#5 The flat roof – what is important…

09 August 2018| News| Mareike Eckhoff


Once a month we give important tips about building a summerhouse in our series: “What makes a quality summerhouse”. Our architects and wood professionals explain which details are important when you want a summerhouse to last as long as possible. From material choice to final assembly, everything will be dealt with. In this way, you can become an expert on wooden summerhouses yourself!


Which roof type do you prefer for your summerhouse? This question is not as easy to answer as you might think. Of course the optic is an important decision criterion, but there are additional aspects that you should consider when choosing a suitable roof. What weather conditions will your summerhouse be exposed to? What are the advantages and disadvantages of which roof type? And what about the construction of the roof? Which roofing is possible?

Even before the start of construction, in the planning phase, you should deal extensively with these issues. The right roof is fundamental. For a long-lived summerhouse, it is therefore important to make an informed decision. With this blog series we would like to support you and introduce you to the different roof types in detail. The last blog post # 4 dealt with the first roof type, the apex roof. In addition to general information on the roof load or tips on different roofing, especially the specific characteristics of the apex roof were covered. The apex roof is a very popular roof shape, as is the flat roof. Flat roofs are characterized by their clear straight shape and are very popular nowadays. They no longer have the reputation of not being tight. Technically perfect, flat roofs create a very modern look. You want to know more? Read this article:

The flat roof and its reputation

Due to frequent design flaws and the choice of inferior material the reputation of the flat roof was really bad in its earlier years. In the 60s and 70s, the flat roof experienced a boom. Everyone saw the advantages of a flat roof. Since there are no more roof slopes, the space in the summerhouse can be fully utilized and even the roof itself offers an additional usable area due to the straight shape. The flat roof itself was very popular, but the technology was not fully developed. This caused a lot of problems. These problems have long been history. With the right planning, construction and choice of materials, the flat roof has been experiencing a comeback for some time now.

Lugarde Flat Roof SummerhouseWhat exactly is a flat roof?

Flat roofs are roofs with a low roof pitch. Compared to other roof types, the flat roof is very minimalistic. It appears extremely modern and offers many design possibilities. It is important that a flat roof is never completely even. The rainwater can’t remain on the roof and must be able to drain. How it works? As mentioned, flat roofs have a low roof pitch angle – or more precisely, the purlins of a roof will be placed that a water drainage can result to a given direction. This occurs, when the individual roof battens (rafters and wooden battens) are attached to the roof purlins. The roof purlins are connected and an inclined drainage for rainwater is created. The following graphic shows the individual parts of a flat roof, for better understanding. Please note: The black arrow indicates the tilted direction, in which the water can drain later.

With this construction, you can be sure that the rainwater runs in a certain direction. There are no puddles on the roof and the water can’t flow off of all sides. If that were the case, the water flowing down could splash against the lower boards of the summerhouse walls. This must not happen, as this could cause considerable damage to the wood over the years. Just to be sure it is useful to install wind boards which, in any case, should be higher than the roof purlins, rafters and wooden battens. This creates some kind of “pool” and allows you to control the water drain even better. Thanks to the wind boards, the water stays on the roof and does not flow off of all sides. The tilt of the roof ensures that the rainwater flows off in a certain direction. If you now attach a downpipe, all the water can simply be drained into a bin or into the grass. This protects the walls of your summerhouse from rainwater. The wood stays dry and does not rot.

Roof covering of a flat roof

The right roof cover is particularly important for a flat roof. A flat roof needs a sturdy seal to protect the roof from rainwater. Should a puddle form on the roof despite the tilt, the seal must be able to withstand it. Therefore, make sure to use only high quality materials. In general, there are different ways to cover the flat roof of your summerhouse. Examples include seals with plastic or even liquid seals. Particularly popular is a roof covering with geomembranes made of EPDM. EPDM is a foil-shaped building material made of rubber, which is of very high quality and very durable. According to the SKZ test, the lifespan is around 50 years. A roof cover with EPDM foil is easy to clean and particularly resistant to UV radiation. The foil is extremely solid and can withstand almost any weather conditions. If it is glued to the roof with silicone, you can be sure that your roof cover is completely waterproof. It is a building material that does not mind if it constantly comes into contact with water. That’s why it’s perfect for flat roofs.

It is important that the EPDM foil closes properly at the edge of the roof. For this purpose, a wide aluminum roof trim, which completely encloses the EPDM foil, is recommended. On the following pictures you can see exactly what this closing looks like.

Lugarde Flat Roof EPDM Roof Covering             Lugarde Flat Roof EPDM Roof Covering Corner

Please make sure that the EPDM foil is always pulled over the wind boards. The aluminum roof trim includes the foil and the wind boards at the highest point. Only then you can guarantee a watertight conclusion. A flat roof should be constructed in such a way that rainwater gathers like a pool and then flows off in one direction. If you wouldn’t pull the EPDM foil over the windboards, this “pool” would leak and water could enter.

A roof covering with EPDM, if processed correctly, is especially waterproof. Even roof vegetation is possible, given you have considered this from the beginning in the planning and the roof is designed for it. A tip: Lugarde offers you a complete EPDM package. Each summerhouse with a flat roof includes a wide aluminum roof trim, EPDM foil, glue, silicone sealant and a rainwater drain.

You find the flat roof interesting, but do not know if it is right for you? In the next blog posts we will discuss the features of other roof types. Be curious about valuable information on pent, pyramid and asymmetrical roofs.

Other blog articles from this series

#1 Why the choice of the right wood is essential
#2 Construction systems – What you should consider!
#3 The choice of the right window and doors
#4 The apex roof – what is important…

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