Downspouts disperse to vegetation, not piped storm-sewer — splash blocks, swales, rain gardens
EPA Stormwater — Downspout disconnection + dispersalDescription
Where local codes permit, disconnect downspouts from storm-sewer pipes and direct them to vegetated areas: splash blocks discharging onto grass; extensions ≥ 5-10 ft from the foundation; flow-spreaders distributing into lawns or rain gardens. This reduces peak flow to the storm system + recharges groundwater. Watch for: soils that don't drain (slow infiltration → ponding); negative grade against the foundation; downhill neighbors who may receive the flow.
Why this exists
Disconnected downspouts are the simplest stormwater BMP — almost free, and surprisingly effective at the watershed scale. Architects should design downspout discharge as a deliberate landscape feature (a swale or rain garden) rather than an afterthought splash block.
Categories
Source
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Exterior ramps: maximum slope 1:12, minimum 36 inch clear width · HUD FHA Design Manual Chapter Two §2.7
- Build to the latest natural-hazard-resistant code edition · FEMA P-2325 §Building Codes Basics
- Coastal-pile foundations should embed deeply to resist erosion + uplift · FEMA P-2325 §Florida Building Code / Sand Palace lessons
- Lowest floor at or above Base Flood Elevation in Special Flood Hazard Areas · FEMA P-2325 §Flood Hazard Provisions
- In WUI zones, protect openings from wind-blown embers · FEMA P-2325 §Wildland-Urban Interface (WUI)
Last reviewed 2026-05-15.