How to Paint Exterior Walls and Render: The Right Way

⏱ Read time: 8 min | 🌿 Difficulty: Intermediate | ⏰ Time: 1 to 2 days | 👷 1 to 2 people

Your exterior walls are up against rain, frost, UV and whatever a British summer decides to throw at them. Done properly, a good exterior paint job protects against damp and keeps the house looking sharp for 8 to 10 years. Done in a rush? You will be back out there peeling and repainting within two.

This guide covers everything you need to know about how to paint exterior walls & render from start to finish.

Why masonry primer matters more than most people think

The first, most important step for painting exterior walls is to prep them with primer.

Skip the masonry primer and the finish coat sits on a chalky, porous surface with nothing to grip. The result? Paint that bubbles, peels or lifts within a season.

Masonry primer or stabilising solution does three things:

1. It binds and consolidates the surface, stopping the top coat from disappearing straight into the wall.
2. It seals porous patches, giving a more even base to work from.
3. It provides a key for the finish coat to bond properly.
   

New render and fresh pointing are particularly thirsty and will soak up paint like a sponge without primer.

On previously painted walls in good condition, apply stabilising primer over any chalky or powdery patches as a minimum.

Where a wall is heavily chalking, very porous, or has been treated with a biocidal wash, apply primer across the whole surface.

Quick test: run a dry hand across the wall. If it comes away dusty, that wall needs priming before it sees a drop of finish coat. No exceptions.

Shop Painting and Decorating supplies at HSS DIY

Can you paint render?

Yes, absolutely.

Painting exterior render is one of the most effective ways to weatherproof it and refresh the look of your house at the same time.

Render is cement-based and naturally porous. Left unpainted, it absorbs moisture, leading over time to cracking, damp patches and algae growth.

A breathable exterior masonry paint seals the surface while allowing moisture vapour to escape from within the wall.

If the render is new, allow it to cure for at least four weeks before painting. Fill any cracks and allow those repairs to cure fully before priming and painting. Rushing this stage is how you end up with a finish that fails before the year is out.

Knowing the perfect weather for painting outside

It’s no secret that the weather in the UK doesn’t always cooperate. Knowing the forecast and understanding which weather conditions are best for painting your exterior walls & render will help you in the long run.

• Paint above 5 degrees C - most exterior masonry paints require a minimum of 5 degrees during application and for 24 hours after. Below that, the paint will not cure properly.
• Avoid scorching heat - above around 25 degrees C in direct sun, paint can dry too fast, leaving brush marks and reducing adhesion. Paint in the morning on hot days or wait for shade.
• No rain for 24 to 48 hours after each coat - check the forecast before you start. In the UK, check it twice. A dry, overcast day with light winds is ideal. Cloudy is actually better than blazing sunshine for exterior painting.
• Best months in the UK: April through to September. May and September are the sweet spots. Temperatures are right, there is less chance of full summer heat, and long daylight hours give plenty of working time.
• Let morning dew dry off: give the wall a chance to dry out naturally before you start. Damp on the surface means poor adhesion regardless of the forecast.
• Painting external walls in autumn?: keep an eye on overnight temperatures and get your second coat on before the evenings cool down significantly.

Tools you’ll need for painting exterior walls

Before you start, make sure you have all the tools you’ll need. There’s nothing more annoying than starting a project to find half way through, you don’t have everything you need!

Whether you’re hiring or buying, you’ll find everything you need at HSS DIY.

Tools to buy

• Exterior masonry stabilising primer or stabilising solution
• Breathable exterior masonry paint (enough for two coats, check coverage rate on the tin)
• Exterior flexible filler for any cracks or repairs
• Fine-grit sandpaper or sanding block
• Masking tape and dust sheets
• Dust mask, safety glasses and work gloves
• Wagner Control Pro Airless Sprayer
• Pressure washer for cleaning the exterior walls

Tools to hire

• Scaffold tower hire for work above single-storey height
• Paint sprayer hire UK for large rendered areas
• Pressure washer hire - that’s right! You can either buy or hire one of these, depending on your preference.

Step by step: how to paint external walls and render

Step 1: Clean the wall (allow half a day)

Using a pressure washer, jet wash the walls from top to bottom.

Remove any algae, moss and grime. If there is significant algae or moss growth, treat the wall with a diluted fungicidal wash after cleaning. This kills spores that would otherwise grow back through the paint.

Allow a minimum of 24 hours drying time before moving on to the next step.

Step 2: Fill and repair (1 to 2 hours)

Check render or masonry for any cracks, holes or loose material.

Chip out any hollow render, fill it with exterior flexible filler and allow it to cure fully. If needed, sand the filler down.

On previously painted walls, sand and feather any flaking paint away.

Step 3: Mask up (30 minutes to 1 hour)

Use your masking tape to create a barrier and cover windows, doors, guttering, pipework and anything else not being painted.

To help protect your flooring, put a dust sheet on the ground below.

Step 4: Apply masonry primer (1 to 2 hours plus drying)

Apply primer across the full surface of the wall if it’s new, bare or heavily chalking.

On previously painted walls in reasonable condition, apply the primer to repaired patches and any powdery areas.

Allow the primer to dry 4 to 6 hours in warm, dry conditions. Always read the product instructions before using.

Step 5: First coat of exterior masonry paint (2 to 3 hours)

Working from top to bottom, section by section, use a 9-inch masonry roller to apply your paint.

An angled paint brush is perfect for following lines and giving you better control when painting around edges and window frames.

For large rendered areas, a paint sprayer will cut application time significantly and give a more even finish.

Step 6: Second coat (2 to 3 hours)

The second coat is where the colour really comes into its own. Before starting, make sure the first coat is fully dried before you start painting again.

Whilst the paint is still slightly tacky, peel off the masking tape around your windows, doors etc. Pulling it off once the paint is fully dried risks the paint coming off with the tape.

Using an airless paint sprayer

For large surfaces, especially smooth or fine-textured render, an airless paint sprayer is worth serious consideration.

Compared to rolling, the process is faster, it covers more evenly and gets into the texture of render properly.

Tips for spraying exterior walls:

• Mask absolutely everything thoroughly - overspray travels further than expected.
• Work in low or no wind conditions - any real breeze and rollers and brushes are the safer option.
• Thin the paint slightly - if the manufacturer recommends it.
• Keep a consistent distance from the surface - typically 30 to 40 cm.
• Use a spray sock or fine-mesh filter - this helps prevent blockages.

How long will it take to paint exterior walls and render?

Here’s how long it would take to paint exterior walls and render on a standard semi-detached house (on average). Depending on your schedule, you might find you want to spread the work over two weekends.

Prepping

• Washing the walls - 2 to 3 hours. Leave to dry.
• Filling & masking - fixing any cracks, sanding down and applying masking tape could take 2 to 3 hours.

Priming and painting

• Primer - 2 hours for application & 4 to 6 hours drying time.
• First coat of paint - 2 to 3 hours then leave to fully dry.

Second coat and finish

• Second coat of paint - another 2-3 hours.
• Remove masking tape - 15 - 30 minutes depending on the size of the wall.

Health and safety

Whenever you’re doing any sort of DIY, it’s important you know and understand how to stay safe, especially when you’re working from a height or using paints & chemicals.

Here are some tips :

Working at height

• Do not use a ladder for extended exterior painting. Use a scaffold tower for anything above 2 metres.
• Follow PASMA guidance for scaffold tower assembly at HSS Training.
• Do not work on the tower in winds above Beaufort Scale 5, roughly 30 mph.
• Always wear non-slip footwear on the platform.

Paints and chemicals

• Wear a dust mask when sanding render or old paintwork, particularly on pre-2000 properties where lead paint may be present.
• Use safety glasses and chemical-resistant gloves when applying biocidal or fungicidal wash.
• Use a respirator-grade mask when using a paint sprayer outdoors, not just a basic dust mask.

External references

For more info on how to stay safe whilst working from a height, check out the links below.

• HSE Working at Height guidance
• PASMA: safe use of mobile scaffold towers

Case study: 1970s semi-detached, three days, two people

The front elevation of a 1970s rough-cast render semi-detached had not been painted in about 12 years. The signs were hard to miss: green algae streaks down the render, hairline cracks around the window lintels and a chalky surface that left marks on everything it touched. A decorator had quoted £1,400 for the job.

Day 1 was entirely prep. A pressure washer hired from HSS DIY cleared the algae and grime. Cracks were filled with exterior flexible filler and left to cure overnight.

Day 2: masonry primer went on first thing and was left for five hours before the first coat of breathable exterior masonry paint went on in the afternoon.

Day 3: second coat applied, masking removed while the paint was still slightly tacky.

Result: a noticeably smarter house and a wall that should resist damp for the next 8 to 10 years.

Total cost breakdown:

• Materials - primer, two tins of masonry paint, filler, tape = approximately £120.
• Scaffold tower and pressure washer hire for three days = approximately £190.

Total: approximately £310, saving over £1,000 on the decorator's quote.

Exterior wall painting: project checklist

Use this checklist before, during and after your project to help keep on track.

Before you start

• Weather forecast checked: 5 degrees minimum, no rain for 48 hours
• Scaffold tower hired from HSS DIY and delivery confirmed
• Paint, primer, filler and materials ordered from HSS DIY
• PPE ready: dust mask, safety glasses, gloves, safety footwear

Prep

• Walls pressure washed and allowed to dry (minimum 24 hours)
• Algae or moss treated with fungicidal wash if needed
• Cracks filled with exterior flexible filler and cured
• Flaking paint sanded back
• Masking tape applied to windows, doors, guttering, pipework and meter boxes
• Dust sheets laid on ground below working area

Priming

• Masonry primer applied to all bare, porous or chalky areas
• Primer allowed to dry fully (4 to 6 hours minimum, check product instructions)

Painting

• First coat applied top to bottom in sections
• First coat fully dry before second coat (check product instructions, typically 4 to 6 hours)
• Second coat applied evenly

After

• Masking tape removed while paint is slightly tacky
• Tower safely dismantled and returned to HSS DIY
• Pressure washer and sprayer returned to HSS DIY
• Leftover paint stored securely and labelled

Hire vs. buy: what makes sense for most homeowners?

Scaffold tower

Hiring: approximately £80 to £200 per week.

It’s quick to assemble, you can return when the job is done & no storage needed.

Buying: £500 to £900 plus.

Makes practical sense only if you will use it every year. Most homeowners do not.

Verdict: We’d recommend you hire it.

Paint sprayer

There’s only one answer for this -

Buy it outright: although the prices are varied, investing in a paint sprayer means you can use it again for other large DIY makeovers. They don’t take up much space either!

For a full comparison of scaffold tower hire versus traditional scaffolding, see the HSS DIY blog: Painting External Walls: Tower vs Scaffold Hire

Useful external sources

If you need more information about working safely or how to prep your surfaces before working, check out these handy resources:

• HSE Working at Height: the Health and Safety Executive's guidance on working safely at height, covering ladder use, scaffold towers and risk assessment.
• PASMA: the UK trade body for mobile scaffold tower manufacturers and training. PASMA training is recommended before using any hired scaffold tower.
• Painting and Decorating Association (PDA): the UK trade association for painting and decorating professionals. Useful for guidance on surface preparation standards and paint specifications.

Ready to start? Here is everything in one place.

Painting exterior walls and render properly is one of the best investments you can make in your home.

It keeps damp out, it adds kerb appeal and, done right, it lasts a decade before it needs touching up.

The prep is everything. Clean the walls, fill the cracks, prime the surface and pick your weather window. After that, the painting is the straightforward part.

Whether you need to hire a scaffold tower for access, buy an airless paint sprayer , masonry paint, primer or PPE all in one go, it is all available online 24/7 at HSS DIY with next day delivery.

Buy the materials. Hire the tools. One order. All in one place.

Please note: tools and materials may arrive in separate deliveries.

Get DIY Happy.

HSS DIY - The Home of Great Projects.

Frequently asked questions

How long does exterior masonry paint last?

A quality breathable exterior masonry paint, applied over a properly primed surface, should last 8 to 10 years before needing significant repainting. Annual checks for cracking or flaking are a sensible habit, particularly on north-facing walls which see less sun and dry more slowly.

Do I need to prime before painting exterior walls?

Yes. Masonry primer or stabilising solution is essential on new render, bare masonry, freshly repaired patches and any surface that is chalky or powdery. Without it, the finish coat will not bond properly and will peel prematurely. It is never time you will regret spending.

Can you paint render?

Yes, and it is one of the most effective ways to weatherproof it. Use a breathable, flexible masonry paint designed for exterior use. Allow new render to cure for at least four weeks before painting. Avoid non-breathable paints, which can trap moisture and cause cracking.

How many coats of exterior paint do walls need?

Two coats minimum. One coat rarely gives sufficient coverage or protection, particularly on porous or previously bare surfaces. Always check the product's recommended recoat time between coats, typically 4 to 6 hours in good conditions.

What is the best time of year to paint exterior walls in the UK?

April to September is the best time of year. May and September tend to offer the most reliable conditions: temperatures consistently above 5 degrees, lower risk of sudden rain and good daylight hours. Avoid painting in direct strong sunlight above 25 degrees C, or when overnight frost is forecast.