LGSF Technology: From a Steel Coil to a Finished Building

LGSF — Light Gauge Steel Framing — is the most promising rapid construction technology in Ukraine. The frame is 9 times lighter than reinforced concrete, is assembled without welding, and requires no "wet" processes. In this technical guide: how LGSF profiles are designed, how they are manufactured at the factory, what a thermoprofile is, and why a steel frame does not burn.

What is LGSF and how it differs from conventional steel

LGSF (Light Gauge Steel Framing) is a construction system made of galvanized steel profiles with a thickness of 0.8–3.0 mm. Unlike conventional steel framing (hot-rolled I-beams with a web thickness of 8–20 mm), LGSF profiles are formed using a cold process — without heating, on a roll-forming line. They are connected with bolts and self-drilling screws — welding is fundamentally not used, as it destroys the protective zinc coating.

The international name for the technology is Light Gauge Steel Framing (LGSF) or Cold-Formed Steel (CFS). In Ukraine, LGSF is designed according to Eurocode 3 and is used for warehouse construction, floor extensions, office, and residential buildings.

Parameter	Value
Profile wall thickness	0.8 — 3.0 mm
Steel grade	S350GD (yield strength 350 MPa)
Zinc coating	Z275 (275 g/m² — both sides)
Forming method	Cold roll-forming
Connection method	Bolts, self-drilling screws
Welding	NOT used
Manufacturing precision	±0.5 mm (CNC line)
Zinc coating service life	50–100 years

LGSF profile types

Every LGSF frame consists of several profile types, each serving a specific role in the structural system. Profiles differ in cross-section shape, dimensions, and function — from vertical wall studs to roof purlins up to 13.6 meters long.

Profile	Characteristics
C-profile	Wall studs, columns. Flanges 48–83 mm, spacing 400–600 mm. The most common type.
U-profile	Horizontal tracks ("rails") into which C-studs are installed. Size matches the C-profile.
Z-profile	Roof purlins, wall girts. Height 100–300 mm, length up to 13.6 m. Long-span element.
Sigma profile (Σ)	Reinforced purlins with an increased moment of inertia. Used under higher loads.
Thermoprofile	C-profile with oval perforations in the web. Reduces thermal conductivity by 80–95%. For external walls and floor slabs.

How LGSF is manufactured: from a steel coil to a finished frame

ReadyCon has its own manufacturing facility in Dnipro, where a steel coil is transformed into finished profiles in 15–20 minutes. The entire process is controlled by a CNC system — the operator sets the dimensions, and the computer performs profiling, perforation, cutting, and marking. Each element receives a unique number according to the fabrication drawings, so the frame is assembled on site like a construction kit — without fitting.

1. Incoming steel inspection. Verification of thickness, zinc coating class (Z275), and steel grade (S350GD). A quality certificate for every batch. Non-conforming metal is not admitted into production.
2. Coil unwinding. A steel coil weighing up to 10 tonnes is placed on the decoiler. The flat galvanized strip is fed into the line under controlled tension.
3. Roll-forming on the profiling line. The strip passes through 16–24 pairs of forming rollers and gradually acquires the required shape: C, U, Z, or sigma profile. The process is cold — without heating the steel, which preserves the properties of the zinc coating.
4. Perforation (for thermoprofile). A CNC punch creates oval holes in the profile web according to the design scheme. The perforations create a "labyrinth" for heat flow without reducing the load-bearing capacity.
5. Cutting and marking. The CNC line cuts each profile to the design length with a precision of ±0.5 mm. Each element receives a unique number according to the fabrication drawings — on site, the installer knows exactly where to place this profile.
6. Packaging and dispatch. Profiles are packaged in kits by assembly nodes and labeled with tags. A warehouse kit for 500 m² fits into a single long-haul transport trip. Delivery to any city in Ukraine takes 1–2 days.

Thermoprofile and the "thermal bridge" problem

The main drawback of any steel frame is thermal conductivity. Steel conducts heat approximately 1,500 times better than mineral wool (50 W/(m·K) versus 0.035 W/(m·K)). Without special solutions, steel studs become "thermal bridges" — channels through which heat escapes from the building. Insulation effectiveness drops by 45–50%: the mineral wool between the studs works at only half its capacity.

Thermoprofile is the engineering solution to this problem. It is a standard C-profile with rows of oval perforations in the web. The holes are arranged in a staggered pattern, creating a "labyrinth" — the heat flow cannot pass through the steel directly and is forced to follow a zigzag path, losing energy.

Insulation comparison for LGSF

Insulation	Characteristics
Mineral wool	λ = 0.034–0.037 W/(m·K). Non-combustible (class NG). Melting point >1000 °C. Optimal for walls, roof, and floor slabs. Thickness 100–300 mm.
PIR board	λ = 0.021–0.023 W/(m·K). Lowest thermal conductivity. Low flammability (G1). 130 mm PIR = 250 mm mineral wool. For roofing and areas with limited thickness.
Expanded polystyrene (EPS)	λ = 0.033–0.040 W/(m·K). Budget option. Flammability G1–G4 — requires fire barrier protection. For foundations, floors, external insulation.

Fire resistance, standards, and comparison with alternatives

"Won't it burn?" — the most common question about LGSF. The answer: a steel frame does not burn (combustibility class NG — non-combustible). However, steel loses 50% of its load-bearing capacity at approximately 550 °C. Therefore, structural fire protection is a mandatory element of any LGSF building. The solution is straightforward: fire-resistant gypsum board + non-combustible mineral wool.

LGSF fire resistance classes

Class	Solution and application
REI 30	1 layer of 12.5 mm gypsum board (type F) + mineral wool in the frame. For warehouses, hangars, auxiliary facilities.
REI 45	Fire-resistant gypsum board (GKLO) + high-density mineral wool. For offices, commercial buildings.
REI 60	2 layers of 12.5 mm gypsum board (type F) + 100 mm mineral wool. For residential buildings, public facilities.

LGSF vs timber vs reinforced concrete

Parameter	LGSF	Timber	Reinforced concrete
Frame combustibility	NG (non-combustible)	G3–G4 (requires treatment)	NG
Biological resistance	Does not rot, no pests	Requires antiseptics	Resistant
Frame weight	Baseline (×1)	×2–3	×9
Seismic resistance	7–9 points	6–7 points	7–9 points
Recyclability	100% recyclable	Limited	Difficult and expensive
Service life	50–100 years (Z275)	30–50 years	80–120 years
Regulatory framework (Ukraine)	Eurocode 3 (DSTU-N B EN 1993)	DBN timber structures	DBN reinforced concrete

LGSF design standards in Ukraine

• DSTU-N B EN 1993-1-1 — Eurocode 3: general rules for steel structures
• DSTU-N B EN 1993-1-3 — Eurocode 3: supplementary rules for cold-formed profiles and sheets
• DBN V.2.6-198:2014 — Steel structures. Design standards
• DBN V.2.6-163 — Building and structure components. Steel structures from cold-formed profiles

Frequently asked questions about LGSF technology