The specialist in Montreal and the North Shore for the installation of tar and gravel roofing
Tar and gravel, also referred to as built up roof, is an excellent solution for any flat roof. Although several other options are available elastomeric membrane, a built up roof provides an exceptional value. In addition to a 15-20 year life expectancy, a built up roof withstands Quebec weather conditions. Built up roofs have long proven their worthiness in residential, commercial and industrial applications.
The advantages to a built up roof
Quebec weather resistant
Solid and durable
White roofs which reflect sunlight
Tar and gravel roof; Mastering the techniques
Installing a built up roof properly requires skilled tradesmen and specialized equipment as well as the proper tools of the trade to handle hot bitumen and layers of felt paper drenched in searing asphalt.
The underlayment membrane consists of several layers of built up asphalt felt paper saturated with hot bitumen between each layer. The felts come in rolls which measure 3 feet wide (90cm). There are essentially two types of felts; #15 asphalt saturated organic felts and fiberglass type IV ply sheets.
Asphalt or Tar
What is commonly known as tar and gravel roofing is referred to as built-up roofing in the trade. Today, coal tar is no longer used in Quebec as it is rather toxic and irritating to the eyes and skin of workers using the product. It has since been replaced by liquid asphalt.
Quantity and Temperature
Workers apply 20lbs of asphalt per 100 square feet of roof surface between layers. The final layer is three times thicker (60lbs/100sq ft.). Asphalt is heated and kept at a minimum temperature of 220 degrees Celsius during installation. It is therefore crucial for the tar kettle to be continuously and increasingly heated.
Embedded gravel is used largely to block sun rays which could temper and eventually deteriorate the asphalt. Gravel also reduces the effects of thermal expansion and contraction, especially during cold spells. The embedded gravel commonly used is made from clean and dry 1/4′ to 5/8′ crushed stone. The required quantity is 4 lbs. per square foot (200kg/square meter).
The roofing membrane should continue 8 inches above the roof surface where it adjoins the perimeter walls, goose necks and chimneys and should be nailed in place at the top. This particular part of the roofing membrane should be sturdier as it must resist cracking. In order to ensure such a resistance, two layers of cotton fabric are placed between each layer of organic felt, all saturated in hot asphalt. Hardened (cold) asphalt as well as fiberglass ply sheets are a poor substitute for this type of flashing.
The main purpose of metal flashing is to protect the underlayment from the sun and strikes. It does not provide a waterproof protection. Metal flashings should be made from 26 gauge galvanized steel (0.56mm) or be at least pre-painted. If aesthetics is not an issue we suggest you choose galvanized steel.
Take a look at our other products available for your flat roof
You may have heard about an elastomeric membrane which provides another viable option for flat roofs. Our experts will gladly guide you along your choices according to your needs and budget. Please click HERE if you have any questions or wish to obtain a free estimate.