How to Rake out old Mortar for a Professional finish
One of the jobs I have been working on this fall is to repair my garage, the condition of the roof and front wall were not the best and I needed to repoint the brickwork.
To prepare the area for repointing I first needed to rake out the old mortar, to give me a good base to work from, and doing this the right way will save you money and time and make your brickwork strong and last for many years.
Here is my guide on how to rake out old mortar for repointing brickwork:
Check the brickwork and assess the area to rake out, split this up into sections of 1m square. Use a 9” angle grinder and mortar cutting disc to rake out the mortar between brick courses. Use a hammer and cold chisel to rake out the perps and tight areas. Clean with a stiff brush and hose pipe to remove dust.
Using the right tools and preparing your brickwork properly by raking the old mortar out the right way will make repointing with new mortar much easier, and give you a professional finish, read my detailed guide below and video at the end of the post to find out more tips.
Inspect the brickwork to be raked out
Before you start cutting away, have a good look at the area of brickwork that needs to have the mortar raked ready for repointing, if it is a large surface consider breaking it down into smaller sections, to repoint a 1m square area will take an average skilled person about 2 hours.
Make sure that you have moved or protected anything that you don’t want to be covered in dust, things like cars and garden furniture should be moved away from the area as brick dust and stone chips can cause some damage.
Cover windows, glass, or items that can’t be moved with dust sheets or thick cardboard.
Check the brickwork for any cracks or cracked bricks, these could be signs of more serious issues and I will show how to deal with these at the end of the guide.
Tools you will need to Rake out Mortar
Even though there are many different types of mortar and brickwork, the tools and methods needed to rake out old mortar are very similar and can be applied to most applications with a few small adjustments.
Typically to rake out old mortar you will need some, if not all of the following tools:
- Mortar rake
- Cold chisel or plugging chisel
- Small Lump hammer
- Builders Bucket
- Hard bristle Hand brush
- 9” angle grinder
- Mortar cutting disc
- 40mm x 8 mm mortar rake bit
- Hammer drill
- Masonry drill bits
- Dust extraction
- Safety goggles
- Dust mask
- Ear defenders
- Dust sheets
- Dust pan and brush
If you are raking the mortar from a large area like a gable wall or a chimney stack, you may also need to use ladders, work platforms, scaffolding, or a work tower to reach higher areas, you can find out more about working at height in our post linked here.
Rake out the old Mortar
To remove the majority of the old mortar I use a 9” angle grinder with a masonry cutting disc fitted, this has the benefit of quickly cutting away the old mortar and leaving a clean finish.
However the downside to this method is the mess, this will create lots of dust. The dust can be greatly reduced by keeping the cutting disc and brickwork wet or by using a good dust extractor.
You can buy or hire wet and dry disc cutters but they tend to be too big for accurately cutting mortar from brickwork, so I prefer to use a smaller 9” angle grinder with a mortar raking diamond masonry blade fitted.
9” Angle grinders are fairly reasonable in price and can be used for plenty of DIY jobs, so it’s worth considering buying one. Take a look at our ‘Recommended Tools’ page for our top picks on this and other useful power tools.
Whenever possible I fit an extraction hose and connect it to a dust extractor to catch most of the dust, remember to keep an eye on the dust levels as they will fill up quickly and will need to be emptied regularly.
When you have no other choice but to use the angle grinder without extraction, try spraying the mortar and brickwork with water before cutting to help reduce the dust.
Remember to always follow the manufacturer’s instructions and wear the appropriate protective clothing.
When I use a grinder I always use a dust mask, safety goggles, and ear defenders, and if I can I use a face shield to stop any rogue pieces of masonry from hitting my face.
Using the angle grinder to rake out the old mortar works best for the horizontal cuts between each course of brick, as you can quickly align the cutting disc and run the grinder along with the mortar.
Be Careful with the grinder and keep it cutting the mortar in between the course of bricks and the disc will also cut the brick leaving an untidy edge and making the job messy.
When you come to rake out the vertical joints between the bricks, which are often referred to as the ’Perps’ (which is short for perpendicular), the disc of a 9” angle grinder is bigger than the 4” (102mm) height of a standard brick.
You will need to plunge the cutting disc in the center of the perp and be careful not to touch the course of bricks above or below otherwise the disc will cut into the brick as well and start to make things look messy.
Once the horizontal mortar is raked out using the angle grinder and cutting disc, I swap over to a 40mm x 8mm diameter mortar rake cutter.
These fit on to most angle grinders and do the same job as a cutting disc however they are much smaller in diameter, typically they are available in 6mm or 8mm dia.
This allows you to rake out the mortar from the perps easily and quickly, and get much closer to the bricks.
This type of mortar rake is really good as they create a lot less dust than a large diameter diamond cutting disc and can be used to get close to the edge of the brick giving a good, clean cut.
You can use this type of mortar rake to remove all of the mortar if you prefer but I find it takes a lot longer as the cut is slower than when using a full disc.
Removing Mortar by hand.
If you do not have access to an angle grinder or the dust will be too much of a problem then using a mortar rake or a cold chisel and lump hammer are your next options.
I have never had much luck with a handheld mortar rake because I find the mortar has either been too hard, so it takes a long time to rake out the mortar to the correct depth or the tip of the mortar rake will catch in a soft mortar and then will pull out too much mortar leaving a big hole to repair when repointing.
I often use a cold chisel and a lump hammer to remove stubborn old mortar that the other methods cannot cut away.
The Hammer and chisel is the most accurate method to cut out the old mortar and can be used in space that an angle grinder will not fit like internal corners or tight gaps.
For small gaps and spaces, a plugging chisel can work better than a cold chisel as the blade is not as wide and can be more easily controlled.
You can even use an old flat-bladed screwdriver to rake out old mortar but these are not as good or as fast as using a hardened chisel which is made for the job.
Remember to always cut in towards the brick when using a hammer and chisel to remove mortar, if you cut away or towards the edge of the brick you risk chipping the brick which will make the job look messy.
How deep should you rake out the mortar?
When raking and cutting out mortar in preparation for re-pointing the brickwork the depth of the cut should be enough to clear the old weathered mortar but not too much to weaken the bond between bricks.
A good rule is to rake out about 3/4 of an inch, or between 15mm – 20mm of the old mortar, this will be roughly the length between the tip of your index finger and the first knuckle joint.
Raking out the joints to this depth should remove all the old exposed and weathered mortar, whilst leaving a good solid base to work with.
If you remove mortar to any more than 20mm deep, you can risk weakening the bond between the bricks.
If you remove less than 15mm of old mortar, any new mortar will not have enough surface to bond fully and will fall out in a matter of months and you will need to redo the job again.
Make sure that the joints between the brick courses are as parallel as possible and that as much of the old mortar is removed as possible, the aim is to have any new mortar bonding to the brick, not the old mortar when the repointing is carried out.
When using an angle grinder to cut the old mortar use the disc guard as your guide to the correct depth or use a depth gauge attachment so that you keep the depth level on all the joints.
If you are raking the mortar out by hand using a chisel and a hammer check the depth periodically to make sure the right amount of old mortar is being removed.
Cleaning the brickwork and preparation for repointing
After all the old mortar has been raked out, the bricks need to be cleaned down to remove all the loose material and brick dust.
Leaving dry dust and bits of old brick will mean the new mortar will not bond to the surface of the bricks and will quickly loosen and fall out.
I use a stiff bristle hand brush to clean the dust and old mortar from between the courses of brickwork,
It can be a good idea to dampen the area down by spraying water over it using a hand spray, or if there is little chance of water getting inside using a hosepipe to wash the brickwork and flush any dust away.
With the raked area cleaned and free of loose bits and dust the brickwork can be repointed with fresh mortar.
check out our guide to color matching mortar and re-pointing for more information.
Dealing with Cracked bricks
So as I mentioned earlier when you are checking over the area you are about to work on, look out for cracks and cracked or spalled bricks, as this is a good opportunity to replace or repair them.
If the area of brickwork you are working on has cracked bricks, it’s a good idea to check over the whole surface and trace where the cracks have started and finished.
If the crack covers more than one or two courses of brickwork it would be a good idea to employ a structural engineer or building inspector to survey the area and check for conditions creating the cracks.
If the cracks are not serious and can be repaired without major building work there are options you can do yourself and you can find out more about repairing cracks for our blog post coming soon.
If the crack is only across one or two bricks or the brick is spalled then it is possible to cut out the brick and replace it without any issues.
Rake out the mortar around the old brick
Use a hammer drill and masonry bit to drill holes in the mortar surrounding the damaged brick. I tend to put a few 8mm diameter holes near one corner, this allows me to start using a mortar rake attached to my angle grinder.
I set the drilling depth by checking a brick at a nearby corner or the end of the wall, just make sure the same bricks have been used as the one you are going to remove.
Then using a mortar rake, cut away the mortar bonding the brick in place. Carefully work on all 4 sides of the brick.
Mortar rakes for angle grinders are available in 100mm lengths which allows the bit to cut all of the mortar away. Helping to release the brick from its joint.
Cut out the old brick
Once the old mortar is raked out, the brick can be broken out using a cold chisel or plugging chisel and a lump hammer; carefully cut the brick out by breaking it up in place and removing the bits as you go.
Place the broken bits into a bucket so they can be thrown away or reused as hardcore on future projects.
Work inwards away from the edges of the brick so as not to damage the surrounding bricks.
Once the brick is freed and removed, clean off any remaining mortar with the cold chisel and clean the dust and old mortar away with a brush in the same way when raking out any other mortar.
Make sure any remaining mortar is removed from the surrounding bricks, do this carefully by hand with a cold chisel and lump hammer. this will allow a new brick to be reset with fresh mortar and bond to the surrounding brickwork.
Check out this video for more details on removing mortar from between bricks:
This article was written by: Richard Quinton – The DIY Help Desk Owner, Engineer & technical specialist.
Richard is one of the key partners in The DIY Help Desk team. He is a qualified Engineer, writer, and publisher, educated to Master’s level. He is a keen advocate of DIY and home improvements.
Richard enjoys helping others to learn new skills and reach their goals and believes that passing his knowledge and experience on through his writing is an effective way to positively impact the lifestyles and well-being of others on a larger scale.