What size is cement board?
Many people are unsure how to choose the right size of cement board. Using the wrong thickness in the wrong place can cause cracks, damage, and costly repairs.
Cement boards usually range from 4mm to 30mm in thickness. Standard sizes are 1200×2400mm or 1220×2440mm, but custom sizes can be made for specific projects.
When I talk with clients, I often hear confusion between thin decorative boards and thicker structural boards. Each thickness has very different uses. Picking the right one is key to both safety and performance.
What size is 18mm cement board?
Many builders wonder if 18mm cement board is overkill or just right for their project. The truth is, this thickness has a very balanced strength-to-cost ratio.
An 18mm cement board usually comes in 1200×2400×18mm and is best for floors, exterior wall cladding, and load-bearing partitions where higher strength is needed.
I often recommend 18mm boards for mid-rise buildings. They are strong enough for elevated floors and outer walls but still easier to handle than thicker boards. For example, we had a client using them for balcony flooring in a coastal project. The 18mm thickness held up well under weight and resisted weather damage without being too expensive.
Understanding strength and application
Different thicknesses determine how the cement board handles load, impact, and wear. Thicker boards like 18mm improve load capacity but add weight and cost.
| Thickness | Common Use Cases | Advantages | Limitations |
|---|---|---|---|
| 6mm | Ceilings, decorative panels, lightweight partitions | Light weight, easy to cut | Not load-bearing |
| 12mm | Interior walls, some flooring | Medium strength, versatile | Limited structural use |
| 18mm | Floors, external siding, heavy partitions | Strong, durable, balanced cost | Heavier to install |
| 24mm+ | Heavy-duty flooring, industrial applications | Very high strength | Expensive, harder to handle |
When I explain this table to clients, they immediately realize that choosing thickness is about safety first, cost second.
What is cement fibre board?
Some people hear “fibre cement board” and think it is a completely different product. Actually, it’s a stronger, more durable form of cement board.
Fibre cement board is cement reinforced with fibres, improving impact resistance, flexibility, and weather durability compared to normal cement board.
We produce fibre cement boards for projects in harsh conditions, like factories, coastal homes, and high-humidity interiors. By adding fibres, the material bends slightly instead of cracking under stress. The extra cost (20–30% more than standard boards) is worth it when longevity and safety matter most.
Why choose fibre cement board over normal cement board
Fibre cement boards perform better in many demanding applications. The fibres (often cellulose or synthetic) bridge micro-cracks in the cement and prevent sudden breakage.
| Feature | Standard Cement Board | Fibre Cement Board |
|---|---|---|
| Strength | High | Very high |
| Flexibility | Low | Medium to high |
| Impact Resistance | Medium | High |
| Cost | Lower | 20–30% higher |
| Best For | General interiors/exteriors | Harsh climates, high-stress areas |
I always advise fibre cement for locations with wide temperature swings, heavy use, or exposure to water over time.
What is 6mm cement board used for?
A common mistake I see is using thin cement board where it should not be used. Many problems come from this wrong choice.
6mm cement board is best for ceilings, wall linings, and light partitions. It is not suitable for any load-bearing surfaces.
One case stands out in my memory. A renovation company used 6mm boards for a structure that needed to carry weight. Within months, cracks appeared. The failure was due to the thin board’s lack of structural support. I explained that while 6mm boards are light and easy to cut, they should never be used for floors or heavy walls.
Matching board thickness to the right task
Correct thickness choice is about balancing safety and performance.
| Thickness | Right Use Cases | Wrong Use Cases |
|---|---|---|
| 6mm | Ceiling panels, decorative walls | Floors, heavy partitions |
| 12mm | Interior structural walls | Heavy exterior cladding |
| 18mm | Exterior siding, flooring | Thin wall decorations |
| 24mm+ | Industrial areas, mezzanine floors | Lightweight décor |
By using the right thickness, builders save time, avoid failures, and deliver long-lasting results.
Conclusion
Choosing the right cement board thickness is vital for safety, performance, and cost-efficiency in any construction project.