Patios & paving

Paving in a rear garden is generally permitted development. The rules tighten in front gardens, near the highway, and where surface water has nowhere to go.

• Front-garden surfaces over 5 m² in impermeable materials need planning permission unless run-off drains to a permeable area on your own land (lawn, border, gravel, soakaway). ^[1][2]
• Permeable surfaces (gravel, permeable block paving, porous resin) of any size are permitted development in front gardens, provided sub-base allows infiltration. ^[2]
• Finished paving must sit at least 150 mm below the damp-proof course (DPC) of the house wall — two brick courses, roughly. ^[3]
• Never bury air bricks / underfloor vents. Where paving rises to the wall, keep the opening clear or fit a periscope (telescopic) underfloor vent — blocked vents cause joist rot, condensation and ground-gas build-up. ^[3][5]
• For flush / level access (bifolds, sliders, wheelchairs) the threshold step is capped at 15 mm (chamfered) under Part M. Resolve the DPC conflict with a threshold / ACO slot drain at the door, with cavity-tray and weep detailing. Mandatory for new dwellings and extensions. ^[6]
• Paving in a listed building's curtilage, a conservation area, or an Article 4 area may need permission even when it would otherwise be permitted development. ^[2]
• BS 7533 is the British Standard family for pavements constructed of clay, natural stone or concrete paving units. It's the document specifiers reach for. ^[4]

Numbers that come from real jobs, not marketing copy. Adjust for ground conditions and product datasheets.

• Before any excavation — even shallow lifts of an existing patio — do a CAT & Genny sweep to locate buried services (HSE HSG47). Plastic gas and water mains do not show on a CAT alone; the Genny is what finds them. Full method in the Safety, PPE & site rules guide.
• Minimum fall away from the house is 1:80 (12.5 mm per metre). 1:60 sheds water faster on slabs that hold puddles.
• On a steep site (>1:20), step the patio with riser courses rather than running one long fall — water sheets off rather than skating across joints.
• If run-off goes to a soakaway, oversize it 20 % for porcelain and other impermeable slabs — they shed water faster than block paving.
• Sub-base of MOT Type 1, compacted in 75 mm layers: 100 mm for foot traffic, 150 mm on clay or for occasional vehicle overrun.
• Natural stone is variable thickness — always lay on a full mortar bed, 30–40 mm thick. Never spot-bed. Spot-bedding is the #1 cause of cracked sandstone.
• Porcelain is rectified (factory-cut edges) and demands a primer slurry on the back of every slab before bedding, plus 3–5 mm joints.
• Cure the bed and joints for 24 hours before walking, 72 hours before furniture or pots.
• Cut allowance: rectangular patio with simple borders ≈ 5 %. Curves, circle features, or lots of obstacles ≈ 10–12 %.
• 45° herringbone in block or rectangular slabs typically wastes 8–12 % to cuts at the perimeter — order accordingly.
• Jointing compound: brush-in resin (~25 kg covers ~6–8 m² at 10 mm joints) or kiln-dried sand for block paving (~4–6 kg/m²).

• Indian sandstone, limestone, granite, slate → full mortar bed + brush-in jointing or sand-cement pointing. Joints 8–15 mm.
• Porcelain → SBR slurry primer + full mortar bed + 3–5 mm brush-in jointing. Skipping the primer is the #1 reason porcelain debonds in winter.
• Concrete slabs (smooth or riven) → mortar bed; lighter-weight slabs can be screed-laid on sharp sand.
• Block paving → 30–40 mm sharp sand bed on Type 1 sub-base, kiln-dried jointing sand, mechanical edge restraint.
• Clay pavers → 30–40 mm sharp sand screed bed, joints 2–5 mm, kiln-dried sand swept in after vibration. Kiln-fired colour is permanent — no fade.
• Granite setts → full mortar bed (30–50 mm) with 10–20 mm pointed mortar joints — never butt-jointed or sand-filled. Heaviest UK paving option for traffic.
• Grass-grid cellular pavers → on 50 mm grit/sharp-sand bed over 100–150 mm open-graded 4/20 mm clean (no fines) sub-base; cells filled with topsoil + grass seed or pea gravel. SuDS-compliant for front drives.
• Pattern-imprinted concrete (PIC) → single monolithic C28/35 pour with A193 mesh; colour hardener broadcast wet, release agent dusted, stamp mats applied, acrylic sealer after 24–48 h. Reseal every 3–5 years.
• Limestone — never de-ice with rock salt; calcium carbonate reacts with brine and acid rain and the surface pits. Seal with a breathable impregnator on installation.
• Slate — riven slate is glass-slippery in shade or N-facing aspects once foot-polished; specify a grit-blasted or textured finish on main approaches, or keep it as a feature only.
• Granite setts — shock-load from cars cycles the mortar joints; expect to re-point every 5–10 years under traffic. Use polymer-modified pointing from day one.
• PIC — micro-cracks in the stamped surface are normal in any C28/35 slab; the re-seal hides them visually. Skipping the re-seal is the #1 reason PIC drives look tired by year 5.
• Grass-grid — grass cover fails under daily car use (compaction + shade). Sell honestly as overflow / occasional / fire-engine access only; for daily parking, fill the cells with pea gravel from day one.