Natural Hydraulic Lime (NHL) 3.5, by Roundtower , is a strong mortar option with all the flexibility that comes with natural lime. We recommend this product for historic structures built with harder brick or stone. Remember the mortar must be softer than the brick or stone it is matched with! This product is not recommend for soft brick or for plaster or stucco.
Natural lime has higher permeability in general, and allows for moisture to enter and escape freely – unlike Portland mortar, which locks in moisture and cracks over time. NHL’s will set in the presence of water which makes it ideal for use in exterior applications.
Working temperatures should not be below 41 degrees F. Dampen the wall 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.
Natural Hydraulic Lime (NHL) 3.5 comes dry in 55 pound bags with no artificial additives. Mix with sharp sand at a ratio of 2 1/2 parts of Mason’s sand to 1 part NHL measured by VOLUME. This equals approximately 3 1/2, 50 pound bags of Sand for NHL, per 1 55 pound bag of NHL. Remember the color of the sand will largely determine the color of the mortar! And add our pigments for even more color variations!
Read the installation guide below and feel free to contact us with questions or a custom quote for colors.