It’s time to replace your flat roof. That’s clear. What’s not always clear? The best way to start. If you’re like me–and most people–you’ll start online. Probably with Google. You might even search for a calculator where you could input some numbers and a cost range would kick out.
Don’t bother, though, because accurate tools like this don’t exist for replacing flat roofs. There are too many factors related to removing and replacing the existing roof–and then selecting one of the various roofing systems to install.
Hopefully, you have a trusted roofing company when the time comes to replace your roof. But if you don’t, this article highlights the top 9 factors that determine the cost of replacing a flat roof:
Access to the roof is a big deal. How close to the roof can we get to bring in cranes, end dumps and materials? How high is the building? Is the building surrounded by other buildings? The harder it is to access the building, the more time it takes and the more expensive the project can become.
2. Roof removal:
Removing the existing roof is a big part of the expense of the replacement. The more difficult it is, the more expensive the process. What most influences the level of difficulty? The type of roof and stuff on the roof. For example, asphalt roofs with ballast rock are more difficult to remove than a EPDM (rubber) roof. “Stuff” on the roof includes anything that will impede the roofing production such as rooftop HVAC units, stacks, vents, solar panels, decks, patios and signs.
3. Commercial building types and usage:
Whether a building is a church, warehouse, restaurant or office space, different buildings have different roofing needs. High heat, moisture, living space and future needs of the building help determine the roof recommendation and costs. Pool rooms and hot yoga studios have high heat and lots of moisture that can cause a lot of roofing issues, if the roof isn’t designed correctly.
When replacing a roof, you need to consider rotten decking replacement and repair. The more extensive the damage to the roof decking the more that will need to be replaced and that can drive up the costs on your reroof.
Common decking in Minnesota includes:
Does the roof have a ventilated joist space? If not, your roofer should have a plan to insulate the roof to code on top of the roof. Flat roof tapered insulation plans are complex and can be a key element in roof drainage.
The main types of insulation are:
- polyisocyanurate (mostly referred to as ISO)
- expanded polystyrene (referred to as EPS or bead board)
6. Substrate (last layer before the membrane is installed):
Given Minnesota winters, one of the most important parts of your roof is the last layer of your roof prior to laying the membrane. Your substrate is takes the brunt of the heavy-snow and ice load. It’s important to consider what is really going on on your flat roof. High amounts of foot traffic? Rooftop solar panels? A rooftop deck or patio?
The main types of substrate are:
- gypsum board
- wood fiber board
How the insulation and substrate are fastened to the roof affects roof replacement costs. The roof decking and the interior of the building determine the fastening method. Fastening is a fancy way to say, “How do we prevent the roof from getting blown off?” If you have finished open ceilings, you cannot put screws through the roof and have screw-ends poking through your beautiful ceiling.
Traditional ways to fasten your roof:
- Loose laid and ballasted rock
- Mopped down with hot tar
- Fully adhered
There are often strong opinions on what type of roof membrane to use, and the costs vary wildly depending on the entire system. The way to choose the best membrane is based on what is happening on top and inside your building, and how long do you want the roof to last. Though you may have a favorite, go-to membrane that you like, every roof membrane has a good application for the right building.
Here are the main types of roofing membranes:
- EPDM (Rubber)
Note: Within each membrane type, there are multiple variations of colors, thicknesses and brands.
The complexities of the labor hours that it takes to remove and install a flat roof all pivot on each of the above steps impact on: How many roofers will it take? How much time does each of the above steps take?
If you need to budget for a flat roof replacement, Rayco will be glad to put together numbers on your roof replacement.