Calculating Core Fill for Blockwork: A Step-by-Step Guide

Core fill refers to the concrete or mortar poured into the hollow cavities of concrete blocks to create a solid structure. Knowing the exact amount of core fill needed is crucial for accurate material estimates and project budgeting. This article will guide you through calculating core fill for blockwork metric.

Understanding the Formula:

The core fill volume is calculated by multiplying the block’s internal volume by the total number of blocks requiring core filling. Here’s the formula:

Core Fill Volume (m³) = Number of Blocks * (Block Length (m) x Block Width (m) x Block Height (m)) – Solid Block Volume (m³)

Explanation of Variables:

  • Number of Blocks: The total number of blocks needing core fill.
  • Block Length (m): The length of a single block in meters.
  • Block Width (m): The width of a single block in meters.
  • Block Height (m): The height of a single block in meters.
  • Solid Block Volume (m³): This term is optional and only applies if the block has solid sections that don’t require core fill. You’ll need to calculate the volume of these solid parts and subtract it from the total volume.

Steps to Calculate Core Fill:

  1. Gather Information:
    • Note down the total number of blocks requiring core fill.
    • Measure the individual block’s length, width, and height in meters.
    • If applicable, determine the volume of any solid block sections (consult manufacturer specifications or calculate for simple shapes).
  2. Calculate Block Volume:
    • Multiply the block length, width, and height. This gives you the volume of a single block.
  3. Account for Solid Sections (if applicable):
    • Subtract the solid block volume (if any) from the total block volume calculated in step 2.
  4. Multiply by Number of Blocks:
    • Take the volume obtained in step 2 (or step 3 if applicable) and multiply it by the total number of blocks requiring core fill.
  5. The Result:
    • The final answer represents the total volume of concrete or mortar needed for core filling.
See also  Estimating Decks


Let’s say you have a wall requiring core fill with 100 blocks, each measuring 200mm (0.2m) in length, 150mm (0.15m) in width, and 400mm (0.4m) in height. These blocks have no solid sections.

  1. Block Volume = 0.2m (length) * 0.15m (width) * 0.4m (height) = 0.012 m³
  2. Since there are no solid sections, we don’t need to perform step 3.
  3. Core Fill Volume = 100 blocks * 0.012 m³/block = 1.2 m³

Therefore, you’ll need approximately 1.2 cubic meters of concrete or mortar to fill the cores of these 100 blocks.

Additional Tips:

  • Always refer to the block manufacturer’s specifications for accurate block dimensions.
  • Account for wastage by adding a small buffer (5-10%) to your final core fill volume estimate.
  • Consider using online block core fill calculators for quick calculations, but double-check the results for accuracy.

By following these steps and understanding the core fill formula, you can efficiently calculate the required amount of material for your blockwork project.

Core Fill Blockwork

Core Fill Blockwork