Project 01 — Residential
A lightweight steel skeleton for a suburban home expansion
This project involved creating a steel frame extension for a two-story residential building. The design focused on maximizing natural light and open floor plans while maintaining structural integrity. We coordinated with the architect to integrate the steel skeleton with the existing masonry, ensuring a seamless transition. The result is a bright, flexible living space that meets modern standards of comfort and sustainability.
The homeowners wanted to add a two-story extension to their existing suburban house. The ground floor needed to open onto the garden with a large glazed wall, while the upper floor had to accommodate two additional bedrooms. The existing masonry structure could not support the new spans, so a separate steel skeleton was required.
We designed a series of HEA columns and IPE beams spaced at 4.8 meters, connected with bolted end plates to avoid welding on site. The frame sits on a new strip foundation, independent from the existing footings to prevent differential settlement. Lateral stability comes from a braced bay in the party wall plane, keeping the garden elevation free of diagonals.
The steel package was fabricated off-site over three weeks while the groundworks were prepared. Erection took four days, with the frame bolted and shimmed before the composite floor deck was installed. We provided the contractor with shop drawings for every connection, including torque specifications for the M20 grade 8.8 bolts used throughout.
One detail worth noting: the beam-to-column connections at the garden wall were designed with a 20 mm slot in the base plate to accommodate the ±10 mm tolerance of the existing masonry. This saved two weeks of on-site adjustment and kept the glazing line perfectly straight.
12.4 tonnes of S355 steel, mostly HEA 200 and IPE 300 sections. The weight was kept down by using composite slabs with shear studs instead of heavier precast planks.
All external columns are wrapped with 80 mm of rigid PIR insulation and the base plates sit on a 20 mm thermal break pad. U-value at the steel junctions stays below 0.25 W/m²K.
The frame is protected with 60 minutes of intumescent coating in the living areas and a double-layer plasterboard enclosure in the bedrooms. No exposed steel remains in the habitable spaces.
The extension was completed in 14 weeks from foundation to handover. The steel frame allowed the ground floor to open up completely to the garden, with a 6-meter clear span glazed wall that was not possible with the original masonry construction. The upper floor bedrooms are quiet and thermally stable, and the client reports a noticeable reduction in heating costs compared to the old single-glazed rear wall.
The full technical dossier, including connection details, section drawings, and site photographs, is available on request. Contact us to review the complete documentation for this project.
Project workflow — 5 stages
A focused project built around practical decisions and constraints. The sequence below maps how a request moves from first sketch to site-ready documentation, with the tradeoffs we weigh at each step.
We start with the building program, plot dimensions, and local zoning limits. For this project, the main constraint was a narrow urban plot with a protected tree line on the north side.
Using a parametric model, we tested three column grids against the facade module. The chosen layout reduces steel tonnage by 12% while keeping the cantilevered canopy within deflection limits.
We detailed all moment connections with preloaded bolts and shim plates to accommodate on-site adjustments. The workshop drawings include torque specs and a tightening sequence for each joint.
For the ventilated facade, we inserted thermal breaks at every bracket. The section drawings show the exact cavity depth and the vapour barrier continuity around the steel uprights.
After erection, we documented the actual bolt patterns and measured the frame alignment. The final report includes a deflection check under dead load and a photographic log of every connection.
The client receives a full package: structural calculations, shop drawings, and a maintenance schedule for the steel finish. We also include a checklist for annual facade inspections.
Every project follows this sequence, but the time at each stage varies. For this workflow, the parametric sketch took longer than usual because of the irregular plot geometry. The tradeoff was a simpler bolting schedule during erection.