3.4 Filling paving joints
Dry fine sand swept into the gaps between pavers. Full joints lock the pavers together so they do not shift, tilt or spread.
At a glance
- Difficulty
- 1 of 4
- Time
- 1–2 hours for 20 m²
- Tools
- Soft broom, plate compactor with a rubber mat, shovel
- Parts
-
- 1 Bedding (laid)
- 2 Pavers (laid)
- 3 Joint sand
What you need per m², 60 mm blocks, 3 mm joints
| Material | Size | Type | Amount |
|---|---|---|---|
| Joint sand | 0–2 mm | Dry, fine, natural or crushed | 4 kg |
| or | clean grit | Permeable paving only, washed |
Why 0–2?
Joints are only 2–5 mm wide. Fine dry sand runs all the way down a narrow joint and packs tight when you vibrate the pavers.
Only for permeable paving, where water must drain through the joints. The grit has almost no fines. See 6.2.
Step by step
-
1
Lay the pavers with 2–5 mm joints.
Many blocks have small spacer lugs that set the gap. Keep the joints even by checking the lines with a string.
Pavers laid with even joints -
2
Spread dry sand and sweep it into the joints.
Do this on a dry day. Damp sand sticks to the surface and does not run into the joints.
Sweeping sand into the joints -
3
Vibrate the paving and sweep in more sand.
Run a plate compactor with a rubber mat over the pavers, at least three passes, and keep sweeping sand in until the joints are full. Stay 1.5 m back from any edge that is not yet restrained.
Plate with rubber mat -
4
Sweep off the extra sand.
Leave the surface clean. Finish the joints and vibrating by the end of each day.
The finished surface -
5
Top up later if the joints drop.
Joint sand settles over the first months. Sweep in more sand and vibrate again where the joints are no longer full.
Topping up the joints
Specifications
| Part | Sieve size | Thickness | How |
|---|---|---|---|
| Joint sand | 0–2 mm | Full depth | Joints 2–5 mm, swept in dry, at least 3 plate passes. |
| Permeable joints | clean grit | Full depth | Washed crushed stone, at most 2 % fines. See 6.2. |
Grading
A US military paving specification uses a masonry sand grading: all passing 4.75 mm, 95–100 % passing 2.36 mm, 40–75 % passing 0.6 mm and at most 5 % passing 0.075 mm. A UK council specification asks for 0/2 mm joint sand.
Joint width
2–5 mm. Fill gaps at edges and drains with cut pavers, so no gap is wider than 6 mm.
Amount
The sand fills the joint volume: joint length × width × paver depth. For 200 × 100 × 60 mm blocks with 3 mm joints that is about 2.6 litres, or 4 kg, per m². With 5 mm joints it is about 7 kg.
Sources
- UFGS 32 14 13.13, Interlocking precast concrete unit paving (US Department of Defense unified facilities guide specification, 2019): a dense-graded base, within 10 mm under a 3 m straightedge; bedding sand screeded to an uncompacted average of 25 mm, left uncompacted and not walked on, and never used to fill low areas in the base; bedding sand to ASTM C33 with at most 1 % passing 0.075 mm; joint sand to ASTM C144 with at most 5 % passing 0.075 mm; joints 2–5 mm; gaps at edges at most 6 mm; at least three plate passes; no seating or joint filling within 1.5 m of an unrestrained edge; joint sand swept and vibrated until no more goes in; finished surface flush with or up to 6 mm above edges and drains
- ACT Government (Canberra), Standard specification for urban infrastructure works, section 12: segmental paving (2002): bedding never used for levelling; screed no further ahead than can be paved that day; joint sand dry when spread; laid joints 2–5 mm; plate fitted with a carpet or roller to protect the pavers; no compaction within 1 m of the working face
- Bedford Borough Council, Appendix 11/1 Kerbs, footways and paved areas: block-paved light vehicle crossovers serving up to two houses: 65 mm blocks on 30 mm of 0/4 mm sand on 225 mm of Type 1 sub-base; sand layer at least 25 mm; joints filled with 0/2 mm sand
- North Carolina DOT permeable paver specification: 50 mm bedding of washed crushed stone; joints filled with washed crushed stone with at most 2 % fines
- Penn State University, CE 584 concrete course notes: aggregates: aggregate for normal concrete weighs 1,520–1,680 kg/m³
- NPTEL (Indian Institutes of Technology), soil mechanics worked examples: dry sand about 1,600 kg/m³
- ASTM C144 Masonry sand grading, used with changes for joint sand by UFGS 32 14 13.13 above
Amounts are worked out from the joint volume and a sand density of about 1.6 t/m³ (Penn State course notes; NPTEL). No waste is included; order a little extra.
GLAREUM.NET · Aggregate Handbook