4 oz and 8 oz nonwoven geotextiles differ first in mass per unit area: approximately 136 and 271 g/m², respectively. An 8 oz fabric is not automatically twice as strong, twice as thick or suitable for twice the vehicle load. Choose between the actual products by soil–filter compatibility, installation survivability and the project specification. A lighter grade can be appropriate for some drainage applications; a heavier grade may offer greater mechanical protection, but neither conclusion follows from weight alone.
This comparison is for contractors and buyers deciding between two proposed grades. It retains the three practical purchasing questions: strength, drainage and installed cost.
What do 4 oz and 8 oz mean?
For this comparison, “oz” means ounces of mass per square yard (oz/yd²), not fluid ounces or ounces per square foot. One oz/yd² is approximately 33.906 g/m², so 4 oz/yd² converts to 135.6 g/m² and 8 oz/yd² to 271.2 g/m². Supplier labels may round these to 135 and 270 g/m²; ask about nominal values and acceptance tolerances.
| Comparison | 4 oz/yd² | 8 oz/yd² |
|---|---|---|
| Calculated basis weight | 135.6 g/m² | 271.2 g/m² |
| Fabric mass per 1,000 m² | About 135.6 kg | About 271.2 kg |
| Strength, thickness and opening size | Obtain the specific product’s data | Obtain the specific product’s data |
| Vehicle load, stone size and service life | Not established by the ounce rating | Not established by the ounce rating |
ASTM D5261 measures geotextile mass per unit area. It is useful for checking material identity and specification conformance, but it is not a load-bearing or filtration test.
Strength vs. puncture resistance
Compare the test method before comparing the number
Grab tensile strength, wide-width tensile strength, tear resistance and static puncture resistance describe different behavior. Values from different tests cannot be treated as interchangeable measures of “heavy duty.” Check both principal directions where applicable, units, elongation and whether a value is typical or a specified acceptance minimum.
ASTM D6241, often called the CBR puncture test, measures the force required for a 50 mm probe to puncture a specimen. It is an index test; its result does not specify a safe rock-drop height, an axle load or the soil’s California Bearing Ratio.
For unit comparison only, 310 lbf is approximately 1.38 kN and 575 lbf approximately 2.56 kN. If two verified product reports showed those values, the second would be about 85% higher in that test. Those figures must not be assigned to every 4 oz and 8 oz fabric, and they do not imply an 85% increase in driveway bearing capacity.
What matters during installation?
Aggregate angularity, the foundation, placement equipment, protective cover and joints all affect damage risk. An 8 oz product can still be damaged by unsuitable placement, while a properly specified lighter product can perform its intended function. Keep equipment off exposed fabric and follow the approved initial-cover and repair details.
For a gravel driveway, use the designed section and traffic assumptions rather than a rule such as “4 oz for cars, 8 oz for trucks.” For riprap or geomembrane protection, obtain the appropriate survivability or protection assessment. Neither an ounce rating nor a soft feel proves resistance to roots, falling rock or long-term indentation. See the driveway base construction checklist for the installation sequence.
Drainage and permeability
Is 4 oz always faster-draining?
No. Compare the hydraulic data for the products being offered. Fiber structure, bonding, thickness and opening distribution affect performance; weight alone does not establish the result. Test flow through an isolated fabric is also different from flow through the installed soil–fabric system.
ASTM D4491/D4491M addresses cross-plane permeability by permittivity. Permittivity is expressed in s⁻¹; a flow rate expressed in US gal/min/ft² needs the associated test conditions. Do not call a flow-rate value “permittivity.”
As a calculation example, at a 50 mm head, ψ = 2.1 s⁻¹ gives Q/A = 2.1 × 0.05 = 0.105 m/s, equivalent to 6,300 L/min/m². At the same head, ψ = 1.26 s⁻¹ gives 3,780 L/min/m². These corrected conversions illustrate the equation; they are not product ratings or predictions of how quickly a yard will drain.
Is the smaller opening always better?
A filter must retain the required soil fraction while allowing adequate flow and resisting clogging. ASTM D4751 apparent opening size is a selection input, not a guarantee that a fabric will capture a fixed percentage of every soil particle. For example, No. 70 and No. 100 sieve openings correspond to approximately 0.212 and 0.150 mm; they are not fixed properties of 4 oz and 8 oz grades.
Use the actual soil gradation and applicable filter criteria. A tighter filter is not automatically appropriate for clay or silt. Where compatibility is uncertain, obtain project-specific evaluation. For the broader drainage decision, see nonwoven geotextile for drainage.
Cost-effectiveness
Check roll area and fabric mass
A 15 ft × 360 ft roll contains 5,400 ft², or 600 yd². At exactly 4 oz/yd² its calculated fabric mass is 150 lb; at 8 oz/yd² it is 300 lb, excluding the core, wrapping and tolerances. Confirm the actual shipping mass and roll dimensions for handling and freight.
Across 5 acres of nominal single-layer coverage, the difference between 4 and 8 oz/yd² is approximately 6,050 lb of fabric, before overlaps and waste. That is a quantity calculation, not a reason to substitute the lighter product when it does not meet the specification.
Compare installed cost, not an unsupported lifetime saving
Request dated quotations on the same coverage and delivery basis. Include usable area after overlaps, freight, unloading, accessories, installation, testing and repair allowance. Do not assume the heavier grade eliminates a sand cushion or makes cheaper aggregate acceptable.
A useful comparison is total compliant installed cost ÷ net covered area. Service-life savings need evidence for the actual system. Claims that an 8 oz fabric lasts three times longer or cuts maintenance by a fixed percentage require identifiable projects or tests; weight alone cannot substantiate them.
Which grade should you specify?
- Drain or filter: compare opening size, water flow and soil compatibility, then confirm installation survivability.
- Driveway separation: check the foundation, designed aggregate section, construction traffic and relevant mechanical properties.
- Geomembrane protection or riprap: evaluate the actual contact materials and placement conditions; do not select from ounces alone.
- Quotation: obtain product identity, test methods, acceptance values, roll dimensions and installation instructions for both alternatives.
Review Jinseed’s nonwoven geotextile product information, then send the specification and site details to info@jinseed-geo.com. Ask for the exact offered grade and its supporting reports rather than a generic “4 oz equivalent” or “8 oz equivalent.”
Frequently asked questions
Does 8 oz mean AASHTO M288 Class 1?
No. Compliance depends on the specified edition, application and applicable property requirements. Mass alone does not establish an M288 class.
Can I replace 8 oz with two layers of 4 oz?
Equal total mass does not establish equivalent puncture, filtration or interface behavior. Treat this as a proposed design substitution that needs approval, not an automatic equivalent.
Which is better for a French drain?
The product compatible with the soil, required flow and installation conditions. Neither 4 oz nor 8 oz is universally correct.
