For small builders and main contractors (England)
Last reviewed: March 2026
This is the bit where driveways, patios and extensions quietly drag you into flood risk and planning arguments, even when Building Regs (Part H) is the only thing you were thinking about.
1. What SuDS is in plain English
SuDS = Sustainable Drainage Systems. It's about keeping rainwater on site and letting it soak away slowly, instead of blasting it straight into the road or foul sewer and flooding someone downstream.
For you, it boils down to:
- Prefer soakaways, permeable surfaces and gardens.
- Avoid sending roof and driveway water into the foul sewer (illegal in most setups) or straight onto the public highway.
2. The rules that bite you most
On small domestic jobs in England, three things matter:
Part H (H3/H5) - Building Regs
- Keep foul and surface water separate.
- Priority for surface water:
- Soakaway/infiltration,
- Watercourse,
- Surface water sewer - only if you can't do the first two.
Permitted Development rules for front driveways
- Paving a front garden with an impermeable surface over 5 m²: needs planning permission unless you direct water to a lawn/border/soakaway and don't discharge to the road.
- Permeable surfacing (resin bound done right, permeable blocks, gravel etc.) generally doesn't need planning - PD covers it.
Local SuDS policies via planning
- Many councils now expect some SuDS thinking even on small extensions and domestic hard landscaping: permeable paths, soakaways, rain gardens.
3. How this plays out on your jobs
New or widened driveway
- If it's impermeable and over 5 m² at the front, either:
- Make it permeable, or
- Provide proper drainage to a soakaway or garden (not the street), or
- Your client needs planning.
- Never just run it into the foul gully because it's "easier" - that's a Part H fail.
Single-storey rear extension
- Extra roof area = extra rainwater.
- You need: gutters, downpipes and either soakaway/infiltration or correct connection to surface water system, not the foul unless there's genuinely no separate option.
New patios and paths
- Large solid patios that fall back to the house or into next door's garden are a damp claim waiting to happen.
- Falls should take water to planting, permeable areas or a soakaway - not to the DPC line or neighbour's fence.
Small sites on clay or high water table
- Soakaways may not fly; percolation tests will tell you.
- You may be into attenuation/rain gardens or controlled discharge to a surface water sewer under planning/Part H guidance.
4. What "good enough" SuDS looks like for a small builder
You're not designing a housing estate system. On a house-scale job, you'll usually be fine if you:
Keep water away from the house
- 150 mm step from DPC to finished level where possible.
- Hard surfaces falling away from walls, not towards them.
Use permeable where you reasonably can
- Permeable block, resin bound (proper build-up), or gravel over a free-draining base for drives and paths where ground allows.
Plan soakaways properly
- Sized roughly by roof/area, at appropriate distance from buildings/boundaries and above the water table, with percolation checks where needed.
- Don't stack them right next to foundations or septic drainage fields.
Keep surface water out of foul drains
- If there are separate systems, use the surface water system for rainwater.
- Only combine where there genuinely is no separate system and BC/water company accept it.
Flag bigger drainage questions early
- On bigger or tighter sites, tell the designer/planner you need a drainage/SuDS plan - don't "make it up with ACOs and luck" after the slab is poured.
Short version: If you're pouring hardstanding or adding roof area, you're in SuDS/Part H territory whether the client knows the word or not. Get the water into the ground on their land, keep it out of foul drains and off the road, and don't drive it back at the house.
This page is a general guide for small builders and main contractors working on dwellings in England. It doesn't replace local SuDS policies, the Building Regulations or planning rules. Always check the latest Part H guidance, local planning conditions, and any site-specific drainage strategy before you start digging or paving. SiteKiln does not provide legal, financial or tax advice. All content is for general information purposes only. Always seek professional advice for your specific situation.
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Working in Wales? The building rules are different. See our Working in Wales guides.
Working in Scotland? Building standards work differently. See our Working in Scotland guides.
Working in Northern Ireland? The system uses Technical Booklets. See our Working in Northern Ireland guides.
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