The depth you need to remove mortar will vary depending on whether you are removing an individual brick or an area of mortar.
If you are removing an individual brick, you will need to rake out mortar to the width of the brick. An average brick has a width of 10-11cm.
Most long mortar rakes that are designed for the removal of individual bricks have a length of 15mm.
If you were looking to remove an individual brick, you should buy a mortar rake with a working length of 110-150mm.
If you are removing an area of mortar and leaving the bricks in position, you don’t need to rake that deeply.
Instead, you should only rake the equivalent of twice the height of the mortar between the brickwork.
This is usually a depth of 25mm.
When removing mortar from between stonework you should rake to a depth between 25-50mm.
If you wish to remove a whole stone, then you may need to use a wider selection of tools than just a mortar rake because a shorter mortar rake may not reach the depth of the joint and a longer mortar rake may snap if the stone is uneven along its depth.
Past a depth of 25mm (using a shorter mortar rake) you may need to use hand-powered tools to remove an individual stone.
When working on traditional or listed buildings, it is recommended you remove the mortar with hand-operated tools.
How do you tell how deep you’ve raked?
The type of power tool and accessory you use with your mortar rake will determine the way in which you tell how deep you’ve raked.
Angle grinders
An angle grinder can be used with a sole plate attached around the spindle base and can be set to a specific depth.
Once the wall or surface comes into contact with the sole plate, you know you’ve reached the depth you set the tool to.
Power drills
Both drills and SDS plus drills can have a gauge bar attached to them, which can, like the sole plate, be set to a specific depth.
You will hit the maximum depth when you hit the tip of the gauge bar.
You can measure the distance between the tip of the mortar rake and the tip of the gauge bar to find out the maximum raking depth.
Most mortar rakes will have their specifications given on the accessory’s casing or instruction manual so you could find out the maximum depth from those.
Alternatively, you can measure the cutting / grinding section of the tool to find its maximum working length.