INTRODUCTION:

Lime putty mortars are flexible, porous and permeable. These were the mortars used to build and plaster traditional buildings and are therefore (with very few exceptions) the appropriate materials for the repair of these older buildings. They do not perform as modern gypsum or cement based mortars and plasters.

Where durability is a concern (because of the exposure of the site for example) and a slightly stronger mortar is required, pozzolans can be added, on site and immediately prior to use. Pozzolans (RJ 7.01) are materials originally identified by the Romans, naturally-occurring or manufactured, which react with the lime in the mortar to produce a weak hydraulic set. Modern hydraulic limes are being increasingly used for the repair of traditional buildings but these produce much stronger mortars than (all but a rare few) traditional lime mortars

USE:

Lime Putty Mortars are supplied in a 'ready-to-use' consistency, but tend to stiffen after long periods of storage or transit; improved 'workability' can be achieved by re-mixing in conventional mortar mixer or by whisking. Avoid the addition of water, as this will increase the likelihood of shrinkage.

Do not gauge with cement or hydraulic lime. Pozzolanic materials are the only acceptable additives if durability or strength is a concern in the particular application or location.

Do not use in extremes of heat and cold. Protect work at all times.

Lime putty mortars must be stored in a frost-free environment, and lime mortars 'in-situ' are vulnerable to frost for longer than cement mortars as they set more slowly. Lime mortars must be protected from drying too quickly in warm/ sunny/ windy weather by periodically mist-spraying with water and covering with wet hessian and/or polythene sheeting.

Thoroughly pre-moisten substrate and/or building materials to reduce suction.

Do not build faster than the slow setting mortar will allow. 'Tend' the mortar during curing by mist-spraying and compressing back any shrinkage cracks until the mortar has "turned" and shrinkage ceased. Pointing mortars are not placed and finished in the same operation. Place the mortar, leaving it proud, tend and compress as necessary, and finish the joint later that day or even the next day (depending on circumstances).

Clean off lime stains immediately with clean water. A diluted citric or clear (distilled) acetic acid is sometimes necessary.

Note that lime mortars form a weak bond with building materials, and therefore good building practice, in particular "bonding" of brickwork and stonework is essential.