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When Does My Commercial Flat Roof Need Replacing?

Posted by Northface Construction  - Owner & Founder

Today we are on site at a commercial flat roof repair that was damaged from extensive stress due to heavy ice and snow this past winter. This is a great example of when flat roofs in Minnesota need to be repaired or replaced due to our severe winter weather.


A flat roof is common on commercial properties and businesses. They are called a flat roof because they are essentially that, but with a very low incline. A basic incline, or pitch, for a flat roof, is around 10 degrees. This is for water to run-off down and off the roof. The overwhelming amount of snow and ice melt this last winter was too much for this roof to drain off, and caused water infiltration under the roofing and into the insulation.

Meeting Minimum Code Standards

In more severe cases, like this one in the video, the damage required us to take the roof off and build a brand new one in order to meet minimum code standards. To meet standards we want to build up the side walls, to keep water confined to the roof, and not leaking places it isn’t supposed to. We also want to ensure the new roof is an improvement on the old one. We are not going to repair that roof in the same way it was built before. The ability to manage the water should be a major improvement and a new style guaranteed to not require another repair down the line. The code states any standing water on a roof needs to be drained and dried within 48 hours of rain. This requires some extra building up of the slope to ensure for proper drainage of water.

How to Allow Water Drainage

First, the flat roof needs to be free of any divots or craters that would pool water in them, causing sinking or collapsing of the roof over time. So, when you are rebuilding that roof, first make sure the slope is enough to guide the water down and out of the gutter, downspout or leader. The parapet walls should also be built up to help guide that water down along the edges of the roof and not pooling in the edges of center. The angle of the slope is generally 1-2% on flat roofs (which aren’t actually flat).

Flat Roof Maintenance and Preventative Care

Flat roofs are sometimes known for being problematic, mostly due to the low slope and water pooling. They are generally chosen for commercial buildings as they are cost-effective and energy-efficient because there’s less volume and space to heat or cool, and they can even be turned into extra patio or garden space in the city. There are some things one can do to prevent water pooling or leaking. First, regular maintenance checks to clear out roof outlets like gutters, downpours, etc. is very important. A clogged roof outlet is a recipe for disaster. Leaves, dirt, snow, ice, can all plug those outlets and trap water from getting out. Water pooling and remaining on the roof for over 48 hours is not only against code but can begin to seep into the roof ruining insulation, windows, apartment ceilings, etc.

Materials used to waterproof and build up flat roofs generally have a lifespan of 20-30 years if well maintained, so it is very important to check the integrity and quality of these regularly. You will also want to be clear about your insurance coverage for your flat roof, especially as a commercial property owner. In a place where snow and ice can cause problems on flat roofs, make sure you have the coverage you need if a major repair occurs down the road.

How We Can Help

Northface Construction will repair or replace your roof with 5-star service, keeping you informed and part of the team for the entire process. We work to make your roof even better than it was when we started and to give you peace of mind and make sure you are getting the very most out of your investment. Contact us here for a free estimate, or just to get in touch for more information!


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