In short
- Definitions of the most common terms used by renderers, manufacturers and building control.
- Linked to more detailed guides where relevant.
A to Z
- Alkali-resistant mesh: glass-fibre mesh embedded in a base coat to reinforce it.
- Article 2(3) land: designated land, including conservation areas and National Landscapes, where rendering an unrendered house is not permitted development.
- Base coat: the layer beneath a thin-coat finish, carrying the mesh.
- Bellcast bead: a bead at the base of the render that throws water clear, placed above the damp-proof course.
- Damp-proof course (DPC): a barrier low in the wall that stops moisture rising; render must not bridge it.
- Dry dash: pebbledash, stones thrown onto wet render.
- EWI: external wall insulation.
- Float: tool, and finish, used to level and texture render.
- Grain size: the size of aggregate in a thin-coat finish, commonly 1–2 mm.
- K-Rend: render brand made by Kingerlee.
- Lime bloom: white deposit on cement-based render, especially monocouche, caused by curing in cold, damp conditions.
- Limewash: a breathable lime-based coating.
- LRV: light reflectance value, from 0 (black) to 100 (white).
- Monocouche: one-coat, through-coloured render.
- NHL: natural hydraulic lime.
- Render board: a carrier board for render on timber frame.
- Roughcast: wet dash, aggregate mixed into the final coat and thrown.
- Scratch coat: first coat of a traditional render, scored for key.
- Stop bead: bead that forms a neat edge where render ends.
- Substrate: the wall surface being rendered.
- Thermal element: a wall, floor or roof under Building Regulations.
- Through-coloured: colour mixed through the material, so no painting.
- U-value: heat loss through an element, in W/m²K.
- weber.pral M: Weber's one-coat monocouche render.
More terms
- Arris: the sharp edge where two render faces meet.
- Biocide: additive or treatment that slows algae and fungal growth.
- Efflorescence: white salts drawn to the surface by moisture.
- Hack off: removing old render back to the substrate.
- Hollow render: render that has lost its bond with the wall.
- Key: texture that helps the next coat bond.
- Lawful development certificate: formal confirmation that work does not need planning permission.
- Listed building consent: permission required to alter a listed building.
- Primer: coat that controls suction and improves bond between base and finish.
- Suction: how quickly a surface draws water from wet render.
- Surrey Hills National Landscape: the designated landscape, formerly an Area of Outstanding Natural Beauty, covering much of central and western Surrey.
- Vapour permeability: ability of a material to let water vapour pass through.