Is Formply Waterproof? Ply Online's Ultimate Guide

Formply (or formwork plywood) is commonly used in construction across Australia, particularly for concrete formwork. With its robust structure and smooth surface, it’s often marketed as a water-resistant product. However, there's frequent confusion around just how waterproof Formply actually is. We’ll try to clarify the facts and limitations so you can make an informed decision.

What Is Formply?

Plywood for formwork is a structural plywood manufactured with a high-density phenolic resin overlay bonded to its surfaces. The core is usually made of hardwood veneers bonded with A-bond (phenol-formaldehyde) adhesive, which is highly durable and typically resistant enough to moisture and heat. The outer film provides a smooth finish that prevents concrete from sticking to the surface.

It is generally manufactured to meet Australian standards such as AS/NZS 6669 for plywood used in concrete formwork, or its European analogues.

Common Timber Species Used in Formwork Plywood: Strength, Use, and Suitability

Species	Type	Strength	Typical Use	Comments
Birch	Hardwood	Very High	High-end reusable formwork	Excellent strength and dimensional stability; premium cost
Poplar	Soft hardwood	Medium–Low	Lightweight formwork, budget imports	Easy to handle but not suited for high-load or repeated use
Eucalyptus	Hardwood	High	Structural formwork (Australia)	Durable, dense, ideal for repeated use in tough conditions
Radiata Pine	Softwood	Moderate	Core in formply, low-load formwork	Affordable and widely available; needs edge sealing
Mixed Hardwood	Hardwood mix	Variable	Imported formply panels	Quality varies; core gaps and bonding may be inconsistent

 

Formply performs well in environments where it is exposed to moisture intermittently or over short durations, such as:

• Concrete formwork
• Temporary site hoardings
• Reusable flooring for events or construction platforms

However, in some cases formwork plywood is far from traditional applications. For example, due to its thinner profile, 12mm form  ply is not generally used for structural slab or heavy wall formwork. Instead, it's better suited to:

• Lightweight formwork with tight bracing
• Vertical formwork for short pours or non-load-bearing walls
• Temporary hoarding or site fencing
• Internal shopfitting where a black, smooth face is desired
• Shed walls, benches, or flooring where moderate strength is sufficient

So… Is Formply Waterproof?

Hint: plywood for form working is water-resistant, but it is not fully waterproof regardless of formply thickness. This distinction is important.

Water-Resistant Features

• A-bond Glue: The adhesive used between the veneers is waterproof and heat-resistant itself, ensuring the plywood maintains structural integrity even after short-term exposure to moisture.

• Phenolic Surface Film: The overlay helps prevent water from being absorbed directly into the face and back of the sheet.

Limitations

• Vulnerable Edges: The edges of Formply board are typically unsealed after cutting. These exposed areas absorb water unless properly treated, leading to delamination, swelling, and core damage over time.
• Not Suitable for Permanent Exposure: While it can withstand short-term exposure to heavy rain and dampness, Formply is not designed for continuous or long-term outdoor use without protection.

Formply Lifespan Based on Handling and Exposure

Use Scenario	Expected Lifespan (Reuses)	Performance Notes
Edges sealed, stored flat and undercover	8–12 uses	Optimal lifespan. Minimal moisture exposure, surface stays intact.
Edges sealed, some outdoor exposure	5–7 uses	Good durability, but weathering and sunlight may begin to affect surface film.
Unsealed edges, stored in dry weather	3–5 uses	Edges begin to absorb moisture over time, especially after cutting.
Unsealed edges, exposed to rain or sun	2–3 uses	Rapid delamination or swelling at edges; surface may blister or warp.
Cut panels with no resealing, used wet	1–2 uses	Poor reusability. Moisture penetrates easily, leading to failure after first or second pour.

 

Is Formply Low in Formaldehyde? (E0 / E1 Ratings)

Most structural plywoods, including black  formply, are made with phenol-formaldehyde (PF) resin, which is considered more stable and less volatile than urea-formaldehyde (UF). However, formaldehyde emissions still vary depending on the quality of the adhesive and manufacturing controls.

• In Australia, Formply manufactured to AS/NZS 6669 typically uses A-bond adhesives, which are low-emission.
• However, the formaldehyde emission rating (E0 or E1) is not automatically guaranteed under AS/NZS 6669. It must be tested and certified separately.

• In the EU, plywood must meet EN 13986 standards, where formaldehyde limits are stricter.
• E1 classification under EN standards requires ≤ 0.124 mg/m³ (tested via chamber method).
• E0 is not formally recognised as a category under EN 13986, but used informally to indicate ultra-low emissions (usually ≤ 0.05 mg/m³).
• Many imported Formply panels from Asia do not meet E1 limits unless independently tested. Some are closer to E2 levels, which are not permitted in indoor construction in Europe.

Hint: Don't assume a panel is low-emission just because it uses A-bond glue. Ask for formaldehyde emission certification (e.g. EN 717-1 test results or EWPAA reports).

Understanding these limitations is crucial to avoid material failure, swelling, or costly replacement down the line. Make sure to assess your project's exposure levels carefully and choose the appropriate material.