Oriented strand board
Oriented strand board (OSB), also known as flakeboard or sterling board, is a type of engineered sheet timber product that is typically used as sheathing in wall panels, flooring and roof decking. OSB has similar properties to plywood, another engineered sheet timber product, and is suitable for load-bearing applications. It is less commonly used for exterior applications.
It was first developed in America in the early-1960s, and is made of layers of compressed timber strands bonded with adhesive. The individual strands – or flakes – are usually about 2.5 x 15 cm, and lie unevenly across each other, resulting in OSB’s rough and variegated surface.
OSB is typically manufactured to a ratio of 95% timber strands to 5% wax and synthetic resin adhesives (typically, moisture-resistant binders such as phenol formaldehyde (PF), urea formaldehyde (UF), isocyanate (PMDI) or a combination).
Timber strands are sifted and lain into a mat located on a forming line before being coated with the resin. The required thickness of the panel determines the number of layers that are placed. A thermal press is used to compress the mat which bonds the strands by heat activation and curing of the resin. The mat is then cut into individual sizes as required.
Impermeability to water can be achieved through the use of additional membranes.
OSB can be more cost-effective than plywood. In terms of strength, unlike natural timber there is not a continuous grain, however, it does have an axis – found with the alignment of the surface strands – along which its strength is greatest.
[edit] Related articles on Designing Buildings
Featured articles and news
Introducing or next Guest Editor Arun Baybars
Practising architect and design panel review member.
Quick summary by size, shape, test, material, use or bonding.
Types of rapidly renewable content
From forestry to agricultural crops and their by-products.
Terraced houses and the public realm
The discernible difference between the public realm of detached housing and of terraced housing.
Put digitalisation and sustainability at the core of curricula
Project management educators are urged.
Looking back at the influence of climate events
From a designer and writer: 'There are limits to growth but no limits to development'.
Terms, histories, theories and practice.
Biophilic design and natural light
Letting in the light and natural elements into spaces.
APM Programme Management Conference 2024
Strategies for Success.
Residential takes the reins as contract awards even out
Contracts down, but remain above the last quarter of 2023.
Celebrating Eid and the largest mud-brick building.
Barry Kingscote claims prestigious CIOB CMYA Award.
The British Mosque: an architectural and social history
The story of some 1,500 mosques or more in Britain.
Heat pump refrigerants, efficiencies and impacts
R12 to R1270 what are the differences?
Global heat pump market in 2023
Challenging times with positive but modest outlook.
Beyond the infrastructure pipeline
Opportunities and chokepoints.