June 17, 2005 Roof Report

Case Study

1. Roof evolution: This roof appears to be in the 10 year old range. Over 330 lineal feet of Portland Type 2 cement has been poured onto the western section. Portland cement is known to solidify and effectively stop a leak for a short duration. Once the cement has released its bond with the surface, the leak may return. There is no way to determine the age of these cement drops or an expected duration of effectiveness, however, one patch appears to be as recent as 48 hours. This is a known, yet unacceptable procedure, in effecting long-term maintenance to a BUR system. A cement drop is intended to be a “temporary” solution to finding a leak. Once the specific leak has been identified, through a successful cement drop ceasing water ingress, common practice is to remove and improve upon that temporary patch. The cement patch should be replaced by one of three longer-term methods. (1) A compatible hot tar, roofing felt and gravel patch, (2) a cold process mastic and mesh patch or (3) a torch-on patch.

2. Roof evolution: This roof appears to be in the 10 year old range. Over 330 lineal feet of Portland Type 2 cement has been poured onto the western section.Portland cement is known to solidify and effectively stop a leak for a short duration. Once the cement has released its bond with the surface, the leak may return. There is no way to determine the age of these cement drops or an expected duration of effectiveness, however, one patch appears to be as recent as 48 hours. This is a known, yet unacceptable procedure, in effecting long-term maintenance to a BUR system. A cement drop is intended to be a “temporary” solution to finding a leak. Once the specific leak has been identified, through a successful cement drop ceasing water ingress, common practice is to remove and improve upon that temporary patch. The cement patch should be replaced by one of three longer-term methods. (1) A compatible hot tar, roofing felt and gravel patch, (2) a cold process mastic and mesh patch or (3) a torch-on patch.

3. The air conditioning unit appears sound and watertight. Conversely, the lead flashings providing a seal for the electrical and gas lines have had Portland cement applied suggesting potential compromise.

4. The air conditioning unit appears sound and watertight. Conversely, the lead flashings providing a seal for the electrical and gas lines have had Portland cement applied suggesting potential compromise.

5. Other independent lead flashings are unsatisfactory either by obvious holes or improper use of caps.

6. Other independent lead flashings are unsatisfactory either by obvious holes or improper use of caps.

7. The mechanical drain is sound and appears unaffected by age.

8. A sample of a Portland cement drop that is no longer effective is detailed below.

9. The primary cause of this roof’s premature deterioration is a combination of the original specifications having been proven, over time, to be less than acceptable, and that of the quality of workmanship at the time of installation, was below industry standards. The 4x8 sheets of fibreboard were universally applied on top of the EPS layer using a “mop-and-flop” technique. If full adhesion was not achieved, the fibreboard’s edges will curl up over time causing the ridging as seen below. Ridging leads to exposed and unprotected felts, which in turn results in the failure of the system.

10. The primary cause of this roof’s premature deterioration is a combination of the original specifications having been proven, over time, to be less than acceptable, and that of the quality of workmanship at the time of installation, was below industry standards. The 4x8 sheets of fibreboard were universally applied on top of the EPS layer using a “mop-and-flop” technique. If full adhesion was not achieved, the fibreboard’s edges will curl up over time causing the ridging as seen below. Ridging leads to exposed and unprotected felts, which in turn results in the failure of the system.

11. Once roofing felts have been exposed to the elements, they quickly lose their integrity and become saturated and unable to withstand moisture penetration.

Customer: Starbucks
Project Completed:n/a
Type of Roof: tar and gravel
Materials:n/a
Location: Ladner, BC

Exterior Overview:

A multi-tenant commercial building of which Starbucks Coffee occupies approximately one sixth of the structure’s floor space.

Interior Overview:

The observation of various sized watermarked ceiling stains on both drywall and drop-ceiling tiles, present evidence towards a past leak history. Floor space occupied is approximately 1200 sq. ft.

Roof Analysis:

This is a 4 ply Tar & Gravel built-up roof applied to 4×8 sheets of 7/16” thick standard High density fibreboard laid overtop of an engineered layer of Expanded Polystyrene (EPS), sloped to provide positive drainage and insulation value. The deck is that of a wooden Oriented Strand Board (OSB).

Issues of note:

See photo descriptions above

Summary, Recommendations & Personal Interpretation:

There is no conscientious reason why temporary “cement drops” have not been removed and replaced with a more effective long-term solution. Cost avoidance is my only speculation. Because of this strategy, this roof will now have an elevated expense in resurrecting the integrity as potential leaks are currently hidden by an excessive amount of cement. All cement must be removed, roofing felts inspected and repairs facilitated where needed. As a measure of comparison, a standard tar and gravel roof should last near to 15 years with a competent maintenance schedule.