Gutters, Downpipes and Where Rainwater Should Go

What do gutters and downpipes actually have to do?

Requirement H3 of the Building Regulations says "adequate provision shall be made for rainwater to be carried from the roof of the building." Approved Document H explains that this is met when rainwater is carried away by a system that minimises the risk of blockage or leakage, can be reached to clear blockages, and lets water soak into the ground without damaging the foundations of the building or anything next to it.

In practice, that means gutters sized and laid to fall towards the outlets, downpipes that are joined and fixed properly, and somewhere sensible for the water to go at ground level. Our guttering, fascias and soffits page covers the repair and replacement options.

Where is rainwater allowed to go?

Requirement H3(3) lists three places, "in order of priority":

1. "an adequate soakaway or some other adequate infiltration system"; or, where that is not reasonably practicable,
2. "a watercourse"; or, where that is not reasonably practicable,
3. "a sewer".

The guidance describes the outfall for roof water as a soakaway, a watercourse, a surface water sewer or a combined sewer. A foul-only sewer and a septic tank are not on that list. Collecting rainwater for re-use, for example in a water butt, is outside this requirement.

These rules matter most when rainwater drainage is being put in or changed, for example with an extension or a new driveway. If you are planning that kind of work, ask building control what applies to your home.

Where can a soakaway go?

A soakaway is a pit or crate system that lets water seep into the ground. Approved Document H (paragraph 3.25) says infiltration devices should not be built:

• within 5m of a building or road, or on unstable land;
• where the water table reaches the bottom of the device at any time of year;
• too close to drainage fields, drainage mounds or other soakaways, so that the ground isn't overloaded and any drainage field keeps working;
• where contamination in the runoff could pollute groundwater.

That third point matters on homes with a septic tank or treatment plant. The drainage field that disperses the treated effluent needs the ground's soakage capacity for itself, and Septic Tank Advice explains why roof and surface water should be kept away from a septic tank drainage field, and why a rainwater soakaway is not a substitute for one.

What about driveways and paved areas?

Hard surfaces around a house collect rain too, and a new driveway often changes where your downpipes discharge. The Planning Portal's guidance on paving front gardens says that for houses in England, you don't need planning permission for a new or replacement driveway of any size if it uses permeable surfacing, such as gravel, permeable block paving or porous asphalt, or if rainwater is directed to a lawn or border to drain naturally. Covering more than five square metres with a traditional impermeable surface that doesn't drain to a permeable area needs planning permission.

Better Driveways goes through the planning rules for driveways and permeable surfaces in more detail. If you are replacing a drive, tell the installer where your downpipes go so the new surface doesn't push roof water towards the house.

What happens when rainwater goes to the wrong place?

Government guidance on damp and mould in the home lists "damaged or blocked pipes, gutters or downpipes" among the outside checks for the source of damp, and says repairing blocked gutters and other sources of water getting in can reduce the risk of damp and mould and avoid more expensive repairs later.

• Blocked or sagging gutters overflow down the face of the wall, soaking brickwork and showing up inside as damp patches near the ceiling. See how roof leaks lead to damp and mould.
• Cracked or disconnected downpipes pour water against the wall and onto the ground right next to the house.
• Downpipes that discharge onto the ground next to the wall, with nowhere for the water to go, keep the base of the wall and the ground under it wet.

What should you check yourself?

From the ground, and ideally during heavy rain:

• Does water spill over the front of the gutter, or drip from joints?
• Are there plants growing from the gutter, or green streaks on the wall below it?
• Does each downpipe run into a gully, drain or water butt, or does it just stop above the ground?
• Do you know where your rainwater drains go? Old deeds, a drainage plan or a CCTV drain survey can tell you.

Don't climb a ladder to clear gutters if you aren't confident working at height. Our seasonal roof maintenance tips cover when to check gutters through the year.

Frequently asked questions