Roundtower NHL 2

*All new Roundtower NHL bag designs will be introduced gradually once old stocks of bags have been used*

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Natural Hydraulic Limes (NHL) are made from limestone containing impurities which enable a hydraulic set. They are supplied as dry powders, when mixed with sand and the addition of water they set through a chemical reaction known as hydration. This chemical set allows for NHL mortars to be used in damp and more exposed locations and produce an earlier resistance to frost than lime putty.

Natural Hydraulic Lime (NHL)is supplied in three European classifications, NHL 2 (feebly hydraulic), NHL 3.5 (moderately hydraulic) and NHL 5 (eminently hydraulic). These grades are based on compressive strength.

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NHL has a number of qualities:

• Lime reabsorbs a proportion of carbon dioxide (CO2) during curing and setting, thus offsetting part of CO2 created from production.
• It allows buildings to 'breathe', and does not trap moisture inside the walls.
• Lime mortars are very workable.
• Lime allows masonry to be recycled at the end of its life and does not damage brick and stone.

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Roundtower NHL 2 is the weakest of the 3 classifications for NHL (Natural Hydraulic Lime) referred to as “Feebly Hydraulic”.

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Roundtower NHL 2 is ideal for:

1. Rendering and plastering.
2. Pointing stonework, brickwork and blocks.

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For lower density masonry (e.g. limestone & sandstone) you may wish to to consider using NHL 2.

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Always remember that the mortar should never be harder than the masonry.

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Working temperatures should not be below 8 degrees. 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 72 hours depending on the time of year.

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Approximate coverage rates

Plastering & Rendering with a mix of 2.5 parts sand to 1 part lime at 10mm thickness covers approximately 8m².

Pointing Rubble Stone with a mix of 2.5 parts sand to 1 part lime covers approximately 10m².

Pointing Brickwork with a mix of 2.5 parts sand to 1 part lime covers approximately 16m².

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