How to Make, Mix and Use Mortar for Repointing Brickwork and Ridge Tiles
This is a guide on how to mix sand and cement to make mortar. This knowledge can be very useful for various DIY projects around the house, including roofing work like the bedding or pointing of ridge tiles, replacing bricks and pointing stone or brickwork.
Although it is not particularly difficult to do, there are a couple of things to know. I've been making and using mortar for years, so read on to find out how to do it right!
What Kind of Sand Should You Use?
If you want the dry mortar to be:
- a middle tone—use builder's sand
- dark—use red sand
- light—use yellow sand
I mostly use red sand, because it's darker and doesn't stand out so much. So unless you have a specific reason to use yellow sand to match what you may already have on there, I'd recommend red.
How to Mix the Sand and Cement
If you're mixing by hand, then you'll need either a bucket or a board, depending on how much mortar you need. If you only need a small amount of mortar, then it can be alright to do it in a bucket.
The easiest way is to put the sand and cement into the bucket or board with a trowel. You can match one heaped trowel worth of cement to three trowels worth of sand. Then repeat with more cement and more sand as you fill the bucket. If you do it this way, then it makes mixing it up easier, as it's already getting mixed up as you put it in the bucket or board.
Don't fill the bucket more than just over halfway, however, or it will make it too difficult to mix it all up correctly.
Note: It's a good idea to mix up thoroughly the sand and cement together with your trowel in a bucket or board before you put any water in. Once you put the water in, it becomes more difficult to mix. (It's a lot easier to mix it while it's dry.)
How to Mix in Water and Plasticiser
Once you've thoroughly mixed up the sand and cement, it's time to start slowly adding the water and some plasticiser. The plasticiser is important to make the mortar easier to work with, and it also stops the mortar from cracking when it dries.
You want to keep mixing the mortar as you slowly add the water until you get the right consistency. The easiest way to check if the consistency is right is to use the top of a clean trowel to lift the mortar from the bucket, then hold the trowel on its side. You want the mortar to stick to the trowel a bit, but not stick so completely that it slides off very slowly. If it's too dry, then it won't point properly. And if it's too wet, then it will slide out.
You also need to check the mortar by smoothing it off in the bucket with the trowel. It should be a nice, smooth finish with a small amount of foam bubbles visible. If you can see any cracking or a sandy texture, then add more cement. If it gets too sloppy, then add a bit more sand. If you don't have enough cement, then the mortar will crumble when it dries.
If you stick to the 3:1 ratio method, you should be fine. But now and again, you'll still need to add a touch more sand or cement. Ideally, you should use the same proportion of sand and cement for all of the pointing you're doing so that it will all dry the same colour. But a trowel worth of sand or cement more per bucket here or there won't make a difference.
Tips for Mixing on a Board or in a Wheelbarrow
If you're mixing on a board or in a wheelbarrow, the same method applies on a larger scale. Mix dry, then add the water. If using a barrow, you can fit two bags of sand and two-thirds of a bag of cement in there without overfilling. You still want to use the plasticiser, and you will still need the trowel to check the consistency after you've mixed everything together. It's also a good idea to put a tarpaulin down underneath your mixing station to contain any splashes.
Tips for Mixing in a Cement Mixer
If you're mixing in a cement mixer for a larger job, then the easiest way to add the water is to spray it in with a hose. Make sure that you add the water slowly and let the mixer do the hard work. If you put too much water in too quickly, it will start splashing out everywhere. And it can fly quite a distance, so be careful! It's also a good idea to use goggles when you're using a mixer, as it can be pretty painful if some does happen to splash into your eye.
The most important thing to remember with a mixer is to not let the mortar dry in there. After emptying it out, put some water and loose half bricks or pebbles in there, let it swill round, and empty it out again. Then hose it out. If you do this while the mix has just been freshly made, it's a lot easier to clean out than if you let it dry.
Wear Gloves When Handling Mortar
Cement can cause a reaction with your skin—drying it out, cracking it, and causing you considerable pain. It doesn't take long for you to feel the effects, so it's best to just wear protection for your hands from the onset.
How to Repoint Properly With Mortar
In order to repoint properly, you need to get as much of the old mortar out as possible. You can use a grinder and then a hand brush to clean the old material out until there is no loose mortar left. If you just go on top of old stuff that's loose, then the new mortar you put in will just come out again. So if you're going to do it, then do it right!
Remove the Old Ridge Tiles
Similarly, if you're repointing or rebedding ridge tiles, then it's normally worth taking off the old ones and cleaning off all the old mortar. You can use either a brush or sometimes a hammer and bolster (a mortar chisel), depending on how stiff the old mortar is. (Although if you don't crack them, you can usually reuse ridge tiles.) If you just go over the top of the old mortar, it's a lot quicker, but what you put on will crack and fall off. What most roofers do is put the mortar line down, then use broken pieces of tile between the ridge tiles—mixed in with the mortar—to add some strength. This stops it from dropping down between the ridge tiles and allows you to build it up effectively.
Add the Mortar in Stages
When you start pointing, it can sometimes be beneficial to add the mortar in stages, depending on how and what you're pointing. If you have large gaps to fill, then put a layer of mortar in rough and leave it to dry for a few hours. You can then go back and point it up with a bit more to finish. If it is a large gap and you try to do it all in one go, it can look great when you've first done it, but then slowly slide out and leave a gap at the top. You don't want this! If you're just doing brickwork or small gaps though, then you don't need to worry and can usually do it in one go.
Keep Your Trowel Clean
Make sure that you keep your trowel clean. This will make the whole process easier. As you point, you will need to repeatedly clean the trowel off on the side of the bucket or something similar to keep it clean and clear. And of course, when you're done, give it a good scrub to keep it ready for next time.