If the houses are close together and you have a roof with a slant it will encourage water to run off into the neighboring houses foundation. When the roof is flat there is drainage installed to safely handle the flow of water, instead of traditional gutters.
Flat roofs were very fashionable in the 1950s and 1960s because they were cheap and quick to build and generally regarded as ``rational''. They soon proved to be subject to pooling of water and resultant distortion of rafters, and leaks.
One of the most common problems you can encounter with a flat roof is the rainwater outlets becoming blocked. The reason these can become blocked is when leaves and other debris are swept into the rainwater outlets by the wind.
Greater usable space
The utilisable space for a house with flat roofs will be larger, even compared to a house with a usable attic. Thanks to the lack of haunches and knee walls, this type of house offers a full two storeys that can be developed according to your needs and preferences.
Bad idea. Low slope and flat roofs, depending on design, are more susceptible to ponding of water which can lead to leaks and failure. Generally speaking a low to flat roof will be restricted to specific roof coverings that will be a pain to maintain and change.
First thing's first, most flat roofs, if properly installed with top-of-the-line materials, will last anywhere between 20-25 years. If you are starting to reach that threshold or are noticing some abnormalities, such as the ones mentioned in this blog, then it may be time to replace your roof.
With a flat roof, you're taking a bit more of a risk. Although there can be wood underneath the roofing material, any standing water on a flat roof will have a higher chance of getting into your building.
Draining, or rather lack of it is the biggest disadvantage. Flat roofs do not drain as efficiently as roofs with a pitch. Water tends to puddle and stay on the roof. The standing water can lead to the breakdown of roofing material or future leaks, especially along the seams.
Flat roofs, or "low-slope" roofs, are also commonly found on commercial buildings throughout the world. The U.S.-based National Roofing Contractors Association defines a low-slope roof as having a slope of 3 in 12 (1:4) or less.
Energy Efficiency: Flat roofs can be more energy-efficient, especially when combined with proper insulation and reflective membranes. This can lead to lower heating and cooling costs.
Whether it's from pooling water, blistering, thermal movement, or roof buckling, cracks are by far one of the most common problems that you will run into with a flat roof.
The California Building Energy Efficiency Standards categorize flat roofs as low-sloped roofs. They are legally defined as having a rise-to-run ratio of less than 2:12, corresponding to a slope angle of 9.5° or less.
Low ceilings and small rooms in these homes were designed so they could be easily heated by a central fireplace. As heating systems and insulation improved, the height of the ceiling rose to the point where, today, depending on a home's style, ceilings may be 9′ high, 10′ or more.
Not only pitched roof windows can be installed on flat roofing. One of the most popular options is glass-domed roof windows. This option is usually used in shopping centers and public spaces. These roof windows are made of polycarbonate and are either single, double, or triple glazed.
Gutters are the most commonly used, and most cost-effective drainage solution for flat roofs. They catch rainwater as it rolls off the edge of the roof and divert the water into a downspout that dispenses it a safe distance from the foundation of the building.
Flat roofs are fantastic for keeping home utility costs manageable, especially in warmer climates. While sloped roofs can trap unwanted warm air or allow cooled air to escape, a flat roof means less overhead space for air to stagnate.
Conclusion. You can cover your new roof with many different material options, such as modified bitumen, fibreglass, or PVC roofing. However, as our guide shows, a rubber roofing membrane is probably the best product of this type that you can get nowadays.
Why not just install shingles on the flat roof? It's true that flat roofs aren't exactly flat, they have a small pitch of a few degrees. Still, you cannot put shingles on a flat roof as water does not drain off them quickly enough. The absolute minimum slope for asphalt shingle installation is 2:12.
Flat Roof Advantages
These roofs are more affordable, require less maintenance, and create additional space for living quarters. These are a few of the reasons why homeowners may be more interested in purchasing homes with flat roofs as opposed to traditional homes with pitched roofs.
Flat roofs generally require a greater degree of maintenance – even more so if the surface is disturbed and damaged by people frequently walking over it. Flat roof drainage is historically not as effective as traditional pitched roofs and standing water (ponding) can be an issue if falls are not adequate.
A flat membrane roof lasts 25-30 years, depending on the type you choose. To be a little more specific, you should get around 25 years out of a TPO membrane or PVC membrane flat roof. On the other hand, an EPDM roofing membrane is more durable than the other two and should last around 25 to 30 years.
Buildings with these roofs have less space for insulation and therefore can be more affected by extreme temperature changes. Buildings with flat roofs have less stability and the ability to withstand weight naturally, so your builders will need to compensate elsewhere in the construction to strengthen the building.
You can use lap sealant as a quick fix when it comes to small rubber roof leaks. But the most common longer-term fix is to do a 'patch repair' where you use self-adhesive flashing and self-adhesive rubber tape to cover the hole.
Flat roofs are generally more expensive than traditional roofs because they are more components to install such as vapor retarders, insulation and a cover board to make it class A fire-rated.