Flat and Sloped Roofs Explained

What’s the difference between a flat and sloped roof – the answer is a thing called slope.

According to the Alberta Roofing Contractors Association’s Standards Manual, SS-2.1.4 SLOPE: 

• A shingle manufacturer will only provide a Warranty Certificate if shingles are installed to match low slope specifications. This requires an underlayment of ice and water shield, or minimum 2 ply’s of roofing felt with laps cemented together. This is good for 3/12 pitch or 1:3.
• Use a membrane roofing system for roof slopes less than 4:12 (1:3).
In respect to roofing materials, SS-2.2.1 GENERAL:
• The roofing materials shall conform to the Alberta Building Code (A.B.C.) and shall comply with their applicable materials standard.
• Materials shall be adequately labeled so that proper identification of the materials may be made.

Combined it means that flat or low sloped roofs require a membrane roofing system and sloped roofs require shingles – these can be fiberglass, wood, or metal. So why do most homes have sloped roofs and most industrial and commercial buildings haveflat roofs? That answer has to do with the advantages and disadvantages of each roof type.

Sloped Roofs provide better drainage from rain and snow; offer more appearance options to match your aesthetics; and allows for more interior space in the form of a loft or attic space that can be used for storage or additional living space. There are also disadvantages that can affect your ongoing maintenance and eventual replacement budget including that a sloped roof must be far greater than the footprint of the building; requires more roofing materials and longer installation times; and, working on sloped roofs requires more caution, which makes repairs and maintenance more difficult.

Flat or low sloped roofs are better for larger buildings; newer materials like PVC membranes provide for a lower per square foot installation costs – and less support structure is required; are longer lasting; and, can have a number of different uses, including roof gardens, solar panels, or to house HVAC equipment. Disadvantages include build up and increased loads from snow and water that doesn’t drain as quickly from flat roofs; and, because it is exposed to the sun all day it results in higher heat gain.

Each advantage and disadvantage comes with different maintenance requirements that should be reviewed in advance of purchase and installation so there are no surprises down the road.

Flat Roofs in Calgary
Calgary’s harsh weather can limit your roof’s life. At Century Roofing Ltd., we offer a variety of flat-roof or sloped-roof options to suit your taste and style. Since 1981, Century Roofing Limited experienced contractors have been providing you with sloped and flat roofing options for your home or business in Calgary. Whether you need a new roof or maintenance, call Century Roofing Limited at 403-235-5457 today. We can tackle any roofing project and provide a free estimate.