There are certain golden rules associated with conserving historic buildings.
One is to never use cement mortar on stonework, another is to always use period-appropriate techniques for period-appropriate buildings and another could be to always check with the appropriate authorities before undertaking any work that is not urgent.
However, one rule that really should be as etched in stone as the ones above is to under no circumstances ever use pebbledashing as a render for the outside of properties, particularly not historic ones.
Whilst perhaps not having as catastrophic a reputation as the somewhat infamous bungaroosh that was localised in Brighton and yet despite being a seaside-based material that would dissolve when exposed to water, pebbledash has become the bane of conservationists everywhere.
What has caused this reputation, why can it lower the value of a property by as much as five per cent and why could it potentially decimate a heritage property?
In this brief guide, we aim to explain the much-maligned render, but to start we need to explain why it ever became popular to begin with.
Why Does Anyone Use Pebbledash?
Also known as roughcasting, pebbledashing is a cement render that is spread onto the outside of a property with small pebbles spread on top of it.
There are a lot of regional variations based on what types of small pebbles are spread onto the mix, with most modern pebbledash using flint chips.
There is also a difference between roughcast, where the small stones are mixed into the cement before it is spread, and pebbledash, where the stones are literally thrown against the surface
It must be noted that pebbledashing is not entirely new. According to a 1911 edition of the Encyclopaedia Britannica, it dates as far back as the Roman Conquest of Britain, with St Albans Cathedral’s central tower being covered in roughcasting dated to the original construction of the building.
However, early pebbledashing up until the late 19th century was made with lime rather than cement.
It returned to popularity from the 1920s onwards largely as a way to cut costs. During a building boom, high demand for affordable housing led to a lot of cut corners, with pebbledashing used to hide the poor quality of brickwork and ensure buildings were suitably weatherproofed.
It does not require (or really can be) regularly painted and is particularly hard-wearing, which became both a blessing and a curse when people wanted to get rid of it.
By the 1930s it had started to become deeply unpopular and whilst it does occasionally return as a design trend, it is also deeply disliked, both for how it looks and the abrasive effect it can have if you accidentally brush against it.
However, whilst a problem for recent buildings, it can be devastating to historic ones.
The Damage Of Pebbledash
Part of the problem with modern pebbledash is the use of concrete, and as our understanding of historic buildings increases, our understanding of the potential devastation pebbledash can cause also becomes abundantly clear.
The first problem is that the concrete used in pebbledash is impermeable, and given that historic stonework and lime mortar rely on water safely evaporating through them, this ironically leads to moisture build-up, damp and decay.
Ultimately, this can cause significant damage to stonework, timber frames and buildings constructed with earth materials, both through the damp itself, and also the expansion and cracking caused by the freeze-thaw cycle.
In particularly bad conditions, it can lead to historic buildings suffering significant structural issues and even collapsing in the worst-case scenarios.
The other part of the issue with pebble dash is that whilst the annoying little pebbles will fall out a lot, it is surprisingly difficult to remove the render itself due to how tough the concrete material is, with most removal methods requiring great care to avoid damaging the underlying masonry.
However, getting rid of this render is also a necessity to avoid further damage and replace the render with more suitable traditional materials.
How Do You Get Rid Of Pebbledash?
You will almost invariably require listed building consent to get rid of a concrete render, and because of this, it is essential to get in touch with an experienced team that specialises in working with listed buildings.
The reason for this is that heavy-duty equipment is often necessary to remove pebbledash, but you must be careful and delicate with the methods you use to avoid damaging and scarring the masonry underneath.
Typically, a combination of hand chisels and power tools are used to take pebbledash render off of the wall bit by bit, but this can take an exceptionally long time to complete and requires a lot of specialised labour to get right.
Power tools such as grinders and rotary hammer drills can help a little bit to reduce the amount of work involved, but they can also run the risk of damaging the masonry underneath it.
Soda blasting or sandblasting can help remove thin layers of pebbledash but also can cause damage to the underlying stonework or brickwork, and so needs to be done by a professional.
Once the main parts are removed, a superheated steam cleaner can take care of the remaining bits.
Once it is removed, the underlying masonry needs to be examined and given time to dry out, often requiring repointing using lime mortar to keep the stonework structurally secure and prevent water from getting in and causing greater damage to the masonry.
There may be additional repairs that need to be made, some of which can be quite significant, but it is important to note that these problems were already extant and were being exacerbated by the cement render.
It can also affect windows and other exterior features that were installed after the pebbledash was, meaning that windows may need to be refitted with the masonry altered to fit them, or the windows will need to be replaced entirely. Sometimes the latter is the easier option.
Ultimately, pebbledashing is a blight that affects too many historic buildings, and it is a positive sign that many homeowners are opting to get rid of it entirely.
However…
Pebbledash shouldn’t be maligned entirely and it certainly has its place, such as at Port Sunlight which features heavy use of roughcast and pebbledash techniques to construct solid walls, with the hard render keeping out the damp. These materials have stood the test of time, it would seem, with many pebbledash finishes still functional because of the techniques used.
One of the biggest issues with pebbledash architecture seems to be when sub-par alterations are carried out. Conservators are still trying to work out how best to go about repairing Edwardian pebbledash and it’s important to find out the cause of the problem before going about any work on the building.
