Mortar joints

Habari Fundi Mtarajiwa! Hello, Future Artisan!

Ever looked at a strong brick wall and wondered, "What is the glue that holds all those bricks together so perfectly?" You see these walls everywhere, from your school to the shops in the market centre. That "glue" is called mortar, and the lines you see between the bricks are the mortar joints. Today, we are going to become experts on these joints. Sawa?

Think of it like this: If bricks are the body, the mortar joint is the skeleton holding it all together, making it strong and protecting it from rain and wind. Getting it right is a true skill!

Image Suggestion: A close-up, vibrant photo of a newly built brick wall in Kenya. The sun is shining on it, highlighting the texture of the red bricks and the neat, grey mortar joints. In the background, you can see a hint of green acacia trees.

What is a Mortar Joint?

A mortar joint is simply the space between bricks (or stones) that we fill with mortar. Mortar is a special mix, like a strong ugali for our wall, made from:

• Cement: The main source of strength.
• Sand: The filler that gives it body.
• Water: To make it a workable paste.

But we don't just slap the mortar in and walk away! A true fundi (artisan) finishes the joint in a special way. This is called "pointing" or "jointing". The shape we give the joint is very important for two big reasons:

1. To keep water out: A good joint directs rainwater to run off the wall, not into it. This is super important in places like Kericho or Limuru where it rains a lot!
2. To make the wall look beautiful: The right joint can create cool shadows and make the wall look very professional and stylish.

Aina za Joints (Types of Joints)

Let's look at the most common types of joints you will see and create. Each one has a special purpose.

1. The Flush Joint (Sawa-sawa)

This is the simplest joint. The mortar is finished flat and level (flush) with the face of the brick wall. It's easy and fast to do.

• Best for: Walls that will be covered with plaster later. Since the wall is flat, the plaster will stick on smoothly.

      BRICK  +-------+
             |       |
      JOINT  |-------|  <-- Mortar is flat, level with brick face
             |       |
      BRICK  +-------+

2. The Weathered Joint (Mteremko wa Nje)

For this joint, the mortar at the top is pressed in, creating a slope outwards and downwards. Think of it like a tiny roof for the brick below it.

• Best for: Outside walls in rainy areas. It's excellent at making rainwater run off the wall and not soak in. A very smart choice for a strong, long-lasting wall.

      BRICK  +-------+
             |       | \
      JOINT  |--------\  <-- Slopes down and out to shed rain
             |       |
      BRICK  +-------+

3. The Recessed Joint (Ya Mstari)

Here, the mortar is pressed back from the face of the bricks by about 10mm. This creates a sharp, dark shadow line between the bricks.

• Best for: Making a wall look fantastic! It highlights the shape of each brick and is very popular for modern buildings and feature walls where looks are very important. You might see this on a new building in Nairobi's Upper Hill.

      BRICK  +-------+
             |  |----|
      JOINT  |  |----|  <-- Mortar is set back from the brick face
             |  |----|
      BRICK  +-------+

Image Suggestion: A clear diagram showing four different brick joint profiles side-by-side. Each joint is labelled clearly: "Flush," "Weathered," "Struck," and "Recessed." A hand-drawn, instructional style would be perfect.

Hesabu za Fundi (The Artisan's Math)

A good fundi doesn't guess; they calculate! This helps to buy the right amount of sand and cement, saving money and time. Let's do a simple calculation for the mortar in one horizontal joint (a "bed joint").

Let's assume:

• A standard Kenyan brick length is 230 mm.
• The width of the brick is 110 mm.
• Our joint thickness (depth) is 10 mm.

The formula for the volume of the mortar in that joint is: Volume = Length × Width × Depth

Step 1: Identify the dimensions.
   Length (L) = 230 mm
   Width (W)  = 110 mm
   Depth (D)  = 10 mm

Step 2: Write the formula.
   Volume = L x W x D

Step 3: Do the calculation.
   Volume = 230 mm x 110 mm x 10 mm
   Volume = 253,000 mm³ (cubic millimetres)

That seems like a big number, but it's for just one joint! Imagine calculating for a whole wall. This is why math is a fundi's best friend!

Story Time: Fundi Wanjiru's Smart Choice

Fundi Wanjiru was building a new kitchen for a client in Nyeri. She knew that Nyeri gets a lot of cold rain. The client wanted a beautiful brick wall that would not be plastered. Wanjiru told the client, "We must use a weathered joint. It will cost a little more time, but it will protect your wall. The rain will flow off, and your kitchen will stay dry and strong for many, many years." The client was very happy with her expert advice. Wanjiru knew that the right joint is not just about looks, but about building something that lasts.

Your Turn to Be the Expert!

Now you know the secret language of brick walls! The next time you walk around your home or town, look closely at the walls. Can you identify the different types of mortar joints? Can you guess why the fundi chose that specific type for that building?

Understanding these small details is what separates a good artisan from a great one. Keep observing, keep learning, and you are on your way to building the future of Kenya, one perfect brick at a time! Poa?