D&A FACILITIES · LIGHT GAUGE STEEL STRUCTURES
Light steel alternatives to heavy steel beams
Not every extension or loft needs heavy steel. Galvanised light gauge steel can often replace parts of the structure: roof and floor joists, lattice joists, dormer and wall framing, and lintels over smaller openings. Members are made to length and ready to fix, and most pieces can be carried by hand, which helps on terraces and upstairs.
WHY LIGHT GAUGE STEEL
Where light steel genuinely helps
Carried by hand
Individual light steel members typically weigh around 20–70 kg, against roughly 100–270 kg for a 4–6 m steel beam that often needs four people or a lifter. Indicative figures.
Made to length, quick to fix
Members arrive cut to length and ready to screw or bolt together, so there is no site welding and less cutting on site.
Lighter structures
Ideal where weight on existing walls and foundations matters: loft and rooftop framing, dormers and upward extensions.
Straight and galvanised
Galvanised steel is straight, does not shrink or twist like timber, and is protected against corrosion as standard.
WHO IT’S FOR
Built for the people who carry the steel
Loft conversion firms
The problem: carrying heavy beams up stairs and through hatches, week after week.
How LGS helps: dormer and roof framing kits and lattice floor joists that go up in hand-liftable pieces, designed with your engineer.
Extension builders
The problem: tight access, cutting timber on site and waiting on heavy lifts.
How LGS helps: roof and wall kits cut to length, or a complete light steel extension shell, priced side by side against timber and steel.
Rooftop, modular & garden-room developers
The problem: every kilo on existing walls and foundations counts, and programmes are tight.
How LGS helps: lighter framing for rooftop and upward extensions, modular units and garden rooms, assembled quickly on site.
HMO landlords & flat converters
The problem: new partitions and floors in occupied or awkward buildings.
How LGS helps: lightweight partitions, floors and rooftop units, with sound (Part E) and fire (Part B) detailing designed in from the start.
AN HONEST COMPARISON
Where light steel works best, and where steel beams are still right
Steel costs about the same per kilogram whether it is a hot-rolled beam or light gauge steel, so light steel is not automatically cheaper. It saves weight and money when members can be deep and lightly loaded. For wide openings carrying walls and floors, a hot-rolled steel beam is often still the best answer, and we will tell you when it is.
| Job | Usually best | Why |
|---|---|---|
| Extension and garden-room roofs and walls | Light steel | Joists and studs cut to length; a 5 m roof joist can weigh around 20 kg (indicative). |
| Complete extension shells | Light steel | Joists, studs and lintels in one kit. |
| Loft dormers and roof framing | Light steel | Hand-liftable pieces up stairs; ridge or purlin support may still need a steel beam. |
| Floor joists and lattice joists | Light steel | Lattice joists can span roughly 5.8–8.2 m at light floor loads (indicative). |
| Rooftop, upward and modular builds | Light steel | Less weight on existing walls and foundations. |
| Small openings at modest load | Light steel | Cold-formed lintels are already common here; useful where access rules out a 100 kg+ beam. |
| Knock-throughs of about 4 m or more carrying walls, floors or roof | Steel beam | Shallower for the stiffness, especially where the ceiling must be flush. |
| Point loads, cantilevers, goalposts and post-free bifold openings | Steel beam | Thick webs carry concentrated loads directly. |
| Any design where the engineer has specified a steel beam | Steel beam | Any substitution needs the engineer’s written approval and Building Control acceptance. |
Figures are indicative only. Every design is checked by a structural engineer and goes through Building Control in the usual way.
HOW IT WORKS
From drawings to frame
1. Send your drawings
Share your drawings or your engineer’s calculations.
2. Compare the options
We show you a light steel option next to the conventional design, with the costs side by side.
3. Engineer and Building Control
Every design is checked by a structural engineer and goes through Building Control in the usual way.
4. Made to length, fitted fast
Members arrive cut to length, ready to carry in and fix.
FAQs
Is light gauge steel cheaper than a steel beam?
Not as a rule. Steel costs about the same per kilogram either way. Light steel saves material on deep, lightly loaded members such as joists and lattice joists. On a typical knock-through beam, any saving is small, so the real benefits are handling, access and speed.
Can light steel replace the steel beam in my knock-through?
Sometimes, for smaller openings at modest load, especially where access rules out a heavy beam. For wide openings carrying walls and floors, a hot-rolled steel beam is often still the right answer. Your engineer decides.
Do I still need a structural engineer and Building Control?
Yes, on every job. Every design is checked by a structural engineer and goes through Building Control in the usual way.
How heavy are the pieces?
Individual members are typically around 20–70 kg, so most can be carried by hand through a house. A 4–6 m steel beam is roughly 100–270 kg. Figures are indicative.
What about fire and sound?
Light steel is boxed in with a tested fire-rated board system rather than left exposed. In flat and HMO conversions, floors and partitions are designed for the sound requirements of Part E.
Steel only where it is needed
Send us your drawings or engineer’s calculations and we will show you a light steel option next to the conventional design, with the costs side by side.