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How to mix mortar for jointing?

How to mix mortar for jointing

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Making a basic mortar mix for jointing

Mortar mix To create a basic mortar mix, half fill a bucket, adding in the ratio of 3 parts sand to 1 part cement (use a heaped trowel as a measurement). Filling a bucket over half full will prevent the mortar from mixing properly.

Preventing the mortar mix from cracking

Mortar Plasticiser

Add some plasticiser according to the container’s guidelines. This will prevent mortar from cracking when it dries.

Creating light mortar

Yellow Sand To create lighter mortar use yellow sand.

Creating dark mortar

Red washed building sand To create darker mortar use red sand.

Testing that the mortar is the correct consistency

Trowel and mortar Add water until the mortar becomes smooth and will slowly slide off a lifted trowel tilted to its side. If it’s too dry it won’t joint properly, whereas if it’s too wet it will fall out of the joint.

Additional tools may be needed to apply the mortar to the joints

Additional Tools You may wish to acquire tools for pushing mortar into the joints. The most commonly-used method is to use a mortar board, sometimes referred to as a hawk. It is a portable flat surface used to hold mortar near to the wall. In conjunction, various trowels such as the finger trowel (pictured) can be used to push the mortar into the joint.

What is the thumb print test?

Thumb print in mortar The ‘thumb print test’ is a test to see if mortar is at a stage where it’s suitable for jointing. Mortar passes the test when a lightly pressed thumbprint (or hoof print) leaves a slight indent, with no mortar sticking to the thumb.


Hoof Print It is important that you carry out this test so that you know the mortar will be easily compacted and compressed against the bricks.

How long do I have to wait?

Stopwatch Before any jointing can take place, you must be patient…..The time you need to wait depends on how quick the mortar takes to set to ‘thumbprint hardness’. Checking should start after approximately 10 minutes.
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Is the mortar too wet?

Mortar that is too wet When the mortar is too wet, it will not form a thumbprint. It just sticks to the thumb.

Is the mortar too dry?

Mortar that is too dry If the mortar is too dry, it will crumble and break away when tools are used.

Consequences of incorrect jointing

Consequences Joints that are tooled early (jointed before the mortar was allowed to dry properly), often have multiple ridges on the surface. This is because wet mortar sticks to jointers and leaves ridges behind where the mortar has piled up, leaving the joint uncompact.

Jointing late causes mortar to have a darker appearance

Jointing late causes discolouring Jointing too late, when mortar is stiff, often leaves joints with a darker appearance as it inteferes with the mortar’s setting process. This is likely to be undesirable as it may detract from the overall appearance of the brickwork. To alter the colour of mortar correctly, choose an appropriate sand colour to mix with cement at the initial stage.

Jointing late causes mortar to crumble

Jointing late can cause a crumbled surface Jointing late also causes mortar to crumble and look untidy against the surface of the brick. Crumbling indicates that the mortar has been left to set for too long and has become too dry for effective jointing.

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