Always nice to collaborate with others in the industry. Outstanding work by ETC’s Chief Structural Engineer, Chris Carlson, PE and Project Engineer, Luke Valentine, PE. Job well done!
On a recent project, we discovered a “scary” sight – an Exterior Insulation and Finish System (EIFS) that was not installed properly. The exposed wall revealed channelized white foam insulation, an inconsistently placed liquid waterproofing membrane applied on the sheathing, several different brands of materials, and incompatible asphaltic flashing to cover the building facade.
The manufacturer issued a warranty for a drainable system, but no weep holes were installed around the windows and doors to allow the water to drain. This cobbled together assembly is not only a problem for keeping the building watertight, but the warranty seems to be invalid.
This highlights the need for field inspections by Certified EIFS Inspectors (CEI) and installation by Certified EIFS Mechanics (CEM) and Contractors as designated by the AWCI (Association of the Wall and Ceiling Industry) to help ensure that the system is installed and performs as it was intended.
It’s hard to find a building today without concrete surfaces stained by rust. Rust stains can adversely transform the aesthetics of a beautiful building. How can rust stains be removed? Let’s find out!
Once rust staining has occurred, it is important to remove the stains without altering the color or finish texture of the concrete. Two techniques which can be implemented are dry methods (i.e. sandblasting, wire brushing, grinding, etc.) and wet methods (i.e. waterblasting, chemicals, etc.). If surface texture is not a priority, the dry methods can be a quick and cost-effective way to remove stains. If the final finish is important, as is commonly the case with architectural concrete, chemical treatments are recommended.
Mild stains usually can be removed with an oxalic acid or phosphoric acid solution, applied to a water saturated concrete surface. Deeper stains typically require a poultice, which absorbs the chemical solutions and then forms a paste over the stain. Older buildings require more attention with stain removal because the chemical treatments may remove other contaminants in the concrete, creating a lighter color than the adjacent concrete.
The rule of thumb when putting a cleaning solution on your stained carpet or clothes applies with concrete. Be sure to test different chemicals on small, inconspicuous areas to evaluate the treatment. Also, the longer you let a stain sit, the more difficult it is to remove, so seek help quickly when rust stains appear!
* Tenrils of ivy will find & enter cracks/breaks in masonry. As the tendrils grow, they can exert enough pressure to break or dislodge bricks & mortar. This is especially true for older masonry, which tends to be softer than the more modern materials. Ivy shoots can also intrude beneath and damage shingles, slates, copings and other roof components.
* Ivy shades building elements from sunlight and wind, which can retard evaporation of water from building surfaces. That can accelerate decay of wood elements and/or promote the growth of mold
* Covered surfaces cannot be easily inspected, maintained and repaired
* Ivy provides a safe harbor for insects and other vermin.
* Ivies of the type associated w/building adornment are invasive and opportunistic. They will overwhelm and displace other plantings if allowed to grow unchecked.
* While ivy may not be a suitable dressing for all buildings, the potential problems can be effectively managed in many instances. Conscientious maintenance will minimize the potential for damage. What’s more, removing established ivy from buildings can cause more problems than the ivy itself. Ivy’s attachment to surfaces is tenacious and remnants can remain visible decades after the plants are gone. The remnants are also resistant to “masonry-friendly” cleaning efforts. Aggresive cleaning can discolor and/or phyically damage building surfaces.
The bottom line is, if you love your ivy-covered walls, keep them. Just be prepared to expend the effort and money needed ot keep the plants in check and your building protected!
Cast-in-place concrete will, more often than not, crack. In a nod to that characteristic, weakened planes (control joints) are formed or cut into conventionally-reinforced concrete slabs and sidewalks to influence where cracks occur. Cracking outside of control joints can indicate shortcomings in concrete placement, finishing, and/or curing, as well as influences from without. Cracks can manifest in a number of forms, most of which are of no structural concern.
Shrinkage cracks are most common and those for which control joints are used. Excessive shrinkage cracks can be caused by high water content in the concrete mix or poor control joint layout.
Plastic-shrinkage cracks are usually shallow and occur when surface water evaporates from the surface of plastic (soft) concrete faster than bleed water from below can replace it. Accelerated evaporation can occur under conditions of low relative humidity, high heat, when wind speeds exceed 5 MPH, or a combination thereof. Plastic shrinkage cracking can be controlled by various methods, including the use of wind breaks, shading provisions, water misting, etc.
Crazing or map-cracking is characterized by interconnected shallow cracks and can be caused by the same conditions that cause simple plastic shrinkage cracks. They can also be caused by poor finishing, particularly on steel-trowel finished concrete. Over-finishing can depress large aggregate and draw excessive paste and fines to the surface. High water content and rapid curing can also produce crazing.
Durability (D)-cracking is caused by the use of porous large aggregates (usually sedimentary materials such as limestone, sandstone, dolomite, shale, etc.) in regions that experience freezing temperatures. It occurs when absorbed water freezes and the resulting expansion (ice occupies about 9% more space than liquid water) breaks the aggregate. The greatest harm is caused by freeze-thaw cycling. The mid-Atlantic region experiences temperatures near the freezing point of fresh water more frequently than most other parts of the country and therefore experiences more freeze-thaw cycles. Deicing agents (such as road salt) creates brines, which have lower freezing points and thereby further increase freeze-thaw cycles.
D-cracking usually occurs near joints and can be partial or full-depth. It will often cause severe spalling and it is considered a terminal, incurable condition.
Displaced or offset cracks are characterized by a height differential on either side of a crack. When they occur at slabs-on-grade, the cause is usually a poorly prepared or unsuitable sub-grade or displacement by tree roots. Significant displacement (one-half-inch, or greater) can present tripping hazards.
Offset cracks in elevated (bridging or cantilevered) slabs could indicate a structural instability. Embedded steel reinforcement would normally prevent displacement and its failure to do so could have serious consequences.
Spray Water Testing is often used to evaluate water leakage of buildings, especially at walls, windows or doors. Although there are many ways to determine if something is watertight, a common and effective field test incorporates two types of wet conditions that a building will encounter during a storm: surface flow and wind-driven rain.
Surface Flow refers to water that flows down the face of a wall due to gravity. This type of flow can cause leaks without the pressure difference that comes along with the wind of a storm. To simulate it, a section of wall is isolated and sprayed with a spray nozzle at flow rates specified by ASTM E2128.
To test the window/wall for wind-driven rain, a pressure chamber is used. This chamber is usually on the inside of the building and a vacuum is placed in the chamber which draws water into the building to generate “wind” (AAMA 511). A spray rack is then used to simulate rain during a storm (see AAMA 502).
These tests are generally judged to PASS or FAIL for the window and/or wall in question. However, we can make the process more diagnostic by isolating a smaller defective section of the wall. This is helpful in determining the necessary repairs because a section of the wall, or a joint of a window may be all that needs to be repaired or replaced instead of the entire wall/window.
A recent ETC investigation of a water leak in an office space utilized a less involved test in which a garden hose and nozzle were used to systemically spray different potential leak areas until the location of the water entry point was discovered. By starting at the lowest elevation and working up, you can eliminate uncertainty about where the leak really is.
Joint sealants (caulks) are often used as a quick fix to address a problem leak, but proper attention to material selection and the joint onto which it is applied can make the difference between a long-term repair and a recurring leak. See our BLOG entry on proper sealant joint preparation, design, and application http://blog.etc-web.com/?p=854.
The most widely used commercial-grade building sealants are made of either silicone or urethane. Other materials regularly enter the marketplace, many of which are specialty products for unusual/unconventional uses. Acrylic terpolymers comprise another family of sealants (and will be a topic for a future blog entry), but silicones and urethanes are mainstays in the construction trades.
Silicones tend to be longer lasting, are resistant to ultraviolet (UV) degradation, and most commonly used on non-porous substrates like metals, window-glazing and certain masonry projects. Paint will not adhere to silicone. Urethanes are normally less expensive and are paintable . They are often used on porous or natural materials like wood, masonry, concrete, and stone repair projects.
Sealants come in a wide range of colors, single and multi-component formulations, and non-sag or self-leveling viscosities. They’re also classified by elongation characteristics. For example, a rating of 50% means that the sealant in a half-inch-wide joint can stretch or compress up to one-quarter of an inch without tearing. There is no single sealant that’s suitable for every application and product selection is key to performance.
Surface preparation is essential to achieving a long lasting bond. Many sealant manufacturers require application of a designated primer to the substrate. Pull tests should be performed on a section of cured sealant to ensure adequate adhesion. In a standard pull test, the sealant should tear before it debonds from the substrate.
Silicone and urethane sealants do not stick to each other and should never be used where such a bond would be necessary to performance. When replacing sealants in a joint, the old materials must be completely removed.
Lastly, always tool the sealant into the joint. This not only imparts a finished appearance, it helps achieve a better bond to the substrate
Alfred Hitchcock had bird issues (especially seagulls), but in the Baltimore-Washington area, the most common pest birds are pigeons, house sparrows, and starlings. These birds are undesirable if they land, roost, and nest on or in our buildings because they bring unwanted noise, odor, and often disease. Plus, no one likes their deck, patio, lawn furniture, or other belongings adorned with bird droppings.
If you’ve ever tried getting rid of pest birds, you probably know that they annoyingly adapt to many control methods and won’t go away without a fight. After all, they’re called “pests” for a reason. So how do you win this battle and get them to leave for good? You have to think like the bird. Birds seek flat, unobstructed roosting surfaces and they are looking for food. If you take these two things away, they’ll find somewhere else to go.
To reduce or eliminate surfaces on which pest birds roost (i.e. ledges, railings, parapets, awnings, etc.) you should consider installing one or more physical barriers, which typically include spikes (plastic or metal), netting, and electric barriers. Physical barriers are humane, eco-friendly and cost-effective solutions that have high success rates. Spikes and netting are inexpensive and easy to install, but are best suited for hidden areas or where building aesthetics is not a priority. Wires and electric barriers (low-voltage, non-lethal) are less obtrusive and often virtually invisible.
Another great way to make flat roosting surfaces unavailable is to cover them with wood or metal sheathing at a 45° or steeper slope. If you are considering a roof or façade repair/replacement project, this would be the perfect time to implement these methods.
Other bird control systems like sound, traps, aversion chemicals and killing are inhumane, expensive, temporary, and/or ineffective options. We and the Humane Society do not recommend them. As for plastic owls and hawks, they only work on the stupid birds. Savvy city birds aren’t fooled.
The last thing to do to keep birds away is limit availability to food. Implementing better trash management and asking residents to not feed them are two ways to encourage birds to inhabit other areas.
Since every building has its own unique roosting sites and bird access, there is no “one size fits all” bird control option. Be sure to have a qualified professional discuss with you which options are the most appropriate for your building and goals
Three-dimensional Ground Penetrating Radar (3D GPR) allows us to peer inside visually impenetrable building elements. We most often use it locate embedded steel reinforcement,tendons, pipes etc., in concrete slabs. There are other technologies that can perform such tasks, but they have a number of shortcomings.
1. Radiography can produce reliable, high-resolution images, but the process requires a potentially hazardous radioactive source and access to both sides of the scanned item. It’s also tedious and time consuming.
2. Magnetometers can detect ferrous metal (iron and steel), but cannot determine depth or dimensions. Deeply embedded materials can be elusive to most hand-held magnetometers and non-ferrous materials (aluminum, plastic, copper, etc.) are undetectable.
3. Two-dimensional GPR will locate embedded items and gross anomalies in the scanned materials, but depth cannot be accurately determined. It also produces a lower resolution image compared to 3D.
The system we use can scan extremely dense materials (such as concrete) to depths of up to 20 inches in any plane. The three-dimensional aspect reliably depicts the scanned items in context. Please do not hesitate to ask us for a free demonstration of our 3D GPR.
Cantilever balconies are commonly seen protruding from the façade of condominiums and apartments. However, this arrangement can lead to problems arising from heat transfer and condensation, resulting in mold growth.
Typically, steel framed cantilever balconies have beams that extend into the building and connect to the structure. Concrete balconies are usually cast integrally with the rest of the floor. During winter months, the exposed balcony structure becomes cold and when it meets the warm building interior, typically near a sliding glass door, thermal transfer increases, as does the possibility for condensation and mold growth. Building owners should be aware of this possibility and watch for condensation forming in the area under the carpet or wood flooring, near the balcony.
Fortunately, for new buildings with cantilever balconies, products are now being produced to prevent condensation and mold by inserting a thermal break (insulation) between the exterior and interior portions of these structures. These new balcony structural inserts can carry significant weight, while preventing interior heat transfer. The most common materials used for these products are stainless steel and fiberglass reinforced laminate composites. Although these are new products, they appear promising.