Structural Requirements for Conservatories and Orangeries

What This Requirement Covers

Conservatories and orangeries are popular additions to UK homes. While many conservatories are exempt from Building Regulations (if under 30 m² and meeting other criteria), orangeries and larger glazed extensions typically require full Building Regulations compliance, including structural design.

Key Requirements

When Building Regulations Apply

Conservatories are exempt from Building Regulations if

1. The floor area does not exceed 30 m²
2. The conservatory is at ground level
3. It is separated from the house by external walls, doors, and windows
4. It has an independent heating system with separate temperature controls
5. The glazing and electrical installation comply with Parts K and P respectively

If any of these conditions are not met, full Building Regulations compliance is required.

Structural Design

1. Foundations must be designed to carry the loads from the structure to the ground
2. On shrinkable clay, foundations may need to be 1 metre or more deep, depending on tree proximity
3. The roof structure must resist wind and snow loads
4. Glazing bars and rafters must be sized to span between supports without excessive deflection
5. The connection to the existing building must transfer loads without causing damage to the existing structure

Glass Roof Structures

1. Structural glazing systems must be designed by specialist engineers
2. Glass must be laminated (for overhead glazing) to prevent falling fragments if broken
3. Thermal movement must be accommodated in the design of long spans
4. Minimum roof pitch for self-cleaning: 5 degrees

Orangeries

1. Orangeries typically have solid walls (brick or render) with a glazed roof lantern
2. The solid walls are structural and must be designed as load-bearing elements
3. The roof lantern is a structural element requiring wind load and snow load design
4. Thermal performance must comply with Part L if Building Regulations apply

Practical Compliance Tips

1. Confirm whether the conservatory is exempt before starting design; the exemption criteria are strict
2. If the conservatory is separated from the house, the existing external wall must remain (including windows and doors); removing it creates a single space that is no longer exempt
3. On clay soils near trees, expect deeper foundations; obtain a ground investigation or NHBC Chapter 4.2 assessment
4. Specify laminated glass for all overhead glazing; toughened glass alone is not acceptable for roof panels
5. Consider the thermal performance; even exempt conservatories benefit from good insulation and appropriate glazing
6. Plan drainage for the roof; conservatory roofs must discharge rainwater without causing damage to the existing building
7. Obtain Building Control approval for non-exempt conservatories before commencing work