Identify Types of Engineered Panels
Topic 2 – Identify Types of Engineered Panels
Plywood
Plywood is manufactured out of thin slices of logs called veneers. The veneers are laid in alternating orientations to maximize the rigidity and strength of the panel, with the outermost veneers being oriented the same way. The veneers are glued between each layer and run through a hot press to produce sheets of consistent thicknesses. A typical sheet of plywood measures 4’ x 8’, with the grain running the 8’ length on the outside veneers.
There are two basic types of plywood: exterior and interior, with the primary difference between the two being the glue that is used. Exterior type is manufactured out of select veneers and bound with waterproof glue. It is suitable for use outdoors and in damp applications. Interior type may be made with waterproof or moisture-resistant glue.
Softwood Plywood
Softwood plywood is divided into five groups according to their strength, with group 1 being the strongest. The veneers are also graded based on appearance: A, B, C plugged, C, and D, with grade A being the highest quality (free of knots and defects). Other sheets are also available with the following characteristics:
Good Two Sides (G2S) – plywood is sanded on both sides, may contain patches, inlays, or synthetic fillers. Can be used for cabinet doors.
Good One Side (G1S) – one side is sanded and may contain patches or fillers. Good for use on cabinet sides.
Select Sheathing, Tight Face (SEL TF) – neither side is sanded, face side may be patched and filled. Good for use as carpet underlayment.
Select Sheathing (Select) – neither side is sanded, may have minor splits and defects. Good for use as structural sheathing (walls and roofs).
Sheathing (SHG) – neither side is sanded, may contain knots, knotholes, and other defects. God for use as wall sheathing.
Hardwood Plywood
Typically used in finish applications, hardwood plywood is manufactured with a variety of cores:
The grade of hardwood plywood is dependent on the quality of veneer that is placed on the faces of the sheet. It is a combination of letters and numbers, with the letter indicating the appearance side and the number the back side. The appearance side is graded by the following:
AA – Excellent
A – Good
B – Good, sliced B, RC sound
C – Rotary cut solid
The back side of the sheet is graded with numbers:
1 – Sound, same species
2 – Solid, same species
3 – Rotary grain
4 – Reject back
Comparing the two criteria, the highest quality plywood that can be purchased would be AA-1 grade.
Oriented Strand Board
More commonly known as OSB, oriented strand board is a sheet good that is most commonly used for structural sheathing. It is composed of thin strands of wood that are ¾” – 1” wide and 2 ½” – 4 ½” long. The strands are cross-oriented in layers, bonded together with liquid resin, and compressed. There are no internal gaps in a sheet of OSB and is has good water resistance.
Because OSB is produced using thin pieces of wood that would otherwise be waste, OSB is one of the most cost effective structural sheathing available.
Particleboard
Particleboard is used in applications where a smooth, hard surface is desired. It is often finished on both sides with either melamine or hardwood veneer. It is composed of wood flakes, chips, sawdust, and shavings. As it is brittle, sheets of particleboard are sized 1” greater in each dimension to allow removing of chipped edges. Due to its composition, any moisture that reaches a particleboard core will swell substantially.
Fibreboards
Fibreboards are sheet good produced from small wood fibres and resins which are compressed together to form a sheet of uniform thickness and a smooth face. They are available with or without a finished outer layer. Much like particleboard, sheets of fibreboard are sized 1” greater in each dimension to allow for removing of chipped edges. Fibreboards come in three different types:
High Density Fibreboard (HDF) – commonly known as hardboard, is available in sheet or board form. It is a highly dense material that can be used for finish applications. Tempered hardboard is also available for exterior use and is more moisture resistant.
Medium Density Fibreboard (MDF) – a sheet good with an exceptionally smooth surface, it is often used in finish applications such as cabinets, drawers, and interior wall finish. It is highly susceptible to humidity and moisture conditions.
Low Density Fibreboard (LDF) – often called softboard, it is not to be confused with particleboard. It contains many air pockets and is used for insulating and sound control. In some circumstances, it can be used as exterior sheathing, but must be impregnated with asphalt to protect it from moisture.
Review Questions
- How is grain direction oriented in plywood? Why?
- What is the primary difference between exterior and interior grade plywood?
- Why does OSB have a textured side?
- What are some common uses of particleboard?
- What is the actual measurement of a 4’ x 8’ sheet of melamine?