As the days get shorter, there is an urgent need to finish up roofing projects in the northern climates before winter shuts them down – not to mention the pressure to close in the building so other trades can do interior work throughout the winter.
BEFORE
Set up a meeting with the general contractor and other trades to address important issues:
- Identify the critical parts of the project, such as boiler rooms, electrical installations, etc. Prioritize each and protect them accordingly. Discuss storage and roof access.
- If the sheet metal will be installed by someone other than the roofing contractor, establish coordination so metal work is installed without delay.
- Install roof drains and hook them up to the storm sewers before roofing starts. Set roof drains into a sump (a depressed area with thinner insulation) so heat from the building will melt ice and snow at the drain first.
Determine who will decide whether to install temporary roofs. If these were not part of the original bids, prepare documents to cover the costs of installing and removing these membranes. According to McGraw-Hill’s Manual of Low Slope Roofing, temporary roofs are recommended when:
- There is mandatory in-the-dry work inside the building before the weather allows you to install a permanent roof system
- You anticipate a long stretch of rain, snow, or cold
- You need to store building materials on the roof deck
- Trades other than the roofing contractor need to conduct a large volume of work on the roof deck
Don’t try to retain a temporary roof as the base for a permanent roofing system. If you can’t install permanent roofing at the time you’re installing the temporary roof, then the temporary roof is probably not perfect. These imperfections and any damage to it may contribute to the permanent roof’s failure when it’s installed, so the NRCA recommends removing the temporary roofing before you install the permanent system.
Remember to protect all roof system materials from the weather during storage and handling. Any roofing materials that are susceptible to water damage or retaining moisture should be covered or stored in a dry location until you’re ready to install them. Likewise, identify any moisture-sensitive materials and cover them with water-resistant coverings such as tarpaulins. Make sure you protect any water-based adhesives or other water-based materials from freezing.
The puncture resistance of roof membranes can be greatly improved by specifying walkways around roof equipment, especially at roof hatches. Polyester-reinforced SBS cap sheets give outstanding puncture protection when used under sleepers on bituminous and MB roofs, according to the Canadian Roofing Contractors Association. Requiring anyone accessing the roof to sign in and document their presence also helps eliminate puncture or abuse leaks.
DURING
Install membrane roofing over clean and dry surfaces. During winter hours, there is less time to dry wet surfaces and less sunlight to melt ice and snow and evaporate surface moisture. Single-ply membranes such as PVC and TPO will resist moisture, but the speed of the hot-air welding machines used to seal the laps and flashings must be adjusted and the seam welds frequently checked to verify that the welds are perfect.
NRCA recommends that membrane roof systems not be installed if precipitation of any kind is occurring or is imminent. Roofing work can proceed when weather conditions are favorable in accordance with the manufacturer’s recommendations.
In temperatures below 40 degrees F., you may need to keep coated bituminous roll goods in heated storage until it’s time to apply them. Store them vertically on pallets – rolls stored on their sides will result in fishmouths. Cap sheets should be unrolled, cut into one-third lengths, inverted so the non-mineral surface absorbs whatever solar radiation is available (so that they will lay flat), and may require double mopping. Even cartons of asphalt should be tarped to avoid foaming in the kettle because of surface moisture.
Self-adhering membranes may require an air temperature of at least 50 degrees F. Stick to the manufacturer’s guidelines for using hot-air equipment to bond self-adhering polymer-modified bitumen material to itself or a substrate. Pressure should be applied to the sheets, especially around the seams, to ensure proper adhesion. This is typically accomplished by using a weighted roller.
At the end of the day, install the membrane temporary tie-in ply or plies, adhere them to the roof membrane, and adhere or seal them onto the top (bearing) surface of the substrate to protect the exposed ends of insulation boards applied that day. Unless water cutoffs will remain part of the finished roof assembly (in the same location where temporary tie-ins are applied), the tie-ins should be cut and adhered or removed entirely before additional insulation is applied. Pay special attention to the installation of the tie-ins on a steel deck so water doesn’t migrate in the flutes under installed roofing.
When adhering a cover board with hot asphalt, the cover board should also be back-mopped. (Both the substrate and the back of the cover board receive hot asphalt.) That extra heat helps with melding into the substrate as well as the thermal insulation or cover board.
Protected roof membrane assemblies are popular in cold regions that cope with severe winters. The good news is that it’s possible to install the roof membrane and flashings first, direct to a suitable roof deck, and then delay installing the thermal insulation, filter fabric, and ballast until the weather improves. You can also install those items even in inclement weather because moisture won’t affect extruded polystyrene, polyester fabric, or the ballast.
Reflective aluminum roof coatings should never be installed on cold membranes, because otherwise the aluminum flakes won’t “leaf” and protect the membrane. In colder climates, delay the application until spring. Water-based coatings and emulsions must not be allowed to freeze before you apply them and can’t be used in weather that’s too cold, too cloudy, or inclement.
AFTER
Generally, no one should be traipsing around on a roof in bad weather. Single-ply membrane roofs can be very slippery when wet, and the lighter colored ones will be slow to melt ice compared to a dark-colored roof. With the introduction of roof-mounted photovoltaics, there may be only narrow paths to navigate the roof, increasing the possibility of falling.
HVAC maintenance or repairing rooftop equipment may become urgent if it affects building operations. However, wind damage or falling ice may result in electrical hazards. Insulated boots, helmets, and gloves should be on hand for the emergency crews. If they head up to the roof to remove snow or ice, they should use plastic shovels and try not to damage the roof membrane.
Some thermoplastic roof membranes (PVC or TPO) can be heat welded if they do need a repair. However, the heat welders require electricity, and wet cables can be a hazard. (A trained roofing crew will bring their own electrical generators, properly grounded.) You may be better off to make emergency patches with asphalt mastic or peel-and-stick membrane, even though the mastic will contaminate the patch areas and must be cut out and replaced when the weather improves. For smooth, exposed single ply membranes, duct tape will provide temporary protection.
Torching grade of polymer-modified bitumen can be used to patch BUR and MB membranes. If you’re planning this kind of repair, send your critical personnel to a Certified Torch Applicator Training Program (CERTA) course offered by NRCA or MRCA.
Locating active roof leaks is very difficult on completed, ballasted, or vegetated roofs, as well as with PMRs. The common moisture detection devices (nuclear, capacitance, infrared, and vector) are difficult or ineffective with ballasted EPDM, so it’s worth the effort to use thicker membranes to enhance puncture resistance, plus stone mat if the ballast contains “sharps.”
One final word: Keep the drains clear of debris!
Richard (Dick) L. Fricklas was technical director emeritus of the Roofing Industry Educational Institute prior to his retirement. He is co-author of The Manual of Low Slope Roofing Systems and continues to participate in seminars for the University of Wisconsin and RCI Inc. - The Institute of Roofing, Waterproofing, and Building Envelope Professionals. His honors include the William C. Cullen Award and Walter C. Voss Award from ASTM, the J. A. Piper Award from NRCA, and the James Q. McCawley Award from the MRCA. Dick holds honorary memberships in both ASTM and RCI Inc.
Get Ready for Winter Weather
These winter weather problems won’t affect your facility if you take appropriate action.
The Basics of Roof Maintenance
Prevent problems and increase performance.
The Where, What, and Why of Thermal Insulation Systems
How to pick the best insulation for your needs.
