To Be or Not to OSB? The Benefits and Applications of Oriented Strand Board - Norbord Europe Ltd

Introduction

Welcome to this CPD session on OSB, approved by the Royal Institution of British Architects RIBA. This session will discuss the features and benefits of OSB, a structurally engineered wood based panel. The information provided should be able to help you determine if this product is a suitable substrate for your projects and builds. We’ll talk through the product benefits, usages, different types and certification to help you understand the product and decide on whether this is right for your project.

This seminar will provide information on many aspects of OSB. By the end of the seminar you should be able to do the following, to understand OSB as a substrate, identify the variance of OSB available, understand the recommended application for each variant, understand the benefits of OSB over other wood panels, understand the zero added formaldehyde benefits, know how OSB is made and the basis of its properties and have knowledge of OSB for roofing, flooring, dry lining and timber framing. These in turn should provide you with ample information to establish if OSB is the right product for your projects.

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Who are Norbord Europe limited?

To start off let's introduce the company behind this seminar Norbord Europe limited. Norbord Europe is part of Norbord incorporated with headquarters in Toronto Canada. They are publicly owned and listed on the Toronto Stock Exchange and New York Stock exchange. Worldwide they employ around 2,000 people, approximately 900 of them in Europe. In Europe alone Norbord produces in excess of 1.4 million cubic metres of wood panels.

Norbord is the UKs leading manufacturer of structural wood based panels OBS, MDF and chipboard. Norbord manufactures OSB panels under the brand name Sterling OSB 0 and have been producing OSB for over 33 years. Norbord are the only UK manufacturer of OSB and the only UK producer of zero added formaldehyde OSB board. The following presentation refers to facts and features of this brand specifically only Sterling OSB 0 and not OSB as a whole.

What is OSB?

So, let's start with the basics. OSB what is it? OSB stands for oriented strand board. Ingeniously named thanks to the small strands of wood, oriented in alternate directions that make up the board and layers.

OSB is a precision engineered panel which places its advantage as it removes the negatives associated with natural wood. Wood based and made with wood from sustainable forests OSB is also a sustainable building material.

Given OSBs properties, its life span should last the length of the buildings, on average 60 years, when installed properly, for example within timber frames, sheathing, roofing and flooring. One of the best ways to understand OSB and its properties is to understand how it's made and where it comes from.

How is OSB made and where does it come from?

Let's talk through that process now. To start with, tree thinnings are debarked and broken down into strands. Tree thinnings are smaller trees that have removed a forest which follows larger older trees to gain more light and space. Thus, benefiting the forest and making for a sustainable use of wood.

Strands are then dried and combined with a resin and wax before being layered into long mats. The resin is what gives OSB its moisture resistant properties. Strand resin mat is then compressed under great pressure and heat to intended thickness. This compression is what gives OSB is consistency and core strength. The mats are cooled and cut into precise size ensuring all panels are identical and consistent.

Variants of OSB

OSB has many variants for a variety of applications, although bespoke sizes are possible the following measurements are typically readily available, 2,400 by 1,200 a standard size panel, 2,400 by 590 smaller in width for flooring and roofing, 2,700mm by 1,200mm in 9mm thickness for timber frames, 2,400 by 597, a specialized size for dry lining. Thicknesses available are 9, 11, 15, 18 and 22mm.

OSB is all a grade OSB 3 and comes in both square edge and tongue and groove edge profiles. OSB boards have evolved to make construction easier by fitting to specific applications. Variants include OSB3 square edged, OSB3 with tongue and groove edge, primed and filled OSB, fire resistant OSB and application specific OSB.

Now let's talk through these variants in a bit more detail.

Firstly, OSB3 square edged this board is a straight edge profile as can be seen in the image as with all OSB discussed in the seminar the board zero added formaldehyde. This board is ideal for applications such as timber frame, outbuildings, flooring, hoarding, roofing and face fixed dry lining.

Here is OSB 3 tongue and groove with a tongue and groove edge as can be seen in the picture. The boards are available with tongue and groove on 2 or 4 edges. These boards lock together and are ideal for roofing and flooring. The tongue and groove elongates the lifespan of the roof as it reduces the panel movement. Tongue and groove also means no need for noggins or drawings in floorings, as tongue groove provides support at long edges. OSB3 also comes primed and coated. This fills the OSB and creates a smooth surface on top of the usual flake surface.

Benefits of this include nonsolvent coating, sealed edges for additional durability and weather protection, and smooth surface for painting and neat look. These properties make a primed OSB board ideal for hoarding, partitioning and shed lining.

Fire resistant OSB is an OSB board designed to reduce fire spread during construction. The board has an intermittent coating on both sides of the panel. Each board designed to match the categories in STA reference W7 and W8 when used with rockwool insulation. FR build deck or FS 300 is most popular in 15mm and can be used in timber framed walling and also flooring when used as the I joist web. We’ll talk in more detail about this fire rated board later on.

OSB is also available that has been engineered for a specific application. The primary example of this is OSB for dry lining. This board is smaller than the norm at 2,400mm by 597mm with a pre-inserted groove to fit metal C stud frames at 600mm centres. This variation saves time and installation while still having great benefits. The board can also hold up to 400 kilograms and is consistent with no notes avoids meaning fixtures can be made anywhere on the panel with surety of strength.

Benefits of OSB

Let's talk about some of OSBs benefits as a wood based panel. All of their 4 mentioned product variations have the following qualities of OSB3.

Firstly, it's strong thanks to the make-up of thousands of wood strands alternately oriented. It's consistent OBS has no notes voids or weak spots in any part of the board. It's durable the board won't delaminate overtime. OSB is easy to work with. It can be worked in many different ways: saw, drill, file, sand, plane, route and so on. It is also moisture resistant, the resin used to bind the flakes with an OSB means it carries great moisture resistant properties, meaning it holds up well in high moisture applications, such as sheds. A sustainable product OSB is made from tree thinnings from sustainable forests and is FSC certified making for an economical board. Made with zero added formaldehyde, no added formaldehyde is added to the resin meaning less emissions, greener and safer building. And of course, it's inexpensive compared to traditional building boards such as plywood OSB cost less per sheet and still delivers great value and properties.

OSB is often compared to plywood; a traditional construction board OSB actually contains many benefits over plywood such as, no knots or voids. Plywood is made from large sheets of veneered wood meaning it often contains the natural defects of wood such as knots and weak spots. OSB is made from small flakes bound by resin and pressed meaning each board has the same consistency, and no voids. Thanks to the lack of voids OSB has an improved strength and consistency because of the strands oriented in opposite directions that make up the board. The resin and OSB also means that OSB has great moisture resistant properties without delamination. Plywood is prone to delamination in high moisture conditions. OSB contains zero added formaldehyde. Plywood contains formaldehyde to heighten the glue used in the board. Zero added formaldehyde means a greener board with less emissions. OSB typically costs less than plywood per sheet but can still match most of the applications plywood is typically used for. OSB sustainable and many OSB plans are FSC certified using wood from sustainable forests. Sometimes the origins of the wood used apply which is unknown and cannot be sure of its sustainability.

As mentioned OSB contains zero added formaldehyde but what are the benefits of this over standard OSB which contains formaldehyde?

Benefits of the zero added formaldehyde product include, a more environmentally friendly product thanks to the minimal formaldehyde emissions, the only familiar had present naturally occurs in the wood. None is added to the reason like traditional OSB. A greener board less resin and more wood is used in the board. The continuous press used to create this ZAF board means less variation in the boards and more consistency. Smoother board surface so smooth that sanding of OSB is not required for GRP or fibreglass roofing systems. The board also meets strict IKEA formaldehyde standards easily. OSB comes with various certifications so you can be confident of its origin and properties. The CE certification shows that the product has made stringent regulations for use in construction. It's also BBA certified. BBA is a third party assessment and guarantees that OSB will perform to modern construction applications. 

Gaining certification for OSB

In order to gain the certification, OSB is put through a series of structural and weathering tests over a prolonged period of time to test their ability of the board to perform on construction sites. Certain brands of OSB also come with the BM Trada Q mark used to demonstrate fitness for the purpose of manufactured panels. BM Trada offers certification to quality environmental information security and health and safety management systems as well as a chain of custody and personnel schemes. Certain brands of OSB also carried the FSC certification. 
FSC stands for forest stewardship council. The FSC product label allows consumers worldwide to recognise products that support the growth of responsible forest management. In an increasingly environmentally aware marketplace many demand the FSC mark on their wood products. OSB manufactured in the UK is particularly environmentally friendly, as no imports means less carbon miles. 

Environmental aspects of OSB

There are some additional points to make on the environmental aspects.

Transportation

The UK manufacture of certain brands means less carbon miles are used transporting the product to end users. 

Manufacture

Certain brands but not all and made in plants with energy generated from biomass, by-products are burned to generate heat energy to power the plant. 

Recycling

Where OSB has to be disposed of it can be recycled at wood recycling centres meaning it never has to go to landfill.

Resin

Zero added formaldehyde in the product resin means less emissions unless resin transportation needed, overall making it more environmentally friendly.

Packaging

The cardboard packaging used for OSB packs is recyclable too.

OSB - regulations and standards

OSB meets the following standards BS EN 300, BS 5268 2 and Euro code 5, EN 13986: 2004. The zero added formaldehyde boards also meets the iOS Mat, IKEA of Sweden materials specification, with ease.

OSB is ideal for timber frame structures which can meet the required building regulation levels with ease. Given correct design standards of manufacture and application.

As with all structure’s timber frames must comply with relevant regulations and legislation including the following considerations: structural, fire, sound, energy. Following the Grenfell tower fire much emphasis is now placed on the importance of fire safety. Please see below for guidance and information on the fire safety related to a standard OSB.

Most OSB is not fire rated unless specifically stated or manufactured to be so. OSB reaction to fire information can be found in EN 13986: 2004 section A1:2015. Norbord have not tested the products as part of a building system for example at height and alongside other building products. Norbord’s OSB panels have been tested as units and rate spec D under the BS EN 135 01-1. Norbord are only able to provide information on testing of the boards as a single component. Boards as part of a complex system or multi storey building have not been tested. For fire resistant properties refer to fire rated OSB we’ll talk about this next. 

Norbord’s fire rated OSB has been developed specifically in response to the STA guidelines for reducing fire spread during construction, before finishes are in place such as, dry lining and controls risk of fire to neighbouring buildings. When used on floors and walls with rockwool insulation, this can achieve as high as category C7 points fire spread resistant. Points noted on this slide Show the level of risk and the points required. We’ll go through how to achieve the higher point scale on the next slide. Please note these panels have not been tested as part of a complex system only as part of the system with rockwool insulation and the other components mentioned. The fire rating is during construction but once completed with finishes such as dry lining, the building will be fully compliant with building regulations and fire requirements.

Shown here are various systems that can be combined to gain more points and a higher category rating to achieve fire ratings up to class C7 points which means fire resistant. Fire rated board shown here must be insulated properly with Rockwool ProRox SL 930 to achieve the STA rating noted. The FR build FS300 board can be used on both walls and on floors. Unprotected OSB can be used for the floor combined with treated I joists using OSB webbing. Please note Norbord only manufactured 15mm FS 300 fire resistant board currently, which can be applied in place of the 9mm sheathing pictured above.

Shown here at the various floor deck and more combinations using the different combination of the diagram shown previously to achieve fire resistance. These all achieve at least a B3 the second highest classification. Now let's look at various applications of OBS. OSB can be used in a variety of ways thanks to instructional and physical attributes.

OSB for roofing

First off roofing. OSB is perfect for flat and pitched roofing. This is because OSB is available tongue and grooved which improves the roofs lifespan by reducing movement to boards. Tongue and groove also removed needs for noggins or dwangs as it provides structural support and long edges. The smooth surface of the continuous press manufactured OSB panels enables greater adhesion for glues, felts, self-adhesive and bitumen in GRP glass reinforced plastic systems.

OSB is also ideal for flooring thanks to its BBA certification and properties. These properties include consistent boards ensuring a flat even surfaced to work on when using OSB is a subfloor. Thicknesses, 15mm and 18mm are the recommended flooring thickness options. When using OSBs as a floor deck bear in mind that a low OSB is moisture resistant, and an OSB floating floor will require a damp proof membrane.

Strength and consistency also make OSB ideal for timber frame constructions and vertical diaphragms. OSB has moisture resistant properties which help elongate the life span of the product and meets building regulations EN300 and Euro code 5. Becoming more of a requirement for building it is also a sustainable building material. Strength consistency and fit for purpose makes OSB ideal for dry lining as well. Pre-cut panels are available with a groove for metal C studs ready to be inserted.

The OSB panels hold up to 400 kilograms at 600mm centres. OSBs moisture resistant properties help elongate the life span of the product. No knots or voids mean consistent strengthening fixtures can be made anywhere on the panel. OSB comes in the following sizes each fairly large at around 2400mm by 1200mm. In sheet form OSB can present a manual handling risk due to its physical dimensions and weight. Good lifting practice should be followed such as the wearing of gloves and safety shoes. A 2440mm by 1220mm, 8 foot by 4 foot sheet of 18mm, three quarter inch OSB3 weighs approximately 33kg or 73 pounds.

Real life OSB examples

Now let's take a look at some real life examples. Here is a case study example of OSB used in timber frames but in a slightly unique manner. In this example Scotframe have used Sterling OSB and a curved fully circular timber framed building. Scotframe state OSB can be manoeuvred quite easily without risk of damage showcasing the versatility and structural capabilities of the product.

Another example here shows OSB used in a build of a two storey cabin. The project was used due to being sturdy, structural but also cost effective total cost of £1,480. The cabin measured 8 by 6 by 12 foot and OSB was used to construct the roof walls and floor and appeared on George Clarke's amazing spaces.

Although OSB is a fantastic choice for many things as with all products it does have its limitations. Unsuitable use of this product includes extra heavy loads, depends on span width, board thickness and load duration, see tables in our literature to Eurocode 5. Directly under tales, a thin sheet of plywood should be used first before placing tales on top of OSB. Water based paint; oil based paint should be used. As a wood product OSB should not be used untreated as a permanent outdoor structure in contact with the elements and moisture.

Here are some useful links to Norbord's products including OSB, available as BIM objects. We are also present in the RIBA product selector database as well as NBS plus. For more information about us under products visit norbord.co.uk.

Overview of OSBs

Now this presentation should have given you the following learning outcomes. You should be able to; identify the variance of OSB available; understand the recommended application for each variant; understand the benefits of OSB and other wood panels; have a basic knowledge how OSB is made on the basis of its properties; and I’ve gained good knowledge on OSB for roofing, flooring, dry lining and temper streaming applications.

For any enquiries on OSB you can contact our business development managers who work across the UK. Literature and product samples can also be ordered free of charge from the Norbord website norbord.co.uk. This concludes this OSB CPD presentation. We hope you have found this useful. If you would like a certification of completion for your records, please email info@norbord.net