Structural Joists and Flooring

Whenever a loft is converted into a living space or a room is extended, new structural joists are required to support the increased weight. Your old loft joists were originally designed only to hold insulation and light storage, not furniture, people, or plasterboard ceilings.

Why Joists Matter

Proper joists ensure:

• The floor is strong enough for everyday use
• No sagging or bouncing over time
• The structure meets UK building regulations
• Noise reduction between floors
• A solid base for flooring materials

Without correctly sized joists, a loft conversion may not pass inspection or feel stable.

Sizing and Spacing

Structural engineers usually specify joist size and spacing based on:

• Span length
• Weight load
• Roof shape
• Existing timbers
• Room purpose

Common joist sizes include 47×195mm or deeper, depending on the load.

Installation and Strengthening

Joists are installed carefully to avoid damaging existing ceilings or rafters. The process can include:

• Doubling up joists
• Adding steel flitch plates
• Fixing joist hangers
• Strengthening weak areas with additional timbers
• Ensuring level alignment

Secure fixings prevent movement or squeaking later.

Adding Flooring Safely

Once joists are installed, flooring options include:

• Structural plywood
• Chipboard flooring
• Acoustic flooring systems

These create a smooth, robust base for carpet, engineered wood, or laminate.

Long-Term Safety and Comfort

Good structural joists make the difference between a room that feels solid and one that feels flimsy. With professional installation, your loft or extension will be safe, comfortable, and fully compliant..