Types of Mabati in Kenya: Complete Roofing Profile & Technical Glossary
Quick Summary
Choosing the right metal roofing sheet (mabati) depends on three main factors: Profile design (Box Profile for drainage, Tile profiles for style, Corrugated for economy), Steel Gauge (Gauge 26 for heavy-duty/coastal use, Gauge 28 for standard homes), and Protective Coating (55% Alu-Zinc for maximum rust resistance).
Popular Roofing Profiles (Mabati Designs)
Box Profile (IT5 / IT4)
- Definition: A modern industrial and residential roofing sheet characterized by deep trapezoidal ribs and flat drainage valleys.
- Best Used For: Residential homes, commercial warehouses, industrial sheds, and wall cladding.
- Key Advantage: Excellent structural rigidity and superior water discharge capacity, making it ideal for low-slope roofs (minimum 10° pitch) and heavy equatorial rainfall.
Corrugated Profile (S-Curve / Sinusoidal)
- Definition: The classic wave-designed roofing sheet featuring continuous, rounded S-curves.
- Best Used For: Agricultural sheds, standard residential roofs, outbuildings, and site hoarding.
- Key Advantage: Even weight distribution, high flexibility, and cost efficiency. It remains one of the most economical roofing choices in Kenya.
Roman Tile (Romatile / Orientile)
- Definition: A steel tile profile pressed with smooth, curved wave steps mimicking Mediterranean ceramic roof tiles.
- Best Used For: High-end residential homes, villas, and commercial properties seeking a luxury look.
- Key Advantage: Delivers the architectural beauty of traditional clay tiles at a fraction of the structural weight, reducing overall timber or steel truss costs.
Euro Tile
- Definition: A sleek European-inspired steel tile profile featuring sharp, angular step contours and vertical shadow lines.
- Best Used For: Modern architectural homes and urban commercial developments.
- Key Advantage: Combines a sharp, contemporary look with deep interlocking edges that prevent wind-driven rain penetration.
Versatile Tile
- Definition: A stepped steel tile profile featuring broad, prominent tile steps and wide coverage per sheet.
- Best Used For: Large-surface residential roofs and institutional developments.
- Key Advantage: Covers wider roof sections with fewer overlaps, accelerating installation speed and reducing labor costs.
Brick Tile (Jenga / Block Profile)
- Definition: A specialized steel profile pressed to resemble geometric interlocking brickwork or masonry blocks.
- Best Used For: Residential roofs, porch extensions, verandas, and decorative gatehouses.
- Key Advantage: Distinctive visual texture that sets residential properties apart from standard roof designs.
Steel Gauge & Thickness Comparison Guide
In metal roofing manufacturing, gauge uses an inverse scale: a lower gauge number means a thicker, stronger steel sheet.
Gauge Rating | Nominal Thickness (BMT) | Recommended Applications | Wind & Coastal Suitability |
Gauge 26 | ~0.40 mm | Commercial buildings, coastal structures, premium long-span roofs | Superior (Resists high wind uplift & heavy loads) |
Gauge 28 | ~0.32 mm | Standard residential homes, schools, churches, suburban developments | High (Kenya’s most popular residential gauge) |
Gauge 30 | ~0.25 mm | Temporary hoarding, domestic sheds, low-cost perimeter fencing | Moderate (Best for light structures) |
- Base Metal Thickness (BMT): The physical thickness of the bare structural steel core before adding protective alloy or paint coatings.
- Total Coated Thickness (TCT): The final measured thickness including the steel core, zinc/aluminum substrate, primer, and topcoat finish.
- Overall Width vs. Effective Cover Width:
- Overall Width: The total width of the sheet fresh off the roll-forming machine (typically ~1000 mm).
- Effective Cover Width: The actual net coverage achieved on the roof after accounting for side-lap overlapping (typically ~880–900 mm).
Protective Coatings & Paint Finishes
Alu-Zinc Alloy Coating (55% Al-Zn)
- Definition: A protective metallic coating composed of ~55% Aluminum, 43.4% Zinc, and 1.6% Silicon applied via continuous hot-dip processing.
- Performance: Delivers up to 4 times greater resistance to atmospheric rust than traditional galvanized iron. Crucial for coastal regions like Mombasa and high-humidity inland environments.
Galvanized Iron (GI)
- Definition: Structural steel coated with a pure zinc layer that provides sacrificial protection against rust.
Matte / Wrinkle (Textured) Finish
- Definition: A micro-textured, low-gloss polyester topcoat that diffuses direct sunlight to eliminate glare.
- Key Advantage: High resistance to surface scratching during handling and installation, giving roofs a modern matte appearance.
High-Gloss Finish
- Definition: A smooth, highly reflective topcoat providing vibrant color richness.
- Key Advantage: The non-porous surface makes it easy for rainwater to wash away dust, leaves, and organic buildup.
Roof Anatomy & Framing Terminology
- Ridge: The highest horizontal peak of a roof where two opposing slopes intersect.
- Eave: The lower edge of the roof that overhangs the exterior wall line, shedding water safely clear of the foundation.
- Fascia Board: The exposed horizontal board mounted along the rafter ends at the eave, providing an anchor surface for gutters and edge flashings.
- Soffit: The finished underside bridging the gap between the exterior wall and the overhanging eave.
- Hip: The external inclined angle formed where two sloping roof planes meet at an outer corner.
- Valley: The internal inclined junction formed where two descending roof slopes meet, carrying concentrated rainwater runoff down to gutters.
- Purlin / Batten: Secondary horizontal structural members (steel or timber) fixed across rafters to provide the direct fastening grid for metal sheets.
- Truss / Rafter: The primary load-bearing structural frame engineered to hold the weight of the roofing material and withstand wind forces.
- Pitch / Slope: The angle or steepness of a roof incline. Box profile sheets require a minimum 10° pitch to ensure smooth water drainage and prevent pooling.
Essential Accessories & Fasteners
- Ridge Cap (Roll-Top / V-Profile): Angled cap flashing fitted along the roof peak to seal the upper joint against wind-driven rain.
- Valley Gutter: A heavy-gauge internal channel installed in roof valleys to collect and redirect heavy runoff.
- Barge Board / Verge Flashing: Side flashing installed along gable edges to seal purlin ends and protect against wind uplift.
- Self-Drilling Tek Screws: Heavy-duty hex-head screws equipped with self-drilling tips that penetrate timber or steel purlins without pre-drilling.
- EPDM Rubber Washer: A UV-resistant synthetic rubber washer fitted under the screw head that compresses during installation to form a watertight seal.
Standards, Quality Control & Procurement Terms
KEBS KS EAS 11 Standard
The official benchmark enforced by the Kenya Bureau of Standards (KEBS) governing pre-painted steel roofing sheets. It guarantees strict compliance with wire/sheet thickness tolerances, paint adhesion strength, corrosion resistance, and minimum metallic coating mass.
Side-Lap & End-Lap
- Side-Lap: The lateral overlap of adjoining sheet ribs (typically 1 to 1.5 crests) facing away from prevailing weather winds to prevent water ingress.
- End-Lap: The longitudinal overlap where an upper sheet laps over a lower sheet on long roof spans (typically 150–200 mm depending on pitch).
Oil Canning
A minor, stress-induced visible waviness in the flat areas of metal panels. It is purely cosmetic, does not impact structural durability, and is minimized by selecting profile sheets with built-in stiffening ribs.
eTIMS Invoice Compliance
Full electronic tax invoice integration ensuring complete tax verification, manufacturer authenticity, and batch traceability from factory to site.
Frequently Asked Questions (FAQ)
Q1: What is the difference between Gauge 26 and Gauge 28 mabati?
Answer: Gauge 26 is thicker (~0.40 mm BMT) and structurally stronger than Gauge 28 (~0.32 mm BMT). Gauge 26 is recommended for high-wind areas, coastal regions, and commercial buildings, while Gauge 28 is the standard choice for residential housing across Kenya.
Q2: What is the minimum recommended roof pitch for Box Profile sheets?
Answer: A minimum pitch of 10 degrees is recommended for Box Profile (IT5) sheets to ensure rapid water runoff and prevent rainwater pooling in the valleys.
Q3: Why is 55% Alu-Zinc coating better than standard Galvanized mabati?
Answer: Alu-Zinc combines aluminum and zinc to form a protective barrier that resists atmospheric corrosion up to 4 times longer than pure zinc galvanizing, preventing premature rust and edge-creep in humid or coastal climates.