Over the last 70 years the widespread use of cement mortar now means the outside of people's houses have suffered terribly.
Unfortunately, alongside this liberal application of cement, there have been many other modern products which have been used freely and very inappropriately on older properties. Thankfully this is an ever decreasing trend and people are now reconsidering the use of original materials.
Part of this return to basics is the use of lime mortar where repointing, rendering, plastering and building is concerned. It's use stems back thousands of years and is something which has evolved historically in the UK.
As far as mortar joints are concerned, there are many different styles and they now form part of our English heritage - it's something of which we can be proud.
Stone preceded brick which was originally seen as an inferior product in comparison. From what I can ascertain, the popularity of brick only really gathered momentum from the late 1400s during the Tudor period. By that time brick making and brick laying had become two separate trades with most brick being made on site and laid with lime putty and sand with simple trowel finished joints.
By the Georgian age brickwork was becoming more of an art with tuck pointing being of the highest form. This is where a coloured stopper mortar sits around the bricks and thin ribbons of putty are trowelled (or tucked) into a housing using specialist tuck pointing irons.
This is then trimmed with a specially made knife called a Frenchman before being given a light brush.
The technique creates the illusion of very precise joints. Basically it can give irregular bricks the appearance of having defined edges. However, as it is very labour intensive, and therefore the most expensive, so is often exclusive to high profile properties .
To see how it's done, go to https://www.youtube.com/watch?v=A4uNGxkTlJY
You'll find that very few people involved with brickwork have the level of competence to undertake the skilled art of tuckpointing in Oxfordshire.
Penny roll (similar to ruled joint):
Ruling or rolling gives the impression from a distance of more uniform size bricks with sharper edges. In the picture below a purpose made tuck pointing iron is being used.
The example below dates back to the 1500s. Here you can see that the joint has been struck from above and beneath to form a central ridge running though it.
The mortar surrounding such bricks (Either Tudor or Elizabethan) would need to be analysed in order to ascertain its composition before a sympathetic specification could be designed. Aged bricks like this often have a high capacity to retain moisture. Therefore, failure to correctly identify the components of the original mortar could easily result in damage to historic brickwork as the bricks were usually made of clay and kilned on site - this means they will be very soft. The reason they have lasted so long could be due to the spec of the original mortar. It's continuance might be vital to the outcome of the building.
Weather-struck and cut:
A product of the 19h century derived from civil engineering. This method uses a pointing trowel to create a slope away from the upper edge of the brick to the lower. The mortar overhang is then cut away providing a clean edge.
Its appeal lends itself more to aesthetics as it has limited practical value where lime is concerned. The pressing action of the trowel tends to close up the vital pores of the porous mortar thus inhibiting moisture evaporation. Nevertheless, when executed with skill on uniform shaped bricks it is an undeniably attractive finish. Couple to this the fact that both the lime and imperial handmade bricks will move at the same rate thermally, thus negating the possibility of spalling, means that it does have a place in the built environment - specially when matching up with existing weather-struck joints.
Brushed and flush finish:
The mainstay of lime mortar repointing to brickwork is brushed and flush finished. Below is an example of an open texture from which moisture can escape. It's prettied up by brushing the aggregates to the surface.
Lime mixed with nicely blended sand can have quite a dramatic affect on any property.
Brushed is very much the only finish for stone. This is my own personal recipe and is a highly guarded secret.
It's created by knocking the mortar back with sticks and brushes until it's flush all with all the edges. The aggregates are then brushed to the surface.
Please note: both convex (protruding) and raked back pointing is bad practise. In the case of the former, the mortar juts out from the joints where it's unnecessarily exposed to weathering.
In both cases, the upshot is far swifter deterioration. The latter, where mortar is pushed too far back, results in frost sitting on ledges which leads to spalling. It's also not possible for moisture on the outside of the brick to be wicked away by the porous mortar because it sits so far back and therefore the surface stays wet for longer than necessary eventually leaving harmful deposits behind which further erode the brickwork.
Cement mortar is deadly to older properties because as it expands and contracts at a different rate around brickwork eventually crushing it.
Only a hydraulic mortar, which moves at the same rate as the brickwork, is suitably sympathetic.
In cold conditions having cement means rainwater freezes on the face of the bricks because it is not pulled away by the surrounding lime mortar which should be in the joints.
If you would like any of the above repointing styles then please contact me to discuss.
Always bear in mind that it's the mortar which is designed to be the sacrificial element of the property. What you're actually looking for is something which is softer than brick and stone and which can easily be replaced when too badly weathered.