Commercial Roofing Damage Analysis via Solvent Extraction of Reinforcements

Commercial roof impact damage can be difficult to assess without solvent extraction and analysis of the reinforcements, commonly referred to as desaturation.  The presence of damage to the reinforcements will directly affect the repairs, which have a significant impact on the amount of the loss.  This brief article will summarize the process in which low slope commercial roofs, including built-up roof (BUR) and modified-bitumen (MB) systems, are analyzed using solvent extraction of the bitumen to expose the reinforcements.

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Vapor degreaser tank desaturating roofing core sample

Visual Inspection

The alleged impact damage is first documented by simple visual observation of the roof system and associated components and claddings to assess the presence, magnitude, direction, and extent of impact damage present on the building.  Also, the roof system and wearing surface is identified and classified as best as possible.  Single-ply systems such as EPDM, TPO, and PVC are easily distinguished from BUR and MB systems, but classifying BUR and MB systems can be challenging.  For example, a 3-ply and 4-ply BUR with a fluid-applied coating and a smooth surface MB cap sheet can appear similar, but a closer evaluation of the surface thickness and lap width can distinguish the two.  Roof cores are often necessary to identify the number of reinforcing plies, coverboard, insulation, and deck type.  Impact damage to the wearing surface can affect the ultraviolet resistance of the roof system only or it can affect the integrity of the strength of the plies and sheets via reinforcement damage.  The latter could be visually observed by punctures or fractures at unsupported areas such as base flashings, laps, and blisters, but the lack of this visual evidence requires laboratory analysis to closely examine the reinforcements for damage that may not otherwise be seen.  The presence of damage to reinforcements directly affects the repair options available, which must be determined based on an evaluation of the extent of damage observed, type and condition of the roof system, and climate.  Occasionally, a fully system replacement is warranted, but only after all other repair options have been assessed and deemed unsuitable, such as coating or re-coating, flood coating with aggregate, overlay, peeling the system but leaving the underlying components in tact, and others.

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Visual evidence of impact damage to the reinforcement via puncture at a field splice.

Solvent Extraction of Reinforcements

Core samples of the wearing surface can be obtained and analyzed via solvent extraction of the reinforcements, a process commonly referred to as desaturation.  The process utilizes specialized solvents that are able to remove the bitumen saturating the reinforcements, either fiberglass, polyester, or a combination, without actually damaging the reinforcements.  The solvent must be carefully selected and tested to ensure it does not cause damage to the specimen.  A vapor degreaser machine contains the solvent and utilizes a boiler sump, condensing coils, and a spray wand to carefully remove the bitumen from the roof samples.

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Spray wand applying solvent to roofing material

Prior to being placed in the vapor degreaser, a template is created over the roof core and the suspected impact damage locations are marked, later to be overlaid onto the reinforcements so specific areas are analyzed.

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Template and four layers of roofing after desaturation.

Once the template has been created, the sample is ready for solvent extraction of the bitumen.  It is possible to first separate the roof system layers prior to extraction or to submit the entire sample at once, depending on the goal of the analysis.  Separation of the layers can allow for visual inspection of inter-ply voids but at added time and expense.  The reinforcements, once clear of bitumen, are removed from the vapor degreaser and the template is overlaid.  The reinforcements are both visually and microscopically inspected for impact damage consisting of fractures or elongation of the reinforcement fibers.  All data obtained is carefully recorded and photo-documented for future use in the repair viability analysis and report.

Additional Roof System Analysis

In addition to solvent extraction analysis, commercial roof system damage should also be assessed via non-destructive means such as infrared thermography scanning, nuclear survey, or simple moisture scanning, in order to evaluate the presence of moisture within the system when the integrity of the wearing surface is suspected to have been breached.  Gravimetric analysis is possible to accurately quantify the extent of moisture within insulation systems as different insulations have different sensitivities to moisture.  Some insulations can tolerate a greater moisture content without significantly affecting the insulating characteristics or compressive strength so it can remain in-place.  Gravimetric analysis requires roof cores to be taken from the roof system and patched with like material, from the insulation to the roof surface, by a qualified roofing professional.  The building owner and all parties involved should understand the process of obtaining roof cores and the fact that “patches” will be present on the roof surface, which may affect new roof system warranties.  However, the benefits of such analysis of roof cores and wearing surfaces should not be lost due to apprehension regarding obtaining cores or patches, as the repair extent and methodology could well depend on the results of the analysis.

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Summary

Solvent extraction of commercial roof systems is a valuable tool to verify the presence and extent of impact damage that is not readily observable from the roof surface.  The results of the extraction are used when discussing and recommending repair options, especially if the results do not show damage to the reinforcements and repairs other than full system replacement or peeling can be viable and cost effective.

Pie has roofing experts and lab technicians available to assist on large commercial and residential roofs.   Please contact Pie Forensic Consultants at 1-866-552-5246 or at www.pieforensic.com for additional information or to schedule a roof analysis.

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