Post-Mitigation Retesting in Denver, CO

An Installed System Is a Claim, Not Evidence

Look at two houses with identical white pipes running up the side. One is holding the basement under 2. The other has a fan that died fourteen months ago. From the street, and from the driveway, and from the listing photographs, they are the same house. The only thing that separates them is a measurement, which is why we include a post-mitigation test with every system we build instead of selling it as an optional extra. A job that ends without one has not actually demonstrated anything.

When the Retest Is Run

Not immediately. The fan needs at least a day of running for the pressure field under the slab to settle into its new shape, and testing before that gives you a number from a system still finding its feet. After that it is the same protocol as any other test — 48 hours, closed-house conditions, lowest lived-in level, and ideally the same location the original test used, because comparing two readings taken in different rooms is comparing two different things.

What the Gauge Cannot Tell You

The manometer on the pipe is genuinely useful and it is not a measurement. It tells you the fan is moving air. It says nothing about whether the suction still reaches the far corner of an addition, whether a new crack has opened a shortcut across the slab, or whether the level in the house is 1.8 or 3.9. Treat it as a smoke alarm: excellent at telling you something has failed, useless at telling you everything is fine.

Systems Somebody Else Installed

A good share of this work is testing systems we had nothing to do with — a house bought with one already fitted, a system put in a decade ago by a company that is no longer around, a passive stub a builder ran that nobody ever activated. We test first and then say what we find. Sometimes it is a worn fan on a sound design, which is a small job. Sometimes the system never worked and no one retested to discover it, which is a different conversation entirely. The reading is what separates those two, and guessing between them is how people end up paying for the wrong one.

Triggers for Testing Again

Every couple of years as a baseline. Then additionally after anything that changes the house: foundation repair, a new furnace or water heater, finishing a basement, replacing windows, an addition, or any work that cuts into the slab. Each of those alters either the pressure field underneath or how hard the building pulls air, and either can undo a system that worked perfectly the day it went in. If the number has moved, that usually points straight at whichever piece of work came just before it.

How long does it take? The same 48 hours, run at least 24 hours after the fan has been switched on so the sub-slab pressure field has settled.

Questions People Ask First