TECHNICAL ADVICE NOTE FOR BAG RUB FINISH

Bag rubbing is a technique where the pointing of masonry is conducted in a manner closer to rendering, that does not extinguish the 'character' of the wall.

The joints of the masonry are prepared the same as for pointing, being cleaned out to an average depth of 25mm to form a key. This depth will vary according to the nature of the stonework, but should not be less than 20mm.

The joints should be thoroughly cleaned and washed out by use of a hose (fine spray nozzle only) or suitable pump up sprayer. This is best done the day before application and again, immediately before application.

Following any preparation required for deeper pockets, a single coat of lime mortar is applied fully into the joints. Once the mortar has cured sufficiently, it should be rubbed up using hessian sacking or a similar type of material in order to press it home. Once the initial set has taken place, it should be rubbed over again. The rubbing action should be carried out in such a manner as to press it well back into the recessed joint, closing up any initial shrinkage that has taken place. At this point, it is often scoured with a sponge or suitable medium to achieve the desired finish.

Upon completion, the work should be covered over with hessian or other suitable material to offer protection from the elements. This should be kept damp in warm weather. The finished coating should be further dampened down by a fine mist spray as necessary, to allow the 'render coating' to cure naturally. Rapid drying either by wind or sun, will often result in failure and adequate protection is therefore a must.

Bag rubbing is a very simple and cost effective technique that can be subsequently painted with either a lime wash or a lime paint. The overall appearance of the stonework needn't be lost resulting in a surface that has been unified and tidied up at a fraction of the cost of pointing or plastering.

This particular approach does not require a high level of skill to execute, but care and consideration will determine the outcome. The mortar should be mixed using a blend of 50/50 standard coarse and fine sand, mixed at a ratio of 2:5 hydraulic or non-hydraulic lime to sand.

Material consumption will be in the region of approximately 50 square metres per tonne or mortar. This will obviously vary depending on how the wall has been constructed, the actual material used and it's overall condition.

The information provided here is for guidance purposes only.  For further information or assistance, please do not hesitate to contact us.