Pointing Mortars

Preparation

• 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.

Application: Putty lime pointing

• 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.

Application: Hydraulic lime pointing

• 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

Stone Repair Mortars

Preparation

• Carefully remove friable stone using dental tools or a dummy and small sharp chisel. Ensure as much of the original surface of the stone is preserved as possible.
• Key the surface of the stone which is to receive a repair either using a claw chisel, the point of the dental tool or a small drill. Further keying can be done by slightly undercutting the perimeter of the repair.
• Flush loose dust from stone surface and wet stone several times with limewater. This is done to ensure water is not too rapidly drawn from the repair mortar which would cause shrinkage.
• Remix matured mortar to plastic state and add pozzolanic additive if required.

Application

• Prepare slurry of diluted mortar
• Paint slurry onto area to be repaired and allow some slurry water to be absorbed by the stone until the slurried surface appears matt.
• Apply mortar by hand (wearing rubber gloves) or by wooden spatula to a maximum coat thickness of 12-15mm. For deep cavities, broken pieces of pre-wetted stone can be pressed into the mortar.
• Compress mortar after it has stiffened slightly - typically 5-15 minutes after application.
• A second coat can be applied when the first is leather hard and still damp - typically 12-24hrs after first application. The surface of the first coat should be keyed. Build up and compress further layers as required.
• The mortar surface can be textured by scraping back or beating with a bristle brush when leather hard. An open granular texture can be obtained by pressing coarse limestone aggregate into the soft mortar surface with a damp brush or shaped piece of stone.