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Hollow blocks are a staple material for walls in Philippine construction due to their strength, versatility, and cost. This DIY guide will aim to teach you the process of building a hollow block wall, explaining the material, the available sizes, and the building process. We’ll prepare you to build a hollow block fence, garden wall, or partition for your project.

 

What is a Hollow Block?

The hollow block, otherwise known as a concrete masonry unit (CMU), is a precast block with hollow spaces that reduce weight, making it thermally efficient and allowing for added support with the insertion of metal rebar and concrete.

Commonly made with cement, sand, and gravel, these blocks are durable, fire-resistant, and cost-effective compared to their counterparts such as wood or solid concrete. They are ideal for tropical climates, able to endure typhoons, heat, and humidity.

 

Hollow Block Sizes

Hollow blocks come in various sizes, depending on the structure’s requirements. Its dimensions, measured in centimetres (width x height x length), are:

·           4-inch: 10 x 20 x40 cm

·           6-inch: 15 x 20 x 40 cm

·           8-inch: 20 x 20 x 40 cm

The hollow block standard size is the 6-inch block, commonly used for residential walls and fences due to its balance of strength, weight, and cost. The 4-inch blocks are generally used in partitions that are non-load-bearing. The 8-inch is used for heavier structural walls or areas with strong winds, respectively.

When acquiring hollow blocks, confirm with your supplier, as sizes slightly vary. Ensure you source your hollow blocks from a reliable supplier.

 

How to Build a Hollow Block Wall/Fence

Careful planning, the right tools, and basic masonry skills are what is required to build a hollow block wall.

Tools You'll Need: Measuring tape, String line and stakes, Chalk line, Level Bar, Mason’s trowel, Block spacing ruler or gauge, Wheelbarrow, Shovel, Hammer, Chisel, Rebar cutter or bolt cutter, PPEs, Rubber mallet, Brush (for cleaning joints)

Follow these steps for a sturdy wall:

1.  Prepare: Measure your desired wall dimensions and secure the necessary permits, particularly for perimeter fences. Outline the wall layout on the ground with strings and stakes. Dig a 30-60 cm deep trench with a width of twice the required block’s width.

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2.  Pour the Foundation: Mix concrete (A ratio of 1:3:4, cement, sand & gravel, respectively) and pour into the trench. Insert horizontal rebar (10-12 mm) into the foundation for reinforcement. Allow the mixture to cure for 3-7 days.

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3.  Gather Tools and Prepare Mortar: The tools you’ll need are a trowel, level, plumb bob, wheelbarrow, and measuring tape. Mix mortar (1:4, cement:sand) to a thick, spreadable consistency.

4.  Lay the First Course: Apply a 1-inch layer of the mortar along the foundation and place the first row of block, ensuring they’re level and aligned. Tap the blocks gently with a trowel handle to let them set. Insert vertical rebar (10–12 mm) into the block spaces at 80-120 cm intervals, securing them in the foundation.

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5.  Build Subsequent Courses: Spread mortar on top of the initial layer of blocks and lay the next row/course, staggering the joints (running bond pattern) for strength. Check for level and plumb ro in every row. Fill each hollow with concrete around rebar every 2-3 courses for stability.

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6.  Finish the Wall: At the desired height, cap the top with a concrete beam or coping for weather protection. After the Mortar has set for at least 7 days, plaster or paint the wall.

7.  Clean Up and Inspect: Remove any excess mortar and check for cracks or unevenness. Ensure proper drainage around the wall to prevent water pooling.

 

Final Thoughts

Building your own hollow block wall can be a great beginner project for those starting out in the construction industry. Whether you're working for a large construction firm or planning to start your own small business, it's a skill you'll use often. Practice makes perfect, so try assisting with wall construction projects before managing one on your own.

We hope this guide has been of great help and prepared you to build your first hollow block wall. If you need more assistance, our team at Mackun Hardware is always ready to help.

Check out our wide assortment of building materials here.

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