Why openings are tested in place
Windows and doors are among the most common sources of water intrusion in buildings. Every opening interrupts the wall’s water-resistive barrier, and every unit has joints, seals, and drainage paths of its own. When water shows up inside, the openings are usually among the first places investigators look.
Interior stains rarely tell the whole story. Water can enter at a window head and travel down inside the wall, or enter at a frame corner and run along the sill before it appears. Window water testing reproduces wetting and wind pressure under controlled observation, so the actual path can be seen rather than inferred.
Our investigative specialties include windows and doors, including product and installation water testing. This article explains the method in general terms, so owners, boards, contractors, and counsel can follow what a test involves and what it can show.
Testing also confirms repairs. After a repair, the same test can show whether the opening now performs under the conditions that produced the original leak.
Product leaks and installation leaks
The central question in most window investigations is whether the unit itself leaks or whether water is getting around it. A product leak passes through the window or door: a frame corner, a glazing seal, a weep system, or an operable sash or panel. An installation leak passes around the unit, through the rough opening, flashings, or perimeter sealant.
The distinction matters because the repairs differ. A product problem may call for repair or replacement of units. An installation problem may call for removing cladding to correct flashings and barrier laps. Some openings have both.
Manufactured windows and doors carry performance ratings from laboratory testing of production samples. In North America, many products are rated under the North American Fenestration Standard, which includes water penetration resistance. A rating describes how a tested sample performed; it does not describe how a particular unit was installed.
Installation leak paths differ from product paths. Common examples include those listed below.
- A sill pan that is missing or does not drain to the exterior
- Head flashings set on top of the wall barrier instead of beneath it
- Window flanges that are not integrated with the water-resistive barrier
- Gaps or failed adhesion in perimeter sealant
- Flashing tapes at corners that are damaged, unbonded, or lapped the wrong way
How a field water test works
Most field tests use a spray rack: a frame of nozzles that applies water evenly across the exterior at a calibrated rate. To simulate wind, a chamber is often sealed to the interior side and air is drawn out. The resulting pressure difference pushes water toward any gap. Observers watch the interior side for leaks.
Published standards describe these procedures. ASTM E1105 is a test method for field water penetration of installed exterior windows, skylights, doors, and curtain walls under uniform or cyclic static air pressure difference. AAMA 502 addresses field testing of newly installed windows and doors, and AAMA 501.2 describes a hose nozzle check for storefronts, curtain walls, and sloped glazing.
Field test pressures under these documents are often set below the laboratory test pressure. The applicable document, pressure, water rate, and duration are chosen to fit the question being asked, and they belong in the record with the results.
Some investigations begin with a simpler hose test, wetting a defined area with a calibrated nozzle to locate a leak quickly. A chamber test can then examine performance under a defined pressure difference.
Testing in stages
A single test of a whole opening shows whether water gets in, but not always where. Staged testing answers the narrower questions. The perimeter may be masked with tape or film so only the unit is exposed, and then the unit is masked so only the perimeter is exposed.
Sequence matters. Testing typically starts low and works upward, because water applied high on a wall can run down and confuse the result at a lower location. Allowing time between stages, and confirming the interior is dry, keeps one result from contaminating the next.
Where the parties agree, interior finishes such as trim or drywall may be removed to watch the rough opening directly. That turns a leak observation into a leak path, which is often what a repair scope needs.
Doors follow the same logic. A sliding door may be tested at its track and sill, then at its perimeter, then at the deck transition below it. Each stage is isolated from the others.
Documenting what the test shows
A water test is only as useful as its record. Without a clear record, even a well-run test can be hard to rely on later.
We use state-of-the-art cameras and video documentation techniques to provide trial-ready exhibits. Video taken from the interior during testing lets a reader see when water first appears and how it travels. Photographs of the setup, the masking, and any openings put that observation in context.
Gregg de Haan prepares field testing data for trial. In that setting, the record has to be clear to people who were never on site.
A complete record generally includes the items below. Each is captured at the time of testing, not reconstructed afterward.
- The units tested, their locations, and their condition before testing
- The test method, setup, and calibration of the spray equipment
- Pressures, water rates, and the duration of each stage
- The time and location of any water observed
- Photographs and video tied to each stage
What a water test does not show
A field test reproduces defined conditions, not every storm. A unit that passes at the test pressure may still leak under more severe exposure. A unit that leaks during testing may have been damaged or altered since installation. Results are interpreted with the unit’s history in mind.
Testing a sample of openings does not automatically describe every opening in a building. How representative the tested units are depends on how they were selected and how consistent the installation was. That question is often as important as the test itself.
A test also does not assign responsibility. It shows where water entered under stated conditions. Connecting that observation to a design, product, installation, or maintenance question requires the rest of the investigation.
Weather history can help with interpretation. Records of storms, wind direction, and the timing of reported leaks can show whether test results match what occupants experienced.
When the unit itself is in question
If testing points to the unit, the next question is whether the product was defective or was damaged, altered, or poorly maintained. Preserving the unit or its components keeps that question open for later examination. We take field samples to store at our office in case they are needed at trial.
If building materials are found to have manufacturing defects, we are aligned with several laboratories that test and analyze product failure. We are also educated on current and past building product performance testing, which helps place a field result alongside the product’s rated performance.
Manufacturer documentation is part of that review. Installation instructions, product ratings, and published details show what the manufacturer required and how the product was rated.