Ever wondered how a painter paints a rendered wall?
Just open the tin and splash some paint on, yes?
…er… no actually……… there is far more involved in painting over render than you may first think, so here are a few tips on how to do it and what not to do. (By the way, this would be referred to as stucco in the USA)
This article primarily looks at rendered walls and although some aspects of painting other exterior wall surfaces are the same, many are not, and each wall surface (for example pebbledash or brick) requires a different approach, and in some cases, a higher level of expertise.
It is also worth noting that painting a newly rendered wall is a different kettle of fish than painting an older wall with render, so lets looks at both scenarios and maybe you can spot the difference in method and approach.
How to paint a rendered exterior wall
New render, and the painting of it, would at first seem a doddle, after all, no repairs are needed and no prep work in the guide of mould or moss removal, scraping old paint off or crack repairs will be needed, but it’s not as simple as that.
One of the key things to consider about painting new render is drying time, or hydration time.
Remember when we apply render to a wall, water is added to the mix, to consolidate the mortar ingredients and also to aid application.
That water in the mortar mix needs to evaporate first, or painting over it will either trap the water in, causing cracks or damp at a later stage, or it will dissipate out of the wall and make the paint bubble.
So it always best to leave a few days before painting is started, maybe longer in the colder and wetter months of the year.
Before painting starts, make sure you have all the right tools and equipment needed to paint.
The first thing you need to do is to INSPECT the wall as even the best plasterers sometimes miss bits, so go around the house and look closely at the wall to make sure no cracks have appeared whilst the render is drying, and no bits have been missed.
Pay special attention to corners and around doors and windows.
If you find anything, you need to attend to, use a fine exterior surface filler, such as Ronseal exterior ready mixed wall filler, which is about £6 for a 1.2kg tub.
Also look for what a plasterer calls “snots” (no, nothing to do with your nose bogies!) and this is small beads of render that may have been flicked on to the wall or dropped from the trowel during the laying up (applying) of the render. These need to be scraped off the wall, along with any other defects or things that should not be there.
If you find any “proud” spots of render, bits that haven’t quite ended up as flat as the rest of the wall, take a plasterers “float” , wet it, and then vigorously scrub the area using circular motions, which will wear down the bulging area to flat.
How to prepare to paint a dusty or friable wall
If the wall to be painted seems dusty or dirty, take a stiff brush or a broom head and brush over the entire wall which will get rid of any dust or sand that has been left behind as you don’t want that coming out in the paint.
Sometimes a newly plastered external wall can have a surface which we call “Friable” which means that a slightly incorrect mortar mix may have been used (with too much sand, not enough Portland cement, not enough water, or any variety of these common mistakes), resulting in an excessively “sandy” or dusty surface.
Now, this is no good to paint over, even if you take the steps above and brush the dust off, the surface left won’t really be strong enough even to hold paint, so what you need to do is to buy a wall primer and stabiliser, and you can get one from somewhere like Wickes DIY for about 23 quid for 5 litres. You need to paint that across the whole house and then allow to dry.
The resulting paint job on the outside walls will be MUCH better and easier as a result, plus it’s gonna last much longer before you need to repaint.
Once you are confident the wall is fully prepared, now is the time to start painting!
Make sure you keep all your tools, paint and equipment in one place on site and make sure that kids and pets are kept well away. If you are painting from a ladder it is often good practice to have someone hold the ladder for you, especially if there is a breeze on that day.
START AT THE TOP! Then work down using confident strokes with your brush or roller.
TOP TIP: “Do all the cutting in around windows and corners with a small brush FIRST, before you paint the rest of the wall.”
Then once the house is painted, you need to repeat the process (yes, you have to do it again) and you should eventually end up with a nice looking painted rendered wall!
NOTE: Do you see from what I have written that most of the job is taken up by PREPARATION? Make a note of that as that is the key to a good job.
Painting an older rendered wall
One of the key differences between painting new and old render is the condition of the wall to paint.
For example, an older wall is likely to have some defects or points that need attention in relation to the overall preparation needed prior to painting.
The amount of prep or repair work will be, in most cases, far more than is needed on a brand new rendered wall and if you are a novice DIY’er, it can sometimes be daunting, so it’s often best to hire a tradesman for a couple of days to sort the wall problems out before you start any painting.
“Painting an older wall is much more difficult than painting a new one & requires more skill and experience.”
So what sort of prep work does an old wall need?
Well, we can surmise that the typical problems found when getting ready to start painting an old wall would consist of:
- Flaky or loose paint
- Loose or hollow render
- Mould, moss or green growth on the wall
- Previous repairs not finished properly
- Additions and alterations to the house
- Old redundant clips, nails, screws and brackets
- Damp or water penetration
Each of the above needs to be addressed before any painting can be done.
Flaky paint needs to be removed or you will end up painting over an unsound surface, meaning the new paint will not last very long. All old paint needs to be removed back to render for the best finish possible and this may mean removing layers and layers of old paint. You can use a variety of tools such as scrapers, heat guns and paint stripper but be careful when doing so and wear goggles so paint chips don’t get into your eye.
Cracks are common in old walls and they need attention. Cut out old cracks and fill with a good quality filler (NOT SILICONE MASTIC) and small, fine cracked bits need to be filled with a fine crack filler and then sanded down smooth.
TOP TIP: “Use something like Epoxyshield fine crack repair FLS7J, which is about £25 a tub but should make sure the cracks don’t open up again.”
Loose render is something that unless you have some plastering experience, it is best to call a rendering company in to sort that out, or at least your local builder.
Moss or green mould also needs to be removed, and it is best to treat them with a mould remover which can be found on eBay for about a tenner. Then wash the remover off, and then power wash the wall to get all the old green stuff off, as if you don’t, it will come back and ruin your paint very quickly. Don’t use bleach, it won’t work.
Old redundant wall fixings such as nails and brackets need to be removed before you start painting, for a variety of reasons, if not just to make sure the final job looks good, or at best, to make sure you don’t ruin your nice new paint brush by it catching on a rusty nail and ripping the bristles out.
Finally if damp is present in the wall, then this is absolutely something that needs to be done before you even open that can of paint and there is a link there to show you how.
“Can I open the tin of paint now please?!”
Yes, feel free, as long as you have read, and acted upon the advice given above! As we have seen, painting a rendered wall which is new, is far easier (in theory) than painting an old one, but in each case, we can see that most of the job is taken up with preparation work which, if you choose to ignore that, you should not be allowed to make a balls up of the paintwork that you are about to do.
If all this seems a bit over your head, give us a call on 0800 970 4928 and we can quote you to have the exterior painting work done professionally and correctly by our skilled house painting teams.