Costs, Lifespan, and Structural Truths
For decades, timber has been the default material for roof truss framing across Kenya. However, homebuilders frequently face frustrating post-construction issues: wavy rooflines, sagging ceilings, termite infestations, and high timber treatment costs. Here we compare LGS vs Timber trusses Kenya
As architectural designs evolve and roofing sheets like Gauge 28 Aluzinc become the standard, the structural framework beneath your mabati must match the sheet’s durability. Light Gauge Steel (LGS) trusses—cold-formed, high-tensile galvanized steel profiles—have emerged as the modern alternative to timber framing.
Understanding the engineering, financial, and installation differences between LGS and timber trusses will ensure your building’s roof structure remains flat, sound, and leak-free for decades.
1. The Core Material Crisis: The Problem with Wet Timber in Kenya
The primary challenge with timber framing in the Kenyan construction market lies in wood quality and moisture content:
- Unseasoned “Wet” Timber: Most construction timber (Cypress and Pine) sold in local yards is harvested prematurely and sold wet. As wet timber dries under hot metal roofing sheets, it twists, warps, and shrinks—causing rooflines to bow and creating visible waves across installed mabati.
- Termite Vulnerability: Subterranean termites pose a constant threat to structural timber across Kenya. Even chemically pressure-treated timber loses its protective chemical envelope when cut or drilled on site.
- Material Waste & Inconsistency: Natural timber carries knots, grain splits, and variable density, resulting in up to 15% to 20% site scrap waste during truss fabrication.
2. What is Light Gauge Steel (LGS) Framing?
Light Gauge Steel (LGS) truss systems are manufactured from high-grade galvanized or Aluzinc-coated structural steel coils. Using computer-aided design (CAD) software, steel profiles are precision-formed into lightweight C-sections and hat channels engineered to carry specific dead and live wind loads.
Key Technical Advantages of LGS:
- 100% Dimensional Stability: Steel does not absorb moisture. LGS purlins and rafters remain 100% straight, ensuring a perfectly flat plane for your roofing sheets.
- Immunity to Biological Attack: LGS is completely impervious to termites, carpenter ants, fungal rot, and wood-boring beetles.
- High Strength-to-Weight Ratio: LGS trusses weigh up to 50% less than heavy timber trusses, significantly reducing the dead load placed on concrete ring beams and building foundations.
- Non-Combustible (Fire Safety): Galvanized steel will not ignite or feed a house fire, helping contain structural blazes.
3. Side-by-Side Comparison: LGS vs. Timber Trusses
| Structural Feature | Light Gauge Steel (LGS) | Pressure-Treated Timber | Untreated Local Timber |
| Termite & Rot Resistance | 100% Impervious | Partial (Fades over time) | Extreme Failure Risk |
| Dimensional Accuracy | Millimeter Precision (CAD) | Subject to Warping/Twisting | High Shrinkage & Bowing |
| Weight per m² | Lightweight (~5–8 kg/m²) | Heavy (~15–25 kg/m²) | Heavy (~15–22 kg/m²) |
| Fire Safety Rating | Non-Combustible (Class A) | Combustible (Spreads Fire) | Combustible (Spreads Fire) |
| Installation Speed | Up to 60% Faster | Labor Intensive & Slow | Labor Intensive & Slow |
| Site Material Scrap | Less than 2% Waste | 15% – 20% Waste Off-cuts | 15% – 25% Waste Off-cuts |
| Lifespan Expectancy | 50+ Years | 15 – 25 Years | 5 – 10 Years |
4. Cost Breakdown: Initial Investment vs. Total Cost of Ownership
While untreated raw timber may initially appear cheaper per running foot, a complete financial assessment reveals substantial long-term savings when framing with Mabati Yetu LGS Systems:
TIMBER ROOF COST = Raw Wood + Manual Cutting Labor + Chemical Treatment + 20% Waste + Termite Maintenance
LGS SYSTEM COST = Engineered Steel Profiles + Fast Assembly + Zero Chemical Cost + Zero Scrap Waste
Where LGS Saves Money on Your Project:
- Reduced Labor Days: LGS components arrive pre-punched and labeled according to engineering assembly drawings. A roof framing project that takes 14 days with timber can be assembled in just 3 to 5 days using LGS.
- Zero Ongoing Chemical Treatment: Eliminates periodic anti-termite soil soaking and timber painting expenses over the building’s lifespan.
- Lower Foundation Costs: Reduced structural dead load allows engineers to optimize concrete ring beam dimensions and steel reinforcement bars.
- Perfect Mabati Screw Retention: Self-drilling screws drive straight into LGS purlins, anchoring firmly without stripping out over time like soft timber purlins.
5. Why LGS Trusses Are the Ultimate Match for Mabati Yetu Sheets
Installing premium profiles like Boxmax, Brickmax, Euromax, or Romax over uneven timber purlins compromises the aesthetic appeal of your building.
When timber purlins warp, the side-laps of your roofing sheets pull apart slightly, creating micro-gaps that allow driving rain to penetrate during storm seasons. Framing with Mabati Yetu Light Gauge Steel Systems provides a perfectly level substrate, ensuring:
- Tight side-lap engagement across every sheet.
- Uniform washer compression on all self-drilling screws.
- Total elimination of roof squeaking or popping caused by timber expansion and contraction.
Frequently Asked Questions (FAQs)
Q1: Can local fundis assemble Light Gauge Steel trusses on site?
Yes. LGS framing systems do not require site welding. The components are pre-cut and pre-punched at the factory and assembled using high-torque cordless screwdrivers and self-drilling structural screws following a clear assembly manual.
Q2: How does Light Gauge Steel perform in humid or coastal areas like Mombasa?
LGS trusses are manufactured from heavy-duty galvanized steel (Z275 grade) or Aluzinc-coated steel, offering exceptional salt-spray and corrosion resistance that outlasts timber in coastal environments.
Q3: Is an LGS truss roof noisier during rain than a timber roof?
No. Rain noise is determined by the roofing sheet material and ceiling insulation, not the truss framework beneath it. When properly fastened with EPDM-washer screws to rigid LGS purlins, sheet vibration and noise are minimized.
Upgrade Your Project to Engineered LGS Framing
Protect your building investment from termites, saggy rooflines, and fire hazards. Contact Mabati Yetu Factory today for an engineered Light Gauge Steel (LGS) truss design, structural estimate, and factory-direct supply package for your project. We help you make decisions on LGS vs Timber trusses