Guide to Lime Mortar

Hydraulic lime based mortars are usually used for new building work. For stone repair work and repointing lime putty mortars are often used.

Making Mortars, Plasters and Renders

Lime putty and aggegates should be thoroughly mixed in large batches using the paddle or roller mixer.
The proportion of lime putty to aggregate should be 1:2, 1:2.5 or 1:3 depending on aggregate type.
No water should to be added to the mix.
The mortar, plaster or render should be left to mature in airtight containers

Remove loose friable mortar and cement mortar to a depth of at least 1" (25mm) or to a depth of three times the width for narrow joints. Retain as much of the original lime pointing in the joints as possible.
Flush loose material from the joints and ensure the joints are well wetted.
Remix matured putty lime mortar to plastic state and add pozzolan if required or if using hydraulic lime then this should be prepared now.

Pack joints thoroughly using appropriate sized pointing keys and fill joint proud of wall surface.
Compress the mortar using pointing irons after it has stiffened.
Shape and texture mortar surface whilst in a 'green' state using a churn brush for walling and ashlar and smaller brushes or spatulas for moulded work.
Ensure mortar cures slowly and does not fully dry for at least three days. Protect curing mortar from sun, wind and rain using dampened hessian. Dampen down mortar regularly in hot weather.

Pack joints thoroughly using appropriate sized pointing keys and fill to above required level.
Texture the mortar surface whilst in a 'green' state by gently scraping back using metal or wooden spatulas.
Ensure mortar cures slowly and does not fully dry for at least three days. Protect curing mortar from sun, wind and rain using dampened hessian. Dampen down mortar regularly in hot weather