Observe where water arrives and travels
Use dated photographs and notes during different rain conditions where it is safe to observe. Identify roof discharges, hard surfaces, low areas and routes towards the building. Keep plans and previous work information. A patch of standing water describes a symptom but does not by itself determine the appropriate drainage or ground intervention.
Map levels and the complete intended layout
Record thresholds, ground levels, paths, storage areas and the proposed changes. Have the necessary survey information prepared for design. Consider how changing one area affects another and where overflow would go. The landscape plan should account for the finished levels, not only planting and appearance. Do not redirect water towards neighbours or the building on an untested assumption.
Check the constraints before choosing a solution
Discuss soil conditions, existing networks, property constraints and the applicable local prescriptions with the relevant professionals and services. A simple observation does not confirm infiltration capacity or justify excavation beside foundations. Keep the investigation and design questions explicit. This page does not authorise a connection, an infiltration system or a drainage detail for the site.
Compare the complete work and access needs
Ask for the arrangement of collection, conveyance, any storage or infiltration and the handling of overflow. Include excavation, soil management, reinstatement and maintenance access. Assign interfaces between earthworks, pipes and landscaping. A product catalogue does not establish the suitability of the complete system or identify which contractor checks each element.
Keep the final plan and observe operation
Retain levels, routes, installed references and relevant checks before buried elements are covered. Agree maintenance responsibilities and safe access. Document remaining standing water or unexpected flow with the conditions in which it occurs and ask for review. Observations after one small rainfall cannot demonstrate performance under every future condition.
Your preparation checklist
- Water paths observed.
- Finished levels mapped.
- Soil and local constraints investigated.
- Overflow route considered.
- Complete scope and interfaces assigned.
- Final layout and maintenance retained.
Questions before you commit
Does standing water always justify a drain near the house?
Have the cause and the effects of any intervention assessed before excavation or selecting a solution.
Can a catalogue specify infiltration capacity for my site?
Site conditions and applicable constraints need investigation; a generic product description does not establish them.
Sources and the scope of this guide
This English guide covers the same project need as its French counterpart, with an editorial explanation in English. It is not a professional survey or a translation of foreign rules to France. Check current official requirements and the documents applying to your building and contract.
French reference: Cerema : l’eau de pluie, une amie qui refait surface
French reference: Cerema : zonage pluvial et infiltration au plus près de la pluie
French reference: Cerema : solutions de gestion des eaux de ruissellement pluvial