Painting exterior masonry is a fairly simple process of adequate preparation and selection of paint colour. The choice of paint is usually a matter of budget and/or personal bias because exterior masonry paints are all the same right?
Not really no.
There are water based paints, oil based masonry paints and mineral paints as well as a rubber based paint known as Pliolite. Factor in also the new ‘Eco Paints’ and you’d be right to be a little confused.
So which is best and does it really matter?
First of all the choice of paint will depend upon the type of wall surface and whether it has been painted before. Generally, the exterior walls of your property will be plain brick or stone or finished with some kind of cement based render – older properties (particularly those with a single thickness of wall) may have a lime based render finish.
Previously Painted Walls
For previously painted walls in good condition a standard water based masonry paint such as Dulux Weathershield should be perfectly adequate. If your budget doesn’t stretch that far then an own brand equivalent such as B&Q should be fine.
Most exterior wall paints are water based and contain some form of acrylic binder. They should be micro-porous – in other words, they allow any moisture trapped in the wall surface to evaporate.
Alternatives include solvent-based paints for all-year round application and Pliolite rubber based paints for inclement environments.
Unpainted Cement Rendered Walls
If you have cavity walls and the render is in good, dry condition there is no reason why you shouldn’t use a conventional water based finish. You may need to do a little preparation such as filling any minor cracks and priming any loose or friable areas with stabilising solution.
Afterwards simply coat with two or three coats of masonry paint in your chosen colour (the first coat slightly thinned with water).
Stabilising Primer is ideal for chalky or powdery areas. It acts like an adhesive – providing a solid base for subsequent coats of paint to stick to.
However, it is NOT a suitable primer for ordinary rendered walls despite what your neighbour or bloke down the pub may tell you. A thinned coat of regular masonry paint is all that is needed as a primer for sound rendered walls and stonework.
For older properties with a single thickness of wall it will be necessary to ensure that the wall is able to breathe (in other words, the surface should be permeable and allow any trapped moisture to escape). Ideally the render will be lime based or with a low cement content finish.
In theory a quality water based system, such as Dulux Weathershield, will perform quite adequately and should last many years.
However, you may consider using a mineral based paint which could perform considerably better?
Mineral Based Exterior Paints
Put simply, mineral paints are made with a silicate binder which reacts with the surface of the wall to form a long-lasting bond, unlike traditional paints which simply form a skin. They are naturally alkaline, so inhibit mould growth and carbonation; mineral paints also have the added advantage of being eco-friendly too.
The disadvantage is that they require more thorough preparation, special primers and are, initially, much more expensive – although the increased performance should pay back over the long term.
There are a few specialist manufacturers of mineral based paints – the main two being Keim and Beeck.
Each have their own detailed specifications for different kinds of wall surface and these must be followed to the letter in order to enjoy the maximum performance.
Lime Rendered Walls
For old buildings with a lime based render or lime based pointing a traditional Limewash is ideal. Limewash is simply a paint made from lime powder and water together with a colourant.
The main advantages of limewash are they bind to the surface very well and are totally breathable – another benefit is that they are relatively inexpensive.
Care needs to be taken with application and sometimes additional binders need to be added to aid adhesion.The finished result can be very striking though – looking much more natural than a traditional paint finish.
Limewash paints are available from a number of sources including Ecos, Ty-Mawr, Little Greene and Farrow & Ball.
ECO Paints
Technically, an ECO paint is simply a paint which has a very low or zero volume of Volatile Organic Compounds. While some ECO paints are obviously superior to others there isn’t any case for suggesting that an ECO paint will perform any better or worse than any other form of exterior paint – it will simply be a matter of personal choice.
It’s worth noting, however, that mineral and lime based finishes, mentioned above, are by their very nature eco-friendly – so would make a good choice if you wanted to be as environmentally friendly as possible?
A Little Preparation Will Go a Long Way
As always, the amount of time you spend preparing the surface will show in the end result and, if done properly, a painted exterior wall will last at least ten years before it needs re-coating.
Bear this in mind when making your choice of materials as it really isn’t worth skimping and a few extra pounds spent at the outset will go a long way.
Gordon
My house is a Victorian terrace, built in 1840, and has solid sandstone walls. It’s also right by the sea so subject to some pretty nasty weather. The front of the property (which is on the lee side from the sea) has been coated at some time in the past with what looks like a cement render. It’s bossed in many places and water runs between it and the sandstone so I intend to remove it. Having removed a test area, some comes off easily whereas other parts take a layer of stone off with the render, so I may need to repair some of the blocks. Once I’ve done all of that though, I’d like to paint directly onto the stone. This has been done on neighbouring properties and looks much better than render. Planning constraints (as well as erosion) prevent me from leaving the stone natural so it has to be painted but I keep getting conflicting advice on which paint to use. A local painter, who has painted several of the properties around here, says he would only ever use a pliolite paint. from what I understand though, this would trap moisture and damage the stone (this is already evident on many of the properties he’s painted). Others recommend Dulux Weathershield (trade) as the best product but the local Dulux shop say they do not recommend it for sandstone, and would never recommend painting directly onto sandstone with any product. Grateful for any advice and recommendations.
Decorator
Your local painter is an idiot, pliolite-based paints have one purpose and one purpose only. That is that they are not damaged by sudden rainfall immediately after application. There is no domestic use case at all.
Secondly, people who work in paint shops are not experts and any advice they give can usually be discounted as nonsense.
On a positive note, it sounds like someone you have consulted does have an idea as to what the best paint to use is. That is Dulux Trade Weathershield or, if you want to push the boat out, Dulux Trade Weathershield Maximum Exposure Smooth Masonry Paint
There is a case for using a silica-based painted system that will bond naturally but this is a specialist job and doing it yourself or employing someone with no experience of such systems can end up being more bother than it is worth.
When you have removed the existing coating back to bare stone I suggest you leave it alone for a full year in order to ‘weather’ before attempting any painting so that any loose material and excessive trapped moisture has chance to escape naturally which should reduce the chance of any subsequent problems.
Sandra
My son has a grotty back yard that he wants to spruce up. The ground is just concrete, not paving stones etc. He has seen that some people have simply painted over the ground in their back yards, and he thinks this could be a straightforward and affordable option. He was thinking of painting the yard grey. Are you able to recommend what sort of paint he would need for this purpose, and what preparation would need to be done? Thank you very much.
Decorator
I imagine his neighbours are using a standard floor paint that is normally used for painting garage floors and such. I would recommend the same but make sure it is water based since this will make the job a lot easier. He’ll need to make sure the floor is as clean and dry as possible.
Here is one example: https://www.wickes.co.uk/Ronseal-Diamond-Hard-Floor-Paint—Satin-Slate-2-5L/p/153832
Anything similar will do.
With a water-based finish he won’t need any special primers, just make sure the first coat is thinned with water just enough so it soaks into the surface but not so thin thin that it is just coloured water. A bit of trial and error on a small test area first is advisable.
Then just apply one or two more un-thinned coats to finish.
Bear in mind that moisture will still be absorbed by the concrete from the ground so, over time, you will get bits flaking off and bubbling. There isn’t anything you can do about this since it depends on the water level underground. A bit of regular maintenance will do the trick though.
Joy
Hi I have a large breeze block shed with rain coming through the walls. It hasn’t been painted for years. What do I need to apply as base, first and top coat ? Do I need it to dry out before starting work ? Thanks
Decorator
A single skin breezeblock wall is going to difficult to make water-tight but painting might help? Also bear in mind that how the walls are constructed will be a facture as essentials such as a damp proof membrane and proper detailing around openings is often omitted.
Yes, you do need to allow the walls to dry out in depth so it is a project left until the end of summer rather than right now. You don’t need any specialist primers or finishes, ordinary masonry paint with the first coat thinned sufficiently that it soaks into the blocks and provides a key for subsequent coats.
I should re-iterate, this isn’t going to make the walls ‘water-proof’ but it should mitigate the worst of the problem.
Sonja
I have a raised flower bed made with breeze block. It has been painted before, but moisture from the soil comes through and destroys the outer surface with damp and algae and generally looks awful. I thought that if I removed the soil and painted the inside of the flowerbed wall, would this be the best answer so that I can paint the outer side of the wall. Or should I paint the outer side with stabiliser and then exterior paint ?
Decorator
You will still get damp penetrating from the ground so you would be wasting your time. The only way it’s going to work is if you remove the blocks and paint all sides. You will also need to ensure that all the blocks are thoroughly dried-out first.
John
Bubbling paint on render my bungalow walls where rendered 4 year s ago with sandtex water based paint the render was left Un painted for 3 months be for painting I have removed all loose paint from the walls when I run my hand over the render it is quite dusty would it be best left to spring repaint. Or. repaint now using a pliolite based paint your advice would be appreciated
Darren
I would leave until next Spring John, the chances are that there are still bits of loose paint and painting now will just make matters worse.
Anthony
Does the surface need to be perfectly dry before applying masonry paint?
Darren
If you paint onto a damp surface then the paint is going to fail at some point. If it’s really damp the paint will just run off the wall and onto the floor.
So, no.
Mike
I have bought a bungalow painted with eco masonry paint with silicon in it, can I over paint it with deluxe weathershield.
Darren
You’d be wasting your money using weather shield since it’s only as good as what you’re painting over. Ordinary masonry paint will be fine.
Not sure how a paint can be labelled ‘eco’ if it has silicone it though?
Rob
I have an old outer brick building. Which I will be painting , should I use primer paint first?
Darren
No, assuming the surface is sound, just prime with a thin coat of masonry paint. A bit of trial and error is in order since you want to dilute the paint so it soaks into the surface but not so thin that it’s juts coloured water. Then paint as normal.
Philip
Is there such a product as an oil based masonry paint. If so could you let me know if it is better than a water based masonry paint such as Dulux Weathershield. Also could you let me know who manufacturers it.
Darren
Yes, it’s widely known as ‘Pliolite‘ or ‘all-weather’ masonry paint, Pliolite is a rubber-based resin developed especially for use in paint products. Most of the major paint brands have a version available.
The only valid reason for using these products is that they become surface-dry much more quickly than water-based products. This is a useful property if you have to paint a wall when the weather isn’t predictable and rainfall is a possibility. In a domestic situation you can always wait for a better time but in some commercial situations the job has to be completed by a certain date regardless; that’s where these products come into their own.
Generally speaking, a water-based paint is always better. It’s easier and more pleasant to use, is moisture vapour permeable (so doesn’t trap moisture in the fabric of the building) and, when dry, remains elastic for longer than an oil-based product would.
Steve
What is the correct paint to use on external wall insulation?
Darren
Where external insulation is applied it will normally be finished with a proprietary render. In most circumstances you can over-paint this with regular masonry paint. The exception would be where the render used is supposed to be a finish in itself.
In all circumstances though, you are best checking with the manufacturer of the system used and ask what they specify. This way you will not be in breach of any warranties or guarantees.
I would be careful of asking the actual installer though as the answer you’ll get is highly likely to be unqualified and wrong.