Natural Hydraulic Lime: Secil NHL2, NHL3.5 & NHL5

Natural hydraulic lime 3.5
Natural Hydraulic Lime NHL2Natural hydraulic lime 3.5Natural Hydraulic Lime NHL5Secil NHLSecil NHLSecil NHL

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Natural hydraulic lime (NHL) is used to create mortars and plasters which are generally more vapour permeable (breathable) than sand/cement mixes. Lime mortars and plasters are particularly beneficial where sympathetic materials are required, such as in traditional buildings.

Natural hydraulic lime is supplied in three European classifications: NHL2, NHL3.5 and NHL5. These classifications are based on the compressive strength of laboratory mortars after 28 days. These are often somewhat misleadingly termed ‘feebly hydraulic’, ‘moderately hydraulic’ and ’eminently hydraulic’ because the qualifying strength bands for each classification overlap each other (see table below).

Described as:

Strength (@ 28 days) MPa

 Examples of use:
Feebly hydraulic
>2 to <7
Internal plastering or  soft masonry
Moderately hydraulic
>3.5 to <10
Bedding and pointing mortars
Eminently hydraulic
>5 to <15
Limecrete floor systems and exposed areas

The strength of a hydraulic lime mortar (HLM) also varies depending on the manufacturer and origin of the natural hydraulic lime. Some NHL will be high in the qualifying band and some will be low. Hydraulic lime mortars and plasters will also vary depending on the ratio of lime binder to aggregate, and the type of aggregate or sand used.

Secil Natural Hydraulic Lime (NHL) is a unique binder because, although it features a predominantly hydraulic setting process. It also features a carbonation process that occurs simultaneously, but for a longer period of time.

HLMs are useful for building with stone or brick where the earlier set may speed up construction. We suggest that for external bedding and pointing late in the year natural hydraulic lime should be used. It is capable of a faster initial set in cold weather.

Secil Natural Hydraulic Limes are certified to the current version of EN 459-1 and nothing is added to the raw material…. it’s 100% burnt limestone!

Secil started business in 1930 and has a huge contribution to the construction market in Portugal. Secil and Mike Wye & Associates have collaborated to provide this high quality Portuguese natural hydraulic lime to the UK.

We believe Secil Natural Hydraulic Lime will offer an excellent and cost effective option for those wanting to use powdered NHL in their work.

  • Secil NHLs have similar strengths to French NHLs.

Wikipedia Hydraulic Lime


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Secil NHL is supplied in 25 kg moisture resistant bags.

(individual bag)
(full pallet)
25 kg
NHL 3.5
25 kg
25 kg