There is a lot to know about flat roof coatings, as there are many different types and products for upkeep. A flat roof is an economical approach to roofing that can have numerous upkeep issues that you should consider before installing. Unlike the pitched roof, water drainage, heat and cold expansion and solar degredation are more of an issue. Because of this, choosing the right flat roof coating is important if you are redoing a roof of this type or adding one to your home, garage or carport.
Tar and Gravel Coating
Flat roofs traditionally had a coating of tar and gravel. These were very sturdy and tar and gravel would be added on top over the years to keep it waterproof and in good shape. The problem with this type of roof is that with each layer the roof increased in weight and it could cause sagging of the roofing structure over time. Another problem is tar is a known carcinogen and it is almost never used anymore. So if you have this type of roof and it is leaking, chances are it will need replacement.
Rubber and Acrylic Sheetings and Coatings
Modern flat roofs are almost always continuous filament roofs of a rubber like sheeting that is placed on and sealed with heat. These roofs are known as CSPE or more commonly by the retail term Hypalon. These come in black, white and gray and are often also used on mobile and modular homes. They only need to be re-coated on a regular schedule for upkeep. This usually occurs about every 8 to 10 years primarily, depending upon your climate. The coatings come in 1 and 5 gallon cans and are an easy do it yourself job if you follow directions. Many of the coatings are rated for the type of surface and for the flexibility you need in your climate. There are both cold applied and heat applied roofs of this type and it usually just depends upon your roofing contractor which type will be used.
Copper and Tin
If money isn't a huge concern you may want your flat roof to be seamed metal or copper. These roofs are practically non leak and need very little upkeep but they are pricey and finding a roofing contractor that can do this kind of work may also be difficult. This type of roofing requires no coating.
A new approach among the green movement is to actually apply topsoil, sod and plants to a flat roof surface and let it grow, much like what you see in European countries. The theory is while the soil will soak up water the plants and grass will then use the water. It is also claimed that this type of roof helps clean the air and also keeps the room below it cooler than traditional roofing materials. It is also fire proof. Never think of a flat roof as a patio area because they puncture easily which will cause a leak immediately. Even going out onto a flat roof to wash windows or do other household chores should be done with caution.
Avoiding the Upkeep
If you must replace your entire roof, be sure to talk with your roofing contractor about the pitch of the roof. Many older homes had a roof that was totally flat. This can lead to problems with water pooling and standing in spots which will eventually cause a leak. They should be rebuilt with a pitch so water runs off easily. This will also prevent snow and ice build up and damming in the winter months.