Bonding coat
The bonding coat, bond coat or base coat in construction terms usually refers to the first coat of gypsum plaster which is laid on the existing surface such as stone, brick or existing plaster. The term base coat is usually used to mean the same but for lime based plaster products or clay based plaster products. Base or bond coat can also be used to describe the first layer of external render applied directly to the existing external structure of a building such as stone or brick, though this is most often referred to as a parge coat.
The bond or base coat is usually a coarse plaster or render which can be applied in thicknesses between 10-20mm, it has greater adherence qualities and is used to even out the existing surfaces of the wall, internally in the case of plaster and externally in the case of render. Once hardened one or two more layers can be applied, finished by the final coat, finish layer, sometimes called skim coat which is normally a thinner layer applied at 2-5mm thickness.
See also: plaster, lime plaster and clay plaster
[edit] Related articles on Designing Buildings
- Boss plaster.
- Caulk.
- Cement.
- Cement mortar.
- Clay plaster.
- Daub.
- Decorative metal ceilings.
- Dry lining.
- Drywall.
- Finishes.
- Fresco.
- Grout.
- Gypsum.
- Inspecting historic fibrous plaster ceilings.
- Lath and plaster.
- Lime plaster.
- Making Magnificence: architects, stuccatori and the eighteenth-century interior.
- Mortar.
- Parge coat.
- Plaster.
- Rendering.
- Stucco.
- Tanking.
- Tiles.
Featured articles and news
Managing building safety risks
Across an existing residential portfolio, a client's perspective.
ECA support for Gate Safe’s Safe School Gates Campaign.
Core construction skills explained
Preparing for a career in construction.
Retrofitting for resilience with the Leicester Resilience Hub
Community-serving facilities, enhanced as support and essential services for climate-related disruptions.
Some of the articles relating to water, here to browse. Any missing?
Recognisable Gothic characters, designed to dramatically spout water away from buildings.
A case study and a warning to would-be developers
Creating four dwellings... after half a century of doing this job, why, oh why, is it so difficult?
Reform of the fire engineering profession
Fire Engineers Advisory Panel: Authoritative Statement, reactions and next steps.
Restoration and renewal of the Palace of Westminster
A complex project of cultural significance from full decant to EMI, opportunities and a potential a way forward.
Apprenticeships and the responsibility we share
Perspectives from the CIOB President as National Apprentice Week comes to a close.
The first line of defence against rain, wind and snow.
Building Safety recap January, 2026
What we missed at the end of last year, and at the start of this...
National Apprenticeship Week 2026, 9-15 Feb
Shining a light on the positive impacts for businesses, their apprentices and the wider economy alike.
Applications and benefits of acoustic flooring
From commercial to retail.
From solid to sprung and ribbed to raised.
Strengthening industry collaboration in Hong Kong
Hong Kong Institute of Construction and The Chartered Institute of Building sign Memorandum of Understanding.
A detailed description from the experts at Cornish Lime.