Please Make Your Selections Below

Home

Expert Witness and Testimony Services

Product Liability

Construction Accidents

Industrial Accidents

Ladders and Scaffolding

Structural Investigation

Testing Services

Roofing Systems Testing

Fiberglass and Plastics Testing

Material Failure Analysis

References

Other Links

Roofing Materials

Need for Testing

Whenever a roofing consultant is asked to inspect a roof to either determine its current condition or to investigate a potential problem, it is vital that this roofing consultant know the material properties of the roofing system. The actual roof can only be accurately determined by testing. EF&T has provided complete laboratory "autopsies" to roofing consultants for over 25 years in the areas of single ply membrane, built up roofs (BUR) and modified roof systems.

(Click for more information)

Single Ply Systems
BUR and Modified Systems
List of Roofing Papers by EF&T

For immediate assistance, please call us toll-free at
1-800-535-6640
or
Email us at info@engineeringforensics.com

Selected Roofing Tests
for
Single Ply Membranes

(Click for more information)

D297, Specific Gravity
D412, Tensile Strength & Elongation
D471, Rubber Property, Effect of Liquids
D751, (Section 9) Sheet Thickness
D624, Tear Strength
D1203, Volatile Loss
D1204, Dimensional Stability
D1876, T-Peel
D2136, Low Temperature Bend
D2240, Durometer Hardness
D5602, Puncture Resistance
E96, Permeability (Desiccant Method)

D297 - Specific Gravity

Purpose:

The purpose of this test is to determine the specific gravity of the material and compare the results to the manufacturer's specifications.

Value to Consultant:

The value of this test is two-fold. Firstly, it provides an indication of any changes such as a loss in plasticizer, and secondly, it may help in material identification (or in some cases actually rule out a specific membrane).

Ramifications:

1. If specific gravity of the specimen is lower than it should be, it indicate that the material is or has started to deteriorate. This in turn would likely would cause all strengths to be reduced and susceptible to failure.



2. Shrinkage could expose reinforcing fibers with subsequent degradation.

D412 - Tensile Strength & Elongation

Purpose:

The purpose of tensile tests is to determine the tensile strength and the percent (%) elongation which can then be compared to the manufacturer's specifications.

Value to Consultant:

The value of performing the tests is in being able to quantify any deviation or reduction in physical properties and in establishing the actual remaining strength and the ability of the membrane to elongate.

Ramifications:

1. A reduction in tensile strength will result in splitting when the membrane experiences tensile stresses above the actual tensile strength. Such tensile stresses can be induced by cold temperature contraction, the result of wind uplift forces, structural movement of the substrate, etc.



2. A reduction in the percent (%) elongation will cause splits to occur at a lower stress level due to its lowered ability to re-distribute the induced stresses.

D471 - Rubber Property, Effect of Liquids

Purpose:

The purpose of this test is to determine the comparative ability of the material to withstand the effect of liquids.

Value to Consultant:

The value of performing the test is to expose test specimens to the influence of liquids or contaminants under definite conditions of temperature and time. The resulting deterioration is determined by noting the changes in physical properties before and after immersion in the test liquid.

Ramifications:

1. If the material cannot resist the liquids as it should, it will cause physical property changes making it weaker, less able to elongate, etc.



2. The material needs to withstand liquids or contaminants as in case of water from:



1. ponding
2. poor drainage
3. snow, ice build-up
4. grease
5. industrial effluents
6. acid rain



3. Absorption may indicate that the membrane may affect dimensional stability, thickness, which may cause internal stress leading to cracking.

D751 - (Section 9) - Sheet Thickness

Purpose:

The purpose of this test is to determine the thickness of the membrane which then can be compared to the manufacturer's original specifications.

Value to Consultant:

The value of this test is in comparing the thickness of the sample to the manufacturer's specifications, to determine compliance, and to determine loss of plasticizer. The test may sometimes be used to possibly identify a manufacturer's membrane.

Ramifications:

1. A membrane that has lost thickness may be deteriorating or have a loss of plasticizer.



2. A loss of thickness can significantly change the physical property of the membrane.

D624 - Tear Resistance

Purpose:

The purpose of tear resistance is to measure the load required to tear a specimen of the membrane which has a v-notch and subjected to a tensile load.

Value to Consultant:

The value of performing this test is in being able to quantify any deviation or reduction in physical properties and in establishing the actual remaining strength.

Ramifications:

1. If the membrane's tear resistance is lower than the manufacturer's specifications, the membrane would have a greater tendency to split when the membrane is under tensile loads caused by wind, membrane shrinkage, and/or building movement.

D1203 - Volatile Loss

Purpose:

The purpose of a volatile loss test is to determine the amount of plasticizer (oils and extenders) that are still present in the specimen.

Value to Consultant:

The value of performing this test is to quantify the percentage of plasticizer lost when compared to the manufacturer's specifications.

Ramifications:

1. A loss of volatiles results in the membrane material to:



1. become brittle
2. loose its elongation capability
3. loose its elongation capability
4. lower the ultimate tensile strength
5. loss of impact strength
6. loss of flexibility
7. shrinkage with build-up of internal stress



2. The amount of loss of volatile gives a qualitative measure of age, exposure, weathering, etc.

D1204 - Dimensional Change

Purpose:

The purpose of this test is to determine the change of length and width in the material when subjected to elevated temperatures over a period of time and recorded as a percent (%) change.

Value to Consultant:

The value of performing the test of the membrane material during the manufacturing process is to give an indication of lot uniformity.

Ramifications:

1. If the material has too much strain "built into it", then when the temperature is elevated the material could relax (expand) and not be able to come back to its original form causing loose ripples which could result in wind damage.



2. Cause excess build-up forces within the roof system due to shrinkage

D1876 - Peel Resistance of Adhesives (T-Peel Test)

Purpose:

The purpose of this test is to determine the peel strength of the seam bond made with adhesive, tape, solvent, or heat laminations and to compare these results with the manufacturer's specifications.

Value to Consultant:

The value of performing the test is to determine whether or not the actual strength is equal or greater than the strength required by the membrane during its life on the roof and if it differs from manufacturer's specifications.

Ramifications:

1. If the bond is weaker than the tensile loads developed by design loads or by deterioration of the membrane, the seam will fail.



2. This is also a method to provide quality control during construction; and to measure the change in strength due to aging.

D2136 - Low Temperature Bend

Purpose:

The purpose of this test is to determine the membrane's ability to flex at low temperatures.

Value to Consultant:

The value of this test is to determine if a membrane has the ability to flex without cracking, or fracturing at a given temperature.

Ramifications:

1. A membrane that does not have the ability to flex at low temperatures may become brittle and crack or split and allow water to enter the roofing system.



2. A membrane which does not have the ability to flex will have a greater tendency to split and may not hold up well in cold temperatures and fail prematurely

D2240 - Durometer Hardness (Shore A)

Purpose:

The purpose of this test is to determine the indentation hardness of the material and to compare the test results with the manufacturer's specifications.

Value to Consultant:

The value of performing this test is in being able to quantify any deviation or reduction in the material's physical properties in comparison with the manufacturer's specifications.

Ramifications:

1. If the durometer hardness readings are higher than the original values, the material has begun to loose its plasticizer and volatiles and is getting "brittle". This will cause a loss of strength and loss of elongation.



2. If the hardness readings are lower than the original values, the material is softening and could be losing its strength due to contamination (environmental) or by a liquid substance affecting the material (oil, gas, etc.).

D5602 - Puncture Resistance

Purpose:

The purpose of this test is to determine the membrane's relative ability to resist puncture.

Value to Consultant:

The value of performing this test is to show that a membrane is pliable enough to withstand a puncture load without failure.

Ramifications:

1. If the membrane has become too brittle it may not be able to withstand an impact force (such as hail, etc.) without puncturing or fracturing the material resulting in a future vulnerability of the membrane.



2. A membrane which cannot withstand a puncture load, may crack or split and let water into the roofing system.

E96 - Permeability, Water Vapor Transmission (membranes and insulations)

Purpose:

The purpose of this test is to determine the amount of water vapor transmission through the membrane or insulation and to compare the test results to the manufacturer's specifications.

Value to Consultant:

The value of this test is to help determine what changes (if any) in the permeability of the membrane has occurred over time.

Ramifications:

1. If the roof membrane is too permeable (too much water passes as vapor by diffusion), it could be letting moisture into the roof system particularly when roof is ponded in hot weather.

BUR and Modified Membranes

(Click for more information)

Photographic Documentation
Felt Lay-Up (Felt Sequencing)
D36, Softening Point of Bitumen
Moisture Content
D2829, Asphalt Weights
D146, Fiber Weights
D2523, Tensile Strength & Elongation (Room temp or 0°F)
Induced Loads
Rigid Insulation (Compressive Strength & Moisture Content)
D2240, Durometer Hardness
D5602, Puncture Resistance
Lightweight Insulating Concrete (Compressive Strength & MoistureContent)

Photographic Documentation

Purpose:

The purpose of the photographing of the samples is to record on film the "as received" condition of the sample(s). In some cases, to document on film the test results after testing to show the condition of the specimen.

Value to Consultant:

The value to the consultant is that photographs record the as was field condition of the sample prior to sample being sectioned for testing. Photographic documentation enhances written description in his report, verifies sample tested as being from a particular roof, i.e., establishes chain of custody.

Ramifications:

1. Eliminates questions of sample originality.



2. Micro photographs can show latent defects, magnify faults, establish visual relationship to failure type.

Felt Lay-Up (Felt Sequencing)

Purpose:

The purpose of the felt sequencing is to determine the felt sequence and to show the number of plies used in the roof system and to determine the over laps.

Value to Consultant:

The value to the consultant is that it will show the type of roof system, which can be used to compare to the system specified. Also to help determine if the roof was laid properly. Felt sequencing will also show where laps are in the sample, which helps determine the locations for taking test specimens.

Ramifications:

1. Missing head laps that form focal point for splitting.



2. Relationship of laps to insulation joints to identify a potential split site.



3. Relating errors of installation with splits in membrane.

D36 Softening Point of Bitumen (Ring-and-Ball Apparatus)

Purpose:

The purpose of the softening point test is to determine the type of asphalt and to compare test results with the specifications for the particular asphalt.

Value to Consultant:

The value to the consultant is in being able to quantify any deviation or reduction in properties of the asphalt and also to verify the type of asphalt that was used.

Ramifications:

1. If the wrong type of asphalt is used or if the asphalt was oven heated, it could cause "fall back"; the asphalt could begin to flow thus destroying the integrity of the roof system by exposing the felts and/or being displaced down slope.



2. An asphalt of too high a softening point due to improper selection or aging could expose the reinforcing felts, shortening the life expectancy.

Moisture Content

Purpose:

The purpose of the moisture content test is to determine the amount of moisture present in the roofing sample in the "as received" condition.

Value to Consultant:

The value to the consultant is it shows the amount in percent (%); the amount of moisture present totally and/or the percent moisture in each ply.

Ramifications:

1. The presence of moisture will lead to roof deterioration and a weakening of tensile strength and elongation.



2. The presence of moisture could mean the system is letting in water (a leak) or that water (moisture) was allowed to be "built into" the roof system by the contractor, or water has entered from condensation from the interior.

D2829 - Asphalt Weights

Purpose:

The purpose of the asphalt weights is to determine the amount of asphalt applied overall and between each layer of felt and also the amount of aggregate applied to the top (if used).

Value to Consultant:

The value to the consultant is in being able to determine if the proper amount of asphalt was applied.

Ramifications:

1. If too much asphalt is applied:



1. there will be an added weight to the structure;
2. it would cause higher induced loads; and
3. the sequence was staged.



2. If not enough asphalt is applied:



1. increased chance of voids,
2. de-lamination of plies,
3. reduced ability to withstand leaks,
4. lower tensile strength, and
5. blistering.

D146 - Fiber Weights (of Organic or Fiberglass Roofing Felts)

Purpose:

The purpose of fiber weights is to determine the weight of the felt after de-saturation. From this, one can also determine the type of felt used and its general condition.

Value to Consultant:

The value to the consultant is being able to verify the type of felt used and its general condition.

Ramifications:

1. If the condition of the felt is found to be in poor condition; examples:



1. Tears easily;
2. Has holes due to deterioration and loss of binder;
3. Basically deteriorating by loss of binder or prolonged water saturation;
4. Tensile strengths will be reduced resulting in splitting of BUR membrane

D2523 - Tensile Strength & Elongation

Purpose:

The purpose of tensile tests is to determine the tensile strength, tensile modulus, and the percent (%) elongation before failure.

Value to Consultant:

The value to the consultant of performing the tests is in being able to quantify any deviation or reduction in physical properties and in establishing the actual remaining strength and the ability of the membrane to elongate.

Ramifications:

1. A reduction in tensile strength will result in splitting when the membrane experiences tensile stresses above the actual tensile strength. Such tensile stresses can be induced by cold temperature contraction, structural movement of the substrate, etc



2. A reduction in the percent (%) elongation will cause splits to occur at a lower stress level due to its lowered ability to redistribute the induced stresses.

Induced Loads

Purpose:

The purpose of the induced load test is to determine the amount of load the specimen induces upon its self as temperatures are lowered by contraction for new and aged specimens.

Value to Consultant:

The value to the consultant is it can determine the magnitude of the induced loads at cold temperatures. It also shows how much the roof is affected by aging and a subsequent increase in shrinkage.

Ramifications:

1. If the induced loads are greater than the tensile strengths, the roof will split or break apart which will let water in which will cause leaks and deterioration of the affected area.



2. If the induced loads are too great, the roof could "pull away" from flashings, the roof's edge, etc.

Rigid Insulation (Compressive Strength & Moisture Content)

Purpose:

The purpose of this test is to determine the moisture content of the insulation board. Also, the compressive strength can be determined and compared with manufacturer's specifications.

Value to Consultant:

The value to the consultant is being able to see from the results the percent (%) of moisture present in the insulation and be able to compare the compressive strength with manufacturer's specifications. Also, to help determine if insulation used was correct for the particular application.

Ramifications:

1. If too much moisture is present in insulation, it could reduce insulating performance. Percent water vs. R factor graphs allow economical determination of "R" factor.



2. If wet, it will increase dead load weight, which will cause the building structure to deflect more.



3. When wet and heated, the insulation could expand and buckle.



4. Wetted and subsequently dryed insulation could cause permanent shrinkage (loss of thickness to cause loosening of fasteners) and collapse, thereby causing fasteners to protrude up into roofing membrane.

Lightweight Insulating Concrete (Compressive Strength & Moisture Content)

Purpose:

The purpose of this test is to determine the compressive strength of the insulating concrete. Also, strengths can be compared between the "as received" (wet) and samples which have been dried.

Value to Consultant:

The value to the consultant is being able to determine if the strength of the insulating concrete is as strong as it should be and being able to determine the existing moisture content of the insulating concrete.

Ramifications:

1. If the insulating concrete is saturated with moisture, the compressive strength will be low.



2. If wet, it will have a lower insulation value.



3. If wet, it could transfer moisture to the roof membrane and roof components.



4. If wet, it will increase the dead load weight which will cause the building structure to deflect more.



5. Fastener holding strength reduced and fastener could corrode making membrane susceptible to wind blow off.

Selected List of Papers Published in:
International Roofing Symposiums

1991 - "Computer Simulation to Avoid Ponded Roofs"

1991 - "Nondestructive Methods for Determining the Waterproof Integrity of Roof Membrane and Seams"

1985 - "Expansion and Contraction Characteristics of Lightweight Insulating Concrete in Roofing Systems"

1981 - "The Role of Aging on the Splitting of Organic Built-Up Roofing Systems"

1981 - "The Role of Moisture on the Splitting of Built-Up Roofing Systems"

1981 - "The Role of Temperature on the Splitting of Built-Up Roofing Systems"

1977 - "Field Measurement of Asphalt Temperature During Cold Weather Construction of BUR Systems"

1977 - "Experimental Determination of Temperature Induced Loads in BUR Systems"

1977 - "Physical Properties of BUR Membranes Tested at Low Rates of Loading"

For immediate assistance, please call us toll-free at
1-800-535-6640
or
Email us at info@engineeringforensics.com