Tag Archives: masonry

Long Term Impacts of Masonry Waterproofing Sealers

Product X works as a masonry sealer, but what are the long-term ramifications of using Product X on masonry buildings? Masonry sealers come in a wide variety of formulations, but how do the various chemical compositions react to environmental conditions and what affect does the formulation have on the masonry? Most masonry waterproofing sealers specified by architects and conservators, installed by contractors, and requested by property owners are based on Silicone (═Si═ ) chemistry. There are three popular groups of silicone based materials being used as waterproofing materials: 1) silicates, 2) the group of silane, siloxane, siliconate; and 3) silicones. Silicates, similar to Product X, provide waterproofing properties by filling the pore structure of building materials with silicon dioxide (SiO2) precipitation. Common silicates are sand, Portland cement, and other natural occurring minerals. Silanes, siloxanes and siliconates provide waterproofing properties by bonding with the substrate. They are often referred to as penetrating sealers. Silicones do not form chemical bonds with the substrate. Silicones provide waterproofing properties by forming a non-bonded film. Such products are labeled as thin-film sealers.
Silicates are most commonly used in crystalline type water proofing agents for concrete. Their use is generally focused on concrete substrates. However, it is known that strongly alkaline, aqueous solutions of methyl silicates can be used to impregnate masonry. Such solutions often depend upon caustic soda for their alkalinity. Impregnation of masonry with such solutions is often disadvantageous, however, particularly due to the high alkalinity. For example, the high caustic soda content of the solution will cause a gradual removal of the organosilicon compounds from the interstices of the masonry by chemical combination with the surfaces of the masonry surrounding the interstitial voids. Moreover, the caustic soda solution reacts with carbon dioxide or other acidic components of the air which gives rise to salting out and the formation of efflorescence on the masonry. (1)

Silane, Siloxane, Silconates
Silane, siloxane, silconates are penetrating type of sealants. Their effectiveness is dependend on the porosity of the substrate and the dosage of repellant applied. Each manufacturer will have unique requirements for the application and dwell time of their sealer. Silanes and siloxanes form a chemical bond with siliceous containing materials. Silanes and siloxanes go through three reactions when applied to a masonry surface: hydroloysis, condensation, and bonding. During the condensation phase, the moisture vapor transmission rate is critical to preventing moisture accumulation behind the sealer layer.

With penetration type sealers, it is critical to the longevity of substrate (masonry) that the moisture vapor transmission of the sealer is actually known. There has been very little third party testing of vapor transmission and each product manufacturer provides varying ways of testing transmission. In addition, the active ingredient content of the sealer formulation and the coverage rate will greatly affect the moisture vapor transmission. In other words, performance in the field will vary greatly from highly controlled laboratory testing.

Siliconates are water soluble and they impart water repellency on porous surfaces. A drawback to using diluted siliconate solution for waterproofing applications is that siliconates react with carbon dioxide and carbonatious matters present in the substrate to form a water repellent, water-insoluble, white colored precipitate. This white layer may become quite visible and require aggressive removal procedures resulting in objectionable appearance or scarification of the surface during removal processes.

The effectiveness of silicone sealer depends on the alkyl group used (which directly influences its resistance to alkaline conditions), the amount of exposure to ultraviolet light and the level of moisture in the masonry when the silicone is applied. (2)

The proliferation of masonry coatings on the market, and the continued pervasive use of the coatings, requires the architect, engineer, contractor, and conservator become more knowledgeable on the wide variety of coating formulations, the continued evolution of those formulations, and understand both the right application of the product and potential detrimental effects of using the wrong product on historic substrates.

In preparation of a major renovation, Peter Meijer Architect, PC was retained in 2010 to conduct a general exterior condition assessment of Duncan Dunn Hall on the campus of Washington State University, Pullman, Washington.

Duncan Dunn was constructed in 1926 as a women’s dormitory for Washington State University, then named Washington State College. It is located in the heart of the WSU campus, facing north towards Linden Avenue. First known as the “New Dorm,” the building cost $150,000.00 to build at that time, and could house 140 students. The architect, Stanley Smith, was the head of the department of architectural engineering and was also the official University Architect.
The predominant material present on Duncan Dunn is a solid brick unit, brownish red in color, and approximately 8” x 3 7/8” x 2 3/8” in size. At the time of assessment the brick had a very prominent unsightly, white coating over 60% of the masonry facades.

WSU-PMAPDX_masonry_sealers-003Believing the white haze was a result of UV degradation of a masonry sealer, PMA conducted Reunion Internationale des Laboratoires D’essais et de Recherches sur les Materiaux et les Constructions (RILEM) tube tests of water absorption on the exterior brick on Duncan Dunn Hall. The area of brick chosen for the test was out of direct sunlight to avoid affecting the results and was conducted during dry weather. No movement of the water over a 45 minute period was recorded during the test. Masonry units, even those constructed with high quality clays under controlled firing conditions will absorb some water. The results of the field test on Duncan Dunn, along with the white surface haze, reinforced the assumption of the presence of a masonry coating.

Communication with WSU personnel and their internal research surmised that “the building may have had a sealer put on after the original construction. [WSU cannot verify the application through original records] but do know [that a sealer] was not used on a regular basis after [construction completion.] Back in the 70’s some “miracle sealer” of some sort was introduced on Campus and used at a few locations. Duncan Dunn Hall was among the buildings [receiving masonry sealers.] Today you can see the remnants of this as a white powdery surface that almost looks like efflorescence. [WSU] does not know the name of [the sealer] product.”

To confirm the presence of the sealer, PMA conducted lab testing via polarized light microscopy (PLM) episcopic microscopy, capillary fusion and Fourier-transform infrared spectroscopy (FTIR) per ASTM D1245 and E1252, respectively. FTIR indicated the material to be Poly(2-hydroxypropyl methacrylate), an initially water-miscible acrylic polymer that in these samples is at present very brittle and sloughs rather easily.Testing confirmed the presence of a “water-miscible acrylic polymer”. Due to chemical breakdown under UV, the chalky coating remaining on Duncan Dunn is no longer soluble in water.Because of the insoluble nature of the white haze, low pressure hot-water cleaning methods would not be successful. PMA recommended the Rotec Vortex cleaning system using a mirco-abrasive mixture of dolomite, water, and air. Ultimately this removal processes was successful with no damage to the masonry surface.

(1) Patent application for new formulation of sealers. (2) Types of Masonry Water Repellents, GSA web site. Information derived from ProSoCo Inc. product literature.

Written by Peter Meijer AIA, NCARB / Principal

Analyzing Historic Masonry Wall Performance

Wilmer-Davis Hall is a residential complex on the Washington State University (WSU) Pullman campus. Built in 1937 by Architect Stanly Smith, with John Maloney, the six-story structure is composed of masonry and concrete with a masonry/brick veneer in the classical and Georgian Revival architectural styles. For a recent feasibility study of the complex, PMA provided an exterior assessment and a limited moisture study utilizing Wärme Und Feuchte Instationär (WUFI), an industry standard application in predicting wall performance to determine how additional insulation may impact the existing constructions and wall performance.

The primary concerns of this analysis included increased potential for freeze thaw action and increased mold growth as a result of added insulation. When historic buildings are insulated the insulation is typically added to the interior of the structure to prevent alterations to the exterior appearance. This often causes the outer layers of the wall to be both colder and wetter as the materials are no longer warmed and dried by the interior heating system. The additional water and more extreme temperatures can result in an increase in freeze thaw action, corrosion of metal reinforcement, and/or increased mold growth.

Additionally adding insulation to a wall changes the location of the dew point within that construction (the point at which vapor in the air condenses into water). A dew point within the middle of the wall can also result in increased moisture within the wall cavity. If a wall has difficulties drying due to any of the above causes it is possible that over the course of several years the quantity of water within the wall will consistently increase. Accumulation of water will exacerbate reinforcement corrosion and mold growth and can result in increased freeze thaw action. This study focused on the following metrics to analyze proposed wall performance: quantity of water in the assembly, quantity of water in each material layer, relative humidity in layers susceptible to mold growth, and isopleths.

As in any simulation analysis a number of assumptions were made regarding the existing wall construction and the proposed design conditions. A variety of different conditions were analyzed in order to explore the range of conditions and variables. Below is a description of the inputs as well as an analysis of the results.

Four (4) proposed wall constructions were analyzed to determine how different types, quantities, and configurations of insulation would impact the existing constructions. The configurations were based on outlined solutions for meeting Washington State Energy Code (WSEC) or providing improved thermal comfort. Two of the proposed constructions meet WSEC (Option 1 and Option 2), while two of the solutions (Option A and Option B) fall short of fully meeting WSEC, but would provide improved insulation values. The options simulated included:

Base Case (Existing Conditions) (R-4.8)
3-1/2” Masonry
1” Air Gap
7-1/2” Hollow Clay Tile Back-Up Wall
1-1/2” Plaster

Option 1 (Meets WSEC) (R-15.4, continuous insulation)
3-1/2” Masonry
1” Air Gap
7-1/2” Hollow Clay Tile Back-Up Wall
1-1/2” Plaster
2” Expanded Polystyrene
Vapor Retarder (1perm)
0” Gypsum

Option 2 (Meets WSEC) (R-20.9, insulation is not continuous)
3-1/2” Masonry
1” Air Gap
7-1/2” Hollow Clay Tile Back-Up Wall
1-1/2” Plaster
3” Batt Insulation
0-1/2” Expanded Polystyrene
Vapor Retarder (1perm)
0-5/8” Gypsum

Option A (R 17.4, insulation is not continuous)
3-1/2” Masonry
1” Air Gap
7-1/2” Hollow Clay Tile Back-Up Wall
1-1/2 Plaster
2” Foamed-In-Place Polyurethane
Vapor Retarder (1perm)
0-5/8” Gypsum

Option B (R-18.4, insulation is not continuous)
3-1/2” Masonry
1” Air Gap
7-1/2” Hollow Clay Tile Back-Up Wall
1-1/2” Plaster
3-1/2” Batt Insulation
Vapor Retarder (1perm)
0-5/8” Gypsum

Materials It should be noted that no material testing was performed during this phase of the project – instead default material properties were chosen from the WUFI database. Materials used include:

  • Masonry: The material ‘Brick (Old)’ was used to simulate the existing masonry. The material is a generic historic brick material compiled from a variety of different bricks and included in the WUFI database.
  • Airspaces: All airspaces were modeled without additional moisture capacity which according to WUFI, models more realistic moisture storage in air cavities.
  • Hollow Clay Tile: The historic drawings indicate that behind the masonry is hollow clay tile. WUFI does not have a default material for hollow clay tile. Instead a masonry material ‘Red Matt Clay Brick’ was used to represent the solid portions of the clay tile. Air spaces were used to simulate the hollow portions of the tile.
  • Historic Plaster: The WUFI database does not have a default historic plaster material. The ‘Regular Lime Stucco’ material was used to simulate the existing plaster.
  • Batt Insulation: ‘Low Density Glass Fiber Batt Insulation’ was used in simulations.
  • Rigid Insulation/Expanded Polystrene: ‘Expanded Polystyrene’ was used in simulations.
  • Fomed-In-Place: ‘Sprayed Polyurethane Closed-Cell’ was used in simulations
  • Gypsum: ‘Interior Gypsum Board’ was used in simulations.

  • Weather/Interior Conditions In each simulation the model was set to mimic extreme situations to verify that the existing walls will perform in all conditions. The Spokane, Washington weather file indicates that the south elevation should have the most wind driven rain and moisture impacting the wall. Given this information the analysis used south exposure and the Spokane weather file to simulate exterior conditions. For the interior climate conditions the following profiles were used:

  • Interior temperatures ranging from 69 °F to 72 °F
  • Relative humidity ranging from 50% – 60%

  • The above values represent a relatively high moisture load which is consistent with the existing use as a residential facility.

    Water Intrusion Additionally as per ASHRAE 160 a small leak (1% of driving rain) was introduced into the exterior assembly to simulation a scenario where water was penetrating the exterior surface. This could occur at bondline failures in the mortar or penetrations through the wall assembly. The leak was placed past the masonry veneer on the face of the hollow clay tile backup wall.

    Initial Conditions Lastly the initial conditions of the materials were determined using ASHRAE 160. For existing wall materials EMC80 was used as the initial moisture content. (EMC80 is a value expressing an equilibrium of water and material masses at 80% humidity). For new components the expectation was that the materials would be installed from the interior and would remain dry during the construction process – thus EMC80 was used for new components as well.

    Four metrics were used to interpret and analyze the following WUFI results: Total Water Content/Water Content in Material Layers, Temperature, Relative Humidity, and Isopleths.

    Total-Water-Contents-WSU-Wilmer-Davis-WUFI-Report-6Total Water Content WUFI can predict the total accumulation of water over the time frame of the simulation, in this case five years. Over the course of each year a wall assembly will be wetted by the rain, and dry over the summer months. Differences in humidity and temperature between spaces may cause water condensation within the walls. If conditions do not allow condensation or other water to dry, materials may accumulate water over a period of time.

    The chart above shows how each of the different simulations performed. Note that total water content is measured per ft2 of wall. Walls that are thinner (existing construction) will inherently have less capacity to hold water. In general all of the walls performed in a similar manner – an indication that the retrofit strategies should perform in a comparable manner when compared to the existing walls. As can be seen in the chart, all of the simulations, including the base case showed some accumulation of water over the five year simulation. These results, however, do not conclusively show that the proposed walls will accumulate water. The results indicate that even the base case is accumulating water over time. During PMA’s site visit, however, the existing exterior walls appeared to be performing well – which would not be the case if they were consistently accumulating water. Additional analysis showed that the gradual accumulation of Total Water Content appears to be a result of initial instability within the wall construction that equalizes over time. A 20 year simulation showed accumulation over the first five years, after which the water content stabilizes.

    Water Content in Material Layers Each of the individual layers of material in a wall assembly have the capacity to hold and retain water. A high water content in any individual layer can indicate the potential for mold growth, the possibility for damage associated with freeze thaw, and a reduction in R-Value based on moisture content. Mold growth is possible when the moisture content is above 20% and if the material has the capacity to feed mold growth. The charts below show how each simulation performed for each layer within the wall.

    Water-Content-Materials-WSU-Wilmer-Davis-WUFI-ReportIn general most layers remained well below the 20% threshold for mold growth. The insulation layers, however, are an exception. Options 2 and B both had batt and/or foam insulation which yearly exceeded 20% water. This quantity of water is somewhat concerning for the batt insulation as it may reduce the material’s R-Value and/or contribute to mold growth depending on the composition of the material. Solutions that used foam insulation performed better than those with batt insulation.

    Temperature One common result of insulating a historic building from the interior is increased freeze thaw action. Insulation prevents the interior conditioned space from heating and drying the exterior masonry. As a result the masonry is typically saturated with more water and exposed to colder temperatures. The analysis looked at the temperature within the middle of the masonry to determine how added insulation would impact the material. A chart comparing the base case to the four options for insulation is located below. As can be seen the brick temperature remains consistent with the base case in all retrofit options. This is an indication that the masonry may not by exposed to additional weathering as a result of added interior insulation. It should be noted that not all masonry reacts to water saturation and freezing conditions in the same manner. To further analyze the masonry’s susceptibility to freeze-thaw action lab analysis is recommended to determine material performance. If results indicate that the masonry is susceptible to freeze-thaw it will be critical to ensure new constructions do not lead to a significantly colder/wetter exterior wall.

    Relative Humidity The relative humidity of the air within the wall construction also has an impact on material longevity and mold potential. A high relative humidity in plaster or batt insulation layers may indicate mold growth, while a high relative humidity in layers with reinforcement may indicate the potential for corrosion. A constant and high relative humidity (above 80%) indicates the potential for mold growth. The charts to the right focus on several susceptible layers, the existing plaster, batt insulation, and gypsum board. In general the majority of the layers susceptible to mold remained below 80% relative humidity, or consistently dropped below 80% relative humidity allowing the material to periodically dry. An exception was the existing plaster layer. The addition of interior insulation caused the relative humidity within the layer to increase approximately 15%, from 65% (base case) to just over 80% (all options for added insulation). This spike in relative humidity is concerning and could indicate the potential for mold growth within the layer.
    Isopleths WUFI can also predict mold growth by plotting isopleths on the interior surface. The isopleths are plots of the temperature and the relative humidity for every time period calculation. When the temperature and relative humidity both exceed the limiting lines calculated by WUFI there is the potential for mold growth. The simulations indicate that there is very little potential for mold growth. All of the simulations begin above the limiting lines, but over time equalize and remain well below the threshold calculated by WUFI.
    The results described above indicate that there could be some challenges to designing an appropriate insulation system for Wilmer Davis Hall. Three of the primary concerns noted in the above analysis are: increasing total water content quantities; high quantities of water in the batt insulation layers; and consistently high relative humidity’s in the existing plaster layer.

    In general Option 1 and Option A performed better than Option 2 and Option B – primarily because they relied on only foam/rigid insulation. This resulted in no risk of mold growth within the insulation layers and no reduction of the R-Value. Concerns were still identified with both Options in terms of total water content and relative humidity in the plaster layer.

    Prior to detailing a new wall for construction additional analysis is recommended. Minor changes in material properties can have significant impacts on wall performance. The above analysis has indicated that there is a potential for mold growth, but has not confirmed its likelihood. Most of the metrics indicated no risk of mold growth – however because some of the metrics showed a potential for mold, additional analysis is recommended. Testing of the existing materials and specific data on proposed products should be used to refine this analysis and determine extent of mold growth risk.

    Written by Halla Hoffer, Associate, Architect I

    When Field Performance of Masonry Does Not Correlate with Lab Results

    First presented at RCI 2015 Symposium on Building Envelope Technology, Nashville, TN


    When it was completed, Grant High School was typical of the high schools constructed by Portland Public Schools in the pre-World War II era. In addition to being an extensible school, including educational buildings constructed between 1923 and 1970, the school was also reflective of fire-proof construction through its use of a reinforced concrete structure with brick in-fill. (Portland Public Schools, Historic Building Assessment, Entrix, October 2009)

    Over the last fifteen years, Portland Public Schools (PPS) noted an accelerated degree of masonry face spalling on the original 1923 main building and 1923 Old Gym particularly when adjacent to concentrated sources of surface water. Other areas of spalling were not as obvious including protected wall surfaces. The masonry spalling was not occurring on later additions including the north wing (circa 1925), south wing (circa 1927), and auditorium building (circa 1927). Upon closer visual examination, it was observed that individual units were failing in isolated protected areas of the wall surface. Failures in such areas could not be accounted for under direct correlation of heavy water intrusion and typical failure mechanisms.

    The failure of the brick was potentially due to a number of separate or cumulative conditions including 1) excessive water uptake by the brick; 2) sub-fluorescence expansion of salts in the masonry, 3) freeze thaw; 4) low quality of the original 1923 brick; and 5) the application of surface sealers preventing water migrating to the exterior surface.


    Field Investigation
    In order to determine if the damage to the masonry was deeper than the surface, several wall-lets, an invasive exterior wall opening, were performed confirming the assembly of a multi-wythe masonry wall constructed in a typical fully bedded bond course with interlocking headers and no cavities between the first three brick courses. Hooked shaped, 3/32” gage, steel wire masonry ties in alternating courses and approximately twelve inches (12”) on center ties were found to be in good condition with no deterioration. The absence of corrosion on the in place brick wire ties indicated that little moisture was present inside the multi-wythe wall.

    As a result of the hypothesis and field observations, it was prudent to conduct a series of lab tests to the brick, mortar, and patch materials to assist in the determination of 1) the quality of the brick; 2) the physical composition of the brick; 3) the quantity of naturally occurring compounds in the masonry and mortar, particularly salts in the masonry; and 4) the quality of the mortar. The findings would help narrow the potential cause of the spalling and lead to a more focused repair and maintenance process. Bricks were removed for testing of Initial Rate of Absorption (IRA – a test for susceptibility to water saturation) freeze thaw testing, and petrographic analysis, a way to determine the inherent properties of the clay and manufacturing process. Both pointing and bedding mortar samples, as well as, the previous patching material were removed and also tested. To rule out damage caused by maintenance procedures, faces of the brick material were sent to determine if sealants were used on the brick and, if present, determine the sealant chemical makeup. The presence of a surface coating may lead to retention of water within the brick and thus prevent natural capillary flow, natural drying, and water evaporation.


    Testing & Results
    Samples sent to the lab for coating assessment were analyzed via episcopic light microscopy, and Fourier- Transform Infrared Spectroscopy (FTIR) per ASTM D1245 and ASTM E1252. The results found no hydrocarbon or organic formulations used on the surface of the brick refuting the hypothesis of a surface sealer.

    Following modified ASTM standards, a 24-hr immersion and 5-hr boil absorption test on the brick were performed. The brick have a very low percent of total absorption at 9.5% for the 5-hr boil and 7.5% for the 24-hr test. The maximum saturation coefficient is 0.79 which is 0.01 over the maximum requirements for Severe Weathering bricks recommended for Portland climate (ASTM C216-07a Table 1). The Initial Rate of Absorption (IRA) is 5.7g/min/30in2 which equates to a very low suction brick or brick with low initial rates of absorption. The freeze thaw durability tests resulted in passing performance. All of these tests refuted the hypothesis that freezing temperatures were the cause of masonry spalling.

    A brick material analysis was performed in general conformance with ASTM C856, ASTM C1324 (masonry mortar) and included petrographic analysis, chemical analyses, x-ray diffraction and thermogravimetric analysis. Samples were analyzed under a polarized light microscope for information such as materials ratio and presence or absence of different deterioration mechanisms. These tests were used to assess the overall quality of material, presence of inherent salts, excessive retempering, cracking, ettringite formation, and potential alkali‐silica reactivity.


    The Petrographic Characterization resulted in the most unusual findings and the most relevant results related to the observed failures. The polarized light microscope indicated carbonate based salt crystals seeping into the masonry from the mortar. No sulfate based salts, typically associated with the clays used for making brick, were present. Furthermore the inherent properties of the brick showed very small rounded voids and interconnected planer voids. Planner voids result from poor compaction during the raw clay extrusion process prior to firing.

    Performance of brick in the field is a result of both material properties and resistance to micro-climates within the brick’s capillary void structure which cannot be repeated in the lab. Studies have shown a connection between small voids in the material property and susceptibility to longer water retention near the surface. With natural absorption properties, the brick is taking in a small quantity of water in very small pores. 24-hour immersion results are very low (7.5%). Publication of more in-depth studies correlates maximum saturation values for brick with low 24-hour immersion values. The effect of low immersion values and small quantities of absorbed water may increase the susceptibility in brick with small pore structure to freeze thaw failure.

    The presence of salt migration out of the mortar and into the brick, plus small pore structure and low immersion values, combining with a cleavage plane resulting from manufacturing are contributing to the Grant High School brick spalls. Brick with smaller pores are less capable of absorbing the expansive forces of freezing water and drying salts. Interlaced pores creating linear plains parallel with the face of the brick create stress failure points resulting in surface spalling. Since the characteristics of the brick resulted from the firing and manufacturing process, the brick will remain susceptible to the failure mechanisms.

    Field observations of masonry failures generally correspond with known failure mechanisms. However, it is not unusual that further analysis is necessary to confirm in-field performance and that typical laboratory test results are in conflict with in-situ performance.

    The best corrective action is to minimize the amount of surface water and proper mortar joints and mortar composition. Additional spalls are likely to occur in the future due to the accumulation of expansive forces over a long period of time. Replacement of the spalled bricks is recommended over further patching. Leaving spalled brick in place will continue to worsen the condition over time and affect adjacent brick.


    Written by Peter Meijer, AIA, NCARB, Principal

    Assessing Union Station to be Part of Our Future

    Portland’s Union Station is the only major railroad station built in Oregon, and one of the oldest major extant passenger terminals on the West Coast. From its inception, Union Station has functioned as a major transportation link to Portland and the west coast, with a continued vital role to play in future rail and multimodal transportation planning.
    A Sense of Place
    Critical to adapting Union Station, and other historic structures, for current and future use is to thoroughly understand key elements and components that convey the sense of place and rich history of the structure. A deeper understanding enables informed decisions to be made about the potential of key characteristics to remain for future generations. Union Station was constructed between 1892 and 1894 and was designed by Van Brunt & Howe architects in the Queen Anne style with Romanesque detail. From 1927 thru 1930, the Main Concourse was modernized by Portland’s internationally known architect, Pietro Belluschi, to reflect the streamline era of rail technology. Like the original 1892 elements, the Belluschi modernization’s are equally important stories to tell.

    Creating a graphic document annotating “changes over time” is an essential tool for evaluating how Union Station has adapted to improvements in rail technology, fluctuations in passenger volume, cultural shifts regarding train travel, as well as modifications to specific architectural elements that impact the historic integrity and interpretation of original design intent.
    Methodology for Assessment
    Our method of developing the graphic drawing is to compare historic floor plans and historic photographs to current plans and images through a process of layering plans from different eras over one another and drawing the altered, or missing, elements (e.g. walls, furniture, spaces, etc.) in different colors. This methodology provides an easily interpreted floor plan. The use of color enhances the image and creates a visual record of both changes and original historic fabric. In reading the graphic drawing, it becomes readily discernible that changes include: wood floors replaced with concrete and new floors added; openings in the main concourse were moved and enlarged; the women’s waiting room and toilet were removed to widen the south hall, the stairs were renovated, and a new baggage counter was constructed. The covered concourse was glassed in and a section was made into the First Class Lounge, which remains today. And in the 1940s, a nursery, or crying, room was added.
    What is fascinating about the history of a building like Union Station, is that the rail lines and street patterns are also integrated with the function and use of the structure and have changed over time as well. The construction of Union Station came soon after Portland was fully connected by rail in 1883 to California, Montana, and rail lines running to the East Coast across the U.S. The Spokane-Portland-Seattle rail connection was finished in 1908. In 1922, Union Station became accessible to all major passenger railroads operating through Portland.

    When originally constructed, six passenger car rail lines approached the rear of Union Station. The waiting platform consisted of planks on dirt with no canopy. The block across from Union Station consisted of a small restaurant, bar, other stores, and stables. A five foot iron fence bordered a large lawn and sidewalk to the south and west of the station. The High Shed, a large two-story metal shed was the first canopy built to cover the passenger platforms and extended perpendicular to the station. Under this High Shed, two smaller scale platform canopies were erected paralleling the tracks. A mail canopy was built at the north end of the building in 1915.

    By 1920, the block across from Union Station’s main entrance had been converted to parking to relieve congestion. As automobile use increased throughout the city, parking configurations were constantly changing over the years. By 1923, an elevated walkway was built to connect the Broadway Bridge to the main entrance.

    With the introduction of larger diesel locomotives and potential for high speed rail along the northwest corridor, the track, platforms, and canopies have had to be modified. Safety and accessibility have also driven the need for changes and modernization. Documenting these alterations with graphics, provides a foundation from which to advocate for further refinement while recognizing historic precedent and protection of historic elements.


    Written by Peter Meijer, AIA,NCARB, Principal

    PMA is part of the DOWA-IBI Group team for this exciting PDC Union Station Renovation Project.

    Masonry Sealers and Historic Exteriors

    masonry-test-pmapdxAre masonry sealers necessary on historic multi-wythe exterior walls? In general, likely not. Traditional exterior mass unit masonry walls, 3 to 4 wythes thick, leak. But rarely does the amount of water intrusion cause damage to the masonry, the masonry ties, or the interior finishes. Why wouldn’t a sealer be effective for these older walls?

    Traditional means and methods of construction multi-wythe walls consist of course work bonded and tied together with header courses, row-lock courses, hidden headers, and set in full beds and back beds of mortar. There is no direct pathway for water intrusion following the mortar beds. And most sealers do not bridge bond line cracks between the masonry unit and mortar bed.

    brick-test-pmapdxThe porosity and absorption rates of older masonry are often exaggerated because of the brick appearance. Many older masonry units show the results of imperfect firing techniques. It is not unusual to see older masonry with vertical and horizontal cracks due to low firing temperatures or impurities in the original clay mix. The surface cracks may lead to higher rates of absorption around the crack but rarely increase the overall absorption or alter the overall characteristics of the masonry. Masonry sealers will not bridge these firing cracks.masonry-water-test-pmapdx

    If older walls exhibit a level of moisture intrusion, the drying dynamics have traditionally been from warm interior side and evaporation towards the exterior. Interior insulation techniques will result in a colder exterior wall that will stay wetter longer. Masonry sealers can impede the natural drying process and movement of water towards the exterior. Vapor permeable “breathable” sealers limit the outward movement of water by natural capillary action impeding the drying dynamics. The major concern with applying sealers to masonry is related to drying.

    The Brick Industry Association, Technical Note No. 6A states: “Application of a water repellent coating is not necessary to achieve water resistance in brickwork subjected to normal exposures where proper material selection, detailing, construction and maintenance have been executed.” BIA goes further: “Application is not recommended on newly constructed brick veneer or cavity walls…” There is little to no research showing the effectiveness of sealers on reducing water intrusion in masonry walls. Sealers primarily reduce the initial rate of absorption at the brick surface. Sealers also cannot change water intrusion due to poor construction techniques. Wind driven rain is rarely impeded by sealer applications. “the use of water-repellent coatings to eliminate water penetration in a wall with existing defects can be futile.”

    WSU-DD-hall-building-envelope-pmapdxTo control water intrusion and to increase performance of a masonry wall, it is much more effective to maintain mortar joints through re-pointing process, assure that mortar joints have no voids, replace brick with spalled faces, replace brick that are cracked the full depth, and repair bond line failures. The use of masonry sealers should be based on known research and field tested success and not chosen as a means to remedy poor construction methods.

    Written by Peter Meijer AIA, NCARB Principal

    How to Determine the Cause of Masonry Failures

    Visual observations are not sufficient to determine the cause of failures in masonry walls. However, visual observations, combined with technical knowledge, provide a good direction for further investigation. In the Pacific Northwest, with the predominance of rainy winter weather, the effect of moisture saturation on masonry walls is readily apparent. Moisture is the primary cause of masonry deterioration. Horizontal surfaces will accumulate organic growth, mortar and masonry surfaces show rain water runoff patterns, and any discontinuity in roof runoff systems quickly cause further deterioration to the masonry walls. Severe masonry deterioration does occur in the northwest but its occurrence is considerably less dramatic when compared to harsher winter climates in the Midwest and East. For instance, brick spalls due to freeze thaw effect are a rare occurrence in the northwest.

    Masonry-Failures-pmapdx When severe deterioration of masonry walls is not a prevalent condition, what other non-visual processes are employed to determine the cause of deterioration? Two common techniques, well known to historic preservation professionals, are non-destructive testing (NDT) and material testing in the laboratory. NDE methods include RILEM tube water absorption tests, metal detector scanning, video scopes, infra-red photography, ultra sound testing, ground penetrating radar, and in some cases, x-ray diffraction. Common laboratory testing include petrographic examination, electron microscopy, and Fourier Transform Infrared (FTIR) methods.

    Masonry-Failures-pmapdxFTIR, when combined with the diagnostic RILEM tube field test, in particular is an effective evaluation to determine if masonry sealers have been applied to a wall surface impeding the capillary evaporation of trapped water. RILEM tests also provide an observation of a masonry wall’s initial rate of absorption under wind driven rain circumstances. Petrographic analysis of both masonry and mortars determines the material composition and will identify harmful natural elements and harmful additive elements like salts.

    Masonry-Failures-pmapdxA common misconception in the northwest is that surface spalls are a result of freeze thaw cycles. Freeze thaw susceptibility can only be determined through laboratory testing. Visual observations are insufficient to conclude masonry spalls resulted from freeze thaw forces. Since freeze thaw tests are graded either pass or fail, further tests methods are typically required for additional diagnostic evaluation. More likely sources of surface spalls are hard Portland cement mortars which exceed the strength of the masonry, salts introduced into the masonry through incorrect material selection, or surface sealers impeding the evaporation of water and thus creating a saturated sub surface layer which will freeze. (It is important to distinguish that the masonry unit may not be susceptible to freeze thaw but rather the sealer creates a dam like effect inducing a layer of water subject to freezing)

    Masonry-Failures-pmapdxBy combining visual observations with NDE and lab testing, most surface masonry deterioration can be determined and thereby implement proper repair, maintenance, and protection methods.

    Written by Peter Meijer AIA, NCARB, Principal

    Horizontal Ground Motion: A Call for More Seismic Research

    There is a lack of significant research and seismic performance studies on the resiliency and inherent strength redundancy of older buildings.

    U.S. Post Office & Courthouse, 7th & Mission Streets, SF

    U.S. Post Office & Courthouse, 7th &; Mission Streets, SF

    In specific, the capacity of existing buildings to resist ground motion associated with earthquakes has not been fully developed or thoroughly researched. Based on damage from earthquakes, especially the 2010 Canterbury and 2011 Christchurch earthquakes in New Zealand, with additional seismic activity lasting nearly one year, the general thought is that older existing buildings perform poorly in response to ground motion. When analyzed further, the damage from the Christchurch earthquake was predominantly due to acceleration in a vertical direction, literally tossing buildings in to the air. The peak vertical acceleration during the Christchurch earthquake exceeded the design criteria for today’s modern buildings. Not lessening the severity of the event, nor proposing for less stringent seismic codes, the Christchurch earthquake would flatten most modern cities regardless of building age. Adequate resistance to vertical movement cannot be achieved with current engineering techniques and therefore research and performance studies regarding the resiliency of existing structures must concentrate on horizontal ground motion.

    1906 earthquake, Montgomery Street block, SF

    1906 earthquake, Montgomery Street block, SF

    Because little can be done to prevent building collapse during vertical motion, seismic strengthening techniques focusing on dampening and resisting horizontal motion are applicable to existing structures as well as new structures. However, there has not been significant studies documenting and establishing the inherent strength to resist horizontal motion due to redundancy and mass of archaic construction methodologies. Independent performance evaluations of unique structures have occurred in the United State, Italy, Mexico, the Baltic, and others regions around the world without formal comparative analysis of the results or thorough in-depth dissemination and publication of the studies. For instance, in Oregon, informal static shear testing of a circa 1925 public middle school’s interior fire block and plaster wall surprised structural engineers when the walls did not crack at the shear planes (i.e. floor and ceiling connections) and strength measurements exceeded code allowance fivefold. (2001 Portland Public Schools shear test) When calculated and tested, the ½ inch chalk boards added even more in-plane horizontal resistive strength. The result of the testing saved the school district approximately $ 1 million in seismic upgrade costs. There was no formal documentation of the result and there has been no known similar testing performed on other existing school properties.
    The seismic resistance of existing structures is affected by the structural typology, the construction materials, the varying modifications, and deterioration and decay of materials over time resulting in unique conditions that are not readily transferrable to other structures. However, sporadic investigation and research performed on existing structures and published by the international RILEM Technical Committee 20 TBS in the article “Specific recommendations for the in situ load testing of dwellings and of public and industrial building structures,” and published accounts of independent studies in journals such as the Association of Preservation Technology Bulletin offer insight into the potential redundant strength capacity of existing structures to resist horizontal ground motion.

    full scale shake tableThese studies combined with documented field assessments and field evidence of older structures surviving earthquakes and repeated ground motion disturbances over several hundred years are available in numerous communities and offer case study structures for further research. The numbers of university engineering departments with “shake tables” (e.g. Portland State University) create opportunities for joint partnership with private sector consultants, public agencies, and professional organizations to assess and analyze the unique aspects of archaic building materials and methodologies for seismic response. The collaboration between university and private cooperation for seismic research has the potential to develop a wealth of practical and applicable information. The current collaborative efforts involving energy consumption offer the model from which to base seismic research.

    A development of systematic research, publication, and dissemination of the inherent strength of existing structures to resist horizontal ground motion would benefit all communities across the globe.

    Written by Peter Meijer AIA, NCARB, Principal

    The Challenges of Assessing Structural Brick Veneer Panels

    The origin of Structural Brick Veneer Panel dates back to the early sixties when new “tensile strength intensive” exotic mortar combined with steel reinforcing to create a 4-inch thick, single wythe brick panel. Developments continued to occur throughout the 1960s and 1970s, peaking in use during the 1980s. The system was relatively expensive due to the use of the high tensile strength mortar.
    Koin Center brick pane
    Developments in both the high tensile strength mortar and the clay units continued to reduce cost and allow the use of regular reinforcing and standard mortar and grout. Newer systems and manufacturing processes accommodated both horizontal and vertical reinforcing and permitted high-lift grouting. Later advancements in the connections of the brick veneer panel system to the building frame resulted in the use of brick veneer panels system on multi-story high-rise office buildings, schools, apartment buildings, residences and many other applications throughout the United States and the Pacific Northwest.
    cracked brick_design guide
    Major Failure Mechanisms
    There are two major failure mechanisms of Structural Brick Veneer Panels: water intrusion and mortar/grout additives. Water intrusion can occur from a lack of adequate flashing at the window head and sill interface, carbonization of the mortar, and structural cracking. Brick veneer panels are commonly designed to allow for limited cracking at the horizontal bed joints at the brick to mortar interface. Masonry veneer panels leak more through the mortar and brick interface than through the masonry unit itself. If the mortar and brick interface is cracked, as is permitted under structural design calculations, water infiltration will increase. A cement based material, panel mortar will carbonize over time decreasing the protective alkalinity environment surrounding the reinforcing bar and thus increasing the potential for corrosion. The largest volume of water intrusion is typically associated with inadequate window systems that fail to keep water out of both the structural brick veneer panel and the cavity interface.
    The durability of the wall is highly influenced by the quality of the mortar joints and interior cell grout. The specification should require reconsolidation of the grout or the incorporation of additives that balance expanding, retarding, and water reducing agents to provide a slow, controlled expansion prior to the grout hardening. Mortar/grout additives, particularly those developed in the 1970s, containing vinylidene chloride can initiate and accelerate reinforcing steel corrosion under the right conditions. The composition of the mortar/grout is determined through laboratory analysis of chloride content, vinylidene chloride, and pH level.

    Repairs to structural brick veneer panels is labor intensive and may involve panel replacement, panel encapsulation, window system replacement, and/or extensive individual masonry unit repair.

    Written by Peter Meijer AIA,NCARB, Principal

    Acknowledgement: Tawresey, John G. & John M. Hochwalt, KPFF Structural Engineers, Design Guide for Structural Brick Veneer, 3rd Ed, Western State Clay Products Association