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How to Eliminate Tile Hollowness During Installation

How to Eliminate Tile Hollowness During Installation 

Hollow tiles, characterised by a drummy sound when tapped, are among the first things any new property owner checks for when the site is handed over to them. Where even one tile is hollow, it could lead to rectification works that are costly and time consuming. This article explores the causes of tile hollowness and provides practical steps contractors can take to prevent it during installation. 

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Understanding the Causes of Tile Hollowness 

  • Improper Subfloor Preparation: Uneven subfloors create voids beneath the tile, leading to hollowness.
  • Insufficient Mortar Mix: A weak mortar mix due to incorrect ratios or excessive water creates pockets of air, compromising adhesion and causing hollowness.
  • Improper Tile Laying Technique: Not using a full trowel spread or leaving air pockets during tile placement can create voids.
  • Tile Joints That Are Too Narrow: Contrary to popular beliefs, the cementitious substrate that is applied below the installed tiles and mortar has a substantially higher rate of thermal and moisture expansion compared to the tiles and mortar bed. For this reason, it is an industrial norm for tiles to be installed with a minimum gap of 3mm to accommodate for the expansion of the substrate. 
  • Missing Expansion & Perimeter Joints: Failing to leave expansion and perimeter joints can lead to hollowness, as stress built up from the expansion of the mortar bed causes the tiles to push against each other. 
  • Mortar Bed that is Excessively Thick: A mortar bed exceeding the recommended thickness can shrink significantly as it dries, leaving voids

Preventing Tile Hollowness: A Step-by-Step Guide

1.Subfloor Preparation: Ensure the subfloor is level, flat, clean, and free of debris. Address any unevenness by patching or grinding as required. 

2.Mortar Mix: Always follow the manufacturer’s recommended ratios for the mortar mix. Use a consistent amount of water to maintain a proper, workable consistency. 

3.Trowel Spread: Utilise a full trowel spread technique to ensure complete contact between the mortar and the tile. 

4.Tile Laying: Gently press each tile onto the mortar bed, eliminating air pockets. Use a tapping block to ensure full coverage contact between the adhesive and tile.2

5.Tile Joints: Allow a minimum 3mm gap for interior area installations and a minimum of 5mm gap for exterior area installations, especially those under direct sunlight. Use spacers to maintain consistent spacing throughout the installation. 

6.Expansion and Perimeter Joints: Ensure expansion and perimeter joints are incorporated for large spaces and large format tiles. The recommended joint width should be at least 6mm.  

7.Mortar Bed Thickness: Adhere to the manufacturer’s recommended thickness for the mortar bed to avoid excessive shrinkage and potential hollowness.

8.Curing Time: Allow the mortar bed to cure completely before grouting. Follow the recommended curing time based on the specific product used. 


A primer on tile gaps and movement joints required for interior areas and areas exposed to sun. 

Additional Tips to Prevent Tile Hollowness

Regularly check the level of the subfloor and adjust as needed during installation

Use a notched trowel with the appropriate notch size for the specific tile size being used. 

For large areas, work in sections to ensure proper mortar consistency and prevent drying out before tile placement

Invest in high-quality materials, including the mortar mix, to ensure optimal performance and minimise the risk of hollowness. 

By following these steps and adopting a meticulous approach, contractors can significantly reduce the occurrence of tile hollowness, saving time, money, and ensuring a high-quality, long-lasting installation. 

Our experienced team is happy to help with any technical advice you may need. 

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