Heritage Trass Medium Mortar & Render
A multipurpose medium-textured ultra-breathable mortar, render and plaster with a high free lime content to replicate the properties and performance of historical mortars, especially suited for applications in more exposed environments where a Natural Hydraulic Lime mortar may be inadvisable.
"*" indicates required fields
More about Heritage Trass Medium Mortar & Render
Cornerstone Heritage Trass Medium is a dry ready mixed multipurpose lime mortar, render and plaster for general building, pointing and coarse render coats with a minimum of a two-coat render application. Available in the colour tan-beige.
Engineered with precision, utilising Lhoist CL90 and the pozzolan Rhine Trass to create an ultra-breathable and high free lime content lime mortar to closely replicate the historic mix ratios of traditional mortars found in the UK.
In addition, Heritage Trass Medium can be blended with additional conservation appropriate additives to enhance the mortar’s physical and mechanical characteristics while retaining all the benefits of a highly breathable pure lime mortar. Available as standard with Lhoist CL90, with the addition of Trass gauged at 5%, 10%, or 20% to suit specific project requirements. Other mix ratios and the inclusion of fibres are available upon request.
Well-suited for applications requiring ultra-high breathability and low capillary water absorption, making it especially suited for rendering applications in more exposed environments where a Natural Hydraulic Lime mortar may be inadvisable.
- Lower in strength compared to our MK Medium
- Sympathetic for weaker substrates
- Ultra-high vapour permeability and low capillary water absorption
- Suitable for exposed environments
- High free lime content to closely replicate historic mix ratios
- Maintains the natural colour of mortar
- No long-term strength development other than carbonation
- Performance data supports the specification process
- Reduced performance variation compared to onsite mixing
- No risk of pop-outs or pluming common with hot mix
Suitable for internal or external use, where the binder strength is appropriate for the host background or surface.
Relevant for general building, pointing and including coarse render coats, typically including scratch coats and float coats with a minimum of a two-coat render application. For a coarse basecoat, explore Heritage Trass Coarse.
For a similar mortar with additional strength and capillary water absorption with a slightly reduced vapour permeability, explore our Heritage MK Medium. Appropriate for various project types, including conservation or restoration.
A 25kg bag will produce approximately 14.5 litres of mortar or render. For rendering, this covers roughly 1.5m² at a 10mm thickness. For pointing, this will fill roughly 1.5m² of joint at a 10mm depth. The width and depth of the joint will influence this estimation. On-site trials are advised for the best yield indication for your specific project.
Be aware that the finish applied to the mortar will influence the final appearance. Our team can advise you on finish methodology options that might best suit the final texture of colour you aim to achieve for colour-sensitive projects.
As natural products, our kiln-dried sands may exhibit variations in colour, texture, and shape. While these variations are minimal, when colour consistency is crucial, we strongly advise each elevation is completed using material from the same batch.
Supplied in 25kg polythene-lined and colour and batch-coded paper bags for easy identification on-site. Palletised for ease of transport, storage, and handling. FIBC tonne bags are also available.
Do not use in temperatures below 5°C or above 30°C, or if freezing conditions are predicted within the following few weeks, including wind chill. We always advise following best practices for curing and protecting fresh mortars, renders and plasters. Protect from adverse environmental conditions, including frost, rain, direct sunlight and drying winds.
Need help deciding which to choose? See the Download Documents section for helpful comparison sheets, or get in touch with the team.
Store in covered and dry conditions, protected from environmental conditions, including water, damp or frost and clear from the ground. Always reseal packaging if product is still present.
Always read the available documentation before use. See the Download Documentation section below for more detailed product information, application guidance and datasheets.
Related products
Heritage Trass Coarse Mortar & Render
A multipurpose high vapour permeability but lower capillary water absorption mortar for historic buildings in exposed environments.
View Product
Heritage MK Medium Mortar & Render
A multipurpose high free-lime content mortar offering an ultra-breathable, porous and convenient alternative to hot mix.
View Product
Superfine Putty Finishing Plaster
A smooth internal finishing plaster with a superfine texture and refined natural white coloured finish.
View Product