A fantastic, pre-mixed, fine lime mortar, suitable for internal and external fine or topcoat plaster finishes. This mortar is a mix of fine (2 mm down), yellow flint sand and mature lime putty, which gives a buff/beige finish.
Application
When applying a topcoat, follow standard render practices by controlling the background suction, applying at a thickness of 6-7mm, and finishing with a ruled-off and floated texture, optionally sponging for a smoother finish. If a finishing plaster is to be added on top, lightly devil float the surface for optimal adhesion.
For building and pointing, use mortar as stiff as possible while still workable. Typically, the depth of mortar joints should be twice their width; for example, a 10mm brickwork joint should have a 20mm raking-out depth.
For rubblestone walls with large joints, set a nominal thickness of 20-30mm to avoid excessive mortar removal. Ensure the mortar is fully and firmly packed into the entire joint, then finish with a churn brush to compact it and expose the aggregate at the surface, resulting in durable, high-quality masonry joints.
Using CLM35
CLM35 is a versatile product primarily used as a float coat render for both internal and external applications, applied over an appropriately prepared undercoat render. It is also suitable as a building or pointing mortar, particularly in joints less than 10mm.
For wider joints, we recommend using coarser sands, especially when the joint width exceeds three times the largest sand particle. Although it can be used in wider joints, there is a higher risk of shrinkage. This product’s specifications and suitability for different applications are important to consider. Additionally, CLM35 has other appropriate uses; contact us for further information on alternative applications.
Please note, this material cannot be applied directly to plasterboard or tanking materials.
Preparation
This depends on the mortar's purpose and application. Preparation should follow best practices: surfaces must be clean, dust-free, and, if needed, dampened to improve adhesion.
Impervious backgrounds are less absorbent and need minimal dampening, while absorbent materials require dampening to prevent rapid drying.
Mixing
CLM35 is a ready-to-use product that often requires remixing to achieve optimal consistency. While you can add a small amount of water to make the mix softer, it’s important to do so sparingly, as increasing water content can lead to shrinkage cracking. For the best results, mix thoroughly with a whisk until the product is smooth and uniform.
Coverage (Render)
- Coverage for render at 12.5mm thickness: 1 m² per 25 kg, equivalent to 40 m² per tonne.
- Mortar requirements per tonne include brickwork pointing for 100 m², bedding for 20 m², and stonework pointing for 40 m².
- These coverage figures are approximate; uneven surfaces or irregular joint sizes may affect actual consumption.
- Renders are generally easier to estimate than bedding mortars, particularly for stonework.
Avoiding The Pitfalls
CLM35 is composed of lime putty, a Non-Hydraulic Lime that sets by absorbing atmospheric carbon dioxide in the presence of moisture. This setting process varies with climate, behaving differently across seasons based on ambient temperatures. Work should never be carried out in freezing conditions or if temperatures are expected to drop below 5°C during application or until the mortar has fully hardened, which, for non-hydraulic mortars, can take months rather than weeks.
Protective coverings should remain in place as long as necessary. Maintain a consistent drying rate and prevent strong drafts in the work area, especially where windows are removed or doors are open. Heating should be carefully controlled to avoid forcing the mortar to dry too quickly.
Typically, lime mortar dries more slowly in winter than in summer, so proper precautions are essential; it must not be allowed to dry out prematurely. Forced drying using excessive heat should be avoided. If heating is needed to maintain a suitable working temperature, propane heaters are recommended because they generate both heat and moisture simultaneously. Always monitor and regulate the temperature appropriately.
The CLM Range
- CLM28F - Ready-mixed fibred coarse lime mortar (5mm and down).
- CLM28 - Ready-mixed coarse lime mortar (5mm and down).
- CLM66 - Ready-mixed Superfine top coat plaster for internal use.
Delivery
Due to the weight and fragile nature of the tubs, we ship them only on pallets, regardless of order quantity. As a result, delivery charges reflect that cost.
To calculate delivery charges to your location, add the items you are looking to order to the cart, go to the cart, enter your postcode, and click the "Calculate Delivery Cost" button.
Safety & Liability Notice
- Lime mortar is alkaline and can cause skin burns, eye injuries, and respiratory irritation.
- Avoid contact with skin and eyes, and do not inhale dust.
- Wear appropriate protective gear, including gloves, eye protection, and a mask.
- Ensure proper ventilation and keep the product out of reach of children.
By purchasing this product, the user agrees to handle, store, and dispose of it safely. The manufacturer and supplier are not responsible for any injury, loss, or damage resulting from misuse or failure to follow safety instructions and regulations.
Please read all Safety Data Sheets (SDS) before using this product.
Downloads
Links open in a new tab.
