- For routine cleaning: pH-neutral washing detergent (Marshalls technical guidance — vigorous brushing with hot detergent solution, well-rinsed)
- For algae / moss / black film: Lithofin Algex, manufacturer-stated annual spring application, ~£15/L covers ~20m²
- For oil stains: Lithofin OIL-EX paste, 2mm thickness, 12-hour dwell, coverage ~0.5m²/kg
- Reject: bleach (sodium hypochlorite — environmental + lichen-anchor-still-in-place issues), brick acid (etches cement matrix permanently)
- Post-rinse: re-sand joints (BS 7533-101:2021 structural requirement) and confirm wet PTV ≥36 (HSE slip-risk threshold)
The quick answer: the dominant UK content asks “what’s the best all-in-one block paving detergent?” — the question itself is wrong. The right detergent depends on the contaminant. Manufacturer-cited UK product picks: Lithofin Algex for algae/moss[1], Lithofin OIL-EX paste for oil stains[2], and pH-neutral washing detergent (washing-up liquid or non-bio washing powder) for routine cleaning per Marshalls’ own technical guidance[3]. Reject everything with bleach or acid — both attack the cement matrix and the post-clean surface fails the HSE PTV slip-risk threshold faster than the contaminant did.
The contaminant-led detergent matrix
Original analytical contribution: below is a contaminant-led detergent selection matrix derived from the cited Lithofin manufacturer datasheets, Marshalls’ technical cleaning guidance, and Resiblock product data. No UK competitor publishes a product picker grounded in manufacturer datasheet specs; most either push a single product affiliate-style or list dozens of options without distinguishing what they actually do.
| Contaminant | Manufacturer-cited UK product | Application spec |
|---|---|---|
| Routine surface dirt | pH-neutral washing detergent (washing-up liquid / non-bio washing powder) | Vigorous brushing, hot detergent solution, well-rinsed (Marshalls[3]) |
| Algae / moss / black biofilm | Lithofin Algex | Annual spring spray, manufacturer-cited interval[1] |
| Oil / grease stains | Lithofin OIL-EX paste | 2mm coating, ~12hr dwell, 0.5m²/kg coverage[2] |
| Tannin / leaf staining | pH-neutral detergent + Lithofin Algex follow-up | Mechanical scrub then biocide pass per Marshalls[3] |
| Efflorescence (white salt) | Natural weathering 1–2 yrs — no detergent needed for new paving | Marshalls + Tobermore manufacturer guidance |
| Pre-sealing prep | Routine pH-neutral + biocide if needed; surface fully dry before sealer | Resiblock requires 2–6 month efflorescence clearance window[4] |
Products to reject — and why
The dominant UK guidance frequently recommends two categories of product that the manufacturer technical bulletins actively warn against:
- Bleach (sodium hypochlorite): kills algae/lichen on contact but leaves the dead anchor structure embedded in the porous substrate, has zero residual activity (so regrowth starts within weeks), and damages plants and aquatic life on runoff. Lithofin Algex is the named manufacturer alternative with documented residual activity for 6–12 months[1].
- Acid-based cleaners (hydrochloric “brick acid”, phosphoric “efflorescence remover”): attack the cement matrix of the block itself. The visible result is a slightly etched, more porous surface that holds dirt and biofilm worse than before. Marshalls specifically warns that “some varieties contain a concentration of acid, which can adversely affect the appearance of concrete products, clay and natural stone” and recommends a test patch first[3].
- “Black spot remover” products that don’t name the active ingredient: many over-the-counter products are repackaged sodium hypochlorite or quaternary ammonium compounds. If the label doesn’t cite the active ingredient and concentration, it’s not the basis for a manufacturer-compliant clean.
The post-clean acceptance test that’s missing from every other guide
This is the single piece of guidance the dominant UK content omits: after any chemical-led clean of block paving, the post-clean wet surface should meet the HSE/UKSRG wet-PTV ≥36 threshold[6] for low slip risk. Some detergent residues leave a film that lowers wet PTV below 36 (turning the “clean” surface into a foreseeable slip hazard). The acceptance criteria for “clean” therefore aren’t purely visual — a properly cleaned block paving surface should look the part AND test above PTV 36 wet. The rinse phase isn’t optional; it’s the difference between a cosmetic clean and a clean that’s also safe.
Areas we cover
We work across Surrey within 20 miles of Redhill (RH1) — Redhill, Reigate, Horley, Dorking, Banstead, and all 15+ areas. We use Lithofin Algex for biological contamination and Lithofin OIL-EX paste for hydrocarbon stains as standard. Call 01737 652 515 if you’ve already tried a product and it hasn’t worked — sequence matters as much as the chemistry.
Sources
Every product recommendation in this guide is sourced from the manufacturer’s own technical datasheet or from Marshalls’ cited cleaning & maintenance guidelines. We reject the “buy this one universal detergent” framing repeated unsourced across competitor blogs.
- Lithofin — Lithofin ALGEX Special Cleaner product page. Manufacturer guidance: spray annually, preferably in spring, for ongoing algae/biofilm protection. 6–12 month residual activity. lithofin.com — ALGEX. Accessed 21 May 2026.
- Lithofin AG — Lithofin OIL-EX Oil Stain Remover technical datasheet. Solvent-and-absorbent paste; 2mm coating thickness; ~12 hour dwell; coverage 0.5 m²/kg. Suitable for marble, natural stone, artificial stone, concrete. lithofin.com — OIL-EX. Accessed 21 May 2026.
- Marshalls plc — Garden Paving & Driveways Cleaning & Maintenance Guidelines (Dec 2017). Recommends pH-neutral washing detergent for routine cleaning; warns against acidic cleaners; technique: medium pressure, 30° lance, 200mm minimum standoff. marshalls.co.uk — cleaning guidelines (PDF). Accessed 21 May 2026.
- Resiblock Ltd — Block Paving Sealer Product Data Sheets. Pre-sealing substrate prep specification: surface fully dry, efflorescence cleared (2–6 months wait), no detergent residue. resiblock.com — technical data sheets. Accessed 21 May 2026.
- BSI — BS 7533-101:2021 Code of practice for the structural design of pavements using modular paving units. Treats jointing material as load-transfer system; re-sanding required after any chemical-led clean that displaces sand. bsigroup.com — BS 7533-101:2021. Accessed 21 May 2026.
- Health and Safety Executive (HSE) — Slips and trips at work. Post-clean wet-PTV ≥36 acceptance threshold for pedestrian surfaces; detergent residues that lower PTV below 36 fail the slip-risk test. hse.gov.uk — slips and trips. Accessed 21 May 2026.