Cornerstone Heritage MK Medium Mortar & Render

Product Description

Cornerstone Heritage MK 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 buff.

Engineered with precision, utilising Lhoist CL90 and the pozzolan Metakaolin to create a highly 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 MK Medium can optionally 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 Metakaolin gauged at 5% or 10% to suit specific project requirements. Other mix ratios and the inclusion of fibres are available upon request.

Well-suited for applications requiring high vapour permeability and porosity for the conservation or restoration of heritage buildings, aiming to achieve a sympathetic repair or replacement of a historic mortar, render or plaster without the challenges of specifying or onsite mixing a hot mix mortar.

• Higher in strength compared to our Trass Medium
• High vapour permeability and capillary water absorption
• High free lime content to closely replicate historic mix ratios
• No long-term strength development other than carbonation
• Maintains the natural colour of mortar
• Performance data supports the specification process
• Reduced performance variation compared to onsite mixing
• No risk of pop-outs or pluming common with hot mix

Area of use

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 float coats and topcoats with a minimum of a two-coat render application. For a coarse basecoat, explore Heritage MK Coarse.

For similar mortar with less strength, ultra-high vapour permeability, and less capillary water absorption, explore our Heritage Trass Medium, which is ideal for masonry in exposed environments. 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 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-code paper bags for easy identification onsite and palletised for ease of transport, storage, and handling. FIBC tonne bags are also available.