As we noted in a previous blog, quality control is important in making sure that the work you do meets the quality standards and expectations of your customer. Here are 10 areas on the roof to begin a quality control test protocol and tips for making sure the work is done correctly.
1. Test robot welding. Every morning, afternoon, and after any major temperature change throughout the day, the robot welder settings need to be tested. Many companies begin their robot settings at the maximum temperature of 1,148°F, but TPO does not always perform the best at the highest temperature. I like to start at 1,000°F, but this is by no means necessarily the proper temperature for all climatic conditions. Perform some practice robot welds on some scrap membrane. Change only one variable at a time, either temperature or speed. You should have around five different welds with a different variable change. After the welds have cooled, cut a one-inch strip across each weld for each change in temperature or speed. Then perform a pull test. If you get a cold weld or a partial weld, then that temperature and speed are not at the proper setting for the current climatic conditions. Once you have a full or perfect weld, set your robot to the speed and temperature you used. Now you are ready to begin welding the actual membrane on the roof.
2. Probe for voids. After the seam has cooled, come back and probe those seams. If it is a hand weld, you’ll want to have someone else probe the weld. The probe should be filed down so it isn’t sharp and cutting the membrane. If a void is found, mark it with a crayon and have someone come back and patch it with an unsupported membrane on the same day so it isn’t forgotten.
3. Improper perimeter and corner enhancement. Roof failures are most common at perimeters and corners due to lack of enhancements. It is crucial that the correct amount of additional fasteners is added to the insulation for fully adhered and RhinoBond® Roof Systems, and the proper number of perimeter sheets is used for a mechanically attached roof system. The biggest problem is the improper installation of the attachment of perimeter sheets at the corners. Fasteners need to “box” in the corner area. The following pictures show where the fasteners are required to go and which were missing on this project:
4. Base fastening at curbs and penetrations. Membranes at walls must be terminated with fasteners and plates. All penetrations that include pipes and drains must have four fasteners and plates terminating the membrane prior to flashing the penetration. This needs to be done no matter what roof system you have in order to fully adhere.
5. Drain bolts attached properly and waterblock added at drains. Tightening drain bolts is one of the most easily forgotten items on the roof. Without tightened drain bolts, water can get into the system or, as shown in the example below, can actually lift up and cause a catastrophic failure. Waterblock also needs to be added and can easily be verified by reaching into the drain.
6. Roof hatches are properly attached. Once again, this is something that can easily be forgotten and needs to be properly attached.
7. Correct material and use of primer at roof edge. When stripping-in the roof edge metal with cover tape, TPO primer needs to be used. The proper cover tape needs to be used for specific warranties. Cover tape HW (half tape on back for metal and half TPO for welding to field membrane) is allowed on all warranties, whereas the standard cover tape is only allowed on warranties up to 15 years.
8. Priming pourable sealer pocket. Pourable sealer pockets must be primed before adding pourable sealer or grout. If it is not primed, it will not stick to the TPO and could cause a leak.
9. Cleaning. Anytime welding needs to be done after the membrane has been laid out for over 24 hours, or if the membrane gets dirty, the TPO must be cleaned. Therefore, it is ideal to do all welding the same day the membrane is installed including flashing details. In our drive to get the number of squares complete in one day, flashing details are often forgotten, causing more work later on. When cleaning, there are proper steps to follow and verifying can easily be determined. Cleaning begins by using a simple household detergent such as 409, Fantastik, or Simple Green to completely wipe off the dirt and grime. Then, clean the soap film off the membrane with TPO cleaner. If the household detergent is not used first, the TPO cleaner will only spread out the dirt and grime. The picture below shows both a properly cleaned area and an improperly cleaned area. The improperly cleaned area seam will fail.
10. T-joint patches. There is always some confusion about when and where T-joint patches should be used. The first place is at any horizontal transition where the end lap of a roll intersects with the side lap of another roll, or the T-joint intersection. But this is ONLY if the membrane is 60 mil or thicker. GAF does not require it on 45 mil EverGuard® TPO or 50 mil EverGuard Extreme® TPO, but if you want to do it, it won’t hurt. The second place to use T-joint patches is wherever there is a start or stop for the robot. This will ensure there are no voids left that water can get into. Every job will have starts and stops, so they will use T-joint patches. For quality control, check wherever a side lap runs into a curb and wherever a welded lap terminates at a wall or roof edge.
Create your own quality control today!
If you do not have a QC system in place, go and create one today. If you already have one, this may be a good time to start updating before the peak roofing season begins. QC is the true mark of a professional roofing company. Ideally, no mistakes are made, but inevitably some will occur. And it’s not how good the initial work is that counts, but the final roof that matters most.