Granite Tactile Paving Specification: Eight Lines That Decide the Order
A granite tactile paving specification is not a list of sizes; it is eight lines that decide whether the order arrives usable. Directional and warning units cannot be swapped or quoted at one ratio, and 300×300 mm gives 11.1 units per m² theoretical, 10.7 on a 5 mm joint, and only 9 whole units in a one-metre square. Bar direction, corner radius, contrast, bedding and transition units each cost a remade order if left out.
How do I set a granite tactile paving specification, and why start with two unit types?
A granite tactile paving specification has to start from one fact: tactile paving is not one product but two units with different jobs. Directional units (guiding) carry raised bars along the walking line and say keep going; warning units (blister paving) carry domes and say stop, turn, or mind a step or crossing. They are not interchangeable, and they cannot be quoted at one ratio: directional units follow the length of the guidance band, warning units follow the number of decision points. Count the runs and the points on the drawing separately, and only then do you have two quantities. Ask which piece count a quotation uses, too: 300×300 mm is 11.1 units per m² theoretical (1,000,000 ÷ 90,000), 10.7 on a 5 mm joint by area, and a one-metre square actually holds 3×3 = 9 whole units with 85 mm left for cut pieces. All three are right; the question is which one settles the invoice. Tolerance goes in numbers: a plus/minus figure for edge length and thickness, dome height on its own line, checked on arrival against the sealed sample and a calliper.
| Unit size (mm) | Units per m², theoretical | Units per m², 5 mm joint | Units per 1 m band (0.3 m²) |
|---|---|---|---|
| 300×300×30 | 11.1 | 10.7 | 3.2 |
| 400×400×30 | 6.25 | 6.1 | 1.8 |
| 500×500×30 | 4.0 | 3.9 | 1.2 |
Why must bar direction be written into the specification?
Because direction is a machining constraint, not an installation detail. The bars are set when the mould or the grooving is made, so a unit only works one way round; laid at 90° it turns guidance into a lateral obstacle and the unit is scrap. Two sentences belong in the specification: bars parallel to the direction of travel, and all units for one run packed facing the same way with the direction marked on the crate. Without the second sentence, the crew turns every unit by hand to find the bars, and a day's output collapses. Put the return clause on the same line: batches whose bar direction does not match the drawing are returnable, but only if the specification stated the direction in the first place.
Why do profile height and surface finish have to be specified together?
Because they cancel each other out. A flamed face grips better than a polished one and holds up in rain, but flaming rounds the edges of the bars, so the profile feels blunt and the signal underfoot or under a cane weakens. A polished bar keeps a crisp edge and reads clearly, and is slippery when wet. So flamed alone is not enough; write how much edge is kept: sharp, lightly eased, or fully rounded. The wording is one sentence plus one sample: flamed face, bars lightly eased, profile height fixed at the value in the project specification, approved against a sealed sample. What that height should be comes from the footway accessibility rules of the project country and from your drawing, not from us; but the two items must appear together, or the factory follows its own habit and you have nothing to inspect against.
How do I turn colour contrast into a clause that passes inspection?
Luminance difference is an inspection item, not a matter of taste. The band has to be visible against the surrounding paving, and what makes it visible is lightness, not hue: dark grey (Sesame Grey G602) against light grey or cream is the usual pairing, while a dark grey band on dark grey plaza tiles disappears at ten metres. Write that the band must form a clear luminance contrast with adjacent paving, name the stone code and finish of that adjacent paving, and have the factory send two samples from the same block run, one tactile unit and one neighbouring paver, to be laid side by side on site and sealed after approval. Grey drifts between batches even from one quarry, so hang the contrast clause on the sealed sample rather than on words alone.
Why can thickness and bedding not be specified separately?
30 mm is the common thickness for tactile units, and 30 mm Sesame Grey weighs 81 kg per m² (0.03 × 2.7 = 0.081 t); at 20 mm it is only 54 kg, a third lighter. But thickness only governs how the unit resists bending. What decides whether it snaps is the base: mortar bedding, a concrete base, or a suspended platform slab are three different details. Specify thickness without bedding and units still break, over a thin bed with voids, and nobody can say whose fault it was. Put three items side by side: 30 mm thickness, bedding material and compaction, mortar mix and joint width. The conversion is worked through in another article; here one line is enough: every 10 mm less thickness takes 27 kg of stone out of a square metre.
Why do corners, entrances and platform edges need their own transition units, and what goes on the eight-line list?
Standard units run out at a corner: the triangle cut on site has short edges and broken bars, so it neither grips nor guides, and inspection usually fails it. List three families separately: corner units (right angle and radius), end units (where a band terminates), and transition units (platform edge, entrance, kerb ramp). Count them off the drawing: one corner unit set per turn, one end set at each end of every run, platform edges by length. This line is frequently left out, and it is the expensive one to fix later: specials need their own mould or waterjet work and replenish far more slowly than standard units. We cut to your drawing: Guangxi Shicai Stone Industry Co., Ltd. has been running since 2019 with 20 large saws and 500,000 m² a year, standard slabs from 100 m² with 5-day shipment, and specials quoted on their own lead time. Fill in the eight lines before you discuss price.
| Item | How to write it | What it costs if left out |
|---|---|---|
| Unit types and ratio | Directional units by band length, warning units by decision points, two separate lines | Quoted at one ratio, one of the two types always runs short |
| Size and count basis | 300×300×30 plus tolerances on edge length and thickness, stating whether the count is theoretical, jointed or the settlement figure | Three counts on one sheet, three versions at settlement |
| Bar direction | Bars parallel to travel, packed facing one way, marked on the crate | Mixed packing, units sorted by hand on site, 90° errors scrapped |
| Finish and edge | Flamed face plus degree of easing, profile height fixed, sealed sample | A blunt profile with nothing to inspect against |
| Colour contrast | Clear luminance contrast, neighbour code named, two samples sealed | The band vanishes once the plaza is finished |
| Thickness and bedding | 30 mm, bedding material and compaction, mortar mix, all on one line | The unit is guaranteed, the base is not, and it still breaks |
| Transition quantities | Corner, end and transition units counted by location | Triangles cut on site, failed inspection, slowest resupply |
| Delivery and batch | From 100 m², standard slabs in 5 days, specials confirmed separately | Standard units arrive while specials are still in the mould |