St. Astier NHL
St. Astier’s range of pure natural hydraulic limes. NHLs will set and can be used in damp conditions and produce an earlier resistance to frost than Lime Putties. Available in three strengths: NHL2, NHL3.5 and NHL5.
Natural Hydraulic Limes (NHL) are made from limestone containing impurities which enable a hydraulic set. They are supplied as dry powders, and begin to set through a chemical reaction known as hydration, when water is added.
Manufactured in France by St. Astier, a company with a global reputation for its products. Cornish Lime have been working with St. Astier for over 20 years and are proud to have been amongst the first in the UK to be associated with them.
NHL comes in three standard strengths, NHL2, NHL3.5 and NHL5.
NHL2 is the weakest of the 3 classifications for NHL (Natural Hydraulic Lime). It is in our opinion the most appropriate of the 3 NHL types for many applications for the care and repair of older traditionally constructed buildings. It offers a truly breathable mortar/render allowing moisture to be wicked out of masonry and It makes a very appropriate lime render for all but the most exposed locations.
NHL 3.5 offers the medium strength of the 3 classifications for NHL (Natural Hydraulic Lime) and the most popular NHL by far. Suitable for countless applications as a mortar or render in the care and repair of older traditionally constructed buildings. It offers a truly breathable mortar/render allowing moisture to be wicked out of masonry. However, and in our opinion, that does not necessarily make it the most appropriate NHL. While it is without doubt a superb binder and worthy of being the most popular, we believe that in many instances where it has been used that an NHL 2 may well have been more appropriate.
NHL 5 offers the maximum strength of the 3 classifications for NHL (Natural Hydraulic Lime) and as such we would advise caution as to exactly where it’s used. While it can be used for most typical mortar applications especially those in more aggressive environments, and only then onto suitable, durable backgrounds; this is a binder with limitations in conservation. However, it will make an appropriate masonry mortar for marine applications including those within the tidal zone or flow in rivers etc. It works extremely well for other applications where durability is a requirement such as wall capping, chimney flaunching or works below ground where sulphates may be present. It’s used extensively for Lime Concretes.
Area of Use
NHL2: Suitable for Mortars, Renders, Plasters, Grouts and Limewash. Use on a soft or friable backgrounds in sheltered locations.
NHL3.5: Suitable for Mortars, Renders, Plasters and Grouts. Use on reasonably sound to hard backgrounds in sheltered to moderatly exposed locations.
NHL5: Suitable for Mortars, Renders, Lime Contrete and Injection Grouting. Use on durable and very hard backgrounds in exposed locations.
Used In Conjunction With
Mix with a clean and well graded sand at a mix ratio from 1:1.5 to 1:3 depending on the application and/or background conditions, the size of the joint and the fineness of the sand.
Working temperatures: not below 5 deg C or above 30 deg C. Make sure that high suction materials are thoroughly dampened before application. Avoid rapid drying due to high temperatures or strong winds using appropriate curing methods. Protect fresh mortar from frost, rain, direct sun and strong wind for a minimum of 48 hours depending on the time of year; please refer to CLC document Curing Lime Based Renders & Mortars.
Each project is unique, always seek professional advice before undertaking a project.