Glossary of Terms

Term Main Definition
Euro Class A1 Fire Rating A 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 Tightness Air 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
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.
Block and Beam Beam 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 Membrane Breather 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.
BREEAM BREEAM 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.
BS5268 BS 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
Building Envelope The 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

CAD CAD 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
CAT-G CATG 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 Barriers Barriers 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 Wall A 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 Regulations The 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

CFOA CFOA (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.
CLS CLS 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 Homes The Code for Sustainable Homes (the Code) is an environmental assessment method for
rating and certifying the performance of new homes.
Cold Bridging A 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
DPC A 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.
DWG DWG 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.
EC5 The 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 Joists Engineered 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-1 Is a timber frame cavity wall without sheathing board. For more information please
E-WT-2 Is a timber frame cavity wall with sheathing board. For more information please follow
Fabric First A ‘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 Arrest These 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.
Fermacell Fermacell 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 Safety Fire 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.
Firesocks Cavity 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 Cassettes Floor 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
FSC The 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 Panels Gable 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.
Glulam Glulam 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 End The 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.
HRV HRV 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.
HTF HTF = Harmony Timber Frame, that is us!
HTS HTS = Harmony Timber Solutions, that is us too!
HVAC HVAC 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 14001 ISO 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
ISO 9001 ISO 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.
Joist A 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 Block A 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.
LVL Laminated 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.
Masonry Masonry, the art and craft of building and fabricating in stone, clay, brick, or
concrete block.
Masonry Plinth Masonry 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 Joists Metal 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 Wool Mineral 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.
Mitek MiTek® 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.
MVHR MVHR (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
OSB3 OSB3 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.
OSFRA OSFRA 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.
Pamir PAMIR 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 Haus Passivhaus, 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 House Passive 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 Consultant Having 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.
PEFC Programme 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 Foundations Pile 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 Batten Pinch 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.
PIR PIR 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.
Ply Plywood 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 Joists Posi 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 Panels Photovoltaics (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 Code A 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 Foundations A 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 Tie A 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 Roof A 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 Truss Scissors 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
SIPS Structural 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 Panels Spandrel 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.
STA Along 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 Foundations Strip 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 Floor A 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
T+G T+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.
Takeoff A 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 Break A 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 Bridge A 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 Bypass Thermal 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.
Timber Timber, 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 Groove 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 securely.
TR26 TR26 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
TRA TRA (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-Value Thermal 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
VAT VAT 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.
VCL VCL 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.