Drainage reports for listing agents

What you get is deliberately narrow: the direction the ground tips at each wall, how much land drains to each wall, and how deep any hollow near the house fills before it spills. Numbers, with their error bars, and nothing said about the house itself.

The line this product will not cross

We never say a property needs work. Not in a report, not in a summary line, not in an email. The reason is not caution for its own sake — it is that we did not measure it.

Ground falling toward a foundation raises the risk of water reaching it. That is ordinary building science and it is not in dispute. That a particular house has water is a diagnosis, and this instrument does not make diagnoses.

For an agent that boundary is the useful part. A measurement with a stated limit is something you can hand across a table. An opinion about a defect is something you did not want to be holding.

"the ground falls toward this structure on 14 m of its walls" measure · drainage · lead signal

That is the strongest sentence the system will produce about any property, and it is quotable verbatim.

What is actually measured

Each wall is measured along its own outward normal rather than the property getting one slope. The slope is measured from 0.75 m to 3.25 m out, repeated at several stations along the wall and combined so no single reading decides it.

Nothing is sampled nearer than 0.5 m to a wall — inside a footprint a bare-earth surface is not ground, it is the interpolation across a building that was removed.

Then the awkward bit. A published outline is a trace and can sit a meter from the wall it claims to be, so the whole footprint is displaced one meter in each of sixteen directions and every wall is re-measured. Seventeen positions in all, and a direction is printed only when all sixteen agree on the sign.

Walls that fail come back marked undecided, with which way they lean and how many of the sixteen agreed. That is why a report on a house with twelve wall segments may only call seven of them, and why the seven are worth something.

Contributing area, which is the part nobody can see on a viewing

Standing in a garden tells you about the last three meters. It tells you nothing about the two thousand square meters of ground behind the fence that drains through it.

Water is routed across the whole surface, spreading the way overland flow actually behaves — dispersive across a lawn and near-single-channel in a gully. Buildings act as walls in the model, so water routes around a house rather than through it.

The area arriving at each wall is sampled at nine points and published with a range, because one sample on a flow boundary is a coin toss.

Which house we measured, and what happens when we get it wrong

Identity is decided by graded evidence, strongest first. Where the nearest outline is all there is, the answer locates rather than identifies. It is labeled as such and it is never sold as a report.

We publish no headline identification rate, because one figure would hide what actually decides the answer: what identified the building on this address. That ships with the report. Not every disagreement is a different building either — some are our source and somebody else's tracing the same roof differently. If the building is wrong, the property is replaced free.

Where it fits in a transaction

• Before listing. Know what a buyer's inspector is going to be looking at in the back garden.
• Before an offer. On the buy side this is $25 against a six-figure decision, and it runs in the time it takes to make coffee.
• Comparing two houses. The measurement is the same shape on both, which anecdotes never are.

One caution worth repeating to clients. The underlying ground data refreshes on a cycle rather than continuously, so a surface can predate a new patio, a regrade or a fresh retaining wall. The measurement describes the ground as measured.

Questions agents ask