Drainage data for property managers

A measurement is a better place to argue from than an impression — particularly a measurement made by a party with no work to sell on that property.

What you can put in front of an owner

Three quantities per building, and a fourth line that is the honest one.

1. Meters of wall with ground falling toward the structure. Per wall, not per property, because a house can shed cleanly off three sides and collect on the fourth.
2. Contributing area at the worst wall, in square meters — how much land upstream drains into that corner.
3. Standing-water depth and extent within 20 m of the building, outside every structure, with a 3 cm floor because below that is survey noise.
4. What was refused. Buildings we declined, walls we would not call, and why.

The one sentence the system is willing to say about a property, quoted verbatim from the code that generates it:

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

That boundary is the reason the document survives contact with an owner's counsel. Ground falling toward a foundation raising the risk of water reaching it is ordinary building science and we will state it all day. That a particular building has water is a diagnosis, and this instrument does not make diagnoses.

Why the list comes back shorter than your portfolio

This is the part most managers find counter-intuitive, so it is worth being direct about.

A published building outline is a trace and can sit a meter from the wall it claims to be. Shifting a real Pittsburgh footprint north in 0.2 m steps moved one wall from +5.4% to −23.5%, crossing zero inside 1.4 m. So every footprint is displaced one meter in each of sixteen directions and every wall re-measured. Seventeen positions, and a direction is printed only when all sixteen agree on the sign.

Walls that fail come back undecided, with which way they lean and how many of the sixteen agreed — so a near miss reads as a near miss — and they do not put a building on a ranked list.

Separately, the surface itself is tested before anything is routed: the median step between adjacent elevations has to clear 0.004 m, or the data is a coarse source stretched onto a fine grid and the address is declined outright.

The result is a shorter list. A shorter list you can defend in a budget meeting is worth more than a complete one you cannot.

Ranking a scattered portfolio against itself

Managers rarely hold one campus. It is forty houses across nine suburbs, or eleven small buildings in four submarkets, and the ground under each is different.

Every building is measured the same way, so the portfolio can be ordered by a quantity that means the same thing everywhere: meters of wall called as falling toward the structure, with contributing area beside it. That ordering is what turns a grounds budget from a squeaky-wheel allocation into a defensible one.

It is re-run annually, or when new data lands for a metro. The underlying ground data refreshes on a cycle rather than continuously, so a regrade done last spring is not in the record until somebody re-measures it — and the report says as much.

Which building, which is the failure nobody audits

At portfolio scale nobody checks the aerial photo, so a wrong roof propagates into a work order and then into a capital request.

Identity is decided by graded evidence, and the weakest grade — the nearest outline is all there is — locates rather than identifies, and it is labeled that way rather than quietly promoted.

Roughly half the remaining errors are not a different building at all — ten of eighteen wrong rows sit within 5 m of the addressed structure, which is our source and the judge tracing the same roof differently. If a building is wrong, it is replaced free.

What this does not do for you

• It does not schedule work, price work, or specify work.
• It does not see below grade — footing drains, tile and sump condition are invisible to a remote measurement.
• It does not predict a water event at any building, on any timescale, and no version of it ever will.
• It does not replace the person who walks the property. It tells that person which corner to walk to first.

Questions managers ask