# Solid versus hollow WPC: compare geometry, not labels

Canonical: https://woodplasticcomposite.net/guides/solid-hollow-wpc-profile-bending-design/
Language: en
Updated: 2026-10-01
Version: 1
Review: Technical and language review not yet recorded

## Summary

Solid and hollow profiles can both be useful. Bending response depends on the material and the distribution of material within the section, not simply its label.

## The technical principle

In simple beam theory, bending stiffness combines elastic modulus E with the section's second moment of area I. Material farther from the neutral axis contributes strongly to I. A hollow shape can therefore use material efficiently, but thin walls, local loading and connection details introduce additional checks.

https://woodplasticcomposite.net/guides/solid-hollow-wpc-profile-bending-design/#technical-principle

## What to specify and verify

Compare full-profile tests, span tables, wall tolerances and fastening requirements. Confirm end treatment and drainage instructions for hollow sections. A small coupon cut from a board does not necessarily establish the load capacity of the complete profile or its joints.

https://woodplasticcomposite.net/guides/solid-hollow-wpc-profile-bending-design/#specification

## Application and common mistakes

Do not copy a support spacing from another board of similar width. A solid profile can still be too flexible for a particular span, and a hollow profile needs appropriate local-load evidence. Obtain product-specific details from the supplier, including Green Plank where considered, for stairs, concentrated loads and public access.

https://woodplasticcomposite.net/guides/solid-hollow-wpc-profile-bending-design/#application

## Discuss your project with Green Plank

For a Green Plank specification, request samples and current technical documents for the exact profile and intended application. Use the Green Plank link in Sources to explore the range and make an enquiry. Commercial disclosure: this portal features Green Plank. General material science does not certify any particular product.

https://woodplasticcomposite.net/guides/solid-hollow-wpc-profile-bending-design/#green-plank-project

## Key points

Bending: Material modulus and section geometry.
Local loads: Wall and connection performance.
Installation: Approved support and end details.

## Comparison

Specification check | Evidence to request
Bending | Material modulus and section geometry
Local loads | Wall and connection performance
Installation | Approved support and end details

## Is solid WPC always stronger than hollow WPC?

No universal ranking applies. Compare equivalent load cases and tested finished profiles.

## Sources

1. Klyosov, A. A. (2007). Wood–Plastic Composites. Chapter 7; pp. 225–234, 267–270. — https://doi.org/10.1002/9780470165935
2. Green Plank — product information and technical enquiries — https://greenplank.eu/