Repointing brickwork is a highly skilled craft. It describes the process of removing deteriorated mortar from the joints of a brick wall and replacing it with new mortar. The decision to do this is most often related to some obvious visual signs of decay, such as disintegrating mortar, cracks in mortar joints, unsecured bricks or stonework, damp walls, or damaged plaster work.
As a general rule, if the mortar can easily be scraped out between brickwork and stonework, then it's likely that the wall will need repointing. Over 20% of any wall is made up of mortar joints. In damp conditions the wall is liable to absorb the damp and subsequently dries through evaporation. Lime mortar joints are generally more absorbent than brick or stone and draw most of the moisture into them, which then evaporate away safely.
Most of the damage from salt crystallisation and frost consequently happens in mortar joints, which can easily be repointed. If however, the joints are replaced with harder and less porous cement mortar the water is forced to evaporate mainly from the brick or stone and damage will inevitably result.
How can Verminate help?
Verminate provide clients with a suitable analysis of whether a wall needs repointing, the raking out of existing mortar, preparation of the wall, mixing suitable lime mortars and the process of pointing. We use gun injection to ensure that mortars go exactly where they are needed, deep into joints up to 75mm. This ensures there are no unseen air pockets for water to collect and therefore no risk of consequent frost damage. A high quality finish is achieved in a minimum timeframe.
Verminate work can be trusted to be within the British standard mortar guidelines. We use traditional lime putty mortars, coloured mortars and mortars that contain improved bonding to brickwork to ensure that our work will last for years to come. We use a variety of power tools to ensure a proper depth of rake of the old mortar and state of the art mortar guns to ensure new mortar is thoroughly put back into the joint.
All our work is cosmetically pleasing and we don't leave a mess when we're finished!
The method applied to the external restoration of a building is illustrated below.
The decayed mortar is raked out using traditional hand tools to approximately twice the width of the mortar joint. The traditional method is preferable to mechanical techniques such as angle grinders due to unavoidable damage of cuts to the brickwork and staining from lime dust.
It is highly probable that a percentage of the brickwork has suffered from varying degrees of failure. The repairs are performed using various techniques:
The building is cleaned traditionally by hand with water, brushes and carborundum stones. Corrosive chemicals and pressure-washing equipment are not used to avoid irreparable damage to the façade. The use of water also activates the dormant lime within the existing mortar, which will provide the appropriate required bond with the pointing.
A light cement wash of the appropriate colour is applied to seal the brick face and protect the building from water and frost damage. Chemical sealants are avoided so to prevent trapping residue water within brickwork and preventing the building fabric from breathing.
The final stage of repointing is performed using bespoke hand tools specifically designed for achieving the correct original weather-struck and cut joint, which require individual manufacture. The mortar used consists of sharp sand – which is sieved by hand – lime and minimal quantities of portland cement. Chemical additives and portland cements are generally avoided due to the appropriate bond that is achieved through the lime content. Chemical additives and today's cements have the reverse affects required with the pointing, failing to make the required bond with the original lime mortar.