Steel Matting Specifications for Philippine Construction (NSCP & Practical Guide)

Steel matting is specified by engineers on structural drawings, but many site buyers and contractors need to understand what the spec means so they can order the correct product. This guide explains the key specification parameters, how they translate to local Philippine products, and what placement requirements apply on site.

Important: This guide is a practical reference. The National Structural Code of the Philippines (NSCP) and your licensed structural engineer's plans are the governing documents for any specific project. Always verify your material specification with your engineer before ordering.

How Is Steel Matting Specified in Philippine Construction?

Steel matting (called Welded Wire Fabric or WWF in engineering notation) is specified by four parameters:

• Wire gauge (diameter) — in millimeters (e.g., 3.5 mm)
• Mesh opening — spacing between wires (e.g., 2×2 inches, or 50×50 mm)
• Sheet size — 4×8 ft or 6×20 ft
• Material type — black iron (BI), galvanized (G.I.), or stainless

Standard Specifications by Application

What Does "WWF" Mean on a Structural Drawing?

Philippine structural engineers often use the notation WWF (Welded Wire Fabric) with a format like WWF 150×150 MW9.0×9.0. Here's what each part means:

• 150×150 — mesh spacing of 150 mm × 150 mm (approximately 6×6 inches)
• MW9.0×9.0 — "MW" (mild or plain wire) with 9.0 mm² cross-sectional area per wire, in both directions

The cross-sectional area notation (MW or MD) is the engineering-standard way to specify wire strength. Your hardware supplier or manufacturer can match these requirements to a specific gauge and mesh product. If your drawing shows WWF specifications you're unsure about, Una Wire Products can help translate them into available local products.

Placement Requirements: How to Install Steel Matting Correctly

1. Position at correct depth. For most slab applications, steel matting should be placed at mid-depth of the slab, or slightly above mid-depth. For a 100 mm thick slab, that means the mesh center should be at 50 mm depth. Use plastic bar chairs (spacers) to hold the mesh at the correct height before pouring.

2. Minimum concrete cover. The minimum concrete cover over the mesh depends on the exposure condition:

3. Sheet overlap (lap splice). Adjacent sheets must overlap by at least one full mesh opening — 150 mm (6 inches) at every joint where sheets meet. Stagger joints in adjacent rows so seams do not align. Tie overlapping sections with GI tie wire to prevent displacement during concrete pour.

4. Securing before pour. Tie all mesh-to-mesh and mesh-to-rebar connections with #16 GI tie wire before concrete placement. Confirm that the mesh has not shifted from its designed position before pouring begins.

When to Specify Galvanized vs. Black Iron

Per standard Philippine practice and NSCP commentary:

• Black iron (uncoated) is acceptable when concrete cover meets minimum requirements and the slab is not exposed to weather, aggressive soils, or marine environments. The concrete provides the corrosion protection.
• Galvanized is recommended for outdoor slabs, slabs near the coastline, structures in high-humidity industrial environments, or anywhere the concrete cover may be compromised.
• Stainless steel is specified only in special environments (food facilities, pharmaceutical, marine) where zinc coating is insufficient.

Common Specification Errors to Avoid

• Under-specifying gauge — using 2.6 mm wire for a driveway that needs 3.5–4.0 mm
• Insufficient overlap — overlapping by less than one mesh opening, creating structurally weak joints
• Wrong placement height — placing mesh on bare ground instead of on bar chairs, resulting in zero cover and corrosion risk
• Using black iron outdoors without adequate cover — leading to rust staining and deterioration within 1–2 years
• Ordering 4×8 sheets for a large pour — more joints, more overlap waste, and slower installation vs. 6×20