What Lime Mortar For Pointing? How To Mix Lime Mortar?
What Lime Mortar For Pointing?
The best lime mortar for pointing is a natural hydraulic lime (NHL) mortar. NHL mortars are softer and more porous than cement-based mortars, allowing moisture to evaporate from the joints more freely.
The mortar should be workable without being too wet, and should be pre-mixed for a minimum of a couple of weeks before use.
When mixing the mortar, start with an empty mixer and add 1 part sand, followed by 1 part lime and 1.5 parts sand.
Mix dry for at least 5 minutes before slowly adding water until the desired consistency is achieved.
After application, the mortar must be allowed time to cure/fully hydrate before it acquires strength and hardness.
How To Mix Lime Mortar?
The correct mix ratio for lime mortar for pointing is 1 part lime to 2.5 parts sand. This ratio should be measured by volume, not weight.
The mix should be thoroughly mixed in a conventional cement mixer or paddle mixer for larger projects.
The mortar should be workable without being too wet and should be compacted into the joint with a churn brush after it has hardened enough to not smear.
It is important to note that the 1:3 ratio of lime to sand is a myth and does not apply to all types of lime mortar mixes.
Lime putty based mortars should be pre-mixed for at least two weeks before use and then “knocked up” (agitated/mixed) again prior to use to plasticise them.
Additionally, 20 kg of Lime Mortar will cover approximately 4-5 m² at 10mm thick when pointed with a trowel or hawk.
What Is The Best Lime Mortar For Pointing?
The best lime mortar for pointing stone masonry or brickwork is a hydraulic lime mortar.
Hydraulic lime contains impurities that allow it to set in two stages, making it ideal for pointing due to its strength, durability and frost resistance.
The strength, colour and texture of the lime mortar will be affected by the sand or aggregate used, with a washed sharp sand being ideal as the angular grains create a good bond.
Generally, a ratio of three parts sand to one part lime is used when mixing the mortar, but it is important to match the ratio of the existing historic mortar for best results.
Additionally, care should be taken to ensure that once the mortar is placed it is not allowed to dry out too quickly.
What Do You Mix With Lime For Pointing?
Lime mortar is a type of mortar made from calcium carbonate, including limestone, bone, and shell. It is used for the sympathetic restoration of masonry in properties dated before 1910.
The typical ratio for mixing lime mortar is three parts sand to one part lime. However, it is important to match the ratio of the existing historic mortar for best results.
Lime mortar can be mixed by hand or in a cement mixer. When mixing by hand, it is important to mix the dry materials evenly prior to slowly adding water and mixing with hand tools until a smooth malleable consistency is achieved.
When using a cement mixer, start with an empty mixer and add one part sand followed by one part lime and then 1.5 parts sand. Mix dry for at least five minutes before slowly adding water.
It is also important to cure/fully hydrate lime mortars before they acquire strength and hardness. This process involves keeping the mortar/render under a damp cloth or plastic sheeting for several days after application.
What Is The Ratio Of Lime To Sand For Pointing?
The best mortar mix ratio for pointing mortar is typically 1 part lime to 3 parts sand. This ratio creates a type N mortar with a strength of 750 psi.
However, it is important to match the lime to sand/aggregate ratio of the existing historic mortar for the best results.
The average lime:sand ratio on the organization’s entire database of historic mortar samples is around 1:1½, and specifications calling for ratios of 1:2, 1:3 or 1:1 lime to sand are misleading and could be wrong.
For brickwork, a ratio of 1 part cement, 1 part lime and 6 parts sand is recommended, while for stone wall joints, a ratio of 1 part cement, 1 part lime and 6 parts sand is recommended.