Quality Control Saves Time and Money on Low-Slope Roof Jobs


Nothing is more frustrating in a commercial roofing project than to complete an installation, pack up your materials, and return to a previous worksite post-inspection to correct faulty workmanship. Mistakes can cost contractors big. In addition to a loss in billable hours and reputation, callbacks can result in fines when dealing with time-sensitive commercial projects like medical and educational facilities.

Establishing in-process quality control programs are vital for making commercial roofing projects efficient and profitable. That was one of the major takeaways from a recent low-slope labor study commissioned by CertainTeed and conducted by Trinity | ERD, a consulting firm that provides forensic analysis, testing and design services to the roofing and waterproofing industries. A lack of quality control programs among construction companies was identified as a major drain on resources and time during low-slope projects.

Even with the fastest products and the most skilled workers, a lack of quality control can slow work progress to a crawl and make projects more trouble than they are worth. Here are some insights from the study that can help commercial contractors improve their workmanship and speed, all while realizing savings.

Managing Your Tools and Accessories

The efficient use of tools and accessories has a direct impact on installation times. Improper tool maintenance, insufficient power sources, and tools not set to the proper settings can lead to lost profits. CertainTeed’s labor study identified the following as common items contractors should pay attention to in order to achieve time and labor savings.

  • Multi-torch cart (modified bitumen applicator) – In APP (atactic polypropylene) installations, how well your torch cart is maintained can have a huge impact on the speed and consistency of your installations. According to CertainTeed’s research, installing a bituminous cap membrane with a torch cart is 86 percent more efficient than hand-held torch application. Proper materials staging is also key. Having a team prepare rolls (i.e., open, relax, re-roll and set the rolls on the cart), stage propane canisters, and properly adjust carts prior to work ensures materials go down as intended in a timely fashion. It’s also important to have a crew member on the roof who can repair or adjust the cart while the job is in progress—otherwise contractors may find themselves on the roof with nothing to do if something breaks down.
  • Automated Screw and Plate Installers – Machines that automate screw and plate installation offer a significant time advantage. These machines, however, can break or jam, so it is important to have a knowledgeable mechanic or crew member on the roof with spare parts ready. Don’t rely solely on automatic machines, as having no alternative method to install screws and plates can result in lengthy downtimes.
  • Automatic Welders – For single-ply, TPO/PVC (thermoplastic polyolefin/polyvinyl chloride)  membrane applications, automatic welders are essential. Poorly maintained welders, inconsistent power, and damaged parts (nozzles and silicone wheels) can decrease productivity and hinder the quality of an application. Keeping a maintenance schedule will help prevent automatic welders from becoming a disadvantage in the field.
  • Reliance Power Sources – Rooftop power typically comes from a rooftop generator or by tapping into the building’s power. Rooftop generators can reduce power cord lengths and voltage drops. A sophisticated power management system with built-in ground fault interrupters and a single heavy duty power line tapped into house power offers better results than a maze of overlapping power cords plugged into multiple outlets. Doing the latter typically results in tripped breakers and overloaded circuits. Resetting breakers constantly wastes valuable labor time.
  • Blowers – Stationary blowers are a big help on roofs to clean surfaces and move large sections of membrane on a cushion of air. Make sure they are well-maintained and replaced when necessary.
  • Power Tools and Bit Holders – Using hand-held screw guns is only efficient when they are properly set up with the correct accessories. Worn or improperly sized power bits dramatically slow screw installation. Improper tool adjustments also result in over- and under-driven screws—a common cause of leaks. Maintaining proper power bits can help save projects from catastrophic failure later on.

Make a List, Check it Twice

Making a quality control checklist and applying it consistently will help keep your projects on-time and on-budget. Salt Lake City, Utah-based roofing company Brady Roofing recommends the following checklist for all low-slope jobs:

  • Introduce yourself. Knock on the door at the start of the project and introduce yourself as the project foreman.
  • Prepare the grounds. Walk through the grounds at the perimeter of the roof to make sure there are no breakable tables, vases, equipment, etc., that are in line of falling objects and debris from the roof. Proceed to tarp the ground in areas where debris will likely come off the roof. Plants and shrubs should be protected in addition to the tarps where necessary.
  • Prepare the deck properly for dry-in material. Make sure all nails are removed and new nails are installed flush with the deck.
  • Lock the drip edge, but not too tight in corners. Miter the hip corners (unscratched).
  • For TPO jobs, clad the drip edge. Color the TPO to match the fascia unless the customer requests otherwise. TPO membrane is to be heat-welded to the drip edge. Joint covers are to be welded to the face of the drip edge. Fasteners should be installed every 12 inches with barbed plates.
  • Seams should be heat-welded. Use a high-speed automatic welder when possible and a handgun for details. All seams should have a minimum one-inch weld. Patches will be placed and welded over areas with less than one inch.
  • Apply straight cuts. Use chalk lines if necessary for straight lines.
  • Side laps should have no less than four inches of overlap.
  • Valleys should be secured with fasteners and plates.
  • Term bar and/or counter flashing should be used against exposed brick substrates.
  • Pipe flashings should be probed and fixed at seams.
  • The swamp cooler should have new flashings tight against the ducting (not just against the base skirt).
  • Don’t forget scuppers. TPO-clad metal should be used at the scuppers or the draining system.
  • Install proper attic ventilation per National Roofing Contractors Association guidelines (applies only to roofs with a 2:12 pitch or greater).
  • Satellite dishes should be removed and sealed under flashing, rather than going around the base of the dish with tar. Suggest to the building owner that the dish be relocated to a surface other than the roof membrane.
  • Clean the grounds daily with a magnet (and lawn rake if necessary).
  • Probe and fix all seams to ensure proper seals.
  • Replace all items removed for safe keeping to their original locations at the end of the job.
  • Do a final walk through with the building owners. Present the warranty, lien waiver, invoice, and answer any questions the client may have.

For more labor-saving tips, visit www.certainteed.com/laborstudy.

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