Building materials glossary
51 terms you will meet when ordering materials, in plain English.
- Aggregate
- Granular material such as sand, gravel or crushed stone used in concrete, mortar and sub-bases.
- Aircrete
- Lightweight aerated concrete blocks with good thermal performance and easy cutting.
- All-in ballast
- A ready blend of sharp sand and gravel up to 20 mm, mixed with cement to make concrete.
- Architrave
- The moulded trim around a door frame or window opening.
- Batten
- A small timber section used to support roof tiles, cladding or linings.
- Bulk bag
- A large woven bag for sand and aggregate, typically around 850 kg, lifted by crane.
- C16 / C24
- Strength classes for structural softwood under BS EN 338; C24 is stronger and stiffer.
- Carcassing
- Strength-graded sawn timber used for the structural frame: joists, rafters and studs.
- Cavity tray
- A preformed damp-proof tray in a cavity wall that directs water outwards over openings.
- Cement
- The binder in mortar and concrete, sold in 25 kg bags in the UK.
- CLS
- Canadian Lumber Standard: kiln-dried, planed timber with rounded edges for stud walls.
- Crane offload
- Unloading pallets and bulk bags with the delivery lorry's own crane.
- Damp-proof course (DPC)
- A strip built into a wall to stop moisture rising through the masonry.
- Damp-proof membrane (DPM)
- A sheet under a concrete floor that stops moisture coming up through the slab.
- Dense block
- A heavy concrete block made with dense aggregate, used for strength and sound separation.
- Dry-fix
- Mechanical fixing of ridge, hip and verge tiles without mortar.
- Dry-lining
- Lining walls with plasterboard fixed to battens, studs or adhesive dabs.
- End bearing
- The length of a lintel or beam that sits on the supporting wall at each end.
- Engineering brick
- A dense, low-absorption clay brick in Class A or Class B for demanding conditions.
- ETA
- European Technical Assessment: independent assessment of a product's performance, often used for anchors.
- F2 / S2
- Durability designations for clay bricks: F2 is freeze-thaw resistant, S2 means low soluble salts.
- Facing brick
- A brick made to be seen on the outside of a building.
- Frog
- The indent in the top of some bricks that helps the mortar key and reduces weight.
- Gauge
- The spacing of roof battens, which sets how much of each tile is exposed.
- Hardwall
- A gypsum undercoat plaster for high-suction backgrounds such as brick and block.
- Joist hanger
- A galvanised steel bracket that supports the end of a joist from a wall or beam.
- Kiln dried
- Timber dried in a kiln to a controlled moisture content so it moves less once fitted.
- Lambda value
- Thermal conductivity in W/mK; the lower the number, the better the insulation.
- Lintel
- A beam over an opening that carries the masonry above.
- MF ceiling
- A suspended plasterboard ceiling built from steel channels hung from the structure.
- Mineral wool
- Glass or stone fibre insulation in rolls, batts and slabs; usually non-combustible.
- MOT Type 1
- Graded crushed stone sub-base to Specification for Highway Works clause 803.
- Mortar
- The mix of cement, sand and water that bonds bricks and blocks.
- N/mm²
- Newtons per square millimetre, the unit used for block compressive strength.
- Noggin
- A short horizontal timber between studs or joists that stiffens the frame and supports board edges.
- OSB3
- Oriented strand board for load-bearing use in humid conditions, under BS EN 300.
- P5 chipboard
- Moisture-resistant load-bearing chipboard used for floor decking.
- Padstone
- A concrete block that spreads a concentrated load at the end of a beam or lintel.
- PAR
- Planed all round: timber smoothed on all four faces.
- PIR
- Polyisocyanurate: rigid foam insulation board with foil facings.
- Plasticiser
- An additive that makes mortar easier to work and improves frost resistance.
- Radon barrier
- A gas-resistant membrane used in radon-affected areas.
- Restraint strap
- A steel strap that ties walls to floors and roofs.
- Screed
- A layer of sand and cement, or a flowing compound, laid over a slab to give a level floor.
- Coarse, angular sand for concrete, screeds and paving beds.
- Soft sand
- Fine building sand used for bricklaying mortar.
- Sub-base
- The compacted granular layer under a drive, patio or slab.
- Thermal laminate
- Plasterboard bonded to a layer of insulation.
- U-value
- The rate of heat loss through an element in W/m²K; lower is better.
- Use class
- A category under BS 8417 describing where treated timber can be used, from 1 (dry, internal) to 4 (ground or fresh-water contact) and 5 (sea water).
- Weep vent
- A small vent in the outer leaf that lets water drain out of the cavity.
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