Building Regulations: Structural Openings

After sealing your new extension against the weather, you'll typically cut an opening into your home's existing external walls.

If you're only removing pre-existing French doors, sliding patio doors, or windows, and you don't increase the span or the load on the current lintel above them, you might not require any extra support.

However, if you're making a completely new opening or expanding an existing one, you must provide support for the wall above it. Typically, you achieve this by installing one, or more commonly two, new beams. Each new beam usually needs a minimum of 150mm bearing – that's an overlap onto the existing wall – on both sides of your opening. You might also need to strengthen the existing wall directly beneath these bearings to prevent it from crushing. This often means putting in dense concrete 'padstones' to help spread the load. Remember, the size of these padstones will vary based on your project's specific requirements.

Fire Safety for Beams

• Steel Beams: If you install a steel beam, you typically need to add fire protection to ensure it achieves at least 30 minutes of fire resistance, as confirmed by a standard test. You often accomplish this by properly fixing two or more layers of plasterboard; the manufacturer will specify the exact thickness required.

• Exposed Timber Beams: Should you prefer an exposed timber beam, you'll generally need a calculation to demonstrate its inherent fire resistance. This resistance depends on the beam's size and the specific timber species used.

• Concrete Beams: Concrete beams, which usually incorporate steel reinforcement, typically possess sufficient fire resistance. This is true as long as the steel components are adequately encased within the concrete.