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Home » Roof Types » How A Flat Roof is Constructed

How A Flat Roof is Constructed

For modern homes, flat roofs are a popular architectural choice, emphasizing the horizon and giving your home a tasteful simpleness about its overall appearance. However, because this kind of roof is more susceptible to accumulating heavy snow or pools after heavy rainfall, it must be precisely constructed. When constructing a brand new roof like this one, there are a few things that you’ll want to keep in mind.

Firstly, it’s important to consider the regulations that your area will have on the pitch of the roof. Obviously, you’ll want to construct your flat roof with as little slope as possible, but the fact is that it won’t be completely flat. Most areas will require 1/4 of an inch per square foot while other areas require only 1/8 of an inch. Typically, the slope will end up at 10 degrees or less. This slop will allow water to run-off and into the entrances to your home’s downspouts, preventing possible leaks that could happen if the water was just let to pool up. Once you have the slope figured out, you’ll move onto the actual construction.

The most basic layer will be the joists, typically wooden, which you would space evenly and run from wall to wall. You’ll build the roof’s decking on top of the frame created by the joists and the ceiling inside your home will be made below it. After you install all the joists, you can choose to either go for a “cold roof” design or a “warm roof” design.

For a cold roof design, you’ll place the insulation between the joists and install the decking a little higher up, leaving an air gap between the decking and the insulation. You’ll install the vapor barrier between the bottom part of the joists and the ceiling of your home. For the decking over the joists, you’ll want to use a material like plywood or OSB timber. A roofing membrane, such as EPDM rubber, will be attached to the plywood with adhesive.

For a warm roof design, the wooden decking is built right on top of the joists, usually with small gaps in between each piece of plywood. These gaps, about 1/8 of an inch, will allow the deck to expand and contract with the changing temperatures and humidity. You’ll install the vapor barrier on top of the decking and the insulation atop the vapor barrier. You could install the roofing membrane directly on top of the insulation, but installing another timber deck on top of the insulation before the roof covering is typically a good idea.

Generally, warm roof designs are better for homes that cold roof designs, since they keep the temperature within the ceiling about the same as the interior of the house. Both warm and cold roof designs are simple, luckily, and are both DIY-friendly. Flat roofs are desirable for their simplicity, though consulting someone with experience installing roofs would be the right move to ensure your flat roof is built with the proper precision to make it last.

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