subject: Painting exterior house walls with wall coatings which also stops render problems and penetrating damp [print this page] PREPARATION!!!!! This is essential and is carried out always, before we can apply any of our long life paint and coating products, especially damp proof coatings for walls.
As we offer a 15 year guarantee on all works we do, using the correct preparation techniques is paramount when either having professional work done by a contractor, or in fact, doing it yourself. Any tradesman (or woman) who value their reputation and have pride in their work will tell you that unless the walls are properly prepared, the job will not look as good and not last as long and it will cost twice, or frequently more, in terms of time and money spent. So in essence, if a job's worth doing, it's worth doing right especially if it something as important as waterproofing or damp proofing rendered walls or brick walls.
Which is where we come in!
So with the above considered, how can we distinguish what type of wall needs what. Here below is an explanation of the different types of exterior walls, typical problems, and an explanation of what an Authorised NPA contractor actually does to each individual project?
There are many types of house walls.
There are many different types of exterior walls that one can see in a typical town or city in the United Kingdom. Many exterior wall finishes are appropriate to certain factors such as the age of the house, the method of construction, the typical weather at the location, and other factors such as people extending houses, converting them, and so on. Maybe in the future, houses will have to be adapted to combat changes in temperature etc caused by Climate change?
When NPA does work on a house or applies a wall coating to a commercial premises such as a shop, we first ascertain what the existing wall surface is, and then tailor our repair and preparation methods accordingly.
Here's a selection of different exterior walls, and the methods we use to repair them.
Exterior wall coating on Brick and stone walls
Brick walls are arguably the most common one in everyone's mind, even spawning the phrase "hitting a brick wall", not literally, but meaning coming to a dead end, perhaps in researching something, for example? Brick walls are what most walls nowadays are made of and this also included block walls, made from breeze blocks or large faced blocks, such as bath stone walls.
The bricks are laid end to end, one course (or layer) at a time, in a specific fashion, by a bricklayer or builder, leaving gaps for opening such as doors and windows and the installation of lintels above the openings to carry the course of bricks over the window, for example. The bricks are arranged in a specific fashion for the best strength.
These ways of laying the bricks have certain names such as Flemish bond, stretcher bond, running bond, pattern bond, and refers to the specific way they are laid. They are held together by mortar joints, often called "Pointing", which consists of a mortar mix laid on the top of one brick, and the bricklayer adds a small lump of mortar to the side a of a new brick, lays it on top of the existing brick, and repeats, until the desired wall is completed. The mortar is sometimes referred to by "brickies" (Bricklayers) as "muck", "compo", "mix" or if you're from the east end of London, "German Band an' cemun'".whatever that means!
The bricklayer will smooth the mortar joints and remove excess mortar as he or she goes along. It would be another article altogether to explain in full, all about bricks and bricklaying, so we'll leave it there for now!
. and onto what NPA would do in this case.
If NPA was refurbishing a brick (or stone) exterior wall, we would have 2 options.
The coloured wallcoatings would be the most labour intensive, and would require identifying any loose, missing or broken bricks and repairing or replacing them. (The coatings are special damp resistant coatings, and not only do they make the outside of your home look great, the anti damp nature of the coatings means your house will also feel warmer inside.)
Then we would repair and fill any loose or missing pointing or mortar joints, then we would mask up and protect all areas not to be coated, such as doors and windows, and also of course protect the path by laying dust sheets. We would then do a process known as "Bagging" or "Bag rubbing", which involves making (by the bucket load each time) a liquid mixture of sand and cement and a PVA Bonding agents, such as Unibond. This should be mixed to a smooth "creamy" paste, and applied with very thick brushes, or small broom handles. Gloves are essential when doing this, as if not worn, the cement will eat into your skin and cause great discomfort.
We then apply the bagging mixture to the wall, starting from the top and working downwards, and being careful not to let the mixture thicken as this will create an uneven surface and "brush lines" in the surface, which would show through to the top coating and look unsightly.
One this has been done and the cement coating has dried out, we then apply an "off-white" waterproof primer by hand, and then, using a GRACO president airless spray machine, we spray apply our textured exterior coatings, which once applied to the external wall, will not chip, crack, flake or peel, stops damp, and has a 15 year insurance backed guarantee. The same method would be used on walls made of stone. After the coating is applied to the house, you would still be able to see the natural stone outlines, preserving the character of the property, but with the added benefit of the house walls being resistant to penetrating damp, plus also being maintenance free. Again, please ask us for more information about what we would do to your house and how much it would cost.
Our Clearshield system is suitable for stone or brick walls and it does not change the appearance of the house in any way.
We carry out all repairs as stated above, and then we apply 2 coats of silicone based sealer, which soaks into the brickwork, as opposed to laying on the top surface, which means it is not subject to normal erosion from the weather and has a life expectancy of at least 10 years. Click the link above to read more.
Exterior wall coatings and painting hung slate walls
Generally speaking this was an old and fairly effective way of weatherproofing a house in the "olden days". The house walls would be made either from cob, stone or brick, and left unfaced, that is, it would not have a mortar or render coating over the bricks or block wall of the house. Wooden battens (thin pieces of wood) would be nailed to the walls, and then slates would be hung, literally, as in the manner of the roof of a house. This forms an effective barrier against the weather.
Although they can be painted, both with normal masonry paint and exterior wallcoatings, we can do a tremendous amount of repair to this, save for replacing any broken tiles or rotten battens behind the tiles. We would then apply a coat of stabiliser, a coat of waterproof primer, and then spray apply our NPA exterior wall coatings over the top.
THIS WALL TYPE IS NOT SUITABLE FOR THE RENDER-BASED TROWEL APPLIED WALL COATINGS and you should contact your local wallcoatings specialist for advice.
Devon cob walls
Devon cob walls are normally found on VERY old houses, often subject to preservation regulations and/or listed status and great care must be taken when working on this type of house. The building method used goes back hundreds, even thousands of years and evolved as the builders would have used whatever was to hand in the immediate area. These houses are often also referred to as "vernacular" houses.
This type of wall construction is also known as "Rammed earth", "pis de terre" and Adobe or clay lump. Adobe houses can still be found in South and central America, amongst other places. (The Eden project in Cornwall uses adobe (mud) walls which are very effective.) Houses of this type should be treated with great care and refurbishment and repair of such walls requires specialist skills and advice and is not recommended for DIY projects. The house with this type of wall is usually made by mixing ingredients such as mud or clay, gravel, straw or horse hair and water. Walls of this construction are usually up to half a metre thick and examples can be seen in the English countryside, and the houses often benefit from excellent insulation, which coupled with a thick, thatched roof, can make a nice cosy home!
As mentioned above, GREAT CARE should be taken on this type of house. Repair should be carried out using the same or similar methods or materials that had originally been used, which is often why a specialist contractor should be called. A good exterior coating that I would recommend on this type of house would be a limewash or some other breathable coating, but again, remember on traditional houses, traditional methods should be used.
IMPORTANT NOTE: Exterior textured wallcoatings, either spray applied, ORtrowel and roller applied wall coatingsshould NOT IN ANY CIRCUMSTANCE be used on this type of dwelling.
Textured coatings and paints on Render or stucco walls
NPA has over the years applied exterior textured wall coatings and protective weatherproof paints to a range of rendered houses across the Uk and Ireland. A rendered house requires us to check the entire wall surface for defects such as loose and hollow render, poorly done DIY or cowboy builder repairs, scars and uneven wall surfaces where alterations have been carried out to the house and of course cracks in the external walls.
We cut out the cracks with an angle grinder and fill them with a special expoxy resin mortar which binds the 2 parts of the building together, and then we "face" off the repair with a final coat of sand and cement, smoothing with a "float" 1st and then a damp sponge at the edges. Quite often on smooth rendered walls, it is advisable once the waterproof primer has been applied (and has dried) to further smooth out the edges of the crack repair in the wall buy "floating" or "skimming" small quantities of the textured coating product, using it as a fine surface filler.
Once the exterior walls are repaired to our satisfaction, we mask up the doors and windows, cover the ground with dust sheets and then hand apply our weather resistant, waterproof primer paint. Once this has dried, we spray apply a damp proof paint coating on top, which is available in either smooth or textured exterior wall finishes.
After this, the masking is removed, and the whole site is tidied up. The coating is 20 times the thickness of normal paint and as such takes longer to dry so you should avoid placing anything against the wall, or touching it, for at least a week. It would be touch-dry in 24 hours and fully hard in about 28 days. The coating will remain breathable, similar to the human skin so that moisture is allowed to evaporate out of the coating film, but cannot get back inside and cause dampness.
Wallcoatings on Tyrolean, Pebbledash and Spar dash walls
Pebbledash, tyrolean and spar dash walls go in and out fashion every few years. If you've ever tried painting a pebbledashed wall, you know how tough it is! The methods we use are very similar to the brick wall system above, so instead of repeating myself again, take a look at this page all about painting exterior pebbledashed walls, but remember to click your BACK button to come back here afterwards!
Pebbledash is a nasty substance and was invented purely to cover poor quality brickwork during the building boom in the UK during the 1920's and 1930's. A pebbledashed exterior wall finish is created by rendering the house with a soft sticky render coat and literally throwing stones or small pebbles at the house. Traditional pebbledash is made from small pebbles, but modern dash is usually spar dash or spa-dash and is applied in the same method above but small flint chips are used instead of pebbles. This inferior external wall finish is very coarse to the touch and the editor himself has literally taken the skin off the back of his hands when accidentally brushing up against a wall that has been spar dash, and let me tell you.IT HURTS!
Tyrolean, also sometimes called "Sprayed cement" is brittle and doesn't usually last very long unless it has an exterior coating treatment on it. Contact your local wallcoating specialist for advice, but to read more about tyrolean, follow the link posted in the previous paragraph above.
And finally..
As you can see, there are a variety of exterior wall finishes on existing houses, and this article has only touched on some of them. When we work on your home we take many factors into consideration which is why, much as we would like to, we don't have any "average" prices, preferring as we have done since 1986, to come and see your home and give it a full survey. More details of this can be found HERE
I hope that upon reading this article, we have given you, our valued customer, an insight into what we do and how we do it. No matter how old your home is, no matter where it is (We cover the UK, Ireland and Spain), and no matter what your home is made of, we can refurbish and beautify almost any property, in any condition so what are you waiting for?
Give us a call on 0800 970 4928 (or 0044 121 286 8558 from Spain) and have a chat with one of our friendly surveyors. This is totally without obligation, and you never know, you could end up saving a small fortune of home maintenance!
This is an original article written by Guy Bell of NPA. If you choose to use this text you must put a live link back to our exterior wall coating website.
Painting exterior house walls with wall coatings which also stops render problems and penetrating damp
