Polished plaster and specialist surface finishes explained
Polished plaster is just an evolved form of venetian plaster which has been around for hundreds of years and has been adapted to the modern day for better workability and aesthetics. Along with all the classic Venetian finishes the modern day plasters and decorative finishes have allowed a wider range of finishes and colours to be achieved. The applicator is also now able to make completely bespoke and unique finishes by mixing products and colours together or tinting to make brand new finishes and textures for interiors and exteriors. Finishes can be made as traditional as travertine stone to a modern contemporary highly polished piece of marble.
But It’s more than just a finish
All though the the finishes are the visual selling point there is much more going on with these finishes . Due it’s flexibility , durability and environmental benefits it makes it a brilliant choice for interior and exterior design.
In most cases it’s seamless look gives you a finish that no other product can achieve with its changing looks depending on where you stand in the room or how the light hits the surface. It can be applied in kitchens, bathrooms and wet rooms or just a feature walls and ceilings. Due to its breathable and anti fungicidal nature it offers no where for the formation or mould or bacteria to build up or get trapped if using in areas where there is moisture.
Below are just some of the finishes available but if your looking for the full range of finishes and colour pallets then get in touch for a consultation.
Micro cement is a polymer modified cement based coating which offers a great solution for floor areas due to its durability but also versatile enough to go on any surface around your living space. At only 3mm in thickness it offers great space saving solutions as it doesn’t raise finished floor levels very much compared to other floor finishes . Its totally impermeable and easy to clean. It can be created with little or no movement to vast rustic concrete effects in a whole range of colours.
Quartz plaster is a new innovative non combustible decorative finish which enables it to be applied in places where extreme heats are present. This offers a great design solution for making your fireplaces a real feature .its not only decorative but completely functional and practical for these spaces.
Its natural quartz binder gives a semi polished finish with pearlescent reflections similar to slate or marble . It’s natural organic movement offers something truly unique to the world of seamless finishes.
Quartz plaster is an eco friendly and fully vapour open allowing the system to be used almost anywhere and in any building, new or old.
Tadelakt is a waterproof plaster surface used in Moroccan architecture to make baths, sinks, water vessels, interior and exterior walls, ceilings, roofs, and floors. It is made from lime plaster, which is rammed, polished, and treated with soap to make it waterproof and water-repellant. Tadelakt is labour-intensive to install, but durable. Since it is applied as a paste, tadelakt has a soft, undulating character, it can form curves, and it is seamless. Pigment can be added to give it any colour, but deep red is traditional. It may have a shiny or matte finish.
Plastering & Re-Skims
We can cover over existing walls and ceilings or new board work.
Prep work is key to the longevity of your work and your only ever as good as what your substrate is .
Plastering should be right first time every time and that starts with the preparation .
Once dried the plaster should be allowed to fully carbonise for 30 days before paining or tiling over but generally after it’s all gone a light pink colour ( usually a week depending on conditions ) you’ll be fine to proceed with the next stage.
Sand & Cement Rendering
There is a very big difference between rendering and plastering. Rendering internally is the backing coat or roughing coat that will be finished with gypsum plaster and usually covers brickwork, blockwork or stonework. You don’t see this too much internally anymore as more often than not drywall is specified instead but there are still cases where sand and cement renderring is specified.
External rendering is applied and finished slightly differently and in 2 coats normally. First a ‘scratch coat’ is applied which is generally a stronger mix and has a waterproof additive included in the mix. The second coat or ‘top coat’ is applied when the scratch coat has completely dried and is slightly weaker and has a hydrated lime added to give extra workability in the floating up stage. This is then finished with a sponge to bring a uniform pastel like finish. Sponging the surface also brings a tiny bit of aggregate to the surface which provides a good key for the paint to adhere to. Once the cement has set, the hydrated lime offers no extra flexibility to the cement.
Choosing the right product for your jobs is very important and it’s important to understand the characteristics of the products. As well as lime based products natural roman cement is a very good alternative when flexibility, durability and breathability are needed.
Hydraulic lime (nhl) sets by hydrolysis whereas non-hydraulic lime (putties) sets by carbonation. The hydraulic lime can set underwater, that’s because hydrolysis is a reaction caused by water. The non-hydraulic lime needs air to carbonate and thus set. In physical terms, the two materials are very different to work with. Hydraulic lime is available as a bagged powder whereas the non-hydraulic lime is a putty, hence the name fat lime putty. This makes working with hydraulic lime much easier as it has a similar setting and working as a cement even though the set is slower.
Non-hydraulic lime is softer and sets much more slowly. The carbonation process is very slow and the material remains soft and flexible. The hydraulic lime is available in degrees of strength, is faster setting and more durable. It will depend on the type of job your doing that dictates the choice of which lime to work with.
Natural Roman cement (NRC)
In 1796 the Reverend James Parker Patented Roman Cement and it became highly desirable for its long term durability. After 1824 Roman cement declined due to the introduction of Portland cement which in the present day, as an Ordinary Portland Cement (OPC), is burnt at fusion temperatures and can have some undesirable effects on historic buildings. Natural Roman Cement (NRC) is now available to blend with hydrated limes for a reliable set.
NRC has a better compatible strength with historic masonry and renders due to the special processing of the gault stone and the lower kiln temperatures used. NRC is suitable for conservation and new build projects where characteristics such as breathability, flexibility and colour are important. The lower shrink rate avoids cracking.
NRC can be blended with up to 2 parts lime; when mixed with the right aggregate it will produce a more flexible material with a vapour open quality which is similar to air lime. NRC has a unique buff colour which, unlike other cements, does not produce any grey tones. NRC is unique because it is cement without mineral or chemical additives to control the speed of set.
Lime Vs Cement
|Hydraulic lime||(NHL)Non hydraulic lime||(putty)Roman cement||(HNRC)Cement|
Traditional Damp Solutions
All houses no matter their age will contain moisture . It’s found within the building materials ,in the air inside and outside the building and naturally occurs in the ground and falls from the sky.
Damp is just an excess build up of naturally occurring moisture. The excess build up is commonly caused by one of two things.
A build up of moisture entering the building or a slow build up of moisture not being able to escape from the building and in some cases you can get both acting together.
There are two common causes of moisture retention in buildings ,condensation and damp.
Both are very different things and are commonly mis diagnosed and treated the wrong way.
So the very first thing that needs to be established when taking about condensation and damp is the primary causes of the problem rather than just trying to cover it up which I see all to often. This is only ever going to be a short term fix and will not stop the problem from recurring in the future.
Below I will try and explain the difference between condensation and damp and some of the key factors contributing to theses problems.
Now depending on the age of your house will depend on how it’s been built to combat moisture. I’m guessing if your reading this 9 out of 10 times you will have an old house that has no cavity walls and was built of permeable or breathable materials to let moisture freely pass back and forth through the walls floors and ceilings.
If you have a modern house you will have cavity walls and damp proof membranes in place to act as barriers to prevent the moisture from freely passing and the materials used are non breathable products like cement as its main mortar. This doesn’t mean you still can’t get damp problems but if you do it would suggest a different problem to that of an old building.
Well keep this on the topic of old buildings as 99% of the time these problems only occur in old or historic buildings.
The reason for any dampness in your house in the modern day is the failure for moisture to escape efficiently and the main reason for this is normally inappropriate building works being carried out. Historically it would have pointed to a lack of maintenance over time that then leaded to leaks or failures.
Now when this occurs in the modern day its given a number of names like rising and penetrating damp. Both are slightly different in how they have affected the building to become damp but essentially are the same thing and that’s an excess of trapped moisture.
Dampness that appears very quickly and with substantial volume usually points to something of the leak variety and is normally quite easy to diagnose.
Things to look out for
- Down pipes
- Leaking gutters
- Undersized gutters
- Holes in the roof
- Lack of overhang on roof tiles on gable end walls
Damp normally caused by trapped moisture that slowly builds up over time points to other areas.
Sometimes it can be years before theses signs become noticeable so you have to realise just how much moisture has built up before its saturated the background enough to show visible damp areas.
The slower build up can lead to a harder diagnosis of the problem and in many cases there can be more than one contributing factor. Now all though modern building work is generally the cause, the fact that there is such a time difference between the work carried out and the problem showing up its very difficult to make a link between the two and it’s not always obvious what the problem is and it can be quite time consuming finding the problem.
Things to look out for:
- The use of cement based products for repairing mortar and pointing
- The use of cement based products to render the outside of buildings of which is normally cracked through failure
- Gypsum and cement based plasters on internal walls
- Modern non breathable paints applied infernally and externally
- Use of wallpaper on solid walls
- High ground levels or paving also running tight up against the building
- Replacement solid floors
- Injected or mechanical damp proof course
I just want to take a second to elaborate on this as it’s one of the most controversial areas I work in and come across the argument lots. Chemical or mechanical injected damp proof courses are designed to work with dry walls and will not successfully work with a damp wall. They can either be water based solvents or wax based products used for this . Water based solvents must completely evaporate in order for the chemicals to cure and this will never happen as the walls are still damp, in fact your actually introducing more moisture into an all ready saturated wall. The walls on the inside will either be re plastered with a waterproof based cement or salt inhibitor which acts a barrier to stop the damp from coming through for the remainder of the guarantee. By adding this barrier of either a waterproof render or damp membranes , it stops the moisture freely passing from the walls into the air and will ultimately make things worse. It goes back to my original point of solving the problem before fixing the problem. This only solves the problem for a short term “quick” fix .It does not fix the problem as you still have a damp wall except now it been trapped again and eventually will just find the nearest place come through again . Which will normally be in any areas not been treated with a waterproof material or barrier.
Adding to this further means that having a damp wall that cant dry out leads to a thermal lose too as damp walls offer no thermal value.
Should rarely require any buildings works to remedy the problem and apart from decoration wont be harmful or damaging to the structure of the house but can be harmful to human health if left un treated.
Key signs of condensation are:
Most commonly shows up as patches of dark mildew and Can cause soft furnishings ,cloths etc… to smell.
Different parts of your house are different temperatures ,even within the same room and you will always have hot and cold points even in the newest of buildings. For example, outside walls are cooler than inside walls, windows are cooler than outside walls, corners are cooler than their surroundings, etc. Different construction materials also affect the temperature of surfaces . One of the best examples of this is the difference in U value between a wooden lintel and a metal lintel. Most commonly you will have a lintel or beam over every outside door and window in your house , If it is wooden, that bit of the wall will be warmer and if it is steel or concrete, that bit of the wall will be colder. You won’t be able to feel these temperature differences via touch but you looked at a thermal imaging camera you can actually see the temperature differences . When the air in your room comes into contact with different surfaces it is either warmed or cooled to match the temperature of what it touches. This changes how much the water molecules act their ability to join together. If the surface cools the air enough a lot of the magnetic water molecules join together to form droplets which settle on the surface as condensation. If the air contains a large number of water molecules all crammed together, they hardly need be slowed down at all before they start to join together. This means even the slightest brush against a slightly cooler surface will make the water molecules form droplets. So when water molecules are warmed they move around more and disperse from each other and the droplets disperse and visa versa.
This is why it’s a modern myth about using a dehumidifier to resolve any issue regarding condensation or damp to try and extract excess moisture as it doesn’t warm or cool the room for the water to change on a molecular level and also that there is moisture all around us all the time . A dehumidifier would only work in a perfectly sealed room so adding a source of heat is a far better way to help this.
So with that being said the two things that need to be done to help prevent these issues are:
Raise the temperature of the areas/surfaces where the condensation occurs or reduce the amount of water present in the house via slight ventilation and I emphasise the word “ slight”.
The most obvious option and depending on where the condensation is present ,simply keeping all windows and vents closed and turning the heating up or on for longer is one way.
Another way is to simply rearrange furniture. If your finding the issue only behind certain parts of furniture then it could be that the furniture is just stopping that part of the wall from “ warming up”.
Another option which would require some level of building work is to increase the U value of the affected areas by adding insulation.
Another obvious way of reducing water in the air is through ventilation.
The most common ways in which we introduce excess water into our buildings are through bathing, showering, drying clothes and tumble drying. When we do any of theses tasks you would normally have some kind of mechanical ventilation active by way of an extractor fan. If that’s not possible or not present then you will have to rely on opening a window. You don’t need the window wide open or open for too long as you only need to equalise the water vapour in the room with that of outside , however you are relying on the weather for this …. so opening the window on a Cool wet or misty day will have little difference.
If the problems persists and none of the above solutions help then you may need to seek further advice and a more in depth survey.
Products to use when tackling these issues
- Lime based mortars or putties
- Roman cement