Watch where rain already goes
Start with observation rather than a paving catalogue. Walk the site during steady rain and again after a short, heavy shower. Mark where water arrives, the route it takes and where it remains once the rain stops. Photograph downpipes, gullies, low points, soft lawn edges and staining at walls. Note whether water comes from your roof, a higher neighbouring plot or the public highway. A dry-day inspection alone can miss the one route that matters when the ground is saturated.
Measure levels relative to doors, air bricks, damp-proof courses, sheds and boundaries before changing them. Existing paving may already fall away from the building even if its surface looks tired. Raising a patio to hide an awkward step can reduce clearance below openings or direct runoff back towards the wall. If there is recurring internal damp, a collapsing drain, sewage, rapid ground movement or water entering the building, investigate that defect before treating the garden surface as the solution.
Separate a surface problem from a soil problem
A puddle can result from a local hollow, compacted construction soil, heavy clay, a blocked outlet or a naturally high water table. These causes need different responses. Digging a soakaway into ground that barely absorbs water does not make the water disappear. The RHS recommends assessing the cause and destination before installing drains. A simple percolation observation may help, but difficult sites need competent design and checks for underground services, tree roots and nearby structures.
Avoid promising that one channel drain, crate or gravel strip will cure every wet garden. A drain needs a lawful, suitable outfall and access for maintenance. Water should not simply be moved onto a neighbour's land, towards foundations or into a place where it creates another hazard. Combined and surface-water sewer arrangements vary, and connecting runoff may require consent. Ask the designer to show the catchment, expected route, storage or infiltration area, overflow and maintenance access on one plan.
Check the planning boundary before ordering materials
Rules depend on the nation, local planning authority, property and site constraints. The Planning Portal's current England guidance says that a new or replacement front-garden hard surface over five square metres can require planning permission when it uses traditional impermeable material and does not direct water to a permeable area within the property. Permeable surfacing or runoff directed to a lawn or border can fall within permitted development, subject to the actual circumstances. Treat that as a starting check, not universal approval.
Listed status, conservation controls, flood risk, a dropped kerb, highway visibility, trees, lease terms and restrictive covenants can add separate questions. Planning permission and building suitability are also different decisions. Save the council page, drawings and the date checked with the project record. If a contractor says permission is never required, ask them to identify the rule and site facts used. GOV.UK's permeable-surfacing guidance explains the policy intent, but local advice should resolve a borderline proposal.
Choose a surface as part of a drainage system
Permeable paving is not just a block with gaps. The surface, jointing, bedding and sub-base must work together so water can pass through and be held or dispersed as designed. Substituting an ordinary compacted base can defeat the intended route. Gravel, porous asphalt, resin-bound systems and permeable blocks have different edging, gradient, maintenance and accessibility needs. Ask for the complete build-up, finished levels and material specification rather than approving a photograph of the top surface.
Impermeable paving can still form part of a responsible plan when it falls towards a suitable rain garden, planted border or other designed permeable area within the property. The receiving area must have enough space and suitable soil, and its overflow must be understood. The RHS notes that permeable paving can reduce surface runoff while retaining a firm usable area. Keep access routes practical for wheelchairs, pushchairs and bins; loose or uneven materials are not automatically the best choice for every household.
Write a buildable brief before work begins
Record the dimensions, current and proposed levels, threshold clearances, falls, edges, sub-base, drainage components, service routes and waste disposal. Mark where rainwater pipes discharge and whether they will change. Request a written variation before accepting a different material or outlet. For driveways, include expected vehicle loads and turning areas. For patios, include furniture, steps and the route between house and garden. Good drainage is inseparable from safe access and stable construction.
Excavation can strike electricity, gas, water, telecoms or drainage services. Do not assume a shallow dig is harmless, and do not enter unsupported excavations. Tree-root disturbance and digging close to foundations require particular care. Use competent contractors for uncertain services, structural effects or new drainage connections. Keep surface water away from electrical equipment and ensure exterior lighting or power changes are designed for the location by a competent person rather than improvised during the paving job.
Test the finished route and keep it working
Before final payment, inspect levels and thresholds, then observe the surface with controlled water and during real rain without creating artificial flooding. Water should follow the agreed route, not sit against the home, cross the pavement or collect at a gate. Photograph the completed layers where possible and retain delivery notes, specifications and any permissions. If a channel or silt trap is part of the design, make sure its cover can be lifted and the household knows where the water goes.
Permeable surfaces still need maintenance. Leaves, soil, sand and construction dust can clog openings, while settlement can create new low points. Follow the surface manufacturer's cleaning guidance, keep planted receiving areas healthy and recheck the scheme after storms and winter weather. A dated annual photograph from the same positions can reveal gradual movement. If drainage performance worsens, investigate the route and outlet rather than immediately adding another surface layer over the evidence.
Set hold points before drainage work is covered
Agree inspection hold points in writing so the water route can be checked before paving hides the evidence. The first should follow excavation, when soil conditions, unknown services, roots and the actual depth of existing construction are visible. The next should show the prepared formation, edges, sub-base, inlets, channels, infiltration area or lawful outlet before the surface layer is installed. Photograph each stage from fixed positions and annotate door thresholds, air bricks, damp-proof courses, boundaries and the direction of fall. If the discovered ground differs from the survey, pause for a written design change rather than allowing a deeper hole, different base or improvised pipe to become invisible. Ask who is responsible for planning, drainage consents and any specialist assessment, and keep that answer with the GOV.UK, Planning Portal and RHS guidance used for the brief. A product label such as permeable does not compensate for an incompatible base, blocked route or receiving area that was never assessed.
Define acceptance around observable behaviour and maintainability, not a perfectly dry photograph immediately after construction. Before final payment, check finished levels and clearances, open every accessible cover and confirm where each channel, downpipe or overflow leads. Use controlled water in a way that does not create artificial flooding, then repeat the observation during real rain when safe. Water should follow the agreed route without being directed towards the home, across a public path or onto neighbouring land. Record any standing water, settlement or silt and require the cause to be addressed rather than disguised by another surface layer. The handover should identify cleaning methods, access points, replaceable components, planted receiving areas and the person responsible for routine inspection. Keep material specifications, delivery records, photographs, permissions and variations together. Revisit the same viewpoints after severe weather and seasonal leaf fall; if performance changes, investigate the inlet, surface, storage and outlet as one system before adding another drain.
