What are 'Pointing Mortars'
Using pointing mortars to fill the gaps (joints) between the brick slips is important to achieve a finish that looks like real brickwork.
The mortar used on conventional brickwork makes up about 17% of the overall area so can impact the overall colour and final appearance of the slip installation.
In traditional bricklaying the mortar is buttered on the brick and becomes a structural load bearing element of the wall but in brick slip installations it is piped in and is purely aesthetic.
Is it just sand and cement?
Yes it is but there are a few other things to consider.
The mortars we supply are colour consistent factory mixed lime based mortars. We supply several colours as standard but if you have a large project with a specific colour in mind our supplier is capable of making nearly any colour to suit.
So what makes this different from standard sand and cement mortar?
Sand and cement mortar (Portland Cement mortar) is typically 1 part portland cement and 6 parts aggregate (fine sand) for a mid-to-soft pointing mortar. The more cement you add the harder it becomes.
Our mortar however has 1 part lime (not the fruit) added to it. The lime further softens the mortar but also adds some flexibility (modulus of elasticity) and gives self-healing properties to the mortar. It self-heals fine cracks when water leaches through the mortar ‘washing’ some of the lime into the hairline cracks.
Historically lime mortar was used to lay bricks so if you are doing restoration work or trying to make a brick slip installation appear old it can help using similar materials.
So why is having a flexible mortar important?
Thermal Expansion and Settlement
No matter what you bond slips to there will always be small imperceptible movements in the subsequent days, months and years particularly on framed systems. If these are not allowed for there can be quite serious consequences.
For example if you were building a south facing wall using a dark coloured slip your building designer should be allowing for thermal take-up of the slips and boards and allowing for the expansion by including movement joints.
On top of the thermal takeup there is always a ‘settling’ of structures particularly timber frame constructions but not limited to.
Having a soft mortar allows for some of this movement.
If it is just plain old sand and cement with a bit of lime why not just mix it on site?
Our mortars are made by a specialist mortar manufacturer using a quality controlled mixing facility using hydrated lime.
With the best will in the world people make mistakes. This can lead to colour banding due to the way a mortars true colour only appears after fully curing. If this happens you may have to repoint or colour tint the mortar which can be a costly excercise.
Tooling the joint
Filling and tooling the joint requires skill and the right tools for the job.
If you have never done this kind of work before do not underestimate how much skill can be involved to get a good finish.
If you hear your labourer saying they will ‘grout’ the joint just make sure they understand grouting glazed wall tiles is very different to pointing brickwork as the mortar cannot be wiped off if smeared on the surface.
Filling the joint with pointing mortar is very similar to repointing failed mortar joints. This can be achieved either using a finger trowel to push it into the joints or more commonly today by ‘gunning’ or ‘piping’ the mortar in.
Some prefer pointing guns and some prefer piping bags. In our experience the manual guns have a tendency to clog the nozzle if the mix is not just right. The piping bags are low-tech and reliable with clogs easily removed by squeezing the tip of the bag.
The mortars we supply are ‘gunnable’ being made with very fine graded sand and aggregates. Some pointing mortars use quite coarse aggregates (fine pebbles down to grit) which is the reason some mortars frequently clog the nozzles.
While our mortars are meant for gunning the addition of mortar plasticiser can help the mortar flow better.
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