Roofs and flat roofs
A pond sits at one outlet of a flat roof and the rest of the field drains. Why is that an outlet note rather than a failed deck everywhere?
It is an outlet note because the pond sits at one outlet and the rest of the field drains. Water is holding at that outlet, not standing across the deck. A flat roof that drains elsewhere is still shedding, which points to the outlet being high, blocked or poorly placed, rather than a covering that has failed over the whole roof. The survey has recorded a local pond. It has not said the deck has collapsed, and it has not water-tested the membrane. The defect to read is the outlet that is not taking the water the rest of the roof is sending.
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?
Flat roofs are laid to falls towards outlets. A pond at one outlet means water reaches that point and then stays, while the rest of the field clears. That pattern fits a blocked grate, a lip at the outlet, or a local sag at the mouth. It does not fit a deck that is ponding from edge to edge. The surveyor saw where the water sat. They did not core the roof, and they did not treat the pond as a measured structural deflection.
Ask a flat-roofing contractor to clear and check that one outlet, and to say whether the lip or the fall at the mouth needs altering. Tell the solicitor the rest of the field drains, so this is not a note that the whole deck has failed. The survey has not specified a new roof. If the outlet is simply blocked, clearing it is maintenance at that point. If the mouth is too high, that is a local alteration, not a failed field.
What should you ask your surveyor?
- Which outlet holds the pond, and does the rest of the field drain?
- Why is this an outlet note rather than a failed deck?
- Was the membrane left untested?
What are the typical next steps?
- Read the pond as an outlet problem, not a failed deck everywhere.
- Ask a roofer to check that outlet before anyone prices a new roof.
- Do not describe the draining field as failed.
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 ceiling below is stained, has the whole deck failed?
A stain below shows water has got in somewhere. It does not turn a local pond at one outlet into a failed deck across the roof. The rest of the field drains. The survey has not tested the membrane. Ask the roofer to relate any stain to that outlet. Do not skip the outlet and condemn the field the report said drains.
Does one pond mean the falls were never designed?
The survey has not said that. It has said water sits at one outlet and the rest of the field drains, which is why the note is the outlet. Falls elsewhere are doing enough to clear the field. Whether the original design was right is not a calculation this inspection made. Keep the defect at the mouth that holds the pond.