The procedure of placing wood flooring in the area where it is to be installed to enable it to ‘acclimatise’ or adjust its moisture content to correspond with that of its surroundings.
Ted Todd recommends that all floors are acclimatised within their packs for 2 to 3 days in the room to be installed to allow the temperature of the floor to equalize with its environment ensuring job site conditions are met.
Ensure that the building is enclosed.
Verify that the building is maintained at normal living conditions for temperature and humidity.
Where building codes allow, permanent heating and/or air-conditioning systems should be operating at least five days preceding installation to promote proper acclimatisation.
If it is not possible for the permanent heating and/or air-conditioning system to be operating before, during and after installation, a temporary heating and/or dehumidification system that will mimic normal temperature and humidity conditions can enable the installation to proceed until the permanent heating and/or air-conditioning system is operating.
Packs should be stacked flat on the floor or on battens (not upright) allowing for airflow around the stacks
If the delivery is for more than one room the order should be broken down into the individual room quantities and stored in the respective rooms.
Paste used for fixing flooring to its subfloor. Usually spread with a notched trowel – it is important to use a trowel with the correct sized notches so as to apply the correct quantity of adhesive.
A method of drying timber by atmospheric conditions between its natural state as a tree and its use in building. Air-dried timber is not usually sufficiently dry for hardwood flooring and kiln drying is required to achieve a moisture content of 8 to 10%, which conforms to BS8201.
An implement for applying adhesive, oil, seal or other dressing.
A wooden frame for doorways. Usually requires undercutting to permit wood flooring to fit under it.
A piece (usually) of softwood which supports the hardwood flooring and to which it is often fixed by nailing.
A decorative feature whereby the sharp edge of the board is planed off. The bevel more clearly defines the boards edge, but this can add to the beauty of the floor. Sometimes also called an ‘eased’ edge. There is no industry standard for bevel size, so it varies from producer to producer – however, it is usually angled at 45 degrees and between 0.5mm and 2mm deep.
A distinctive figure in Maple which is said to look like a bird’s eye.
The process by which a chemical is applied to timber in order to lighten it. Certain hardwoods are bleached by sunlight – ie Walnut, Cherry and Oak.
A distinctive type of Oak that is a deep, chocolate colour. English Brown Oak is actually white Oak that has turned brown due to a fungal infection (beef steak fungi) that causes a chemical change in the tree. It is a rich honey brown colour.
Blocks or Parquet Wood Blocks
Pieces of flooring timber, varying in size, but usually in the region of 200-275mm x 65-75mm x 20mm. Most blocks are tongued and grooved (see below) and adhered to a screeded subfloor with adhesive. Can be laid in different patterns; basket weave, herringbone, half bond etc.
Blocks (or Planks or Strips)
A form of wood flooring composed of elements from 60-200mm wide (sometimes smaller or larger) and from 500mm to 2500mm in length, often random lengths. Boards can be secret nailed (see below) or glued. Solid boards must never be fixed by the ‘floating floor’ method.
A feature in a floor, whereby a contrasting timber is inset around the perimeter. Sometimes called an ‘inset strip’.
Brinell Scale of Hardness
A scale that compares the hardness of various species of timber. On the Brinell scale, Oak has a value of 5 whereas Jatoba has a value of 7 indicating Jatoba is harder than Oak.
Case hardened is used to describe timber that has been improperly dried. If dried too quickly, wood shrinks heavily on the surface compressing its still damp interior. This results in unrelieved case-hardened wood which may warp considerably and potentially dangerously when the stress is relieved by sawing. This is a commonly known term, but case-hardened timber is not as common as people think.
The carbohydrate that is the principle constituent of wood. It forms the frame work of wood cells.
A lengthwise separation of the wood which extends across the rings of annual growth, usually resulting from stress, set up in wood during seasoning.
A board made from particles of wood, mechanically compressed with glue or other binders to produce a board. Chipboard is a very common subfloor material today, particularly in new construction. It should be avoided in damp conditions although you can source flooring grade chipboard that is damproof. Serrated nails are recommended when fixing, as chipboard does not retain standard nails well. Resin-bonded ply is an alternative.
The Convention on International Trade in Endangered Species of Wild Fauna and Flora is an international agreement aimed at regulating the trade in wild life. Species can be listed on one of three appendices to the treaty which impose levels of restriction on international trade. Although there have been attempts by environmentalists and some governments to list a range of over-exploited timber species on CITES, there are currently just 46 CITES-listed trees by Species or Genus listed under this agreement, of which only a few are major timbers. Producer countries frequently oppose moves to list species to protect their logging interests, although some appreciate the help it can provide in controlling trade in over-exploited species
A method of joining the boards of floating floors together without using glue. The tongue is made with a protrusion that fits over a corresponding rebate in the groove, so called because the elements often “click” when pushed together. Not recommend for use with solid boards as the precise jointing mechanism is susceptible to slight changes in moisture – rendering the system useless.
Piling (stacking) of wet timber (not kiln-dried) without sticks, even for a few days is a cause of staining and if prolonged, may result in serious losses from fungal decay.
A type of galvanised nail with a large head, sometimes used as a decorative/period feature when face fixing solid boards.
Coeffecient of Expansion
Timber expands and contracts with changes in moisture. The rate of this change varies according to a timber’s porosity. The rate of this change can be measured to produce a table showing the varying coefficient of expansion – it is measured by the change in the width of a board that happens when the moisture content goes from 20% to 10%. Beech has a high coefficient whereas Oak has a low one. In layman’s terms this could be called a timber’s “stability”.
The manufacturer’s guide to the safety aspects of the product, produced in accordance with the Control of Substances Hazardous to Health.
A process usually used at the end of the drying process used to create an equilibrium in moisture content.
A wide gap in the timber, often caused by shrinkage of timber containing a shake.
A method of slicing veneers whereby the average inclination for the growth rings to the wider face is tangential or less than 45 degrees. This method is also known as flat cut.
Distortion of boards or blocks so that the surface is convex. Usually caused by very damp atmospheric conditions, whilst the subfloor remains dry.
Cumulative shrinkage or ‘rafting’ is caused by a lacquer applied to the surface of a floor, running down the edges of the pieces and sticking them together like strong glue. When the floor shrinks (with its natural seasonal movement) instead of each piece shrinking a fraction so that there is a tiny gap between each piece, the pieces are stuck together in ‘rafts’ and wide gaps open at weak spots. It is sometimes possible to fill the gaps, but floors subject to bad cumulative shrinkage may have to be completely replaced.
Cupping is the opposite of crowning and is infinitely more common. It is almost always caused by moisture under the floor, whereby the moisture content of the bottom of the board is raised to a higher level than the surface, distorting the board. Whilst minor cupping, less than 0.5% of the board width, might be sanded out, there is a slight danger that, if the board should return to a stable form, crowning might result.
Damp Proof Membrane
A layer of impervious material, often polythene, built into the subfloor to prevent moisture affecting the flooring. Liquid DPMs are recommended when the existing moisture content of the screed is too high to fit a timber floor. BS8201 advises a slab moisture content of 4% or 75%RH. However, for flooring with a moisture content of 8 to 10% a slab must not exceed a moisture content of 2% or 40%RH. Residual moisture content in a newly laid concrete slab can be sealed with a proprietary product, but rising damp will need to be treated by a specialist.
The manufacturer’s guide to the technical details of the product.
The measurement of the floor’s sound insulative properties. Db = decibel – a unit of sound measurement. There are various sound reduction underlays available that will enable the use of a timber floor whilst meeting all of the current sound reduction regulations.
Different cuts of the same wood species can shrink at different rates. The most stable section is the quarter sawn section, this is far more stable than a plain sawn section. Different species of timber expand and shrink at different rates.
This refers to the varying propensity of different wood floors to expand/contract. For example, wide engineered wood floors are more dimensionally stable than wide solid boards. Installation methods will/should reflect on a product’s dimensional stability.
The tongue and groove profile on the end of a board. This profile on structural flooring enables individual planks to straddle a joist, rather than being cut back to end on an individual joist which is wasteful.
When boards were introduced having a 3mm or 4mm hardwood surface, a 7mm softwood core at right-angles to the hardwood and a 3mm ply backing, they were called ‘Laminated Hardwood Boards’. With the advent of plastic laminate flooring, the word ‘laminate’ or ‘laminated’ has become synonymous with this cheaper imitation of wood flooring. In order to avoid confusion, the original hardwood variety became known as ‘engineered’ boards, because they are manufactured. Subsequently, there was a move to use the name ‘multilayer’ which we believe is a more accurate description of the product. However, the term ‘engineered’ is still widely used. Engineered boards can be laid as a floating floor, because they are very stable, due to their cross-grained construction. The boards are far more dimensionally stable than solid boards and as such can be installed by the ‘floating floor’ method of installation. Structural engineered boards are now also available; they are usually made with a plywood backing. These boards can have a thicker wear layer and can also be laid over joist.
Wood is a hygroscopic material. It expands only due to the absorption of moisture, and shrinks when it loses moisture. In the UK, the moisture content of wood flooring is at its highest in summer, when windows and doors are open and the air relatively moist, and is at its lowest in winter, when windows and doors are closed and central heating is running on full, creating very dry air. A moisture content of 8-10% assumes a humidity level of 35-65%. So if during winter you fail to ‘air’ your rooms and the humidity drops to under 35% shrinkage will occur – at 20% major damage to all floors is evident (even engineered).
A gap left at the perimeter of a wood floor to allow for seasonal expansion. The gap is usually 15mm or 30mm per line arm across the grain.
Fair and average moisture content. Any moisture content is always an average of different readings across a batch of products, and this is why a spread of content is detailed – ie 8-10%. This figure is still only an average and therefore can still contain some boards with a higher or lower reading than 8-10%.
Boards nailed through the surface. Nails are usually punched and filled. Often necessary with boards exceeding 100mm in width in order to comply with the requirements of BS8201:1987 which states that boards exceeding 100mm in width should not solely be secret nailed. This requirement is now seen as being restrictive as widths up to 180mm are successfully secret nailed. In this instance, the humidity levels of both the sub-floor and air are crucial.
Fibre Saturation Point
This is the theoretical point when the cell cavities are empty of free water and the cell walls remain saturated. The average moisture content of wood at moisture saturation point is between 23-30%.
The beautiful appearance of the timber created by the grain and growth rings. Certain timbers have particular figures, eg the ‘bird’s eye’ figure in Maple medullary rays in quarter sawn Oak.
A fillet is a small batten (see above) often used on joists in order to pack up the floor level.
Wood flooring loose laid over a resilient underlay. Engineered or multilayer boards are usually laid as floating floors, but never solid hardwood boards. Floating floors laid over concrete must include a vapour barrier. The boards that constitute a floating floor must be fixed together, usually by gluing the tongues and grooves.
A heavy-duty lacquer applied to the surface of wood flooring. Usually maintained by sweeping and damp-mopping. Can be very hard wearing.
Forest Stewardship Council® – an independent, non-governmental, not-for-profit organization established to promote the responsible management of the world’s forests.
There are various grades of timber, variously called prime, first, second, country, factory etc. There are no British standards or industry standards for wood floor grades – so you need to check what the grades include/exclude. It is also important to remember that grades are species specific – ie Prime Oak might not contain either knots or sapwood but Prime Walnut might allow for some of both.
This is a general term for unseasoned timber. Green timber cannot ever be used internally for wood floors.
A term used to describe sandpaper, the lower the grit number – (ie 40) – the more coarse the paper.
Oil finishes are an ideal alternative to floor seals or lacquers, where a more natural appearance is desired. Oil finishes usually require marginally more maintenance than floor seals, but when properly maintained, can last longer. Hardwax oils can be easily re-coated and ‘spot repaired’. Please note that UV oil finishes are not compatible with hardwax oils. The closed surface of the UV finish restricts the hardwax oil from penetrating the wood – which results in drying difficulties as well as heavy residues left on the surface of the floor.
The joint between two ends of boards.
The core of the tree from which growth rings emanate.
When wet wood is exposed to dry air it loses water to the air and when dry wood is exposed to humid/damp conditions it absorbs water and swells.
A device for measuring the moisture content of air. Hygrometers are calibrated in % relative humidity or RH. Hygrometers used in flooring consist of a polystyrene box about 300 x 300 x 75mm which traps air in a void under the box. The humidity box, as it is called, is fixed to a subfloor with an adhesive sealant strip and left for 12-60 hours. Moisture from the subfloor exchanges with the air above it until the two are in equilibrium, so that ascertaining the moisture content of the air under the box is the same as testing the screed itself. The British Standard code of practice for the installation of hardwood flooring (BS8201:1987) specifies that the RH should not exceed 75% when flooring is to be laid on a screed. With the modern practice of gluing boards directly to a screed, this is considered by many to be too high and 70% is more realistic for this purpose. As an alternative to humidity boxes, humidity sleeves are now in common use.
Interior checks caused when timber has been case hardened. The outer zones of the wood set without shrinking and when the centre core dries, it is restrained from shrinking and interior checks may result.
Feature of contrasting wood inset into a floor.
A layer of material, often built into the subfloor as a barrier for heat or sound.
A joist is a wooden strut, nowadays usually softwood, used to support floorboards to which the boards are usually nailed. The size of the joist will depend upon the expected load and the span.
A chamber in which the temperature, humidity and movement of air is controlled and is used to dry wood.
Timber for wood flooring is usually dried in a kiln to reduce its moisture content to 8-10%. This level is selected because it is the moisture content wood flooring usually assumes in buildings in the UK. In excessively dry conditions wood flooring will reduce to a moisture content of 5% – at this level significant gaps will appear, even in timber that has originally dried in accordance with British standards.
A knot is a figure in the grain of wood where a branch once grew, created during the growth of the tree. Small knots or burrs can be quite attractive. Some timbers, like Cherry, contain many knots; others, like Birch, very few. The knot content in timber can vary depending on the specific tree variety and is usually controlled in the grading process during production.
Another name for floor seal. Lacquers are often polyurethane-based in a water-borne solution.
This is a plastic imitation wood flooring which has become popular in recent years, due mainly to its competitive pricing structure. However, whilst its general appearance is good, being produced photographically to look like wood, it lacks the warmth and resilience of real wood and cannot, of course, ever be sanded.
See “Engineered Boards” above.
When floor layers are faced with solid subfloors that are not sufficiently flat, they use a smoothing compound. Smoothing compounds, or as they are often incorrectly called, self-levelling compounds, are latex-cement powders which are mixed, either with water or latex paste, to form a grey cement which can be applied with a screeding trowel in thicknesses of 3mm, and in some cases even less.
Very small bevel. See ‘bevel’ above.
Iridescent streaks found in quarter sawn material.
See ‘Engineered Boards’ above.
The amount of moisture contained in a material. The moisture content of most wood flooring is 8-10%. The moisture content of a screeded subfloor when laying wood flooring ought not to exceed 40% RH which is about 2%.
A device used to measure the amount of water in a particular material. Moisture meters used in flooring are calibrated to a scale called ‘wood moisture equivalent’ (WME). This is because wood is fairly consistent with regard to moisture content, even within different species, whereas of the materials, like sand, cement or plaster, vary according to their particular composition. Consequently, they are measured on the WME scale which would be equivalent to the moisture content a piece of wood would assume if placed in contact with the material being tested.
The variation in moisture content between the surface and the core of a piece of wood.
Movement is the swelling or shrinkage when wood is exposed to various humidity conditions. (See hydroscopic moisture)
There are various nailing machines on the market, perhaps the best known of which is Portanailer which drives nails into the flooring at exactly the correct angle. Machines can be either manual or pneumatic.
A measurement of force. For the technically minded, it is the amount of force that imparts the acceleration of 1 meter per second to a mass of 1 kilogram.
The reason for applying adhesive (and other materials) with a notched trowel, is that the manufacturer of the product will have calculated the optimum quantity of adhesive required, and applying it with the correct notched trowel will ensure that exact quantity is applied, thus ensuring a perfect bond.
A preparation for finishing wood floors. (See also ‘Hardwax Oil’ above). There are many different types of oil on the market. It is important to know the requirements of the floor and recommended maintenance procedure. Different oils have varying ‘high solid’ content. The high solids are the wax residues that are left once the ‘spirit’ (or carrying agent), has evaporated.
Parquet flooring is formed from battens, usually 200-300mm x 60-100mm x 6mm or 10mm in thickness. Traditionally, parquet battens were face pinned and glued to wood subfloors, but today they can be laid over solid subfloors too. Traditionally laid in a herringbone pattern, but can be laid in many patterns and often with a border. Parquet flooring is also made in many elaborate patterns, eg Versailles. Parquet has also, incorrectly, become a generic term for wood flooring.
Programme for the Endorsement of Forest Certification Schemes – An international non-profit, non-governmental organization dedicated to promoting sustainable forest management.
Often called ‘washer joints’, these are gaps left between every board, or every few boards, for additional expansion provision within the body of a boarded floor. They are called ‘penny’ or ‘washer’ joints because pennies or washers were used in order to achieve an even gap. Can also be left for decorative purposes to create a traditional/restoration look.
Small clusters of knots, that are collectively called Pips or burrs. The very heavy concentrations are called Burrs. Usually desired in Oak but also found in Elm and Sycamore. They are also mainly found in the United Kingdom, and rarely found in either Europe or North America. They can also be described as cat’s paws – as they look like the paw prints of cats.
The way the raw log is sawn into planks. The two most common formats are plain sawn and quarter sawn. Plain sawn material is the cheaper cut. The log is sawn into slices right across. Quarter sawing involves cutting each plank on the line of a radius from the centre of the log.
A laminated board consisting of thin layers of board bonded together. In flooring, 6mm ply is the most common for underlay purposes over, for example, a floorboard subfloor. Ply can be resin-bonded or WBP (water and boil proof) which means the ply should be unaffected by moisture.
See ‘nailer’ above.
GE-Protimeter are one of the world’s leading manufacturers of moisture-testing equipment. They manufacture hygrometers (see ‘hygrometer’ above) as well as moisture meters (see ‘moisture meter’ above).
A quarter-round beading used in flooring installations to cover the allowed expansion gap. It is usually the same species of timber as the floor, or as near in shade as possible, and is pinned to the skirting.
True quarter sawn Oak boards are cut so that the end grain is at an angle of 90 degrees to the face board. This produces wonderfully straight grained planks. Medullary rays (the iridescent streaks) are then visible as swirls running across the width of the board. The joinery in cathedrals, palaces and fine houses was produced from the finest quality quarter sawn Oak.
Boards which vary in length within one floor.
Boards which vary in width within one floor. Historically through and through, cut planks produced lots of different widths of boards.
See ‘Cumulative Shrinkage’ above.
Humidity in the air is measured using an hydrometer. The amount of moisture air can contain varies according to its temperature. Warm air can hold more moisture than cool air. Warm air gives up its moisture as it cools, so that if warm air comes into contact with a cool surface, we get condensation. The measurement of the quantity of moisture in air is expressed relative to its maximum capacity to contain moisture which would be 100% relative humidity.
As per quarter sawn but with an angle of just under 90 degrees – producing straight grained boards without the medullary rays.
Moisture remaining within a screed even though the surface appears dry.
A slight irregularity in the surface of a hardwood floor often caused by inefficient sanding.
An unusual type of figure that looks like a ripple across the width of a plank. Highly prized and found in Maple and Sycamore.
Occurs in screeds that do not have an effective damp proof membrane. Sub-floor preparation products that pre-seal damp screeds will not (in the long run), stop damp from affecting a wood floor.
A sample is one of a number of pieces set in a kiln or air drying stack used to measure the loss of moisture.
To grind the surface of a wood floor with sandpaper so as to smooth the surface ready for the application of a dressing. Usually carried out using a sanding machine.
The liquid part of a tree. Visible as the light timber on the outer edges of the planks.
A beading, used for the same purpose as a quadrant bead (see above) but concave shaped instead of convex shaped.
Usually refers to the subfloor, which may be a sand and cement screed. Must be dry (below 75% relative humidity) before wood flooring is laid on it. Must be sound and flat too. May also be a latex or other smoothing screed.
A trowel with a smooth surface and without notches for applying sand and cement, latex or other smoothing screeds.
Similar to sanding, but usually done with a rotary disc using very fine abrasives. Ideal for sanding old floors when you want to carefully remove layers of patina.
Common name for polyurethane-type lacquers applied to wood flooring.
The process of drying timber either naturally or in a kiln, to a moisture content appropriate for the conditions and purposes for which it is to be used. For hardwood flooring in the UK, this usually means 8-10% moisture content. ‘Seasoned timber’ is also used as a description of timber that has been air dried for a long time.
The method of nailing tongued and grooved boards through the tongue so that the nails cannot be seen in the finished floor. See also ‘Portanail’ above. Note that BS8201:1987 states that boards of less than 100mm in width can be secret nailed as their sole method of fixing.
Screw & Plug
The method of concealing screws used in face-fixing wood flooring. The screw is countersunk below the surface of the board and a plug of the same grain and shade as the board is fitted over the screw.
See ‘latex screed’ above.
See ‘notched trowel’ as above.
A natural defect in a board, shakes are small cracks in the material. They are unavoidable in many species and may open when the board shrinks.
When wood dries the removal of moisture causes the wood to shrink. Shrinkage normally starts at fibre saturation point (25/30%). All timber shrinks more tangentially than it does radially whereas shrinkage longitudinally is negligible. As a result of the different shrinkage rates radial and tangential, you get different shrinkage which will cause square timber to diamond, but if wood shrank evenly in each section, this would not happen. Every species of wood has a different rate of shrinkage.
The wooden board (usually) fixed to the bottom of walls. If the skirting is removed before the laying of the floor, the required expansion gap can be left underneath so that no additional beading is required. Various moulded profiles are available, including pencil round, torus, lambs tongue, etc.
A powder, often cementitious, mixed with either water or a latex paste, depending upon its type, and used to prepare uneven screeds to a smooth surface. Often called a levelling or self-levelling screed, but this is incorrect as it is very difficult to level floors with such a product. There are companies who pump similar materials onto floors and this procedure will actually form a level base.
Spalting is the result of fungi growing on the tree. The black lines are the result of the roots of the fungi dissolving the wood in order to feed on the nutrients released. It affects both the colour of the wood and the hardness.
Steaming, Fuming and Heat Treating
Processes often used on timber, especially Oak. The procedures both darken the timber and strengthen it.
A type of particle board, used for subfloors.
When wood is stacked for drying, sticks are placed between the boards to enable air to circulate all round. Sometimes these sticks cause marks in the timber itself. This is usually when the wrong species of stick has been used that causes a reaction with the boards being dried.
The surface onto which the decorative wood flooring is laid.
If screed is tested with a hygrometer (in accordance with BS8201) and found to be wet, a surface DPM might be used, subject to circumstances. Such products may be liquids, eg epoxy DPMs, or underlays, such as System Platon or Uzin interlayers.
A source of wood flooring where the forest is sustainbaly managed.
Tar or Bitumen-Centre Building Paper
Used over wooden subfloor as a vapour barrier. Whilst nails puncture polythene, the bitumen centre in this material clings to the nails. It is now accepted that floors laid on joists that are vented should be laid on building paper.
A piece of shaped wood, placed in a doorway so that a higher level wood floor can be smoothly finished to a lower adjoining floor.
Tongue & Groove
A method of joining individual pieces of wood together in a floor to form a homogeneous unit. The tongue is cut from the edge of the block or strip to project outwards. The groove, in the opposite side is made to fit the tongue snugly, but not too tight. Tongues and grooves are always on the long edges; if they are on the ends as well, the material is said to be “ends matched”. In floating floors, where tongues and grooves are glued together, the groove has a void at the inside to accommodate the glue and prevent it from being squeezed to the surface. The tightness of the tongue and groove is called the tolerance. There is no industry standard for the amount of tolerance in a tongue and groove joint.
A strip placed in a doorway between two adjoining wood floors of the same level. Permits the inclusion of an expansion gap in the doorway.
A material placed under a wood floor to smooth the subfloor (eg ply), to protect against damp (eg polythene) or as a resilient layer under floating floors. Can also help to cut down airborne noise.
A method of rapid-drying lacquer in the factory which produces a harder wearing surface. Modified oils can also be UV dried.
A paste applied to the floor surface which protects the wood from traffic wear. Superseded in the 1980s by polyurethane and other lacquers and due to the latter needing less maintenance, it is now rarely used but substituted by Hardwax Oil. Waxes improve the luster of a floor and are used to create a period, restored feel. Several coats are applied to build up the finish, which is then polished either mechanically or by hand to create a warm, shiny floor.
The layer of wood nearest the surface in a multilayered board which receives the foot traffic. Wear layers are normally quoted on a “nominal” thickness basis– this means the thickness before sanding. A wear layer can also be measured on a solid board as being the thickness of wood above the tongue.