How to Re-Sand Block Paving: A Step-by-Step Guide
Why Re-Sanding Block Paving Matters
Re-sand block paving properly and it becomes clear how much this maintenance task protects your investment. When you jet wash a driveway or patio, you're removing years of grime, algae, and moss. But you're also washing away the sand that sits between the blocks. That sand does critical work: it locks the blocks in place, prevents weeds from growing through the gaps, and stops water from pooling underneath.
Without proper re-sanding after cleaning, your block paving becomes unstable. Blocks shift. Weeds take hold. Water pools and causes damage.
The good news is straightforward: re-sand block paving properly, and your patio or driveway will stay level, weed-free, and protected for years. Skip this step, and you're inviting problems.
What You'll Need Before You Start
Materials and equipment checklist
Gather these items before you begin. Having everything ready means the job moves faster and you won't waste time mid-project hunting for supplies.
Sand and cleaning supplies:
Kiln-dried polymeric sand (not regular building sand)
A stiff brush or push broom
A garden hose with a spray nozzle
A bucket for mixing (if using polymeric sand that requires water)
Safety and protection:
Heavy-duty work gloves
Safety glasses
A dust mask or respirator (polymeric sand creates fine dust)
Sturdy boots with good grip
Optional but helpful:
A leaf blower for clearing loose debris
A pressure washer (if you haven't jet washed yet)
A garden rake for spreading sand evenly
A kneeling pad if you're working on a large area
The most important decision is choosing the right sand. Don't skimp here. Regular building sand washes out within weeks. Polymeric sand is engineered to lock together when wet, creating a durable joint that resists washing and weed growth.
Choosing the Best Sand for Block Paving Joints
The sand you choose determines whether your re-sanding job lasts months or years. There are two main types: standard sand and polymeric sand.
Standard sand is cheap and easy to find. It's also temporary. Water washes it away. Weeds push through. You'll be re-sanding again within a season. Most professionals avoid it for this reason.
Polymeric sand contains special additives that harden when exposed to moisture. Once activated, it forms a bond that holds blocks in place and prevents weeds. It costs more upfront but saves money because you won't repeat the job constantly. For driveways and patios that get regular use, polymeric sand is the only sensible choice.
When buying polymeric sand, check the joint width specification. Sand designed for 5mm joints won't work well in 10mm gaps. Match the product to your actual joint size.
Colour matters too, though it's often overlooked. Sand comes in natural grey, charcoal, and buff tones. Choose a colour that complements your blocks and won't show dirt as obviously. Lighter sands show staining faster than darker options.
Re-Sanding Block Paving After Jet Washing
Jet washing strips away dirt and organic growth, leaving your block paving clean but vulnerable. Re-sanding block paving after jet washing is essential to restore stability and protection.
The timing is critical. Wait until the surface is completely dry before spreading sand. Wet blocks trap moisture underneath, which causes problems later. On a sunny day, this takes 5 -24 hours after jet washing. Check by pressing your hand on a block. If it feels cool or damp, wait longer.
Start by clearing loose debris. Sweep away any remaining dirt, leaves, or bits of old sand using a stiff brush. A leaf blower works well for this if you have one. The cleaner the surface, the better the new sand will perform.
Spread polymeric sand evenly across the joints using a brush or broom. Work in small sections, pushing sand into the gaps as you go. Don't rush this. Properly filled joints mean better stability and longer-lasting results.
Once the sand is in place, activate it with water. Use a garden hose with a fine spray nozzle, not a pressure washer. You want moisture to reach the sand without blasting it out of the joints. Spray gently and evenly until the surface glistens slightly. The polymeric sand will harden as it dries.
Let everything cure for 48 hours before allowing foot traffic or vehicles on the surface. This gives the sand time to set properly.
Re-Sanding Block Paving in Wet Weather
Wet weather complicates re-sanding block paving, but it's not impossible. The key is timing and patience.
Never apply polymeric sand if rain is forecast within 24 hours. Water activates the sand before you've had a chance to spread it properly. The sand will clump in the bag and become unusable.
If you're working in damp conditions, prioritise drying first. On overcast days, wait for at least 12 hours of dry weather before starting. A leaf blower speeds up surface drying significantly.
When the weather forecast shows clear skies, work quickly but carefully. Spread sand in small sections and activate each one immediately. Don't leave sand sitting on the surface waiting for water. The longer it sits, the more moisture it absorbs from the air, and the harder it becomes to work with.
After activation, protect the freshly sanded area if rain threatens. A tarpaulin or heavy-duty plastic sheet works well. Secure the edges so wind doesn't lift it. Leave the covering in place for at least 24 hours, longer if possible.
Winter weather is particularly challenging. Frost can interfere with sand setting. If temperatures are expected to drop below freezing within 48 hours of re-sanding, postpone the job. Frost prevents proper curing and compromises the final result.
Preventing Block Paving Sand Washing Out
Block paving sand washing out is frustrating because it means repeating work you've already done. Prevention is far easier than repair.
The most common cause is poor water drainage around the patio or driveway. If water pools on the surface or drains slowly, it will eventually wash sand away. Check the slope of your surface. Ideally, it should slope gently away from buildings and toward drainage areas. If water sits, you need to address the underlying drainage issue before re-sanding.
Use polymeric sand every time, without exception. Standard sand washes out. Polymeric sand resists it. Yes, it costs more. But one application of polymeric sand lasts longer than three applications of cheap sand.
Avoid jet washing immediately after re-sanding. Wait at least two weeks before using a pressure washer on newly sanded joints. The sand needs time to cure fully. Once it's set, jet washing at normal pressure won't dislodge it.
If you must clean the surface during the first two weeks, use a soft brush and water only. No pressure. No force.
Manage water flow carefully. Ensure gutters and downpipes drain away from the patio or driveway. Standing water is the enemy of sand retention. Proper drainage protects your re-sanding work and prevents other damage.
Common Mistakes to Avoid When Re-Sanding
Understanding what goes wrong helps you avoid expensive repairs.
Using the wrong sand type is the most costly mistake. Homeowners often buy standard building sand because it's cheap. Within weeks, it's gone. Polymeric sand costs more but actually saves money over time.
Applying sand to wet surfaces sets up failure from the start. Moisture prevents proper contact between sand and blocks. Wait for the surface to dry completely after jet washing before re-sanding.
Skipping the activation step leaves sand sitting loose in the joints. Polymeric sand must be activated with water to harden. Without this step, the first rainfall washes it away.
Overfilling the joints causes problems too. Sand should be level with the block surface, not heaped above it. Overfilled joints trap water and prevent proper drainage.
Jet washing too soon after re-sanding damages newly set sand. Give it at least two weeks to cure before using a pressure washer.
Ignoring drainage issues means the sand will eventually wash out no matter how well you apply it. If water pools on your surface, fix the slope or drainage before re-sanding.
Not protecting the area during bad weather allows rain to activate sand prematurely or wash it away before it's set. Cover freshly sanded areas if rain threatens.
Re-sanding block paving properly keeps your driveway or patio stable, weed-free, and protected from water damage. The process is straightforward: use the right sand, allow proper drying time, and activate carefully. When jet washing your block paving, plan to re-sand immediately after. This two-step approach restores both cleanliness and structural integrity.
If you'd rather leave this work to professionals, Cotswold Exterior Surface Cleaning handles the complete process: professional jet washing and exterior surface restoration. Our team jet washes your surfaces thoroughly, then re-sands to lock everything in place. Get in touch to discuss your driveway or patio maintenance needs.
Frequently Asked Questions
How do you re-sand block paving?
Re-sanding block paving involves spreading kiln-dried sand across the surface, brushing it into the joints between blocks, dampening it lightly, and allowing it to dry fully. Start with a clean, dry surface, apply sand evenly, brush it into all gaps using a stiff broom, then mist with water to help it settle. Let it cure for 24-48 hours before allowing foot traffic. Proper technique ensures sand stays in place and maintains joint integrity.
What's the best sand for block paving joints?
Kiln-dried sand is the best choice for block paving joints. Unlike ordinary builders' sand, kiln-dried sand has been heated to remove moisture, which prevents it from compacting unevenly or washing out easily. It's also free from clay and fine particles that can clog joints and trap water. Always choose kiln-dried sand specifically graded for block paving, typically 0-4mm, rather than sharp sand or play sand, which won't perform properly in joints.
Should you re-sand block paving after jet washing?
Yes, re-sanding after jet washing is essential. Professional jet washing removes old sand from joints completely, which is necessary for cleaning but leaves joints empty. Re-sanding immediately after (once the surface is dry) restores joint integrity, prevents weed growth, and locks blocks in place. Skipping this step leaves your paving vulnerable to movement, water ingress, and accelerated deterioration. Allow 24-48 hours drying time after jet washing before re-sanding.
How do you prevent sand washing out from block paving?
Use kiln-dried sand rather than ordinary sand, ensure joints are completely filled during application, and allow proper curing time (24-48 hours) before exposing the surface to water or traffic. Avoid over-watering during the settling phase, a light mist is sufficient. Consider sealing the paving after re-sanding, which helps bind sand particles and provides additional water resistance. Regular maintenance and prompt repairs of damaged joints also prevent sand loss over time.