Does 'path and drive' weedkiller work on block paving?

Not always, and this is the bit the branding does not tell you. 'Path and drive weedkiller' is a marketing category, not one formula, and the best-known one is explicitly restricted to permeable surfaces, not the solid block paving or tarmac most people have in mind when they buy it.

Weedol Pathclear Weedkiller, the product most people picture when they hear "path and drive", contains 125 g/L glyphosate plus 20 g/L diflufenican, a residual ingredient that forms a barrier in the soil to stop new weeds germinating for around 3 months after the systemic glyphosate has killed what is already growing. That is real, useful, two-in-one action, and its own label states it plainly: it is for gravel paths and drives, natural surfaces and permeable surfaces overlying soil, and it explicitly says not to use it on impermeable surfaces or surfaces underlaid with impermeable material, including concrete, tarmac, decking and paved areas, because the weedkiller solution can run off into drains, gutters or adjacent land.

That rules out a huge share of UK driveways. Solid block paving, poured concrete and tarmac are all impermeable in the way this label means, so a product bought specifically because it says "drive" on the front is, on its own terms, not approved for the actual surface underneath a lot of drives.

To make it more confusing, not every "path and drive" product is even the same chemistry. The current Resolva Path & Drive ready-to-use is a different formula again, an acetic-acid based contact treatment with no glyphosate at all, which scorches what it touches quickly but does not carry down to the root and leaves nothing behind to stop the next seed germinating. Two bottles under a near-identical name on the same shelf can behave completely differently.

For an actual block-paved or tarmac drive, a plain glyphosate concentrate mixed to the label rate is the straightforward choice, systemic, no residual soil-acting ingredient to worry about, and no permeable-surface restriction to trip over. See the full concentration and mixing-rate breakdown, with real products and worked examples for a 5 or 15 litre tank, on the glyphosate concentrate and mixing rates resource.