KTA Solutions

Improperly Installed Surface Mounted Flashing

Problem:  Flashing Deficiencies

Description:  A masonry building in Ohio was experiencing leaking underneath a drive under canopy.  Leaks were occurring over entrance/exit doors and also storefront windows of conference rooms and offices.  The leaks were causing a nuisance to customers entering and exiting the building during rain and were also contributing to coating failures underneath the canopy.

The drive under canopy was a pre-manufactured structure erected independent of the main masonry building.  The canopy consisted of a structural steel framing and a light gage parapet wall with a metal panel facade.  The roof of the canopy consisted of standing seam panels that were underhung from the structural steel frame above.  A field fabricated flashing system was installed between the main building and canopy.  In addition, overflow scuppers were installed in the main building wall just above the canopy and drained onto the canopy.  The following is a summary of the types of testing and analysis undertaken by KTA to examine problems of this nature.

NOTE: The conclusions provided below cannot be interpreted as being relevant to other failures, even if they are similar in appearance. Likewise, the tests identified below may or may not be relevant or adequate for the investigation of other failures.

Field Sampling/Analysis:

  1. Visual Observations – The flashing system between the main building and canopy was visually inspected.  Fabricated sheet metal flashing was installed between the masonry building and canopy.  The flashing system was one piece that spanned from the masonry wall to underneath the standing seam roof panels.  The flashing was mostly flat and butted the masonry wall.  The top edge of the flashing was not cut into the masonry wall. The top of the flashing contained a thick bead of sealant material.  The sealant material was found to be cracking and separating at the top of the flashing.  Sealant material was also found to be missing in the grooves of the scored block.
  2. Spray Rack Test – A water spray rack test similar in principle to the method in ASTM E1105, Standard Test Method for Field Determination of Water Penetration of Installed Exterior Windows, Skylights, Doors and Curtain Walls by Uniform or Cyclic Static Air Pressure Difference was performed.  The spray rack was placed directly above the canopy and sprayed onto the masonry wall.  A steady stream of water was applied to the surface at 5 gallons/square foot/hour through spray nozzles held 12 inches from the surface.  The purpose of the spray rack test was to replicate the leaking underneath the canopy above the doors and windows so that a controlled examination of potential causes could be made.  The test immediately showed that leaks were coming from deficiencies in the flashing system.


            The single piece flashing system was inadequate to prevent leaks from occurring underneath the canopy.  It is likely the flashing system was originally designed to be a two piece flashing system and only the base flashing was installed; the counterflashing was omitted.    The top edge of the base flashing was simply caulked in an attempt to make it shed water.  Movement between the canopy and building, and movement of the flashing itself caused the sealant to crack and separate over time, allowing rain water to run down the wall beneath the canopy.

The recommendation to repair the leaks above the canopy included modifications to the flashing system.   Modifications included removal of sealant above the base flashing to allow unrestricted movement of the base flashing and the masonry wall.  A detail was developed illustrating a new counterflashing to cover the base flashing.  Prefabricated surface mounted flashings were not an option due to the deep grooves in the scored block.   The detail included cutting in a groove slightly deeper than the grooves in the scored block.  The new flashing detail showed a 90 degree bend at the top of the flashing with another upward bend along the entire edge to create a “friction fit” into the cut groove.  The new counterflashing overlapped the existing base flashing.  Fasteners of like material as the counterflashing were specified to be installed in oversized holes and sealed with urethane sealant.  The cut groove was specified to be sealed with a hybrid urethane sealant material.

Damp CMU In-Fill Insulation


Problem:  Damp CMU In-Fill Insulation


Description:  A single-wythe CMU building was less than 1 year old when blocks on the back wall were damaged and the faces had to be replaced.  When the replacement work started, the contractor notified the owner that the spray polyurethane foam insulation (SPF) in the block cavities was damp.  The owner requested an examination of the insulation around the building to determine if the problem was widespread.  The specified SPF was low density open-cell, 0.8 lb/ft3.  The following is a summary of the types of testing and analysis undertaken by KTA to examine problems of this nature.

NOTE: The conclusions provided below cannot be interpreted as being relevant to other failures, even if they are similar in appearance. Likewise, the tests identified below may or may not be relevant or adequate for the investigation of other failures.


Field Sampling/Analysis:


  1. Visual Observations – Small, isolated patches of efflorescence were visible on the exterior walls at random, but nothing stood out visually to suggest that the block and/or insulation were damp.
  2. Infrared Thermography – IR thermography was used to examine the building walls.  The images showed clear indications of thermal bridging in portions of all walls.  The results of the IR thermography were used to select test locations for in-depth moisture measurements.


  1. Moisture Content – Moisture readings were taken around the building.  Since the purpose of the assessment was to determine whether the in-fill insulation was damp, destructive testing was used.  Two ¼” diameter holes were drilled though the mortar joints or block faces.  Special probes designed in the KTA machine shop were inserted into the holes and connected to a conductivity moisture meter.  The probes allowed for a determination of the presence of moisture at the outer face of the blocks, the interior cavities of the blocks (the insulation), and the inside back faces of the blocks.

    Test sites were selected based on the thermal imaging results in order to obtain moisture readings in areas that did and didn’t exhibit thermal bridging.  In locations where the entire height of the wall appeared to be the same by IR imaging, testing was typically performed at 3 heights (ground level, 10 to 12 feet up from the ground, and below the upper bond beam).   The moisture testing showed mixed results: the in-fill insulation in some block cavities was damp, some was dry, and some of the block cavities were void of insulation altogether.  In some cases, the moisture content was so high that damp insulation was adhered to the probes when removed from the block.


  1. Optical Borescope – A borescope was used to view the inside of random wall cavities in areas where the moisture testing indicated that no insulation was present.  The borescope assessment confirmed that the cavities were empty.


  1. Samples – A few 1” diameter cores were drilled through the block face in both dry and damp locations and the insulation removed.  Each sample of insulation was double bagged and sealed to prevent the ingress or egress of moisture.


Laboratory Analysis:

  1. Samples of damp insulation were weighed upon receipt, dried in an oven, reweighed, and the percentage of moisture by weight of the insulation determined (the mass of moisture per unit mass of dry material).  Samples contained up to 226% of their weight in moisture.
  2. The insulation had open cell properties based upon the rate of absorption that was observed.  Open cell, low density foam had been specified.



While damp insulation was expected to be present to some extent based on the contractor’s initial observations, the investigation revealed a finding that the owner didn’t anticipate – many of the cavities, either in total or in part, were missing insulation.  The IR thermography indicated that thermal bridging was occurring.  Since thermal bridging can be caused by damp insulation or missing insulation, the destructive moisture tests and borescopes were used to investigate the walls further.  It was estimated that insulation was missing in the upper ½ to ¼ of approximately 25% of the wall cavities up to the bond beam.  In areas of thermal bridging where insulation was present, the insulation was damp.  In areas where thermal bridging was not visible, the insulation was dry.  Where the insulation was damp, the moisture content was extremely high as determined by laboratory testing, and because paint is present on both the interior and exterior sides of the walls, there is no opportunity for it to dry.


Determining the source of the moisture was not part of the scope of services, but it is not uncommon to find both missing and damp in-fill insulation in single-wythe CMU construction.  Common causes of damp insulation range from deficiencies in roofing, flashing, and sealants; poor wind-driven rain resistance of the exterior coating; cracks in the mortar and block; and air infiltration/exfiltration leading to condensation in un-insulated block that runs down the cavity to dampen the insulation beneath.


Pinpoint Rusting of a New Bridge Coating System

Problem: Pinpoint Rusting of a New Bridge Coating System


The existing paint system on a bridge over a fresh water lake was removed by abrasive blast cleaning to SSPC-SP10, Near White.  The existing paint contained lead, so surface preparation was performed in an SSPC-Guide 6 Class 1A containment.  Recycled steel grit abrasive was used. The new system was epoxy zinc/epoxy/urethane, applied within the same containment.  An inspection was made 11 months after completion of the work.  Corrosion of a few edges and crevices was present together with patches of deterioration ranging from a “ dusting of pinpoint rusting to discrete nodules of rust.   The crevices and edges were not part of the examination because all parties agreed that the rusting was due to insufficient coverage of the coating and the contractor agreed to make appropriate repairs.  The investigation was limited to the random patches of corrosion.  The Owner was concerned that the rusting might be the early stages of widespread failure.

The following is a summary of the types of testing and analysis undertaken by KTA to examine problems of this nature.

NOTE: The conclusions provided below cannot be interpreted as being relevant to other failures, even if they are similar in appearance. Likewise, the tests identified below may or may not be relevant or adequate for the investigation of other failures.

Field Sampling/Analysis:

Following are the results of the observations and tests conducted in the field to begin determining the cause of the corrosion:

  1. Appearance – When viewed from a distance, the coating on the majority of the bridge was performing well with the exception of very visible failures at some edges and crevices, and random discrete patches of pinpoint rusting.  The visible failures combined covered less than 0.5% of the surface.  However, closer examination revealed that a “dusting” of very light pinpoint rusting was also present on the surface.  There was no pattern to the rusting.
  2. Microscopic Examination – The rusting was examined microscopically up to 30X.  The discrete nodules were removed by careful knife probing.   The nodules appeared to have formed within the intermediate or finish coat.  When removed, the primer beneath the nodules appeared to be intact.  The dusting of rust appeared to be confined to the surface of the finish.
  3. Substrate Condition – Ribbons of coating were removed to the steel in both rusting and non-rusting areas by making very close (1/16” or less) parallel scribes to the substrate, dislodging the coating between them.   In all cases, the substrate had been blast cleaned with a dense surface profile.  There was no evidence of corrosion on the surface.
  4. Coating thickness – Total coating thickness was measured using a Type 2 magnetic dry film thickness gage.  The total thickness ranged from 8 to 15 mils, with no correlation between thickness and corrosion.     Tooke gage measurements showed 3 coats to be present, with the thicknesses in compliance with the specification requirements. There was no correlation between the thickness of individual coats and corrosion.
  5. Adhesion – Adhesion tests were conducted according to ASTM D3359 Method A (X-cut with tape) and ASTM D6677 (X-cut followed by knife probing).  The results were excellent in all cases, including areas that exhibited corrosion.
  6. Samples – Representative samples of coating and corrosion product were removed from the bridge for laboratory analysis.

Laboratory Analysis:

  1. The thickness of the coating on the samples was measured with a digital microscope at 200x magnification.  The laboratory measurements identified three coats of paint with a dry film thicknesses range consistent with that obtained in the field (compliant with the specification).
  2. Microscopic examination of the discrete particles of corrosion at 50-200X magnification showed them to be remnants of steel abrasive.
  3. Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy confirmed that the corrosion was structurally and elementally consistent with steel abrasive remnants.


The discrete particles of corrosion and dusting of corrosion are due to remnants of the steel abrasive used for blast cleaning, rather than corrosion of the steel.  The abrasive became embedded in the intermediate and finish coats before the coating had dried.  The source of the abrasive is not known conclusively, but it is likely due to inadequate cleaning of the containment prior to painting.  Movement of scaffolding or flapping of the containment (physically or by wind), likely dislodged pockets of abrasive and metallic dust which landed on the intermediate and finish coats before they had dried.

The coating can be repaired and overcoated in localized areas, rather than removed and replaced.