Roof inspection report (C)

Date:	August 12, 1997
Report of:	Carolina Office Supply, Inc.
Location:	1514 Grant St. Raleigh, NC
Prepared for:	Mr. Arthur Justin, Plant Engineering Dept.
Prepared by:	William A. Stanton, P.E.

The building facility that was assessed is located at 1524 Grant St. in Raleigh, North Carolina. It is a 30 to 40-year old brick structure with a low-sloped roof system. The building is in good condition overall. The roof appears to be at least 15-20 years old and is in poor condition. The area of the roof is approximately 15,000 square feet. The facility contains administrative offices and much computer equipment. Roof leaks could result in costly damage to computer equipment and interrupt UPS operations.

In recent heavy rains, the roof of the building leaked in several locations. Thirty or forty administrative and technical employees work in the facility. Most of the employees work at computer stations. The facility appears to be a communications center. Because of the type of equipment being used and the nature of the operations being conducted, it is essential that the facility have a dependable roof assembly.

The roof was temporarily patched after recent rains to stop the leaking while more permanent measures are considered. The purpose of this roof assessment is to determine the current condition of the roof membrane and flashings and the reasons that deterioration has occurred, and to prepare for reroofing if it proves necessary.

The evaluation was conducted by William Stanton and Douglas Davidson. Mr. Stanton is a professional engineer with knowledge in building inspection, structural engineering, and construction management. Mr. Davidson is a registered roof consultant with knowledge in roof inspection and roofing technology.

The evaluation was begun by interviewing several building occupants as to the location and severity of the recent leaks. Next, Mr. Davidson and Mr. Stanton went onto the roof and systematically performed a visual inspection of the condition of the built-up membrane, wall and parapet flashings, and mechanical curbs and penetrations. Measurements were taken so that an accurate roof plan could be made. The plan is used to show the location of the deficiencies and as a basis for a future roof repair design. Roof samples were taken at four locations on the roof and parapet wall to supplement information obtained from the interviews and visual survey.

Four evaluation cuts were made to identify the roof membrane and flashing components and determine the general status of the roof system. The results are as follows:

Test Cut No. 1. Test cut No. 1 is located in the center of the roof (for the location, refer to the roof plan in Appendix D and photo TC #1)). The test cut showed that the roof system is supported by a structural concrete deck that has been installed over metal forms. Two and one-half inch thick perlite-foam insulation board provides thermal insulation. The insulation board has been inverted so that the cap sheet is on top and the perlite insulation is next to the concrete deck. The insulation board is adhered to the deck with asphalt. A 3-ply fiberglass felt asphalt built-up membrane provides waterproofing. The surfacing material is 1/2-inch water-worn stone embedded in asphalt.

Test Cut No. 2. Test cut No. 2 is located on the edge of the roof in proximity to a roof drain and in an area where leaks occurred (see the roof plan and photo TC #2). The test cut results were identical to Test Cut No. 1, except that the insulation board contained moisture.

Test Cut No. 3. Test cut No. 3 is located on a raised portion of the roof in the front of the building (see the roof plan and photo TC #3). The test cut results were identical to Test Cut No. 1.

Test Cut No. 4. Test cut No. 4 was made in the membrane flashing at the parapet wall (see the roof plan and photo TC #4). The roofing felts extend up the parapet wall to a point just above the cant strip. A layer of reinforced membrane flashing has been installed from the toe of the cant strip to half way up the parapet wall. The flashing is mechanically fastened to the wall with 1-inch capped nails. The joint between the membrane flashing and parapet wall is protected with finishing felts embedded in roofing cement. The felts extend up to the concrete coping. A lab analysis of the reinforced membrane flashing and finishing felts indicates that these materials contain asbestos (see the P.S.I. Lab Report in Appendix B). Water droplets were observed under the membrane flashing.

Note 2 on the plan and Photo 2. A large built-up membrane overlay patch has been installed adjacent to the raised roof area in the front of the building. The patch is not watertight as leaks occurred in this area during recent rains.

Note 3 and Photo 3. Recent water entry occurred where the repair overlay has separated from the wall flashing. Fiberglass mesh reinforcement and mastic were used unsuccessfully to seal the opening.

Note 4 and Photo 4. A large blister has formed within the overlay described above. The blister is caused by moisture being trapped under the overlay.

Note 9 and Photo 9. Another section of the roof membrane that has been repaired in the recent past.

General Note. Several ponding areas were observed. The locations of the ponds are shown on the roof plan. It had rained the day before.

Note 1 and Photo 1. Vertical joints in the membrane flashing have been temporarily repaired with mastic at several locations along the parapet wall.

Note 5 and Photo 5. Mastic has been recently applied along the edge of the membrane flashing where it has pulled away from the parapet wall to prevent water entry by the windows in the break room. This is a temporary solution.

Note 8 and Photo 8. The membrane flashing at the corner of the penthouse has been repaired.

Note 10 and Photo 10. Metal counter flashing was not installed where the concrete coping meets the membrane flashing, thus making it possible for water to penetrate this joint. The sealant that has been applied to the joint is also deteriorated.

Note 15 and Photo 15. The sealant at the juncture of the metal counter flashing and sawn joint in the masonry has deteriorated. Water entry is likely.

Note 6 and Photo 6. The membrane flashing around the exhaust fan has temporarily been repaired with mastic.

Note 7 and Photo 7. The membrane flashing around the exhaust fan was repaired some time ago with bitumen. The patch is old and "alligatored".

Note 11 and Photo 11. The pitch pocket is not completely filled, thus making it possible for water to penetrate the roof membrane.

Note 12 and Photo 12. The pitch pocket has been improperly sealed with polyurethane foam. Water entry is likely.

Note 13 and Photo 13. The neoprene foam insulation around the tubing has deteriorated where the tubing enters the pitch pocket. Water can penetrate the foam insulation and cause a leak.

Note 14 and Photo 14. Wood sleepers have been used to support the mechanical units. The roof membrane is not designed to support the weight of mechanical units. Also, the area under the sleepers does not dry out readily, thus subjecting the roof membrane to premature deterioration at these locations. For these reasons, the National Roofing Contractors Association (NRCA) recommends that all mechanical equipment be supported on roof curbs.

Note 16 and Photo 16. The reinforced membrane flashing at the mechanical unit has deteriorated to the extent that the reinforcing mesh is exposed. Also, counter flashing was not properly installed under the metal base cap.

Note 17 and Photo 17. The supports for the satellite dish may eventually damage the roof membrane. The satellite dish should have a more permanent support.

Note 18 and Photo 18. Lead pipe flashing has been used where the condenser pipes and electrical conduits penetrate the masonry wall. These penetrations are not watertight.

The roof assembly has been extensively repaired. It is old and has reached the end of its useful life. The recent repairs will not last, and water entry can be expected in the near future.

Ponding was observed in several areas. Ponding is detrimental to the materials in an asphalt built-up roof system. Also, if a leak occurs where there is a pond, much water could enter the building.

The membrane flashing has pulled away from the parapet walls in many places and is susceptible to water entry. The membrane flashing contains asbestos and will require special handling and disposal, if the roof is replaced.

Several HVAC units do not have roof curbs, and mechanical penetrations have not been installed correctly and can leak. These problems should be corrected when a new roof is installed.

Because the roof is not watertight and operations being conducted at this facility are critical, we recommend that additional stopgap measures be carried out immediately to prevent near term water entry into the roof system.

The existing roof system has many significant deficiencies. Since it has reached the end of its expected life, we do not think that it is cost efficient to make major repairs to the roof. We therefore recommend that the existing roof be removed and replaced with a new roof assembly that is appropriate for the facility. A new roof system should include tapered insulation to create better drainage and eliminate the ponding water. It should also include better flashing details at the parapet walls. Most of the HVAC units will have to be raised to accommodate the new height requirements of the tapered insulation. The mechanical equipment should be reinstalled on new or modified roof curbs at this time and roof penetrations for pipes and conduits should be redone in accordance with NRCA roofing practices.

Replacement of the existing roof will entail shutting down the HVAC units for a few days so that they can be positioned on new roof curbs. Therefore, a good time to do the work is between seasons when outside temperatures are such that the building does not have high heating and cooling demands.

We estimate that the cost of demolishing the existing roof and flashings, installing a new roof system, and reinstalling the mechanical equipment, plus the cost of engineering to prepare plans and specifications and monitor the construction work will be $80,000 (see the cost estimate breakdown in Appendix C).

The observations described in the report are valid on the date of the investigation. We prepared the report for the exclusive use of Carolina Office Supply, Inc. and their successors and assignees. Criterium-Stanton Engineers does not intend any other individual or party to rely upon the report without our express written consent. If another individual or party relies on the report, they shall indemnify and hold Criterium-Stanton Engineers harmless for any damages, losses, or expenses they may incur as a result of its use.

The cost estimates are based on our general knowledge of building systems and the construction industry. When appropriate, we have relied on standard estimating sources, such as Means Building Construction Cost Data. For some items for which we have developed cost estimates, no standard guide exists. We have not obtained quotations or estimates from contractors for the work. The actual cost to remedy deficiencies that we have identified may vary significantly from estimates and quotations received from contractors.