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Below is a selection of terms typically used
in the Timber Frame construction industry.
Please
select a letter:
A B C D E F G H I J N O P R S T U V W
ATTIC TRUSSES: Roof trusses constructed with strong timbers to create a habitable or useful storage space in the roof.
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BIRDS MOUTH CUT: The method of cutting the underside of a rafter (seat cut & plumb cut) to form a bearing surface for the timber rafter.
BLOCKING AND BRIDGING (STRUTTING) BLOCKING: Solid pieces of timber in short lengths fixed between floor joists at ends of spans to prevent any movement.
BRIDGING - solid pieces of timber generally at mid spans of floor joists to prevent twisting of timber
BRACING / WIND BRACING: Lengths of timber used to brace components together to distribute loads more evenly throughout the structure to counteract forces such as wind loads.
BREATHING WALL (Hunton Fibre Bitroc): These boards are manufactured from wood chips
& selected wood waste recycled newsprint and have been designed as a sheathing board for the timber frame industry and a sarking board
(Hunton Firbre Sarket) in most forms of construction. In normal situations they do not require a breather paper or vapour barrier. This allows moisture migration from the inside to the outside of the structure.
http://www.hunton.no
BREATHER PAPER: A man made material such as woven polypropylene, generally stapled to the outside face of an external timber frame panel. It allows water vapour to pass through from the inside to the outside of a timber frame wall, but does not allow the passage of vapour in the opposite direction.
In addition to the standard breather paper, reflective types are also
available, these improve the thermal efficiency of the wall by reflecting
any heat absorbed by the brickwork back into the cavity, thus reducing the
temperature difference between the inside an outside of the timber frame.
BRICKWORK LINTELS: Galvanised steel lintels that are fixed to the external timber frame panel and support brickwork / blockwork over window / door openings in timber frame.
BUILDING REGULATIONS: An area of building control that
states how a building should be constructed to ensure safe and healthy
accommodation and the conservation of energy. This form of control is
administered by the relevant local authorities, to whom an application
must be made and permission received (generally a conditional approval)
before work is started.
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CAVITY BARRIER: Either timber, wire reinforced mineral wool blanket or polythene sleeved mineral wool used to seal off the cavities into zones
(around windows, around fire doors, between semi-detached houses etc.)
CONCRETE SCREED: An in situ flooring of cement mortar laid to an accurate flat surface by screeding. Screeds are laid on the structural floor and usually have no reinforcement - in a timber frame situation it would be laid after the structural shell has been erected (commonly approx 65mm deep
and can contain under floor heating pipes).
CRIPPLE STUD: A short stud that is connected to a full height stud to form a bearing for a horizontal lintel for a window or similar opening.
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DAMP PROOF COURSE (dpc): A strip of impervious material that sits underneath the timber frame soleplates or brickwork / blockwork to keep out moisture. The dpc at ground level excludes rising damp but they are also used to divert rain out of the cavity, to drain through weepholes at the lintel above door or window openings.
DPC comes in preformed rolls and made of flexible materials such as bitumen-polymer or pitch-polymer.
DAMP PROOF MEMBRANE (dpm): A wide layer of impervious material such as mastic asphalt or a plastic sheet underlay beneath a ground slab to create a waterproof skin. A surface damp proof membrane can also be used such as what is supplied with a floating floor.
DIFFERENTIAL MOVEMENT: Timber being a natural resource is prone to some shrinkage across the grain although it is stable in the longitudinal section. An allowance is made in the floor where joists do have to lye across the grain. The difference between the timber frame movement and that of the external brickwork is the differential movement.
DORMER HOUSE: Also sometimes known as a one and a half storey house or room in the roof bungalow. This is where the roof space is utilised by using Attic Trusses or similar. The rooms on the first storey will have sloping ceilings and either dormer windows or velux roof lights to allow light into the rooms
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EAVES: The eaves are the roof overhang (usually clad in fascia and soffit) which protects the brickwork, or other external cladding from rain. It generally allows air ventilation to the roof void while keeping out insects and birds
ENGINEERING / ENGINEERS CERTIFICATE: CST Design
utilises the services of structural engineers (all NHBC registered) to provide structural information on the size and nature of the various components that make up structural timber frame kit. Structural calculation, assembly drawings and details are supplied by
CST Design for submission to the Local Authority by the client or the client's representative.
ERECTION / INSTALLATION: The on site construction of the timber frame structural shell by a specialised team that usually include for there own mechanical handling and accommodation whilst working. A structural shell for an average 3/4 bed house will generally take approximately
2-w working weeks.
EXTERNAL JOINERY: The windows and doors etc. produced from high quality planed timber or UPVC.
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FASCIA / BARGEBOARD & SOFFIT: A board which is generally timber or upvc set on edge along the eaves. This covers the rafter ends and will usually carry the gutter. Bargeboard - As above but used on the sloping areas of the roof. They are fixed in pairs along the edge of the gable to cover the roof timbers and protect them from rain. They can be ornately carved or moulded if required to create a feature.
FLOOR JOISTS: A wooden (or steel) beam which directly supports flooring in common with other joists (or a ceiling lining as a roof joist).
The type of floor joists generally recommended by CST Design are metal web
type (e.g Mitek's Posi-joist) - floor joists that consist of timber rails separated by steel
"V's". This gives the timber greater strength (increasing spans) and
reduced weight.
FIRESTOPS: Cavity barriers such as flexible mineral fibre strips in polythene sleeves required at junction of separating and compartment wall and external wall with roof.
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GABLE LADDERS: The structural link between trusses and gable panels that will overhang to form the eaves. They will often be used as a fixing for barge board and soffit
GABLE PANELS / SPANDREL PANELS: Triangular external infill wall panels that form the gable ends of a House and follow the roof profile or pitch.
GLULAM: Large section timber material for structural applications. It is an engineered product built up by gluing together layers of timber boards with staggered joints.
GROUND FLOOR FINISHES:
FLOATING GROUND FLOOR: Ground floor finish
laid when the structure is watertight which generally consists of Vapour barrier /
75mm Polyurethane Insulation and 18mm V313 Moisture resistant floor decking
SCREEDED FLOOR - A finished concrete floor that is
typically poured on top of the 75mm Polyurethane insulation which is laid
onto the foundation (Slab or beam and block). The screed layer can
incorporate under floor heating pipes.
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HEAD BINDER: Horizontal timber member that ties together individual wall panels.
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I BEAMS / SILENT FLOOR - These generally use laminated veneer lumber flanges, routed to accommodate an OSB centre web. They can accommodate larger spans than standard joists and are a lightweight, uniform product. Advantages include reduced shrinkage, cupping, bowing, twisting and splitting that can be associated with standard joists.
INTERNAL PARTITIONS: Timber wall panels that are prefabricated and generally without sheathing unless required for engineering purposes.
INSULATION: The materials used in walls / floors and
roof space to create a warm structure to satisfy the clients requirements
and comply with part L of the building regulations .
Types of insulation are-
TIMBER BATTS - A semi-rigid unfaced slab designed to give thermal and acoustic insulation and fire resistance. It is push fitted between studs at 600mm centres and is made from natural materials and recycled glass. (generally used for external and internal panels)
ROLLS - A product that is produced from fine, non-combustible glass mineral wool and generally used in horizontal applications such as roof and floor areas.
POLYURETHANE - Expanded plastics that have excellent insulation properties. It is generally used as a rigid board for installation in sloping roofs or even between the studs in external wall panels. It can also be sprayed in situ as an expanding foam to follow complex shapes.
WARMCELL - This is an insulation material made from recycled material
such as paper. It is blown into the required area pneumatically by
specialist contractors on site from a van mounted machine. It is used in
wall panels / horizontal and sloping roof areas and floors and can result
in high U values.
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JOIST HANGERS: Galvanised steel hangers that can be nailed to timber or other materials that floor joists sit into for support
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MOISTURE RESISTANT CHIPBOARD (V313): This is manufactured mostly from softwood forest thinnings and timber waste from sawmills or manufacturing processes.
It is the moisture resistant form that is generally recommended for bathrooms and other potentially wet areas.
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NATIONAL HOUSE BUILDING COUNCIL: (NHBC / NHBC Builder) An organisation that encourages better house building. It has a register of reputable house builders and includes services such as conciliation between builders and purchasers, the NHBC
Warranty, ten year insurance on new houses and advice on proper site
practices.
NOGGINS (PLASTERBOARD): A horizontal member fitted between 2 studs, Joists or Trusses generally to supply a fixing for plasterboard.
NOTCHING AND DRILLING (for services): It is important the joists and studs are notched and drilled for services (to run cables and pipes through) in areas indicated by the supplier only. Notching and drilling zones will be indicated by the manufacturer in their standard details so as not to impair the structural integrity of the structure.
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ORIENTED STRAND BOARD (OSB): Timber board generally used to sheath external panels of timber frame. It is manufactured by flakes of timber 'snowed' into a mat using a small electrical charge so the resulting board has a specific strength.
OVER FASCIA VENTS: An eaves vent that runs along the top of the fascia. They can have different size openings depending on the ventilation requirements of the roof (generally 10 - 25mm)
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PANEL CONSTRUCTION: In a panel system the structural studs are spaced at 400 / 600mm centres and carry the loads down to the foundations via the soleplate. Timber frame external walls (and internal loadbearing) are required to carry the dead and imposed loads acting on the structure and transmit them to the foundations. On average the panels can vary from around 2 metres in length upwards if a crane is being used on site.
PARALLAM: This is a beam created from shards of timber formed longitudinally in line with the length of the beam. This product is stronger than conventional timber and is generally used as lintels above windows or beams in floor zones.
PARTY WALL / COMPARTMENTATION: A separating wall between two dwellings that must fulfil two main requirements 1, To reduce the passage of sound between the dwellings to levels set out in part e of the building regulations. 2, To comply with regulations as to give adequate fire protection between the buildings right up to the roof and through the cavities. Timber frame party walls perform well above building regulation requirements and the main components that improve sound and fire insulation is the type and mass of plasterboard used, the addition of insulation and adequate cavities between structures.
PARTY FLOOR: A separating floor between flats that has to perform similar duties to the party wall above. A party floor has to give more consideration to impact sound insulation as well as airborne sound.
PLATFORM FRAME: Most timber frame construction in the UK is generally platform frame. It is where a structure is built sequentially upwards in platforms (floor by floor).
PLYWOODS: These consist of an odd number of thin layers of timber with their grains alternating across and along the panel or sheet. They are then glued together to form a strong board which will retain its shape and not have a tendency to shrink, expand or distort. Generally used for floor decking or as sheathing boards.
POST AND BEAM CONSTRUCTION: A type of timber frame construction where heavy structural timber posts and beams are used (generally 150 x 150mm or larger) to transfer all the loads of the structure down to the foundations.
This is the older of the two types of timber frame construction and
traditionally utilises Oak or Douglas Fir timbers.
PURLINS: Horizontal heavy section timber, steel or glulam that run at right angles to the underside of the roof rafters. They carry the load of the roof to the gable ends of a house and also generally supported on internal panels which transfer the loads to the foundations.
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RACKING RESISTANCE: The wall panel studs (generally set at 600mm centres) carry the vertical loads from the floor / roof down to the foundations. The studs must be restrained using a sheet material such as
OSB (oriented strand board) to provide resistance to racking and stiffen the structure.
RAFTERS: A sloping roof beam that generally runs from eave to ridge. Most roof elements are generally pre-fabricated trusses but rafters are used for infilling and for other areas where prefabrication is not practical. This term can also be applied to the principal rafter of a truss.
ROOF TRUSSES: These are triangulated plane roof frames designed to give clear spans between the external supporting walls. They are delivered to site as prefabricated components and fixed to wall plates generally at 600mm centres. They receive lateral stability through wind bracing timbers that are fixed through them to bind them together.
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SAP RATING: The standard application procedure that defines the energy efficiency of a structure by taking into account items such as heating systems, the position of the site and the makeup and materials of the structure.
SARKING: A material such as OSB applied to the upper surface of rafters on a roof to give a continuous panel support. A system that is used as standard in Scotland, but uncommon in England and Wales.
SCAFFOLDING: These are temporary working platforms erected around the perimeter of a building to provide a safe working place at a convenient height. With timber frame the scaffolding is generally erected around three sides of the building before the kit is delivered. It is then enclosed at a suitable time. The scaffolding is erected far enough away from the external wall panels so it can stay up throughout the build for use by bricklayers and roofers etc.
SHEATHING: Boards laid side by side - tongued and grooved boarding is used for flooring (generally 18 or 22mm moisture resistant chipboard or plywood) and close boarding for timber frame panels and roofs (9mm OSB or plywood generally used for panels)
SOFFITT: A horizontal sheet fixed under the eaves, concealing the rafters and the underside of the roofing. It runs between the back of the fascia and the face of the outer wall. The soffit
can be either flat or sloping.
SOLEPLATE: A horizontal timber member fixed to the ground floor slab to which the wall panels are then nailed to. It is generally treated with a powerful preservative.
SOLEPLATE LAYOUT: One of the first jobs to be done by a timber frame company after receiving an order is to issue a soleplate layout. This is an accurately dimensioned drawing for the ground workers to set out the foundations precisely. It indicates the load bearing and non-loadbearing panels. It is important that the foundations are constructed accurately to the timber frame soleplate to ensure a successful and smooth running project.
SOLEPLATE TIES / FIXINGS: The soleplate fixings serve two purposes, to locate the plates accurately during construction setting out the superstructure. They also transfer wind loads down to the foundations once the building is completed. The soleplates may be fixed by shot-firing through the timber into the concrete slab or using stainless steel soleplate fixing shoes. Soleplates may also be fixed to brickwork substructures using stainless steel straps.
SOUND INSULATION: The reduction of the sound transmission from one space to another especially significant through walls and floors between separate dwellings (see party wall / party floor)
STICK BUILT: A method of timber frame where a structure is built on site from loose materials as opposed to in the factory. This type of construction is more common in the United States and Canada than in Britain.
This type of build is sometimes necessary for extensions where the exact
dimensions cannot be verified preventing a factory build.
STUDS: A vertical timber (generally 90x38mm or 140 x 38mm) that forms the wall panels and is the height of the required wall.
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TANK PLATFORM & WALKWAY: Timber bearers and floor decking such as chipboard or plywood that are installed in the roof space to form a walkway and take the load of the storage water tank.
TCB: A non combustible material (generally flexible mineral fibre strips in polythene sleeves) which cuts off the path of smoke and fire. It is mainly used vertically either side of party walls and up the lengths of the eaves on gable ends. Fire Barrier consisting of 300 x 50mm x 4m wire backed insulation, single folded at floor & ceiling zones, rafter zone and vertically at external junctions and is also used in party wall /floor situations.
TIMBER TYPES: The majority of timber used in the Timber Frame Industry is Scandinavian
or Baltic softwoods.
TOP PLATE: Horizontal timber rail that ties together studs in a wall panel.
TREATMENTS OF TIMBER: It is important that all timber used in the structural shell is sufficiently treated against insect attack and general decay and comply with the requirements of the N.H.B.C. and the Building Regulations 1995. The various types of timber used in different areas will be treated with a different material such as Tanalith, Vacsol
or Protim.
TRIMMER: Cross member between joists or studs to form an opening. A typical example is to trim out an opening in a floor around a staircase.
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U VALUE: The measure of the thermal insulation of a material or group of materials.
Depending on the specification of the insulation timber frame achieves excellent U values such as the ones listed below that are typical for external walls. (based on
140mm insulated timber frame panel
with reflective membrane/ 50mm cavity & 100mm brickwork external skin)
U Value 0.27W/m2K.
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VALLEY SET: A set of diminishing trusses that will infill an area of roof between two different roof directions.
VAPOUR BARRIER: Usually a layer of polythene, generally 125mu
thick, supplied in rolls which is installed to restrict the passage of water vapour, e.g. on the inside of external wall panels on the warm side of insulation.
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WALL PANEL THICKNESSES: External wall panels generally consist of 90x38mm or 140x38mm timber studs, a
9mm sheathing board, breather paper and tape that is factory fixed. The internal panels are usually studwork (some internal panels are sheathed with a
9mm board for engineering purposes) The 140mm external panels are used instead of the 90mm so that higher insulation values can be achieved)
WALL TIES: Stainless steel brackets and nails installed to tie back and brace the external brick or block cladding to the timber frame. Polypropylene tape fixed to the outer face of external wall panels indicate where the studs are so that the ties can be fixed back at approximately 5 per m2. wall ties provide lateral restraint but do not carry the weight of the wall which is self supporting.
WALL CAVITIES: The void between the timber frame wall panel and the external skin such as brickwork or blockwork. The standard timber frame cavity is 60mm below dpc and 50mm above as 10mm is used up by the external sheathing board of the timber frame.
WARRANTIES OF TIMBER FRAME: House builders are required to get adequate insurance and guarantees on what they are building whether it is through the NHBC
or through a company such as Zurich Municipal.
WINDBRACING: A structural tie (generally made up of 100 x 25mm timbers) giving lateral bracing to roof trusses.
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