Fast Delivery UK Mainland

Free Delivery on Full Pallets & Selected Lines

Collection by Appointment

0845 862 1099

(Open 8:30am – 5:30pm)

0 Items in basket
Subtotal: £0.00
Standard & Next Day Delivery Available

Huge Discounts On Bulk Orders – Call 0845 862 1099 For A Bespoke Quote.

Huge Discounts On Bulk Orders – Call 0845 862 1099 For A Bespoke Quote.

Fast Delivery UK Mainland

Free Delivery on Full Pallets & Selected Lines

Collection by Appointment

Open Mon-Fri
8:30-5:30pm

Next Day Delivery Available

To prime or not to prime? A guide to priming pavers

Wondering whether you really need to prime paving slabs, concrete blocks, cobbles or porous pavers such as sandstone? Read on to find out why priming the underside of pavers before laying them reduces cracks, breaks and even reflective stains, plus our expert guide to priming pavers. 

Applying primer to a paving slab
Priming secures pavers in place, reducing the risk of mortar breaks and efflorescence

What is a paving primer?

A primer is an extra-strong adhesive – otherwise known as a bonding agent – that effectively secures paving slabs to bedding mortar, reducing the risk of movement and reflective stains. 

A high-quality primer will seriously extend the life of your hard landscaping project. Find out more about the types of primers below. 

Before we go any further, let’s be crystal clear about what we mean as a ‘primer’. 

A primer is sometimes referred to as a slurry primer, slurry coat, priming layer, bonding agent or bond bridge. They are all the same thing: you are basically bonding the paving slab to the bedding layer. 

There are other great benefits to using a primer on your paving. We go into those in more detail below.

Do I need to use a primer?

There are many commonly used phrases bandied around the landscaping industry. One of them is: “It’s a crime not to prime!”. 

All types of paving slabs, stones and cobbles will benefit from a primer. However, you must always use a paving primer before laying impermeable pavers such as porcelain, granite or slate. They will not bond to the bedding mortar without it. 

When it comes to porous or permeable stones, like limestone and sandstone, they will also benefit from a primer as it will help prevent reflective stains. 

Landscaping experts say that if you want a project that lasts for years, skipping using a primer is likely to get you in the dog house with your clients and handling one of those gut-wrenching phone calls that a job was not fully up to scratch. 

By adding a priming layer between the paving and the bedding mortar you will ensure a high bond strength, which prevents this type of failure from occurring. 

This in turn increases the life expectancy of the paved area and reduces its ongoing maintenance and potential repercussions of having to return to completed paving projects – and unhappy customers.

So what does a primer do? Read on to find out the benefits and which types of primers to use and when.

Benefits of priming pavers

The overall benefits of applying a primer include: 

  • Reduces cracks and breaks in the mortar
  • Protects pavers from efflorescence
  • Secures non-porous slabs in place

Let’s take a look at each one of these benefits in turn to see how a primer can prolong the life and quality of your paving. 

A primer reduces the risk of mortar cracks

You may already be well aware that the major cause of cracks and breaks in paving mortar is not to do with the paving grout. In actual fact it’s down to the pavers moving, which causes the mortar to break. 

Let’s take the example of a Belgian block paver. 

If you laid the slab directly onto the bedding mortar (with no primer), and then jointed to finish the project, over time those paving slabs may start to move as they ‘debond’ from the bedding mortar. 

As the mortar is the only thing that is really securing the pavers in place, any slight movement will cause that mortar to crack and break. 

And if those Belgian block pavers are on a driveway and receive regular vehicle traffic, the mortar is likely to crack sooner rather than later.

Now imagine the same scenario but you have primed each block paver before laying and fitting them securely to the mortar bed before you start grouting. 

Once the project is complete, the pavers do not suffer from the same type of movement because they are fully bonded to the bed below. 

And you have fewer – or none – of the tell-tale mortar cracks. 

A primer reduces the risk of efflorescence

A high-quality primer is an essential tool in a landscaper’s arsenal for the fight against efflorescence. 

Efflorescence, or reflective staining, can be a particular problem when laying porous stones such as limestone, concrete blocks and Indian sandstone. 

There are many reasons why efflorescence occurs (we cover all the details in this article), but one of the major causes is from failing to prime pavers before laying them. 

Alongside providing an exceptional bond between the bed and the slab that we mentioned about earlier, a slurry primer also provides an impermeable protective layer. 

It is this protective layer that helps to prevent water and salts from being absorbed into the porous stone. When the stone dries, the moisture evaporates and – voila – we have reflective stains. 

Don’t be fooled by thinking that only porous stones are affected by efflorescence. Non-porous stones, such as porcelain, can also exhibit the ‘picture frame’ effect. 

Regardless of which type of stone you use, it’s best practice to use a primer each time. 

How to prevent reflective stains
Without a primer, efflorescence is more likely to develop

When it comes to efflorescence, prevention is always better than a cure. Although there are paving cleaners that can help, we always recommend preventing it from happening in the first place. It saves those angry phone calls from disgruntled clients too!

A primer secures non-porous slabs in place

You may be wondering why we’re over-egging the bonding benefit of primers, but this is particularly important if you’re laying impermeable – or non-porous – paving slabs. 

If your hard landscaping job involves porcelain, granite, slate or another type of non-porous stone, you’ll certainly need to use a primer to secure these materials in place. 

Being non-porous, these types of slabs – and especially porcelain as it is completely impermeable – will not bond at all with the bedding mortar. 

Permeable stones, such as sandstone and concrete, will bond to the bedding through their porosity and capillaries. 

But with impermeable stones this porous cement-bonding does not occur at all. They’ll need an extra hand from a primer with exceptional strength. 

A slurry primer acts like a glue to secure these stones in place. 

Read on to find out which primers we recommend for certain materials and types of paving jobs. 

Types of paving primers

There are three main types of paving primers to choose from: 

  • Slurry primers
  • SBR primers
  • Porcelain primers

Let’s take a deeper look into each of these and see which is best for your project.

Slurry primers

We’ve talked a lot about primers in general already. But what’s the deal with slurry primers? 

Slurry primers offer the strongest bond and best protective layer for securing pavers and preventing efflorescence, respectively. 

The name is a bit of a giveaway, but with slurry primers you generally add a powdered mixture to water to create a slurry before painting this onto the underside of paving slabs (read on to see the finer details of how to prime slabs with priming slurry). 

Some of the most popular slurry primers are: 

Pro-Prime from UltraScape

One of the best slurry primers on the market. Pro-Prime offers an outstanding bond to secure pavers in place, and is even highly recommended for use with porcelain. One 20kg bag will cover the underside of 15 square metres of paving. 

Practically impermeable, Pro-Prime also forms a barrier on the bottom of the pavers to prevent minerals and salts being drawn up from the ground below and creating those unwanted efflorescence stains. 

Like many of the other quality products from the team at UltraScape, Pro-Prime meets and exceeds the strict demands of the British Standard BS 7533 and as such is part of the UltraScape Mortar Paving System

Mark Talbot, Director of MPave Ltd, has used many different primers and bonding agents on the hundreds of commercial and domestic projects he’s worked on over the years. These have included “the early days of PVA”, cement, Ronafix and then onto primers such as Pro-Prime. 

He shares, “We’ve tried many different products over the last few decades and have come to respect Ultrascape’s Pro-Prime and Flowpoint

“When installed correctly, in our opinion, there is nothing else on the market that can match the strength and longevity of these two products.”

ProPrime Slurry Primer
Pro-Prime offers an exceptional bond between pavers and the bedding layer below

Larsen Streetscape PS

Another high quality brush-on slurry primer that also adheres to BS7533 is Larsen Streetscape PS Priming Slurry. 

Larsen Streetscape PS is a polymer modified, cement-based slurry that has been specifically designed to meet the recommended performance characteristics of the British Standard BS7533.
 
Just like UltraScape Pro-Prime, Larsen Priming Slurry is pre-blended and only requires the addition of water to produce a high-quality primer.
 
Once applied it improves bond strength between the bedding mortar and either porcelain, natural stone setts, cobbles, flags, concrete and clay pavers. 
 
So what’s the difference between Pro-Prime and Larsen PS?
 
When comparing the two, they both have very similar properties and basically perform the same.
 
Both products are cementitious slurry primers and can be easily mixed with water onsite. And both adhere to the British Standard, which is great news for landscaping contractors. 
 
Really the biggest difference between the two is the pack size and the meterage that they’ll both cover.  
 
Available in slightly larger 25kg bags, a whole bag of Streetscape PS will cover a hard-landscaped area of around 19 square metres (a 20kg bag of Pro-Prime covers 15 square metres).
 
So Larsens is a bigger pack, which means you get more Mars for your money. On the other hand, Pro-Prime lasts longer if you don’t use much.
 
The only other major difference is the shelf life. Larsen PS will last for up to six months, whereas Pro-Prime will last up to eight. 
Larsen Streetscape PS
Larsen's Priming Slurry is also BS7533 compliant

Prem-Prime from UltraScape

Another good choice, particularly for the DIY market because of its more accessible size and packaging, is Prem-Prime slurry primer

Available in a easy-to-mix, 17kg bucket, Prem-Prime is another cementitious bonding agent that offers a high-strength bond between all types of paving stones and cobbles and the UltraScape’s range of mortar beds, such as EcoBed and Perma-Bed

If you weren’t aware, Prem-Prime is actually the same formula as Pro-Prime – and both made by the same manufacturer. The only difference is the quantity and the handy packaging. 

UltraScape Prem-Prime
Prem-Prime boasts the same formula as Pro-Prime but is packaged in a more accessible tub

SBR primers

Styrene butadiene rubber is a bit of a mouthful on its own, so the other type of paving primer is called an SBR primer. 

An SBR primer, such as Nexus ProJoint High Performance SBR, offers increased durability making it ideal for paving areas subject to heavy traffic. They are recommended for protecting light coloured paving slabs against efflorescence.

Although quality slurry primers will do the job – and do it well – SBR primers greatly improve adhesion of paving to the bedding course. 

SBRs have a high level of resistance to salt permeation, which is all down to their fantastic resistance to water and vapour. They block the absorption of water and salts and therefore help to stop efflorescence in its tracks.

SBR primers also stop discoloration coming through soft stone. 

Some believe that SRS primers are just a PVA glue, but they’re far from it. Once dried, PVA glue can still be affected by water. SBRs are completely resistant to water. 

If you hadn’t twigged already, we’re a bit of a fan of SBR primers here at The Paving Experts! They’re also freeze-thaw stable and can be used as an admixture for mortar, screeds or renders.

Nexus ProJoint High Performance SBR
SBR primers are highly adhesive, freeze-thaw stable and completely resistant to water

Porcelain primers

As vitrified paving, porcelain lacks the microscopic capillaries that are found in permeable materials like concrete and sandstone. 

As such, porcelain can be a difficult paving material to prime, which is where porcelain primers come in. 

Technically also a slurry primer, ProJoint Porcelain Primer by Nexus is specially designed for porcelain paving and ceramic tiles. 

Remember, UltraScape’s Pro-Prime (mentioned earlier) also works on porcelain pavers. Handy if you don’t want to branch-out to another product for just the one porcelain paving job.

Nexus ProJoint Porcelain Primer
Some primers are specifically designed for porcelain paving and ceramic tiles

How to prime paving slabs

Here are some quick tips on how to mix and apply a priming slurry. 

You should always follow the manufacturer’s instructions, but this insider advice will help you get the most from your priming layer each and every time. 

How to mix priming slurry

  • Only add fresh, clean water
  • Add the exact amount of water required – always use a measuring jug (that means no guess work!)
  • Always add the mixture to the water
  • Use a paddle mixer to combine the water and formula
  • Aim for a smooth, lump-free consistency
  • Mix the primer slurry away from clean patio slabs to avoid any unwanted spills

How to prime pavers

  • Always use gloves to avoid getting priming slurry on your hands
  • Paint the slurry onto the underside and sides of a paving slab using a thick brush – a paint brush or roller work great
  • For cobbles and smaller setts, simply dip the underside of pavers in the mixture
  • Apply the primer at a thickness of 1–2 mm
  • Once applied, immediately secure the slab in place on the bedding mortar  
  • Use a GraboPro so you don’t get slurry on your hands and avoid any mess
  • Only ever apply the slurry to the underside of pavers
Applying primer to paving
A slurry primer is 'painted' onto the underside and sides of pavers

Avoid spills and clean as you go

As an exceptionally strong bonding agent, the last thing you want to do is get priming slurry on your hands (incidentally, we always recommend using gloves!) or, maybe more importantly, any product surfaces. 

Use tarps or plastic sheets to protect paving and other surfaces from primer spills. 

If slurry primer does get onto the surface of your product, remove it immediately with a soaked wet sponge. Mark explains, “If the primer cures, it will be a bugger to get off!” 

Likewise, you should ideally clean your tools as soon as possible after laying the pavers. Splashes from slurry primer will be difficult – if not impossible – to remove.

Share your primer knowledge or first-hand experience

If you want to add your knowledge or expertise on using primers, we’d love to hear from you. Add your comments below. 

At The Paving Experts, we specialise in supplying and distributing a wide range of materials for highway maintenance, urban regeneration, commercial hard landscaping and domestic paving projects. Explore our full range.

Get in touch if you’d like some further advice on primers – our friendly team is on hand weekdays from 8.30am to 5.30pm on 0845 862 1099

Can you grout in hot weather?

Can you grout in hot weather?

Wondering whether you can grout in hot weather and the maximum temperatures when using mortars, grouts and concrete for outdoor projects? Read our guide to working with these paving materials during warm and sunny conditions including seven essential tips for grouting on hot days.

Read More »
Benefits of Fuga-Pave ABC paving system

Benefits of the Fuga-Pave ABC paving system

Rather than using a four-to-one mortar mix, get the most out of your paving materials by opting for the Fuga-Pave ABC paving system. Find out what the industry says about the superior hybrid bedding mortar, slurry primer and paving grout products and top tips on using the system.

Read More »
Red tarmac repaired with IRR 6mm Red

How to lay and repair red tarmac

Red macadam is often used as alternative coloured tarmac for certain road surfaces and domestic driveways. Find out why highway decision makers and homeowners choose red and how easy it is to lay and repair red tarmac surfaces.

Read More »
Cleaning off Flowpoint Fine with washboy

Cardiff landscapers demo Flowpoint Fine

One of the things we love most here at The Paving Experts is getting out to meet our customers. That’s exactly what we did on a damp day in Cardiff this month when we met the team of experienced landscapers at CC Artificial Grass & Landscaping and helped demo Flowpoint Fine slurry grout.

Read More »
Larsen Streetscape FBC

Review of Larsen paving products

No assessment of paving and patio grouts would be complete without taking a look at the Streetscape range of Larsen paving products. Read our review to find out more about these quality materials and why landscaping contractors swear by them.

Read More »

Leave a Comment

Your email address will not be published.

Related Posts