Types of Mortar JointsHome >> Choosing bricks » Types of Mortar Joints
The impact of mortar and joints
When selecting bricks there is one more thing to consider, namely the mortar colour and joint type. This will profoundly affect the end product, as will the combination of other building materials and colours that get used.
Three important points when selecting bricks
- Customers should research bricks from a variety of sources: ie display houses, display centres, display boards and sample packs, but ultimately it is best for the customer to choose bricks from an actual building or house to ensure they understand what the brick looks like in a finished wall.
- Select mortar colour and joint type with reference to the actual brick that you're using.
- Select the correct grade of brick.
Tip: Order all the bricks, sand and materials for mortar required at the start of the job to avoid batching colour differences.
Prevention is the best cure
As a builder, your goal is a straightforward flow of work on the site to deliver the project in line with your customer's expectations. For brickwork, a few important guidelines will help:
- Always discuss mortar colour and bond with the customer at the time of choosing the bricks, not afterwards. Avoid the term "natural mortar" as sand supply can vary the mortar colour considerably and if in doubt, samples should be made up from your sand supplier.
- Be clear about the environment of the project and whether any special consideration is needed. For instance, if the project is marine-based then the brick and mortar grades must be suitable.
- Make it as simple as possible for customers to select bricks. Use display homes and/or actual walls to assist them with their selection.
- Explain to customers examples of incompatible combinations of brick, mortar colour and joints, and why. Some examples include:
A rough face brick with flush joints because it is difficult to clean, especially with a high contrasting mortar colour.
Rolled edge tumbled bricks with flush joints. These emphasize the irregularity of the bricks and reduce the attractiveness of the finished wall.
Surface coated and glazed bricks with a raked joint. These can expose the body colour beneath the coating.
Tip: Once the customer has selected their bricks, ask the brick sales rep for the locations of other houses with the brick so the customer can confirm their choice, when in a whole wall, is correct.
The four Classes of mortar
In Australia, the Masonry Standard AS 3700 specifies the requirements for mortar in terms of a series of classes from M1 to M4. Class M1 mortar, lime mortar with no cement, is only permitted for use in the repair of heritage structures. The other three classes - M2, M3 and M4- can be used in a range of structures depending on the requirements for strength and durability.
The most commonly used mortar is M3, which typically has a composition of 1 part cement, 1 part lime and 6 parts sand. While it's the most common type of mortar, it's a misconception that it is the 'standard' mortar ratio. M3 mortar is only required in marine environments between 100m and 1km from a non-surf coast, or between 1km and 10 km from a surf coast. Inland of these areas M2 mortar, which is 1 part cement, 2 parts lime, and 9 parts sand, is sufficient. M4 mortar is required for severe marine environments which are up to 100m from a non-surf coast and up to 1km from a surf coast. Brickwork below a DPC or in contact with the ground may require a different class of mortar (and brick) than required for brickwork above, eg. M4 with exposure grade bricks are required in aggressive soil.