When buyers talk about “kerbstone moulds” they often mean only the upright road edge stone. But a finished road edge is usually two precast pieces working together: the upright kerb that holds the edge, and a family of flat-laid stones that carry surface water toward the drain and smooth the transition between carriageway and footway. In Chinese these are ping shi (εΉ³η³, flat stones), tiao shi (ζ‘η³, strip stones) and the large apron slabs. This guide covers how to order them without the common mistakes.
1. The four flat-stone families
- Small square flat stones (8β19 cm). Compact squares for footways, courtyards, patches and borders. Many run as multi-cavity moulds (1-out-5, 1-out-6) to keep high-volume unit cost down. Available in PP and ABS, with plain or chamfered faces.
- Thin veneer / small slabs. Sizes like 18.5 Γ 18.5 Γ 0.5 cm and 18.5 Γ 18.5 Γ 2 cm, including a dished (concave) ABS version. These are thin wear-course / veneer panels β the 0.5 cm thickness is intentional, not an error.
- Strip stones & 50 cm flat kerb stones. The workhorse road module. Narrow 20 cm class strips run 1-out-2 or 1-out-10; the 50 cm class covers gutter strip stones (8β12 cm wide, deeper), round-top strip kerbs (e.g. 50 Γ 8 Γ 19) and flat kerb stones from 50 Γ 10 Γ 10 up to 50 Γ 16 Γ 18.
- Large apron slabs (71β80 cm). Wide transition panels around drains and crossings β 71.5 Γ 40, 75 Γ 25/30/48/49, 78 Γ 50 β including four-hole drainage slabs, beveled faces and tall standing units up to 79 Γ 18 Γ 30.
2. Read dimensions the flat-stone way
Dimensions are length Γ face width Γ height/thickness. For a genuinely flat-laid stone the third number is small (6β21 cm). If the third number is large (e.g. 79 Γ 18 Γ 30 or 75 Γ 12 Γ 30), the unit is actually a standing profile even though it sits in the flat-stone product family β confirm with the drawing. A very small third number on a wide panel (0.5β2 cm) means a thin veneer slab, not an undersized stone.
3. Flat-laid vs upright β the #1 ordering mistake
Buyers sometimes order flat stones where the section calls for upright kerbs (or vice versa) because both are loosely called “kerb stones”. Check the road cross-section: does the unit lie down (flat stone / ping shi) or stand up (kerbstone / lu yuan shi)? The flat stone's face width sets the drainage apron; the upright kerb's height sets the road-edge containment. Get this wrong and either the water won't sheet to the drain or the edge won't contain traffic.
4. Match gutter width and apron width to the drainage design
The narrow gutter strip stone (8β12 cm) sits in the channel and sets how much water the line captures; the wider apron slab (25β50 cm) sets the transition zone back to the footway or road. These widths come straight from the road cross-section and the design rainfall, not from habit. Send the section and we will match standard sizes or quote an OEM profile.
5. Cavities change both price and output
“1-out-N” is how many finished pieces a single mould casts per pour. A 1-out-10 strip stone mould makes ten pieces per cycle; a 1-out-2 makes two. More cavities mean a bigger mould but far lower cost and labour per finished stone. When comparing quotes, compare cost per finished stone and pieces per day, not just the mould price.
6. PP vs ABS
PP (polypropylene) is the default for plain high-volume flat stones β it flexes under vibration and demoulding and reaches 150+ pour cycles. ABS is chosen where a sharp chamfer, a dished/concave face or a thin crisp arris must stay precise over hundreds of cycles. Several small and 50 cm items are stocked in ABS for exactly this reason.
7. Thin veneer slabs and large aprons are both real, and both need care
Thin 0.5β2 cm veneer panels cast fine but demould gently to avoid cracking the thin section. Large 71β80 cm apron slabs are flat panels that gain stiffness from their width and the sub-base; the mould has external stiffening ribs to stay flat. Cast large slabs on a level vibrating table, cure fully, and always store/transport them flat β never on edge.
8. Project and road-authority logos
We already produce project-marked units β for example a 75 Γ 49 Γ 8 cm apron slab with a Guizhou road-bridge authority mark. Standard, four-hole and beveled slabs can be tooled with your logo from artwork. OEM logo tooling typically takes 10β15 days.
What to send for a fast quote
- Road cross-section drawing (or clear photo) showing flat stone vs upright kerb
- Finished length, face width and thickness/height of each unit
- Cavity preference for volume items (1-out-2 / 1-out-10)
- Application: gutter channel, apron transition, footway, median or courtyard
- PP or ABS, any logo artwork, quantities and destination port
Browse the full range on our Flat Kerb & Strip Stone Moulds page, together with the complementary kerbstone moulds and drainage channel moulds.
Have a road cross-section to match?
Send the drawing or a sample photo. We will match standard flat kerb / strip stone sizes or quote an OEM mould with your logo.
Request a Quote Ask on WhatsAppFrequently Asked Questions
What is a flat kerb stone (ping shi) and where does it go in the road section?
The upright kerbstone (lu yuan shi) stands at the road edge to contain traffic. The flat kerb stone (ping shi, flat stone or side-flat stone) is laid FLAT next to it, between the upright kerb and the carriageway or gutter. It forms the smooth apron that guides surface water into the drain. Gutter strip stones and round-top strip kerbs sit in the same flat-laid line. Most road sections use upright kerbs and flat stones together, which is why they are usually ordered as one family.
How do I read dimensions like 50 x 15 x 15 cm or 18.5 x 18.5 x 0.5 cm?
Length x width (face width) x height/thickness in centimetres. For a flat-laid stone the last figure is normally small (6-21 cm); a tall unit such as 79 x 18 x 30 is a standing profile. A very thin last figure is not an error: 18.5 x 18.5 x 0.5 and 18.5 x 18.5 x 2 are veneer/wear-course slabs, deliberately thin.
What do 1-out-2, 1-out-6 and 1-out-10 mean for price and output?
They are the number of finished pieces one mould produces per pour. A 1-out-10 strip-stone mould casts ten small stones in one cycle, so the cost per piece and the labour per piece are much lower on volume jobs. The mould itself is larger. Always compare quotations per finished stone and per daily output, not just per mould.
Which width of flat or strip stone goes next to a drainage channel?
Use a narrow gutter strip stone (about 8-12 cm wide, often deeper) directly in the channel to carry the water, and wider flat kerb apron slabs (25-50 cm wide) as the transition toward the footway or carriageway. Round-top strip stones give a slightly raised rounded edge in the gutter line. The widths come from your road cross-section, so send the section drawing and we will match the profile.
Can a 6-8 cm thick apron slab really span 40-50 cm wide?
Yes. These large 71-80 cm apron panels are flat precast slabs, not beams; they gain stiffness from their width and the compacted sub-base beneath them. The plastic mould has external stiffening ribs so it stays flat under vibration and curing. Cast them on a level vibrating table, cure fully, and always store and transport large slabs flat - never on edge, or they can crack under their own weight.
Should flat kerb and strip stone moulds be PP or ABS?
PP (polypropylene) is the default for plain, high-volume flat stones: it flexes under vibration and demoulding and reaches 150+ pour cycles. Choose ABS where a sharp chamfer, a dished/concave face or a thin crisp arris must stay accurate over many cycles; we stock several small and 50 cm items in ABS. Tell us the profile and we will recommend the grade.
Can you mould a project or road-authority logo into the slab?
Yes. We already produce project-marked units, including a 75 x 49 x 8 cm apron slab carrying a Guizhou road-bridge authority mark. Standard, four-hole and beveled apron slabs can all be tooled with your logo from artwork. OEM logo tooling takes roughly 10-15 days.