Connect to your favourite weather forecaster and look for the following conditions:
Category: Roofing Product: Plastic Cement / cold applied Roof Patch
Temperature Limitations: Varies by product: Use above -5 C (+23 F) to above freezing
Rain Limitations: Varies by product: dry to underwater
Wind Limitations: n/a
Humidity Limitations: n/a
Continuous Conditions: 1 hour to form a skin
Comments: Plastic cements are for repairing asphalt roofing materials. Specific products can be applied in a range from below freezing to high temperatures and from surface dry to underwater application -- similar looking products vary greatly. Comes in liquid, liquid fibre reinforced and cartridge formats. Read the labels and choose the specific plastic cement according to the weather forecast -- or purchase the more expensive ones that work in all weather. Always scrape the surface to clean asphalt before applying. Protect any sun exposed compound from UV sunlight with aluminium paint one week after application.
Weather limitations on most renovation products can be located on the WEATHER tab above.
APPLICATION / INSTALLATION DETAILS
There are so many different plastic cements for roofing and roof patching that you should start by understanding the weather conditions you will be working in -- that way you can specifically look for ones that can work under wet conditions, or specific temperature conditions.
If it is dry and warm out, you can use any of them.
The primary error that people make, professional and DIY both, is to leave plastic cement exposed to the UV rays of the sun. Always use it in hidden places, like between two materials, or cover it with something -- even something as simple as aluminium spray paint, which will stick if you let the plastic cement cure for a week.
Exposed to the sun it may last a year before cracking and leaking. Hidden from UV rays, it will last for years.
The other common error is to imagine that a few gallons of plastic cement will replace proper roof detailing or repairs. Properly made roofs only need adhesives to hold things down against wind up-lift or to close a membrane leak -- not to waterproof the house. Overlapping shingles and overlapping flashings when properly made will run all the water off of the roof.
Plastic cements can buy you time before repairing a flashing properly but should not be considered the primary line of defence against water entry.