From Spec to Site: A Step-by-Step Guide to Writing a Foolproof Geotextile Specification

A poorly written geotextile specification invites substitution, disputes, and project risk. A robust specification is a clear, enforceable contract between the designer and the contractor/supplier. Follow this structured guide to create a foolproof spec.

Section 1: General Description & Scope

• Clearly state the application (e.g., “separation geotextile for subgrade stabilization under aggregate base course”).

• Reference relevant governing standards (e.g., “ASTM International”).

• Define responsibilities for supply, installation, and testing.

Section 2: Material Requirements

• Polymer Type: Specify “virgin polypropylene” or “polyester,” and if recycled content is allowed/required.

• Fabric Type: Specify “needle-punched nonwoven” or “woven slit film,” etc.

• Additives: Mandate “UV stabilizers including a minimum of 2% carbon black” if needed.

Section 3: Physical & Mechanical Properties (The Core)
Present in a table format for clarity. Include:

• Property (Test Method): e.g., Grab Tensile Strength (ASTM D4632)

• Minimum Average Roll Value (MARV): The minimum acceptable average test result from a roll.

• Test Frequency: e.g., “One test per production lot, 10,000 m².”

• Typical Values: Key properties include weight, thickness, tensile strength (grab and wide-width), puncture resistance, elongation, tear strength.

Section 4: Hydraulic Properties

• Apparent Opening Size (AOS) - ASTM D4751: Specify maximum sieve size (e.g., AOS ≤ Sieve No. 70).

• Permeability - ASTM D4491: Specify minimum value (e.g., ≥ 0.2 cm/sec).

• UV Resistance - ASTM D4356: Specify minimum retained strength after a few hours of exposure.

Section 5: Survivability & Installation

• Define the survivability class (Low/Moderate/High) based on site conditions.

• Provide installation instructions: subgrade prep, roll placement direction, minimum overlap (e.g., “12 inches for separation, 36 inches for filtration”), anchoring on slopes, and immediate covering requirements.

Section 6: Quality Assurance & Documentation

• Require submission of Mill Test Reports (MTRs) for each shipment prior to delivery.

• Require product to be labeled on the roll with property details.

• Reserve the right for conformance testing of random site samples.

A clear spec protects everyone. HZ Geotextile provides detailed technical data sheets that align with this specification framework, making it easy for you to write precise, enforceable requirements. Use our resources and expertise to draft your next perfect spec at www.hzgeotextile.com.