There are a dizzying array of boarding types, some general purpose, some very specific, and as with any choice, care should be taken to specify the right product for the job.
Lining boards are applied to the inner studs, joists, or rafters to provide an internal base for finishing.
Sheathing boards are applied to outer studs, joists, and rafters of a building to strengthen the structure and serve as a base for an exterior weatherproof cladding.
Sarking boards are applied to a roof as the base for roof finish.
Strength is a key factor, as is moisture resistance (or contrarily hygroscopicity), fire rating, type of finish, size, ease of use, acoustic and/or thermal properties, etc etc. All boards are covered by British and European standards that differ depending upon the materials and the application – check you have the right board for the job when specifying.
Most boards will come in similar standard dimensions and thicknesses.
To find out more about the different boards available, please click on one of the options below:
Oriented Strand Board (OSB)
Cement Bonded Particleboard (CBP)
Made simply from gypsum and paper, plasterboard is one of the most versatile materials used in modern construction. It is used in a wide range of applications including lining, partitioning, sound control, and fire protection.
Approximately 300million m2 of plasterboard is manufactured annually using 3 million tonnes or 60% of the total annual gypsum output. Environmental impacts associated with plasterboard are due to its production, transportation, and disposal.
Gypsum used in plasterboard is generated from both natural and synthetic sources. Naturally occurring gypsum (CaSO4.2H2O) is the hydrated form of Calcium Sulphate (CaSO4), a by-product of lake and seawater evaporation. The UK is largely self-sufficient in naturally occurring gypsum.
Synthetic or Flue Gas Desulphurisation (FGD) gypsum is a by-product of the desulphurisation of the flue gases of coal-fired power stations. 'Scrubbers' remove sulphur from combustion gases - one particular type of scrubber uses lime or limestone and produces FGD gypsum, which is chemically nearly identical to natural gypsum.
In order that the gypsum is ready for use in plasterboard, 75% of the water is removed by heating to a temperature of over 150°C using natural gas. This 'calcination' changes calcium sulphate from its dihydrate state (gypsum) to its hemihydrate state (stucco).
Water and other additives are added to the stucco and the slurry is poured onto a moving belt of paper, with further paper applied as a top cover. The wet sandwich of paper and plaster is cut to board lengths before being transferred to a gas-heated kiln. When the slurry has dried and hardened it has effectively reverted back to being gypsum rock.
There are a number of materials and chemicals that may be added to the gypsum in order to enhance the properties of the resulting plasterboard:
· Detergent – results in a foamy mix and a less dense plaster
· Lignosulphates - improves the flow of the slurry, less water used, denser plaster
· Starch - protects the physical bond between gypsum crystals and paper
· Potassium sulphate - causes the gypsum to dry out more quickly
· Silicone – improves resistance to moisture
· Wax - also improves resistance to moisture
· Glass fibre - increases fire resistance
· Vermiculite - also increases fire resistance
High sulphate wastes such as plasterboard are not permitted in general landfill, and can only be dumped at a mono-cell at a landfill site - a separate cell which only accepts high sulphate waste. Because of this, and the vast quantities and costs concerned, big efforts are being made to minimise waste and divert plasterboard from landfill to be recycled. The biggest issue with this is contaminated loads.
Plasterboard has a high embodied energy and large CO2 footprint due to its production, calcination, and curing. Production also contributes significant levels of toxicity to land and eutrophication to water. Transportation of plasterboard to site and to disposal adds to its embodied energy.
If high volume production of plasterboards and gypsum plaster can be achieved using FGD, significant improvements will be made to the environmental status of the gypsum industry.
On the positive side, plasterboard enables quick and cheap construction, is non-toxic in situ, can help to regulate internal humidity levels, and at present can include up to 25% recycled material (the paper element is typically 90% recycled material).
Clay board is a combination of 100% natural materials - clay, reed and hessian. Clay boards are heavier and thicker than plasterboards, but have much better thermal and hygroscopic properties - clay also absorbs odours and is an effective sound insulator.
Clay board is suitable for internal use as a practical alternative to using gypsum plasterboard or lath-and-plaster, and since it is breathable, is compatible with clay or lime -based plasters and paints.
Boards such as Fermacell take the basic elements of plasterboard and mix them all up, giving a board with similar properties but with greater strength that will not mould, mildew, or physically break down in the continued presence of moisture. This makes it a particularly useful tile carrier for bathrooms and kitchens.
Wood based panels are covered by various UK and European standards – for guidance on correct specification see http://www.tradatechnology.co.uk/panel-products/panel-products-technical-services.
Called particleboard everywhere bar the UK, chipboard is an engineered board in which wood chips are bonded together with a synthetic resin; it originated in 1940s UK in order to utilise waste timber.
Unsurprisingly, wood chips, largely from coniferous softwoods, comprise the bulk of chipboard (about 85%) - a large proportion of which may be from recycled sources (potentially 95% or more, but generally around 40%). Depending upon the intended end use, the chips are bonded together with a synthetic resin (5%) such as urea-formaldehyde (UF), melamine urea-formaldehyde (MUF), phenol-formaldehyde (PF), or polymeric methylene di-isocyanate (PMDI). Urea-formaldehyde is used most commonly, but is only suitable for use in dry conditions - the other three offer a measure of moisture resistance.
The production process is potentially energy intensive; however, in the UK all chipboard mills use their own wood fuels to generate heat, meaning that as much as 55% of the heat requirement is derived from renewable sources.
Chipboard is commonly used in furniture and worktops, generally with a veneered or laminated finish, and structural flooring. It may be cheap, cheerful, versatile, and full of recycled product, however the formaldehyde resins are toxic either in use or when disposed of, and cannot be recycled.
MDF is an engineered wood-based board made by bonding wood fibres together with a synthetic resin adhesive. MDF is known as a dry process fibreboard. Its manufacture involves reducing forest thinning and sawmill residues (mostly softwood) down to small chips, thermally softening and refining them into fibres, and then mixing them with a synthetic resin adhesive. The dried fibres are formed into a mattress which is pressed between heated plates to the desired thickness.
First produced commercially in Deposit, New York State, USA, in 1966, European production capacity now rivals the USA, with 12.5 million cubic metres produced in 2008.
MDF is available in a wide range of thicknesses and can be finished to a high standard. As such, it is used in a wide range of applications in both construction and furniture manufacture, having substituted solid timber and other wood-based boards. Other additives have enhanced mechanical performance, particularly with regard to moisture and fire resistance.
A typical MDF board manufactured in the UK contains 82% virgin wood fibre (wholly or mainly softwood), 10% synthetic resin binder, 7% water, <1% paraffin wax solids and <0.05% silicon. The most common resin used is urea-formaldehyde, with other options depending upon application, as chipboard above.
Adding to its versatility, MDF can be cut without splintering and can be profiled on the edges and surfaces, making it ideal for furniture, architraves, skirtings etc. The smooth, dense surface provides an excellent base for painting, veneering and laminating.
As with chipboard, the manufacture process is quite energy intensive, but the real environmental issues are with the use of formaldehyde-based resins, which means it cannot be recycled.
This is an FSC certified MDF panel with zero added Formaldehyde, developed specifically for use in environmentally sensitive interior applications, where formaldehyde emissions need to be kept to a minimum.
First developed about twenty five years ago, OSB is a relative newcomer to the board competition, but a huge increase in capacity has occurred over the last decade and by 2008 world capacity was approximately 25million m3.
Similar to the boards above, in OSB production relatively long strands of either soft or hard wood are bonded together with a synthetic resin. OSB consists of three layers, in the outer two of which the strands are orientated in a particular direction to give increased strength.
Unlike in other board manufacture, small particles are removed prior to resin application resulting in much lower amounts of resin use (2-3%) compared with other resin bonded boards. The potential issues with resins are as outlined in the chipboard and MDF sections above.
Due to its rough appearance, OSB is primarily used in construction for site hoardings, flooring, decking, sarking and sheathing, and in industrial packaging – it is generally only used in furniture if not seen.
Its production is less energy intensive than chipboard or MDF, and it contains less resin, however its environmental drawbacks are similar. [see formaldehyde ]
Wet process fibreboards, classified according to their density, are generally produced without the addition of a synthetic resin but instead are formed like paper to make a board. They can be made with softwood or hardwood species (or both) or even recycled paper.
Wood chips are thermally softened in water and refined into fibres. The wet fibres are formed into a mat which is then rolled (softboards), or rolled and then pressed at a high temperature to the desired thickness. The primary bond is generally derived from the felting together of the fibres and the adhesive properties inherent in the timber’s lignum. In some instances, a synthetic adhesive may be added, as might wax, bitumen emulsion, natural oil, or fire retardant chemicals.
Hardboards - Hardboards are used in furniture as drawer bottoms and unit backs, and as caravan interiors for example. They are generally not suitable for exterior use or in damp or humid conditions.
Mediumboards - Low density mediumboards have particular application as pinboards and as components of partitioning systems. Their use today in the UK is limited.
Softboards - Like mediumboards, the range of applications for softboards today has diminished, however, they do find application as an acoustic absorbent.
Wet process fibreboards have great sound and thermal insulative properties (they are the basis for wood waste insulation products, [see link]).Those without additives have a relatively low energy footprint, and are fully recyclable and biodegradable.
Plywood is a versatile material with a high strength to weight ratio that manages to combine an attractive appearance with superior performance in a range of uses. It is available made from hardwoods, softwoods, and mixtures thereof, with the natural properties of the timber and glue used determining the suitable end use.
The veneers that standard plywood is made from are produced by peeling a log - much like a pencil sharpener. Each veneer then has synthetic resin adhesive applied, and is assembled with the grain at 90° to the adjacent veneer. The assembly (‘lay-up’) is then subjected to pressure and heat resulting in a compressed and cured panel.
The resins used in plywood manufacture are as chipboard or MDF, and will depend upon the desired classification and application. The appearance of the outer veneer is also graded.
Because of the range of species, bond qualities, and appearance, plywood can be engineered to have specific properties for particular applications, resulting in a wide range of products available – as an example it is the only wooden board with a variation that can be used in structural applications outside, or a marine variation for boat building.
As variations on a theme, blockboard uses 25mm wide strips of wood for its core, whilst laminboard cores are composed of strips of veneer on edge (or occasionally strips cut from plywood). These lower grade boards are used internally, such as for door blanks.
The manufacture process is not as energy intense as chipboard, but the resins are the same or worse for the environment, depending upon the application.
Strawboard is lightweight, strong, moisture and impact-resistant – and made of 100% waste straw. It is a fully sustainable alternative to MDF or chipboard.
The low energy manufacturing process mixes natural straw (97%) with zero formaldehyde resin (3%). The homogenous material is then heated and extruded, before pressure is applied to produce a compressed rigid straw board. Strawboard is 100% recyclable and biodegradable and has no toxic additives such as formaldehydes or sulphates.
CBPB is a mixture of wood particles, cement, and other additives. Panels are grey, smooth, and heavy. It is a good fire retarder, durable, stable, and provides good sound insulation.
CBPB was first commercially manufactured in the early 1970s and is still manufactured in small quantities in order to satisfy specialised applications. Seasoned softwood logs are chipped, hammered and sized, after which they are mixed with cement and water (cement 60%, wood 20%, water 20%) and other additives to aid setting.
The board is formed in three layers, the outer layers comprising small chips, and the inner layer large chips. The boards are kept under pressure until the cement has set.
CBPB is mainly used for specialised applications in construction, such as internal wall construction in public places, lining of lift shafts, construction of cabling ducts, soffits, motorway acoustic fencing and cladding of prefabricated house units.
Its environmental impacts are relatively large due to the amount of cement used, and heat used in the drying process.