Roofs and flat roofs
A parapet gutter falls towards a stopped end rather than the outlet. What overflow onto the wall does that set up?
It sets up an overflow onto the wall at the stopped end, because the parapet gutter falls away from the outlet and towards a dead end. Water that should run to the outlet runs the other way, ponds where the gutter stops, and then has nowhere to go but over the lining into the parapet or down the wall. The survey has seen that fall. It has not watched a storm fill the gutter, has not measured a depth of overflow, and has not decided how often the wall is wetted. The geometry is the finding. The overflow path is what that geometry sets up.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
A parapet gutter is a channel behind a wall, not an eaves gutter you can see from the pavement. Its only correct low point is the outlet. A fall towards a stopped end makes the outlet the high end, which is backwards. In ordinary rain the channel may hold a little and then spill at the stop. That spill wets the wall head or the back of the parapet, which is how these gutters stain bedrooms and rot plates. The survey can read the fall without filming a flood.
Ask a roofer to correct the fall so the gutter drains to the outlet, and to check the lining at the stopped end where the overflow is set up. Tell the solicitor the survey has described the geometry, not a measured flood. Do not wait for a ceiling stain before you treat the fall as a defect. The overflow onto the wall is what the wrong fall sets up, whether or not this visit caught it dripping.
What should you ask your surveyor?
- Which way does the gutter fall relative to the outlet and the stopped end?
- What lining did you see at the dead end?
- Are you describing an overflow path rather than a depth you measured?
What are the typical next steps?
- Treat the wrong fall as setting up overflow onto the wall.
- Do not add a flood depth the survey did not measure.
- Ask a roofer to put the fall back towards the outlet.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
If the outlet is clear, does the fall still matter?
Yes. A clear outlet at the high end does not catch water that runs the other way. The fall towards the stopped end still sets up overflow onto the wall. The survey has not said a clear outlet cancels that geometry.
Has the survey timed how fast the gutter overflows?
No. It read the fall. It did not watch a storm or time an overflow. The finding is the path that geometry sets up, onto the wall at the stopped end, not a rate. Geometry towards the stopped end is the overflow path, not a stopwatch.