Nexus ProJoint RapidFlow | Brush-In Grout for Porcelain Paving, Natural Stone & Concrete

Nexus ProJoint RapidFlow is one of the best brush-in paving grouts on the market — an excellent example of a product that delivers consistently professional results in real UK conditions. Cement-free, premixed, frost-resistant and usable in light rain, it's the grout we recommend most often for porcelain patios and paths. It's a product our customers consistently come back to tell us they're delighted with: quick to apply, forgiving in variable weather, and brilliant results every time.

Resin-based, premixed brush-in grout for joint widths of 3mm upwards and depths of 20mm minimum — suitable for porcelain, natural stone and concrete paving on permeable, free-draining beds. Cement-free and non-hazardous. Walk-on in 12 hours. Available in five colours: Neutral, Light Grey, Mid Grey, Basalt and Black. £36.99 per 12.5kg tub.

We're a small, family-run business — I'm Cleo, the owner, with over 25 years in the construction industry working with businesses including Tarmac and Instarmac. I work alongside a team of incredibly knowledgeable and caring individuals, and between us we've seen a lot of jointing products come and go. RapidFlow is the one we reach for when someone needs a reliable, easy-to-use grout that consistently delivers professional-looking results — whether they're a seasoned contractor or doing their first patio.

If you're grouting porcelain, natural stone or concrete paving and want a product that's weed-resistant, frost-resistant, cement-free and usable in light rain — RapidFlow is the product we'd confidently recommend. It's equally at home on a 600x600 porcelain patio or a large-format natural stone path. If you're unsure which colour suits your paving, give us a call — samples are available on request.

Is RapidFlow Right for Your Paving? Permeable vs Non-Permeable Beds

Before choosing a jointing compound, you need to answer one critical question: where is the water going to go?

Your paving construction determines which product is correct — and getting this wrong can trap moisture, cause staining, algae growth, cracking and joint failure.

• Permeable paving — water drains through the joints into the ground below. Typically a sand and cement bed (5:1 or above) on a free-draining sub-base. ✅ RapidFlow is the right choice.
• Non-permeable paving — water cannot drain downwards and must run off across the surface. Typically paving on a solid concrete base or impermeable sub-base. ❌ RapidFlow is not suitable — for porcelain on a non-permeable bed, see ProJoint TileJam, UltraScape PorcelPoint or FUGA-PAVE XP instead.

RapidFlow cures by drying out — water must have a clear route of escape through the bed. A permeable sub-base also allows water collecting in the joints to drain freely, preventing it from becoming stagnant. Stagnant water can soften the binder over time and encourage algae growth.

Not sure which system you have? Give us a call — 0330 122 1025. It's a quick conversation and it could save you a very expensive mistake.

Key Benefits

• Precisely formulated for porcelain paving — equally suitable for natural stone and concrete
• Professional strength — suitable for joint widths of 3mm upwards
• Cement-free and non-hazardous — no efflorescence risk, safer to handle
• Weed-free joints — resin binder leaves no loose material for weeds to take hold
• Frost-resistant — suitable for UK climate conditions
• Usable in light rain — no need to wait for a dry day (avoid heavy or prolonged rain)
• Permeable — allows water to drain through, reducing surface pooling
• No staining — won't mark the paving surface when applied correctly
• Premixed and ready to use — no mixing, no mess, ideal for DIY and contractors alike
• Walk-on in 12 hours in dry ambient conditions
• Tub contains two 6.25kg bags to minimise waste and make handling easier
• Five colours: Neutral (buff), Light Grey, Mid Grey, Basalt, Black

Coverage — Approximate per 12.5kg Tub

All figures at 20mm joint depth.

Not sure how many tubs you need? Tell us your area size, slab size and joint width — we'll calculate it for you. 0330 122 1025.

Technical Information

Download the technical datasheet (PDF)

Preparation

Ensure the surface of the paving is clean prior to application. Check the joints are cleaned out to a depth of 20mm, observing a minimum joint width of 3mm. Paving should be firmly bedded and stable on a permeable bedding mix prior to filling the joints. As RapidFlow cures when it dries out, water and rain must have a route of escape.

For sensitive, sawn or highly textured paving, we recommend using ProJoint Pre-Grout Sealer prior to application of RapidFlow to prevent grout haze and surface staining. A neoprene squeegee is ideal for working the compound into the joints quickly and evenly.

Application Instructions

1. Apply ProJoint RapidFlow when the surface temperature is between 3°C and 25°C. If your paving is wet cast concrete, see inside the tub for additional advice.
2. Liberally soak the paving.
3. Empty the mix evenly onto the surface and work quickly into the joints using a brush or squeegee.
4. Mist the surface and compound with a soft spray of water to flush the material down into the joints. Top up any low joints and repeat as necessary.
5. Once the water has drained away, sweep the paving with a fresh soft brush at 45° to the joints and remove any excess. A trowel or iron can be used to achieve a traditional finish if required.
6. Clean all tools with water after use.
7. Leave to cure. RapidFlow cures on exposure to air — as a guide, foot traffic can be accepted 12 hours from installation in dry ambient conditions. Cold temperatures and wet weather can delay curing significantly.

This product can be used in light rain, but prolonged heavy rain will delay the curing process and increase the risk of fluid damage.

Note: ProJoint RapidFlow may highlight and enhance the natural surface colours and textures of the paving — this can be especially noticeable on grey paving including granite, so a test area is advised before use. This is a temporary effect — weathering and foot traffic accelerate its disappearance. Spread the mix across the total paving area to ensure any potential effect is uniform.

Frequently Asked Questions

I'm Cleo, owner of The Paving Experts, with over 25 years in the construction industry working with businesses including Tarmac and Instarmac. I work alongside a small team of incredibly knowledgeable and caring individuals who share the same passion for getting it right. The FAQ answers below come from the questions we're asked every single day.

Is RapidFlow suitable for non-permeable paving?
No — RapidFlow is designed for permeable, free-draining beds only. If your paving is on a solid concrete or impermeable sub-base, you need a product designed for non-permeable beds. For porcelain, we'd recommend ProJoint TileJam, UltraScape PorcelPoint or FUGA-PAVE XP. Not sure which you have? Call us — it's a quick but important question to get right.

How long does RapidFlow take to cure?
RapidFlow typically cures enough for foot traffic in about 12 hours in dry ambient conditions. Curing times can vary depending on the weather — colder and wetter conditions can delay the curing speed significantly. Full strength is reached at 28 days.

What is the best way to maintain my joints?
Keeping your paving joints clean is simple — sweep the area regularly to remove dirt, leaves and debris. This helps stop weeds from taking root. For a deeper clean to remove algae and dirt, our ProJoint Black Spot and Algae Remover will blast through it.

Can it be used on natural stone tiles as well as porcelain?
Yes — RapidFlow works brilliantly with both porcelain and natural stone tiles, giving you versatility across your paving projects.

What weather conditions can I apply RapidFlow in?
Light rain is no problem. Just avoid heavy rain or freezing temperatures, as these can damage the curing process. Apply when surface temperature is between 3°C and 25°C.

Can I open the tub and re-use it on a later date?
Once opened, the air will start the curing process. To stop this, put any excess material back in the tub and submerge it in water — this cuts out the oxygen and can give you up to a month of extra usage.

Where is RapidFlow used?
RapidFlow is perfect for porcelain, natural stone and concrete patios, paths and other areas with foot traffic only. It is not suitable for vehicular areas — for driveways, see ProJoint TITAN.

Is RapidFlow permeable?
Yes — the primary benefit of permeable resin jointing compounds is their ability to let water pass through, reducing surface water and preventing pooling.

Why should the bedding mortar be permeable?
RapidFlow cures when it dries out, so water must have a route of escape. A permeable sub-base also allows water collecting in the joints to drain freely, stopping it from building up and becoming stagnant — stagnant water can soften the binder over time and encourage algae growth.

When you say permeable bedding/base mix, what does this mean?
A 5:1 ratio of sand and cement (or above) is classed as permeable. Using a specific permeable bedding or base mortar is also acceptable.

Can you pressure wash RapidFlow?
Yes, but only after it's fully cured (30 days). Use a fan nozzle and keep the pressure washer at a safe distance from the surface.

What's the difference between RapidFlow resin and epoxy?
RapidFlow is an air-cure resin binder — simple to apply and ideal for pedestrian areas. Epoxy compounds like ProJoint TITAN offer higher durability and strength, with a different application method, making them better suited to vehicular or heavy-use areas.

Note: As sand is a natural product, some minimal colour variance may occur. Colours shown are representative only — samples are available on request. Contact us for samples.

Need Some Help?

See our RapidFlow FAQs or get in touch — we're always happy to help. Call us on 0330 122 1025.

• Brand: Nexus
• Product Type: Brush-in Paving Grout & Jointing Compound
• SKU: TPE-PROPORPAV9B4
• Weight: 12.5 kg / 27.56 lb