or cable?
First, use a multi-detector, and also think about what sits behind the wall. Vertical zones above and below switches and sockets, and horizontal zones near ceilings and corners, are where cables usually run.
