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

'One of the Best Brush-In Paving Grouts on the Market — Cement Free, Rain-Tolerant, and Consistently Perfect Results Every Time'

Nexus ProJoint RapidFlow is one of the best brush-in paving grouts on the market — an excellent example of a product that genuinely delivers on its promises. Precisely formulated for porcelain paving but equally at home on natural stone and concrete, it produces a weed-free, frost-resistant joint without staining the surface. It's a product that time and again earns glowing feedback from both contractors and DIYers: quick to apply, forgiving in variable weather, and consistently impressive results.

Resin-based, premixed brush-in grout for joint widths of 3mm upwards and depths of 20mm, suitable for porcelain, natural stone and concrete — RapidFlow is the go-to choice for patios, paths and pedestrian areas where a clean, professional finish matters.

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 an untrained hand can use to deliver professional-looking joints every single time.

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. Available in five colours: Neutral (buff), Light Grey, Mid Grey, Basalt and Black. If you're unsure which colour suits your paving, give us a call — samples are available on request.

RapidFlow is a premixed, ready-to-use resin jointing compound — no mixing required. Soak the paving, brush the grout into the joints, mist with water to flush it down, then sweep off the excess. It cures on exposure to air, forming a firm, durable joint. Cement free and non-hazardous.

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 — safer to handle, no efflorescence risk
• Weed free joint — 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 water and pooling
• No staining — won't mark the paving surface when applied correctly
• Pre-mixed and ready to use — ideal for both DIY and contractor use
• Foot traffic in 12 hours — fast turnaround in dry ambient conditions
• 5 colours: Neutral (buff), Light Grey, Mid Grey, Basalt, Black
• 12.5kg tubs supplied in 2 bags for easy handling and to reduce waste

Permeable or Non-Permeable? Choose the Right Jointing Compound

Your paving construction determines the correct grout.

Permeable paving — water drains through the joints into the ground.
Non-permeable paving — water must drain across the surface.

Using the wrong jointing compound can trap moisture and cause staining, algae, cracking and joint failure. Always ask: "Where is the water going to go?"

RapidFlow is suitable for permeable, free-draining beds only.

Technical Information

Download the technical datasheet (PDF)

Coverage — Approximate per 12.5kg tub

600 x 600mm Slabs

• Joint 3mm wide x 20mm deep: 34.8m²
• Joint 5mm wide x 20mm deep: 20.8m²
• Joint 7mm wide x 20mm deep: 14.9m²

600 x 900mm Slabs

• Joint 3mm wide x 20mm deep: 41.8m²
• Joint 5mm wide x 20mm deep: 25m²
• Joint 7mm wide x 20mm deep: 17.9m²

600 x 1200mm Slabs

• Joint 3mm wide x 20mm deep: 46.5m²
• Joint 5mm wide x 20mm deep: 27.8m²
• Joint 7mm wide x 20mm deep: 20m²

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 prior to application of RapidFlow.

Application

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 will reduce it over time.

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.

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, which 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 and V400 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
• SKU: TPE-PROPORPAV0ED
• Weight: 12.5 kg / 27.56 lb