When you’re buying a new kitchen, it’s easy to focus on the bits you can see, like the doors and worktops. But the unsung hero of a quality kitchen is the cabinet itself – the carcass. One of the biggest differences between a high-quality kitchen and a cheap one comes down to a few millimetres of board. As the owner of SJB Trade Kitchens with over 20 years in the industry, I’ve seen firsthand why 18mm carcasses are the only way to go.

The main difference between 18mm and 15mm kitchen carcasses is simple: 3mm of high-density particleboard. It might not sound like much, but it has a huge impact on the strength, rigidity, and lifespan of your kitchen cabinets.

• Weight Capacity & Rigidity: An 18mm carcass is significantly stronger and more rigid than a 15mm one. This is crucial for wall units holding heavy plates and for base units supporting heavy worktops like granite or quartz. A 15mm carcass is far more likely to bow or sag over time.
• Longevity: Because they are more robust, 18mm carcasses will last much longer. A kitchen is a long-term investment, and a stronger cabinet structure is fundamental to its durability.
• Hardware & Fixings: That extra 3mm provides a more secure fixing for screws, especially for door hinges which are under constant stress. This means doors are less likely to drop or become misaligned.

Many of the big national kitchen retailers use 15mm carcasses to keep their costs down. It’s a corner they can cut that many customers won’t notice until it’s too late.

It can be tricky to tell the difference just by looking. The best way is to ask the supplier directly for their technical specifications. If they can’t or won’t tell you, that’s a red flag. You can also check the back panel. Many companies that use 18mm sides will cut costs by using a flimsy 3mm or 6mm hardboard back. This creates a weak, wobbly cabinet.

At SJB Trade Kitchens, we use 18mm Egger and Kronospan board for the entire carcass – including an 18mm solid back panel. This is a key part of our commitment to being a leading trade kitchen cabinet manufacturer. Our cabinets are built to last.

We believe in transparency and quality. That’s why we only use high-quality, 18mm board from respected European brands like Egger and Kronospan for our rigid-built kitchen cabinets. We don’t offer a ‘good, better, best’ system; we just have one standard: the best. This ensures every kitchen we supply is strong, durable, and built for the long haul. It’s a simple, honest approach that our customers appreciate.

For more information, check out our main kitchen advice page.