Rappel Inspections: Untraditional, Cost Effective and Time Efficient
Senior Project Engineer
An important aspect of sustaining a building for its anticipated service life is performing regular inspections of building envelope components. Ongoing assessment of the condition of the cladding provides valuable information for building owners to budget for repairs and major renovations prior to system failure.
On the Gulf Coast, the importance of regular inspection has become more evident in recent years with the impact of several hurricanes. Annual or bi-annual inspections of exterior cladding components prior to impact by a hurricane can help to distinguish between hurricane damage and previous cladding damage, as well as indicate proper due diligence by the owner regarding maintenance and upkeep of the facilities, which oftentimes voids an insurance claim. In fact, in some cases, regular inspection of building exteriors can result in a reduction of the building insurance premium.
Ideally, building envelopes should be inspected annually or bi-annually in an effort to preemptively recognize possible building envelope element failures or deterioration. Identification of envelope failures or deterioration can greatly reduce or eliminate consequential interior or exterior damages, which often result in costly repairs or sometimes catastrophic system failures. For this reason, French Engineering, Inc. (FEI) recommends regular (bi-annual) inspections of buildings. Moreover, in many instances FEI recommends rope access inspections, also known as rappel inspections, over traditional swing stage inspections. The rappel process is effective and offers many benefits.
Despite their value and potential to prevent damage, inspections (particularly on high-rise buildings) are often bypassed by building owners and managers due to the costs associated with access, review, and ultimately, repair of the building. If there is no fixed access system designed for the building, traditional swing stage inspections can be time consuming, costly and can potentially damage existing structures. However, the same process done by rappel methods is a viable option to provide lower cost, expedient initial exterior review of buildings, without the complications or interference of more traditional access methods.
The tendency to dismiss exterior reviews all together could be attributed to the pitfalls of traditional swing stage inspections. Swing stage equipment utilizes steel or aluminum frames, outrigger beams on the roof and hundreds of pounds of counterweights. These components are transferred to the roof through interior elevators and stairwells which can interrupt day-to-day operations and result in damage to interior finishes. The various components of the swing stage equipment must also be erected on the existing roof surface, necessitating temporary protection of the roof from punctures or abrasions during assembly and use.
In addition to the risk of rooftop and interior damage as a result of swing stage transportation and erection, use of the swing stage on the exterior of the building also poses an increased risk of impact damage to the cladding. This risk is amplified when installed on easily damaged cladding assemblies such as EIFS. Typically, swing stages are suspended from steel cables that, due to the added mass of the stage, can readily damage roof edges or parapets. The platforms generally rely on rubber rollers to prevent impact of the steel or aluminum platform with the building exterior.
Rappel inspections offer measureable benefits
While the swing stage roller system usually prevents unintended impact with the cladding, damage is still more likely with a swing stage than rappel techniques. Rappel is performed with a soft climbing rope in white soled tennis shoes, which limits the impact with the exterior to two points. In special circumstances stocking feet can be used to prevent marking or impact with the cladding. Additionally, rappel techniques require only a small bag of equipment transported to the roof by the inspector in a backpack. All of the equipment weighs only 75 pounds and does not include any sharp corners that risk damage to the roof.
In addition to logistical differences, one of the most advantageous aspects of rappel inspections over swing stage inspections is their relatively low cost and duration. On average, skilled and competent inspectors can complete a minimum of two to four rappel “drops” per day depending on the cladding system, height of the building, and the condition of the exterior finish. This includes set up, take down, and relocation time required to facilitate full inspections. Based on these average rates, a two-man crew can usually inspect a four sided high-rise building in one to two days performing four rappel inspections a piece (two per elevation). Conversely, more traditional swing stage access systems generally require a minimum of one day for set up and an additional day for each relocation of the equipment. As a result of the added set up and relocation time of the swing stages, a similar review of the four elevations of a high-rise building would likely require a minimum of four days and would more likely require a full week to complete.
Finally, and perhaps most importantly, rappel techniques can provide a more thorough visual analysis than traditional swing stage access in many cases. Use of rappel gear can allow the inspector more mobility laterally across the building. Once the initial few floors are traversed, the inspector is capable of swinging back and forth across the face of the cladding, covering more area than a typical 20 or 30 foot swing stage. This added mobility may allow the rappel inspection to encompass a larger percentage of the building than the swing stage in most cases.
Deciding which way to go
A common argument for the use of swings stages is that they will ultimately be required for any repairs or renovation of exterior components, and therefore should be utilized for the initial evaluation. While it is true that swing stages will likely be required for necessary repair or maintenance work, there is often a lag or delay between the initial inspection and performed repairs, when the stages would be decommissioned. There is also the fact that repair or maintenance may not be necessary at the time of the inspection or may only be necessary for certain components or areas of the building, which could be determined by the rappel process with a greatly reduced initial duration and expense.
Based on French Engineering’s experience, the benefits of regular building envelope inspections greatly offset the cost of the analysis, particularly when rappel methods are utilized. From early detection of building component failures or deterioration prior to consequential interior damage, to added information for the purposes of budgeting required repairs, the information gathered is highly useful.
So, consider these recommendations and facts as you consider building inspections, not only in relation to bi-annual cladding inspections, but also in regard to inspection of remedial work and "punch-out" inspections for new buildings. Inspection of buildings utilizing rappel methods can significantly reduce the cost associated with the initial access and inspection of high-rise buildings. Further, the rappel process is a comparatively inexpensive and thorough option for general exterior inspections, as well as regular performance surveys. These inspections can be performed on buildings as tall as 30 stories with proper equipment and conditions. Rappel techniques provide close tactile evaluation of building cladding components for condition assessment or, in some cases, structural aspects of cladding systems.
French Engineering has utilized rappel techniques for nearly 25 years in order to assess the condition of buildings throughout the United States. The company also follows American Society for Testing and Materials (ASTM) E2505 Standard Practice for Industrial Rope Access, which was approved for use in 2007.
Jeremy Bridwell, PE is a Senior Project Engineer at French Engineering, Inc. A graduate of Texas A&M University’s Civil Engineering program, his professional certifications include Certified EIFS Inspector (CEI), Level I Certified Infrared Thermographer (CIT) and Construction Document Technologist (CDT). Jeremy’s expertise includes the analysis, design, testing, and inspection of various types of roofing and cladding construction assemblies and components intended to resist moisture migration into buildings, as well as wind load resistance. He can be reached by phone at 281-440-8284 or email at firstname.lastname@example.org.