You are here: Home / Questions & Answers / ...

Painting Rendered Walls

Question

My 1860’s house has solid brick walls that have been covered with a sand / cement render followed by a tyrolean finish. I want to paint them with an exterior emulsion to reduce dampness when the walls are subject to heavy rain. They also have some fine cracks but the render seems essentially sound.

One painter I have spoken too would recommend a water based exterior emulsion, but another favours a solvent based pliolite paint. Would the latter be as breathable? I can’t find much info on breathability of pliolite paint.
What would you recommend?
John

Answer

Pliolite paint is formulated for application when there is a likelihood of rainfall within a few hours. It is, by nature, less breathable than regular masonry paint and has no performance benefits. Any painter who doesn’t know this ought not be allowed within a mile of your property.

It sounds like your walls are taking in a lot of moisture and you really need to address the cause of this first. The fine cracks you mention will need to be properly repaired first. If the walls are still taking in so much moisture it may be worth considering a solution that allows the walls to breathe rather than trying to make them water-tight. The solution to this involves both sides of the walls – not just the outside.

The SPAB publication ‘Breathability & Damp‘ is well worth a read.

When it comes to recommending a paint finish I would suggest a mineral based solution such as Keim Granital or Ecopro Silicate Masonry Paint.

Ordinary water based masonry paint is the most economical solution but not ideal.


Question

Hi. I’m about to paint a garage that has been rendered – smooth finish. Built about 5 years ago but never painted. Confused with advice. What should I use to seal it? It’s not particularly flaky. some say water down masonary paint others say don’t. Some say use old undercoat to start first layer. Any advice? Had someone to paint my side of neighbour’s garage years ago and he used tons of tins of paint, but that wall was rough surface.

Answer

Use masonry paint. Thin the first coat so it soaks into the surface. Apply further coats straight from the tin; you can thin it a bit to ease application but don’t over do it. A rough surface may take a lot more paint to cover than you expect, especially if it hasn’t been painted before.


Question

I want to paint the outside of my late Victorian terrace. It has not been painted before so I will be painting onto a rendered surface.

I cannot find out for sure but i am assuming because of the age of the building (It was built in 1901) that the render is lime and sand? is that a safe assumption. Although the decorative mouldings certainly look like cement to me so I wonder if its a bit of both. Is there a way to tell?

My question really is. Do i need a stabiliser? if so what one would you recommend and also would B&Q’s Valspar masonry paint be any good for this job?

I’m concerned about its breathability, I currently don’t have a jot of damp in my house and certainly don’t want to create a damp problem by sealing the house.

Answer

You’d need to have a sample analysed to ascertain if the render is lime based for sure but, given the date, it is a fair assumption. The mouldings could be a different material but it doesn’t really matter in this instance.

You don’t need a stabiliser. A thinned coat of masonry paint is an ideal primer. You only use stabilising primer on small areas if they are crumbly or friable. In most cases this isn’t necessary and using a stabiliser on a large area will just stop any moisture escaping.

The Valspar masonry paint is perfectly OK.



30 thoughts on “Painting Rendered Walls”

  1. Hello Our front garden wall needs painting white every year after a damp and harsh winter. It usually looks dirty, green and grubby after about 6 months after painting it. I use weather shield paint but was wondering if one of your paints would do a better job? The wall is south facing and sits by a main road in an ever expanding village. Many thanks. Kate

    • Not sure what ‘one of your paints’ means but anyhow…

      I wouldn’t waste money painting a garden wall with a premium masonry paint since it will get just as dirty as any other cheap brand.
      There are dirt-repellent finishes available for commercial use but, aside from being very expensive, they are not suitable for surfaces with no protection from internal moisture build-up, garden walls being a classic example. What you would find is a nice clean finish that bubbles and peels away as the trapped moisture forces its way out.

      So the answer really is just to accept the wall is going to need redoing from time to time and to use a cheaper brand of paint in future. You could, however, use a fungicidal wash from time to time in order to mitigate the build up of green mould. For example: B&Q Exterior Fungicidal wash 1L

  2. I have just had my house coated with a pliolote based paint and the finish has crazed all over, very fine cracks are visible and the contractor has said this was not an issue, another contractor has said that it hadn’t been given enough time between coats to cure and I would be grateful for some advice?

    • It does sound like the crazing is due to a second coat being applied before the first coat has dried. Pliolite paint is formulated to set quickly to mitigate the risk of being washed off during a sudden rain downfall, it doesn’t mean it has dried in depth though.

      Not sure why you opted to use Pliolite in the first instance, if it was recommended by your painter then he is not only liable for the inferior standard of work but also for using the wrong product in the first place.

  3. I have an exterior rendered wall that was until recently covered in ivy. That’s all been removed now but it’s left all the dried tendrils still attached to the wall. Whats the best way of removing these?

    • Dig them out the best you can and treat the wall with a fungicidal wash. It’s inevitable some will start to regrow or will decay and damage the painted surface. Without going to extremes, you just have to accept that you’ll need to repaint a bit more often than you might like.

    • Old limewash tends to erode rather than peel or flake off. It can also be non-uniform in colour and will absorb water readily.

      Small flakes will fizz and dissolve when placed in an acid solution such as brick cleaner.

  4. Is it OK to paint Dulux Weathershield masonry paint over limewash. There is no chalk on the surface. I was considering stabilising first to be safe. Thank you

  5. Hi, can i use sandtex exterior masonry paint on my exterior lime washed walls. We lime washed the walls last year and they are now all patchy as we are in a very exposed site.

    • Hi Sarah, I wouldn’t recommend it. Firstly, you’ll have problems getting a traditional paint to adhere to a powdery surface such as lime-wash and, secondly, any paint system is only ever going to be as good as the surface it is applied to.

      Unfortunately, lime wash does look good but it does require constant upkeep. If you are thinking of updating to ordinary masonry paint then the only option is to completely remove your existing finish and star from scratch.

      You will get people telling you that you can use some sort of primer or sealer first but I’d ignore this advice if I were you. Not only will it eventually fail but you’ll also be trapping moisture in the walls resulting in bigger problems later on.

  6. Hiya Darren I have an old terrace which is three storey at the back and two storey at the front. The front is painted in a red gloss and the top above bottom bay is rendered and bottom painted brick. I want to paint the front as its peeling quite a bit on the top half but I want to paint it a much lighter colour. I’ve been told many different types of paint I need to buy so I am now confused! Can you help please…..what paint should I buy to paint over red gloss? I would like a matt not gloss finish. Many Thanks

    • Roof tile/brick paint comes in red and dries to an almost matt finish:
      https://www.rawlinspaints.com/home/roof-paints/roof-tile-paints/751-blackfriar-brick-tile-paint.html

      Alternatively, for a lighter colour, you could use a standard oil-based undercoat and then, for a matt finish, a water-based masonry paint.

      In either case, you will need to ensure that all loose paint is scraped off and the gloss paint is washed-down and abraded with sand-paper first. Also, after using an oil-based undercoat it’s best to leave it for a while to fully cure before attempting to paint over it with a water-based finish (about a week should do it but longer if you can?).

      As an alternative to undercoat you could use a water-based (quick-drying) acrylic primer/undercoat.

  7. I have a 1930’s house covered in the original roughcast render.

    It had an old, but sound coat of masonry paint on it and several years ago I painted over this with a modern water based masonry paint.

    The problem is that it is south facing getting a lot of sun and after a year or so the paint started to bubble, crack and flake off the surface.

    It now seems to trap rain water and is causing dampness in parts of the wall. I can remove the flaking paint easily with a wire brush, but because it is roughcast render it is near impossible to get all of the newer paint off the walls.

    I am concerned that if I overpaint the surface again the same thing will happen?
    I was considering using a stabiliser, but I read that this prevents the wall from breathing?

    Assuming that I am unable to remove all of the paint, only the flaking paint, please can you suggest a paint that will allow the walls to breath and also stand up to large amounts of direct sunlight during the summer months.

    I have read that using a primer before the topcoat of masonry paint may be a good idea?

    Any advise that you can give me would be very much appreciated.

    • If you can’t remove all of the defective paint then you are indeed going to experience the same problems over again. Adding more paint to an already defective coating increases the load it has to bear which just results in yet more loss of adhesion. There isn’t a primer of any kind that’s going to solve this.

      It’s a common problem and, understandably for aesthetic reasons, you don’t want to leave the walls in their current situation.

      From the way you describe the situation it seems the walls have a high moisture content and should really be left dry out in depth before any repainting is considered. This, of course, is not an ideal situation but I don’t think there is any way around it?

  8. We have just had our old cottage walls re rendered with a lime NHL3.5 / sand mix, having had the old inappropriate cement render removed. Three coats followed by a Tyrolean finish. The result looks good and has been done by a professional company with a good track record.
    Is it OK to leave the painting till next year? What do you advise as to a suitable paint that has to be microporous and minimal maintainance in future.
    Thanks

    • Yes it is OK to leave it until next year, I would recommend this anyway to give the walls a chance to dry out in depth.

      Obviously traditional Limewash would be suitable but does need redoing fairly often.

      A mineral based paint such as Keim Granital would be ideal but is expensive and isn’t as easy to apply as regular masonry paint. You need to ensure you are keeping a wet edge when painting and this isn’t easy when covering large areas of wall. It isn’t impossible but takes a bit of planning and is a two man job.

      Alternatively, the Ecopro Silicate Masonry System from Earthborn is worthy of consideration. It works in a similar way to Keim but with the addition of a primer to aid adhesion. This system is more suitable for DIY application too.

  9. I have a 1970’s house with upper storey slate clad and lower storey cement rendered. The masonry paint on the cement rendering in one area bubbles every time there is consistent rain (and has done for years). Is there any solution to this please?
    Thank you

    • The bubbling is caused by trapped moisture. There are a number of causes behind this but the paint coating isn’t helping.

      • Thanks. So I guess I should wire brush off the paint coating where it bubbles even though what is left will be unsightly?

      • Yes, let the wall dry out as much as possible. Don’t repaint until you’ve identified and rectified the source of the damp problem.

  10. Looking at various render systems and not sure which is best in the long term. We have an edwardian 1930’s semi which is currently has a spar dash which is probably 50 years old. It has been patched up in places and looks untidy. Concerned about hacking off to the brickwork due to mess and fear of builder over hacking and damaging bricks. Looked into K-renders and other eco renders including thermal and they are very expensive and as the green deal is no longer available not sure if it’s worth the investment. Considering lime render but not sure if I still need to hack off back to brick work? Is this a better alternative to K renders?

    • Alternatives to traditional cement and lime renders often do not live up to expectations. This is partly due to exaggerated marketing and poor workmanship; you’re best avoiding these products altogether.

      The ideal solution would be a lime render but, as you say, it will need the existing coating to be fully removed in order to get the full benefit. A regular sand/cement render is the next best alternative really. Provide the mix isn’t too strong and there are no underlying damp problems you should be ok with this option.

  11. My son is in process of having an extension added to a 1920’s/30’s house, the old rendering has been removed and new put on, how long does he need to leave this before painting and what would be the best exterior paint to use. The old part of the building is not cavity wall and I don’t know what has been used for the rendering.

    Do you reply direct to sender?

    • Ideally I’d leave it a full year before repainting. If he can’t wait that long than at least 3 months.
      When a render finish dries out in depth you can get hairline cracks developing which allow water to get in. If you delay painting it gives you a chance to spot these and repair them.

      The best kind of coating to use is a mineral based paint like Keim Granital but it’s quite expensive and difficult to apply.

      Alternatively a standard emulsion based paint like Dulux Weathershield will suffice.

      I don’t reply directly anymore since it was taking up too much of my time. A lot of the questions were duplicated many times also, which was quite frustrating.

  12. We have an external concrete block rendered wall round our car park. It has to be painted every year as a large proportion of the paint flakes and bubbles off in big pieces. When the wall was rendered the builder used washing up liquid in the mix – could this be the problem. Have you any advice as how to treat the wall before we paint it yet again.

    • It’s unlikely to be the washing up liquid at play here. More likely the wall has been badly designed or constructed and, as a consequence, is taking in excessive moisture. This moisture will force it’s way out – hence the flaking paint.

      Masonry paints are formulated to allow normal levels of moisture to evaporate through the surface but they can’t cope with a wall that is becoming saturated.

      If the top of the wall is just flat without any capping to shed rainfall this is the most likely cause but it could be a combination of a number of issues?

Comments are closed.