Structural Design & Calculations for Loft Conversions

A loft conversion is one of the most rewarding home improvements, but it's a major structural alteration. We provide the certified structural calculations and detailed drawings required to safely convert your attic space, ensuring your new floor and modified roof meet all load requirements and pass Building Control inspection without delay.

⚙ Key Structural Elements We Design

Loft conversions introduce significant loads that the original structure was never designed to handle. Our design packages cover the following critical elements:

• New Floor Structure: Designing and specifying the new timber or steel floor joists to carry domestic loading (furniture, people) and prevent ceiling sag below.
• Steel Beams (RSJs): Calculating the precise size and specification of RSJ beams needed to support the existing roof structure, often running across the width of the house.
• Load Path Transfer: Ensuring the total load from the new room is safely transferred down to the foundations via existing walls and supports.
• Dormer Construction: Full structural design for the new wall and roof elements of Dormer conversions to guarantee stability and weathering.
• Stairwell Openings: Designing the trimmed openings and supporting headers to safely accommodate the new staircase.

Structural Requirements by Loft Type

We provide expertise across all common loft conversion types:

• Dormer Conversions: These involve complex structural design for the vertical walls and flat roof that extend out from the existing roof slope.
• Hip-to-Gable Conversions: Structural calculations required to rebuild the sloping 'hip' end of a roof into a vertical 'gable' wall, demanding heavy new support.
• Velux/Rooflight Conversions: While simpler, they still require detailed floor joist and support calculations to ensure the attic is habitable.
• Truss Roof Conversions: Often require the most complex structural design, involving the complete replacement of existing roof trusses with new beams and purlins.

Areas Covered

Next Steps: Getting Your Loft Conversion Design

Once your planning application (if required) is approved, we need your architectural drawings and a brief description of the conversion type. We will then perform a detailed load assessment and provide a full package of structural calculations and drawings for your builder and local authority.