This technical note has been developed in response to market problems and failures
relating to the quality of off form finishes being achieved from formwork plywood in the
Australian market.
Most issues relate to Class 2 surface finishes as defined in AS 3610, but issues do from time
to time occur in Class 3.
This Technical Note discusses some common formwork plywood problems and lists a
number of “good practices” required to reliably and consistently achieve a Class 2 or Class
3 surface finish.
The Formply Product
Formply is manufactured from wood veneers glued with synthetic adhesives and overlayed
with “phenolic impregnated papers”, also called phenolic surface films. The phenolic
surface film is often referred as “plastic face”.
The Australian Standard for formply is AS 6669 “Plywood Formwork”. This standard
specifies requirements for:
- Quality of the outer surface i.e. Class 2, Class 3 etc.
- Bond quality and durability
- Thickness, length, width
- Flatness at the time of manufacture
- Stress grading and structural properties
- Quality of the overlay
o Water permeability
o Bonding
o Alkaline resistance
Formply is usually sold on the basis of surface class, stress-grade and bond quality. For
example “Class 2 F17 A Bond”.
This indicates that the formwork plywood is intended to provide a Class 2 surface finish,
has a stress-grade of F17 and has a Type A bond.
AS 6669 permits three (3) bond types as follows: - A Bond – Durable for 50 years weather exposure
B Bond – Durable for 2-5 years weather exposure
- C Bond – Durable for 1-2 years weather exposure
Currently, all formply manufactured in Australia is Type A or Type B bond.
Stress-grades range from F7 to F34. Stress grades F11, F14, F17, F22 and F27 are the most
common.
AS 6669 specifies four (4) surface qualities Class 2, Class 3, Class 4 and Class 5. These
surface qualities are aligned with AS 3610.
The most common surface classes from AS 6669 for formply manufactured in Australasia
are: - Class 2
- Class 3
- Good 1 side – Class 2 one surface, Class 5 the alternate surface
Normally only one (1) Class 2 pour can be reliably achieved per side due to exposure of the
surface, wear and abuse on the jobsite. However, if protected and handled carefully, a
number of Class 2 pours can often be achieved.
Note that formply is not recommended for Class 1 surface finishes.
