What Is A Flat Roof And What Is It Made Of?

Flat roofs have been around for thousands of years. They can be seen throughout history in just about every country in the world. However, today, flat roofs are seen as modern or contemporary due to the geometric design. But what is a flat roof and why are you seeing more of them than ever? That’s what we’re here to explain! 

What Is A Flat Roof?

Flat roofs
Image from Guy Ayers

Because all roofs require some sort of drainage system, especially in climates with a lot of rain, flat roofs aren’t very popular. However, most “flat roofs” aren’t exactly flat at all. They are simply slightly inclined.

In reality, most flat roofs are set at ten-degree angles, sometimes less. This gives the appearance of a flat roof while still giving water somewhere to run. Drainage should be your number one concern when building a flat roof.

Flat Roof Materials

Via EdgeWork Design Build

What are flat roofs made out of? In short, flat roofs can be made out of the same materials that heavily-inclined roofs are made out of. However, because of the design, flat roofs require more water-resistance. 

BUR – Built-Up Roof

This is one of the most common types of flat roofs. It is made with layers of felt and adhesive. It starts with the deck board, followed by insulation. After that, layers of asphalt and felt are alternated, with gravel being put on the top layer of the asphalt. 

The top layer of gravel is used to reflect the sun, keeping the inside better insulated. It also protects the lower layers from weathering. Gravel is easy to replace so if anything happens, you can just pour more on it. 

GRP – Glass Reinforced Polyester 

Also known as fiberglass, GRP roofing is a solid choice. This tongue in groove roofing is made of laminate which has a special resin that is perfect for roofing materials. GRP is easy to install and can be on any flat roof.

GRP lays a lot like tin does so anyone with experience roofing can do it. You may need to take a training course, but this roofing is much easier to lay than BUR, which requires a certified team. Not to mention, BUR is quite messy! 

Bitumen

Since BUR traditionally used tar, bitumen was invented to replace it. Tar can be stinky and very, very messy. Bitumen uses layers of asphalt with a protective topcoat of sealant or other protective material. 

The best part about bitumen is that it now comes in peel-and-stick pieces, so you can apply it easily. That’s right, you can get peel-and-stick asphalt that works just as well as poured asphalt and is more affordable than other roofing options. 

EPDM – Ethylene Propylene Diene M-Class Rubber

EPDM is a single-ply membrane roofing type made with synthetic materials. Most EPDM is a rubber adhesive that is one of the cheapest ways to cover a flat roof. There are other single-ply membrane options, but this is the cheapest.

The only downfall to EPDM is that it absorbs heat. This means that you’ll need to add a top layer to reflect the heat or else you’ll have a house much warmer than you intended. In the end, it may cost as much as other options this way. 

Vegetation 

Vegetation roofings are one of the oldest roofing types in the world. Of course, the popularity quickly faded with the discovery of clay and thatch. But with the new trend of living naturally and efficiently, vegetation roofs are becoming popular once again.

This type of roof consists of vegetation placed over a waterproofing system. It can be sod and often is used as a garden in no-waste homes. You can grow all sorts of plants on your own roof, which isn’t a bad way to go. 

Flat Roof Repair

Repairing flat roofs is said to be easier than repairing sloped roofs. Because there are no angles or curves, you can use flat materials to repair a flat roof. It also helps that most flat roofs are made with felt or asphalt.

Both of these materials are easy to work with and can be repaired easily. You can keep extra asphalt materials on hand for quick repairs. However, calling a professional is recommended if you had a professional install the roof. 

Flat Roof Shed

Flat roof sheds are quite popular. They are a perfect way to test out a flat roof if you’re unsure if you want to have a flat roof house. Since sheds are usually small, around 10 to 16 ft wide, they are easier to roof.

Most flat roof sheds are made with bitumen over tin or plywood.  If you’re buying from a manufacturer, it’s a good idea to add 5-degrees to the pitch to prevent water buildup in sheds. No one wants a high-maintenance shed. 

Pros And Cons Of A Flat Roof

Via Kelly And Stone Architects

All roofing types have both pros and cons. Here’s what you need to know about the dangers and benefits of flat roof homes. 

Pros Of Flat Roofs

  • Roof Space – if roof space is important to you, then a flat roof is your best option. You can use it as an outdoor area, which is perfect when you don’t have your own yard. In some cases, swimming pools are even added to flat roofs. 
  • Easy Repairs – since flat roofs are, well, flat, they are easy to repair. Sloped roofs come with safety concerns when repairing and need special materials to wrap around the curves of the roof’s pitch. 
  • Fewer Materials Needed – if you think about it, you’ll realize that flat roofs can take as much as half the materials as pitched roofs do. This comes with downsides, but it also means that it is much cheaper. 
  • Easier To Heat And Cool – if your roof is well-insulated, flat roofs are easier to keep cool and warm. Especially cool! Air and heat won’t get trapped in the pitch and you can buy smaller HVAC units. 
  • Easy To Clean – flat roofs are easier to clean because you can stand on top of them. For this reason, cleaning them is like cleaning a really dirty floor! You can use a broom or Shopvac and be on your way. 

Cons Of Flat Roofs

  • No Attic Space – because flat roofs don’t have a pitch, you won’t have the storage space that an attic does. This can be overcome by buying an outdoor storage building, but that cost can add up and it’s hard to find room for one. 
  • Hard To Drain – this is the main reason people opt for sloped roofs. Flat roofs offer little to no drainage. This requires a special drainage system or a lightly sloped roof, making true flat roofs nearly non-existent. 
  • Snow And Ice Can Settle – flat roofs allow snow and ice to pack on. This can really weigh down on the roof, and in extreme cases, cause it to collapse. This is why flat roofs aren’t recommended in extremely cold climates. 
  • Don’t Last As Long As Sloped – flat roofs statistically don’t last as long as sloped roofs. They need to be replaced and repaired about twice as often as sloped roofs. Since they are cheaper, it’s hard to decide if it’s worth it or not. 

Gorgeous Flat Roof Projects

Here are some of the most amazing flat roof projects that we’ve covered. 

Cantilevered Flat Roof House By Paulo Martins

If you’ve never heard of the world “cantilevered,” nows the time to learn it. It means “fixed or supported at only one end,” and refers to structures. This cantilevered flat roof house by Paulo Martins is eclectic and inspiring.

This house was built to accommodate the strange land it was built in. Flat roofs are perfect for such a project as they can be built on any house without looking strange. Pitched roofs are less forgiving.

Floating Australian Flat Roof House By FGR Architects 

Here we have another gem that appears to be floating. Designed and built by FGR Architects, this house can be found in Portsea, Australia. The house is very modern and simple, offering a strong geometric design.

In geometric houses like this, a flat roof can work wonders. Imagine a house like this with a pitched or sloped roof. It doesn’t have the same effect, changing the aesthetics entirely. That’s what a flat roof can do for any home.

The Ursa House By Pearson Design Group

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Not all flat roof homes have to be modern and stark. This design by Pearson Design Groupe and On-Site Management proves that to be true. This house portrays the perfect marriage between modern and rustic.

The home has the shape of a modern home with a flat roof but offers rustic textures. The entire thing is done in rough shiplap and earth tones. There’s nothing not to love about this cozy retreat nestled in the mountains. 

Raised Argentinian Flat Roof House By Guaresti/Altieri Arquitectura 

The goal was to build this house on the beach with a view of the sea on each side of the house. So, the house was raised on stilts to protect it from the sea and give homeowners a better view of nature.

Since the homeowners wanted a low-maintenance house but still wanted a flat roof, the builders opted for a concrete roof. Though not as popular due to its high price tag, concrete roofs work well in flat roof homes. 

Brazilian Pool House By Schuchovski Arquitetura

This gorgeous Brazilian home is located on a hilltop and utilizes the amazing views on the property. Each layer of this home also utilizes different flat roof designs. If you look closely, you can see how different each flat roof is.

The entire house is unique and modern, with a spiral staircase, huge rooms, and contemporary furniture. There’s a slight commercial feel to this house which adds to its character and seperates it from the rest. 

Primitive Portuguese Home By Artspazios 

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This project in Viseu, Portugal is absoutlely stunning. The project covered over 7300sqft, making it the largest one on the list. The earthy tones of this house and vintage architecture are what makes it special. 

As you can see, this house utlizes roof space that flat roofs give you with an amazing flat roof deck on the uipper levels. This is similar to the way hotels and apartments allow for external access on the top floors.