A guide to flat roofs: what you need to know

UK Home Improvement

A Guide To Flat Roofs: What You Need To Know

Flat roofs have numerous advantages over pitched roofs. They are quicker and cheaper to construct, and the materials needed cost a lot less too. 

They are also a more modern and efficient design than traditional roofs and can be used to create more internal space on a property or to incorporate a ‘green roof’ on a new build or existing building. If you are a DIY enthusiast looking to maintain an existing flat roof or construct a new one, then there are some things you should know before beginning the work.

building with a flat roof

Coverings on Flat Roofs

The most critical component of any flat roof is its covering. It has a lot of work to do, and if it fails to keep the structure dry and leak-free, the rest of the roof fails too. Getting the covering correctly installed, and maintaining it going forward, is the key to a trouble-free flat roof.

There are many different types of flat roof coverings on the market, and each has its benefits and disadvantages. EPDM roofing, or an Ethylene Propylene Diene Monomer membrane, has become the go-to roof covering for most people because of its extensive list of benefits and ease of use.

It is heat-resistant, weatherproof, and exceptionally durable, making it ideal for use on flat roofs. The amazing benefits of EPDM membranes have made EPDM roofing one of the fastest-growing roof coverings in the residential sector, both for new build extensions and for existing roof projects. 

Planning, preparing, and installing a flat roof is complicated so you should consult some experts and see how they can help you plan and execute the work correctly. Roofs are an integral part of any building’s structure. You may be required to have professional help during an installation for building insurance or to qualify for any guarantee on your materials, such as an EPDM membrane.

The team at Rubber Roofing Direct are EPDM roofing experts that can help you to learn more about flat roofing and how to install a flat roof covering correctly. Their popular training centre is a place many handymen and women go to learn the tricks of the trade before beginning the work, and their online resources can help you to get the right amount of EPDM roofing for your flat roof.

Pitches on Flat Roofs

Flat roofs may be smooth, but they are laid at a pitch. This means water will pour in one direction off the flat roof. Planning your pitch, deciding where the water will run, and what your drainage system will be, are all important parts of successfully executing a flat roof installation.

The pitch of the roof creates a slope that the water runs down. In roofing terms, this slope is known as the ‘fall’, and a flat roof fall should have a gradient that is never less than 1:80. Having a gradient of 1:40 is usually the sweet spot. This is enough for the water to run away quickly, but not too much so the roof looks angled and not flat and level to the naked eye.

Planning your pitch is important, as it will influence many other design choices you are going to make. How you pitch the roof internally is one major concern. Many people do not like the aesthetics of an internal sloped roof. This means you will have to plan how to pitch your roof externally while keeping a level ceiling inside the building.

A simple solution is ‘firring strips’. These are angled battens that are placed on top of roof joists. These batons support the roof construction you lay above them, providing the angle you need while keeping a level surface internally.

With your pitch planned and your covering chosen you can now start to gather the supplies you need to get the job done and schedule the work. Laying a flat roof can be complicated, but with the right planning and preparation, and the right tools and materials for the job, anything is possible. 

Constructing Flat Roofs

Every flat roof is unique. You can even refurbish and replace a flat roof that you have previously installed, and it will be a completely different experience. There are some rules that you can follow, and design choices that you must make, that can help you out and make the construction of a flat roof simpler.

The first decision you need to make is whether you will have a hot roof or a cold roof. This choice is about where you will place your roof insulation, and how you will work that into your construction schedule. The cheapest, simplest, and most popular choice is to have a warm roof.

Warm roofs have the insulation laid directly on top of the timber roof structure, with the roof covering laid over the insulation. This will keep the space below the flat roof warm and makes the insulation quicker to install. It also makes it easier to plan the work than choosing a cold roof construction.

Cold roofs have insulation installed between the rafters with plywood sheets as a covering above them as the first layer of the flat roof. This technique is rarely used when building flat roofs today but can be found in many older flat roofs. There are pros and cons to both warm roofs and cold roofs, you should take a closer look and decide which is best for your flat roof construction.

New build extensions may need a cold roof due to local building regulations, so it is best to check this during the planning stages of your build. Having a warm roof raises the profile of the flat roof, and this may not be possible if an extension has to match existing properties in the neighbourhood, or the height of an extension is limited by existing obstacles or to reduce the shadow it casts on adjacent property.

A well-constructed flat roof can last a lifetime and be leak-free throughout. They can be complicated but with the right information, support, and planning anyone can correctly install a flat roof on their home or start a career as a flat roof specialist.


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