Glossary of Terms

TermMain Definition
Euro Class A1 Fire RatingA product can be described as non-combustible if it receives a Euroclass A1 rating under BS EN 13501-1. A product with a Euroclass A2 rating indicates “limited combustibility”, which will be appended with the smoke emission and flaming droplets ratings for further context. In addition, a separate test for non-combustibility is defined in BS 476-4:1970: Non-combustibility test for materials and BS 476-11:1982: Method for assessing the heat emission from building products.
Air TightnessAir tightness testing is carried out by using a method known as a ‘blower door test’ in accordance with BS EN 13829. The measurement is taken by blowing air into the house via a particular door that is mounted in the main entrance. By the use of thermographic equipment, leakage paths can be identified.
Attic TrussAttic trusses serve as both a structural roof and a structural floor in a single section. This means that there is increased living space without having to change the footprint of the house. Thanks to the utilisation of this space, there is a reduced build cost per square metre.
Block and BeamBeam and block floors incorporate clay or concrete blocks, either solid or hollow (sometimes referred to as 'pots'), supported on a series of parallel, typically pre-cast, pre-stressed concrete beams or ribs.
Breather MembraneBreather Membrane is suitable for timber frame constructions either factory or site applied. The product is water resistant and is used to prevent water passing to the timber structure. It is water vapour permeable thus allowing the timber structure to breathe. Breather membrane is fixed to the exterior of the timber frame wall to the exterior of the studwork and structural sheathing board.
BREEAMBREEAM is the world’s leading sustainability assessment method for masterplanning projects, infrastructure and buildings. It recognises and reflects the value in higher performing assets across the built environment lifecycle, from new construction to in-use and refurbishment. BREEAM does this through third party certification of the assessment of an asset’s environmental, social and economic sustainability performance, using standards developed by BRE. This means BREEAM rated developments are more sustainable environments that enhance the well-being of the people who live and work in them, help protect natural resources and make for more attractive property investments.
BS5268BS 5268 is a compendium of Codes covering the structural use of timber. It brings together design stresses, design methods, and some general guidance on the structural use of timber. It covers the major structural uses of timber, particularly in buildings, and can be used as the basis for design of all timber structural members such as floor and ceiling joists, wall panels, roofs, trussed rafters, and fabricated structural components, such as glued laminated structures and plybox beams. It also covers related information for design against fire and protection against fungal decay and insect attack.
Building EnvelopeThe building envelope (or the more modern term, building enclosure) is all of the elements of the outer shell that maintain a dry, heated, or cooled indoor environment and facilitate its climate control. Building envelope design is a specialised area of architectural and engineering practice. The three main catergories that constitute the building envelope are:

Support - To resist and transfer Structural and Dynamic Loads

Control - The flow of all energy types which include heat control, vapour control, rain penetration and air permiability

Finish - For the general look of the building, inside and outside
CADCAD is Computer-Aided Design. It is typically the method for designing, modifying and optimizing design. It is software that allows a standardised exchange of information between designers, contractors and engineers. Dimensions are precise which reduces any variances between design professionals.
CAT-GCATG is one of the UK's leading timber and construction certification, examination and notification bodies. CATG provide accreditation for our manufacturing and processing business.
Cavity BarriersBarriers used to close concealed spaces and prevent penetration of smoke or flame to restrict the movement of fire within a building. Cavity walls and ceiling voids would be considered concealed spaces and would generally be fitted with cavity barriers during construction.
Cavity WallA cavity wall is a type of wall that has a hollow center. They can be described as consisting of two "skins" separated by a hollow space (cavity). Cavity walls can be formed by using two walls of any wall wall type, timber frame or masonry. Cavity walls are often insualted to assist with thermal heat and sound transfer. Cavity walls also assist in reducing the ingress of water into the 'inner' skin of the buidling. Cavity walls in timber frame construction are also utilised both on exterior applications as well as interior applications.
CDM RegulationsThe Construction (Design and Management) Regulations 2015 (CDM 2015) cover the management of health, safety and welfare when carrying out construction projects. CDM Regulations aim to improve health and safety in the construction industry by assisting you to:

1) Plan work so any risks involved are identified and managed

2) Ensure that qualified and/or competant people are assigned to the correct roles

3) Co-operate and co-ordiante work with others

4) Have the right information about the risks and how they are managed

5) Communicate risk information effectively with those who need to know

6) Ensure consultation and engagement with your workforce about the risks and how they are managed

More information can be found at
CFOACFOA (Chief Fire Officers Association) is the professional voice of the UK fire and rescue service. Construction of timber frame may require information to be sent to the CFOA for notification of works and potential risks involved.
CLSCLS Timber – “Canadian Lumber Size” or CLS is finished on all sides giving a smaller cross-section than traditional sawn timber. Originating in the Canadian market, hence the name it is mainly used for timber frame home construction and for internal and partition walls. CLS Timber is typically now purchased from Scandanavian Timber Suppliers.
Code for Sustainable HomesThe Code for Sustainable Homes (the Code) is an environmental assessment method for rating and certifying the performance of new homes.
Cold BridgingA thermal bridge (sometimes referred to as thermal bridging, a cold bridge or thermal bypass) describes a situation in a building where there is a direct connection between the inside and outside through one or more elements that are more thermally conductive than the rest of the building envelope.
DPCA damp proof course is one of the most important elements of a property. The DPC protects the property against moisture rising from the ground. It is therefore vital that you ensure that your property has an effective damp proof course in place to repel water from the ground.
DWGDWG is a drawing file that is an electronic version of your building. An architect or draftsperson will save a CAD drawing as a DWG file. This DWG file will be reuqired by us in order for us to design and engineer your timber frame building.
EC5The Eurocodes are a series of standards that establish common rules across the European Economic Area (EEA) for structural design using main construction materials such as concrete, steel, masonry, timber, aluminium and glass. For more information please follow Trada
Engineered JoistsEngineered joists are typically Metal Web Joists or I-Joists. There are many trademarked names for engineered joists such as FJI joists, JJI Joists, Posi Joists and Easy Joists. Essentially engineered joists are manufactured joists rather than straight timber joists. These engineered joists generally have a better structural performance than timber joists. Engineered joists often also have different service voids to reduce the requirement for any drilling or adaptions whilst ventilation, electric or plumbing services are being run in. Enginnered joists can also be utilised for roofing applications.
E-WT-1Is a timber frame cavity wall without sheathing board. For more information please follow
E-WT-2Is a timber frame cavity wall with sheathing board. For more information please follow
Fabric FirstA ‘fabric first’ approach to building design involves maximising the performance of the components and materials that make up the building fabric itself, before considering the use of mechanical or electrical building services systems. This can help reduce capital and operational costs, improve energy efficiency and reduce carbon emissions. A fabric first method can also reduce the need for maintenance during the building’s life.
Fall ArrestThese systems arrest and restrict a fall preventing you from colliding with the ground or structures, whilst limiting the forces on the body. These can be arrestor bags, nets, lanyard systems, decked systems.
FermacellFermacell is high performance alternative to plasterboard or sheathing board. Fermacell combines structural stability with fire resistance, acoustic insulation and impact strength. For more information please go to
Fire SafetyFire safety is the set of practices intended to reduce the destruction caused by fire. Fire safety measures include those that are intended to prevent ignition of an uncontrolled fire, and those that are used to limit the development and effects of a fire after it starts. Fire safety measures include those that are planned during the construction of a building or in structures that are already finished. Fire safety with timber frame structures can be mitigated through fire treated timber, the use of A1 class building materials. These mitigation processes are often highlighted in an OSFRA report or fire mitigation report.
FiresocksCavity Stop Socks are designed to prevent the passing of fire and smoke through cavities in walls. They can be used throughout cavity walls, but are normally reserved for use at the wall junction. They also provide excellent acoustic insulation.
Floor CassettesFloor casettes are manufactured in our timber frame factory. They are pre-made floor panels that provide many benefits. They are becoming increasingly popular due to the fact that they can improve safety on site and dramatically increase the speed of the timber frame erection process. Floor cassettes are have built in lifting straps so that they provide safe lifting for transportation and also site erection. Different decking types can be used to finish the top of the cassettes to match the requirement of the timber frame specification
FSCThe FSC (Forest Stewardship Council) run a global forest certification system. The two main components are Forest Management and Chain of Custody. The FSC system allows businesses and consumers to identify, purchase and use timber, wood, paper and other forest products made wit hmaterials from well managed forests and / or recycled sources. For more information please go to
Gable PanelsGable wall panels are generally triangular-shaped wall panels, placed in the roof/ attic cavity of a housing structure. These are used in modern timber frame housing developments and can aid the speed of erection of the overall structure. Gable panels can also be used to replace blockwork gables and are tied back to the timber roof trusses to provide structural stability. Once again replacing block work gables with timber gable panels can reduce site erection time.
GlulamGlulam is glued laminated timber. It is an engineered timber product which his manufactured from multiple layers of parallel timber laminations. Glulam can be manufactured from vaious timber species and treated with various paints and finishes to create different aesthetics and looks to compliment your project. Glualm, as it is structural, can be used to replace steel beams and act as a lintel or purlin replacement. Timber frame homes often use Glulam to act as structural components in either the timber frame walls, engineered floors or timber roof structure to support the roof trusses.
Hip EndThe hip is the external angle at which adjacent sloping sides of a roof meet. The degree of such an angle is referred to as the hip bevel. The triangular sloping surface formed by hips that meet at a roof's ridge is called a hip end.
HRVHRV is Heat Recovery Ventilation. Heat recovery ventilators (HRV) and energy recovery ventilators (ERV) are air exchange systems that help to enhance indoor air quality and minimize heating costs. These mechanical systems use fans to maintain a balanced airflow into the house while exhausting stale indoor air.
HTFHTF = Harmony Timber Frame, that is us!
HTSHTS = Harmony Timber Solutions, that is us too!
HVACHVAC stands for Heating, Ventilation and Air Conditioning, sometimes known quite simply as 'climate control'. The main purpose of HVAC systems or climate control systems is to control the environmental conditions inside a home or property.
ISO 14001ISO 14001 is an internationally agreed standard that sets out the requirements for an environmental management system. It helps organizations improve their environmental performance through more efficient use of resources and reduction of waste, gaining a competitive advantage and the trust of stakeholders.
ISO 9001ISO 9001 is defined as the international standard that specifies requirements for a quality management system (QMS). Organizations use the standard to demonstrate the ability to consistently provide products and services that meet customer and regulatory requirements.
JoistA joist is a horizontal timber or manufactured joist that spans between two walls and / or beams. Joists are the load bearing members that take the weight of walls, people, furniture or appliances that we place on them.
Kicker BlockA kicker block is a concrete block that sit on top of the block and beam floor. They should be a minimum height that matches the depth of the finished floor level. Our DPC and soleplate will sit on top of the kicker block. Kicker blocks allow the base, that the timber frame will sit on to be flat, level and square. Kicker blocks are typically 140mm wide for the external walls and 100mm wide for the internal walls. Kicker blocks are essentially in making sure that the building will eb set out correctly for the placement of the timber frame.
LVLLaminated veneer lumber (LVL) is a type of high-strength engineered timber that can be used as an alternative to solid timber, concrete and steel for structural applications.
MasonryMasonry, the art and craft of building and fabricating in stone, clay, brick, or concrete block.
Masonry PlinthMasonry plinths are essentially identical to the kicker blocks but this term can be used more gerally for masonry construction as well as timber frame costruction.
Metal Web JoistsMetal web joists are engineered joists. There are many trade names but we at harmony tImber use the Mitek Posi Joist system. Metal web joists / Posi Joists have a huge benfit of being structurally superior to straight timber of the same cross sectional size as well as having open webs allowing greater freedom when running services through them.
Mineral WoolMineral wool is any fibrous material formed by spinning or drawing molten mineral or rock materials such as slag and ceramics. Mineral wool is often used as insulation for cavities and thermal bypass applications.
MitekMiTek® is a global company focused on providing integrated software, services, engineered products and automated solutions for the building industry worldwide. Mitek provide us with there software as well as supplying their metalwork for our timber roof trusses and Posi Joist systems. Their software is one of the market leaders with MBA, Wood Engine and Pamir.
MVHRMVHR (Mechanical Ventilation with Heat Recovery) provides fresh filtered air into a building whilst retaining most of the energy that has already been used in heating the building. Heat Recovery Ventilation is the solution to the ventilation needs of energy efficient buildings. Mechanical ventilation with heat recovery (MVHR), heat recovery ventilation (HRV) or Comfort ventilation are all names for the same thing. A heat recovery ventilation system properly fitted into a house provides a constant supply of fresh filtered air, maintaining the air quality whilst being practically imperceptible.
OSB3OSB3 is an engineered, load bearing wood-based panel product. It is free of knots and voids and is suitable for structural use in external situations. OSB stands for Orientated Strand Board.
OSFRAOSFRA is a short version of Off Site Fire Risk Assessment. It is a fire mitigation report for defining the building class of a timber frame structure. An OSFRA can depict the requirement for fire mitigation materials to reduce the risk of fire spread during timber frame construction. An OSFRA report is often required when there are neighbouring buildings and structures take could be at risk if a fire was present in a building. An OSFRA or fire mitigation rpeort is often required by the Health and Safey Executive and for compiance with CDM regulations.
PamirPAMIR is MiTek’s industry leading Roof Truss and Posi-Joist design software. Developed by our European software development team, PAMIR is a powerful and versatile fully integrated CAD, layout and engineering package, with full EC5 engineering to the very latest design codes. PAMIR is only used by licensed MiTek Roof Truss and Posi-Joist manufacturers.
Passiv HausPassivhaus, literally passive house in English, refers to buildings created to rigorous energy efficient design standards so that they maintain an almost constant temperature. Buildings constructed to Passive standards are designed to reduce energy demands by looking at renweable eneryg inputs, continus airtight and insualtions layers and optisimising solar gains from natural sunlight for warmth and eneryg. Builders of energy efficient homes and buildings can apply to have their buildings certified by the Passivhaus Institute should they meet the energy demand criteria set by the Passive House Institute.
Passive HousePassive House or Passivhaus, literally passive house in English, refers to buildings created to rigorous energy efficient design standards so that they maintain an almost constant temperature. ... Builders of energy efficient homes and buildings can apply to have their buildings certified by the Passivhaus Institute. Harmony Timber are fortunate that we have an in house Passive House Consulatant.
Passive House ConsultantHaving Passive House expertise within Harmony TImber is a clear demonstration of a commitment to energy efficiency, fuel poverty reduction and to taking action on climate change. Given the number of businesses, nations, regions and cities signing up to commitments such as Net Zero Carbon Buildings, and the UK’s ‘Climate Emergency’ motion signalling potential weightier sustainability policies in future, it is a good time for Harmony Timber to have an in house Passive House Consultant.
PEFCProgramme for the Endorsement of Forest Certification. PEFC care for forests globally and locally. We work to protect our forests by promoting sustainable forest management through certification. This means we can all benefit from the many products that forests provide now, while ensuring these forests will be around for generations to come. Harmony Timber Solutions and Harmony Timber Frame are accreditted by PEFC and we are proud to stand next to them in the promotion of sustainable buildnig techniques. More information can be found at
Pile FoundationsPile foundations are deep foundations. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete, or sometimes timber. A foundation is described as 'piled' when its depth is more than three times its breadth.
Pinch BattenPinch batten is a cavity closure that is mounted around the opening formed for doors and windows within a timber frame building. The timber batten is wrapped in DPC to provide weather proofing and then nailed around the outside of the formed opening. They close off the external cavity around the openings and also provide addtional fixing points for the window and door frames if required.
PIRPIR is a widely-used shorthand term for 'polyisocyanurate', which provides us with one of the most thermally efficient commonly available insulation materials in the industry today. Like other organic materials, it is composed of complex hydrocarbon chains. PIR insulation comes in various sizes and can be cut precisely to ensure a tight fit preventing cold spots within a timber frame wall.
PlyPlywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another.
Posi JoistsPosi Joists are a trade name for Mitek's metal web joists. They are structural floor joists that are constructed with timber top and bottom flanges and diagonal metal webs. The metal webs provide the structural stability whilst their orientation allows for better access for services to be run through.
PV PanelsPhotovoltaics (often abbreviated as PV) are simple devices that provide us with an elegant method of harnessing the sun's energy. PV devices (solar cells) can directly convert the incident solar radiation into electricity. They produce no noise, produce no pollution, and do not include moving parts. Solar energy is seen as clean and sustainable energy. Harmony Timber can allow for the loadings and fixing details that PV panels require within our Timber Frame and Roof Truss designs. Early planning for PV's will allow you to lower your carbon footprint, decrease reliance on fossil fuels for your energy and even allow you charge EV vehicles with the green energry.
QR CodeA QR code is a type of digital barcode that can be read by most digital devices. The square has a number of pixles that can send clients to different websites, further information or resources. Harmony Timber utilise QR codes to provide our clients with 3d models, fixing details, and technical information relating to roof truss and floor joist hangers.
Raft FoundationsA raft foundation is a reinforced concrete slab under the whole of a building or extension, 'floating' on the ground as a raft floats on water. This type of foundation spreads the load of the building over a larger area than other foundations, lowering the pressure on the ground.
Raised TieA raised tie roof truss is a truss where the bottom chord making up the triangle shape moves towards the top of the triangle. Unlike other trusses which support on the ceiling tie- the bottom chord, raised tie trusses are supported partway up the lower end of the rafters.
Room in The RoofA Room in the Roof truss is essentially an Attic Truss. Attic trusses serve as both a structural roof and a structural floor in a single section. This means that there is increased living space without having to change the footprint of the house. Thanks to the utilisation of this space, there is a reduced build cost per square metre.
Scissor TrussScissors trusses are used almost entirely in building construction to support a pitched roof, where a sloping or raised ceiling surface is desired. This can create additional headroom as well as a nie aesthetic feature. Harmony Timber Solutions can design the scissor truss on our Pamir software and provide roof truss profiles and a 3D roof layout model to give a full visual effect of the scissor trusses.
SIPSStructural insulated panels (SIPs) are a high-performance building system for residential and light commercial construction. The panels consist of an insulating foam core sandwiched between two structural facings, typically oriented strand board (OSB).
Spandrel PanelsSpandrel Panels are pre-assembled structural panels used as a separating wall or as a external gable roof panel. They conform to 'Robust Details'. Spandrel Panels are used to replace the need for a masonry wall or part of a timber frame structure. The spandrel system satisfies sound and fire separating requirements within the building regulations. SPandrel panels are used in the construction of semi detached houses, terraced houses and also within flats and apartments.
STAAlong with quality and safety, the Structural Timber Association's (STA) core objective is to be a leading provider of technical research and industry insight. Their Technical Committee work closely with the HSE, TRADA and BRE to ensure our members have technical insight and industry intelligence to enable them to compete against other methods of construction. Harmony Timber are Gold members of the STA Assure scheme. This gives our clients the comfort in knowing that their timber frame structure, roof trusses and engineered floors are designed, manufactured, supplied and erected to the high standard that both you, as our client, and also the STA expect.
Strip FoundationsStrip foundations (or strip footings) are a type of shallow foundation that are used to provide a continuous, level (or sometimes stepped) strip of support to a linear structure such as a wall or closely-spaced rows of columns built centrally above them.
Suspended FloorA suspended floor is a ground floor with a void underneath the structure. Supports underneath the floor are permanent and include sleeper walls or timber props placed at regular intervals. Unlike standard ground floor construction, suspended floors are not sitting directly on the ground.
T+GT+G stands for tongue and groove. It is a method by which floor decking or cladding are connected together. One edge of the floor decking or cladding has a protruding section that slots into a receeding edge of the next board. Our floor decking is supplied with D4 glue which is applied along these intersecting edges and then expands to seal the join compliantly.
TakeoffA timber frame, roof or floor takeoff is a process by which the plans are assessed and broken down to individual components. These components are then totalled and a price applied to them in order to produce a quotation for our clients.
Thermal BreakA thermal break is a material with low thermal conductivity, placed in an assembly, to reduce or prevent the flow of thermal energy between the inside and outside of a building.
Thermal BridgeA thermal bridge, also called a cold bridge, heat bridge, or thermal bypass, is an area or component of an object which has higher thermal conductivity than the surrounding materials, creating a path of least resistance for heat transfer.
Thermal BypassThermal bypass is heat transfer that bypasses the conductive or conductive-radiative heat transfer between two regions. Furthermore it is an acknowledgement that air movement can lead to a significant increase in the heat loss when compared to predicted values.
TimberTimber, also known as lumber, is wood that has been processed into beams and planks, a stage in the process of wood production. Timber is mainly used for structural purposes but has many other uses as well. Timber may be supplied either rough-sawn, or surfaced on one or more of its faces.
Tongue and GrooveIs a method by which floor decking or cladding are connected together. One edge of the floor decking or cladding has a protruding section that slots into a receeding edge of the next board. Our floor decking is supplied with D4 glue which is applied along these intersecting edges and then expands to seal the join securely.
TR26TR26 timber is classified as a sustainable source of timber in accordance with the BS EN 14081. The timber is lighter in weight but this does not compromise the strength capabilities that it has. It is designed to improve dimensional stability, all whilst being regularised to a consistent finish. TR26 Grade timber is used within timber roof trusses and also within our Posi Joist floor system.
TRATRA (Trussed Rafter Association) is amn accreditation body that we, at Harmony Timber, are proud to be members of. The TRA is the respected voice of the trussed rafter and metal web joist industry in the UK. The Association is committed to stringent standards of quality and service and sets a professional benchmark for the industry. Members include the principal manufacturers of trussed rafters, metal web joists, suppliers and professionals involved in roof and floor design and construction. The TRA requires all its manufacturing members to have third-party supervised Quality Assurance and Professional Indemnity insurance so helping to ensure quality and peace of mind for the customer. More information can be found at
U-ValueThermal transmittance is the rate of transfer of heat through matter. The thermal transmittance of a material or an assembly is expressed as a U-value. Although the concept of U-value is universal, U-values can be expressed in different units. Essentially U-Value depicts a figure that expresses how efficient a component is at preventing heat loss. The lower the number of the U-Value, the better the item is at preventing heat loss. U-Vlaue is measured in W/m2K (Watts per metre squared Kelvin).
VATVAT is Value Added Tax. It is a tax impossed by the UK government. Most new build properties do not attract VAT but there are some that still qualify to be chargable with VAT. VAT is typically 20% but this may be different depending on how the VAT is measured.
VCLVCL is a vapour control layer. Vapour control layers are fixed to the inside of a timber frame panel and it restricts the movement of warm, moist air from the inside of a property into the fabric of the building.
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