Flat roofs have become popular for those looking to build a modern home. They are often cheaper than pitched roofs since they require fewer materials for the same span and they free up internal space. If a flat roof is to work correctly, it needs to have a slope, also known as a fall, to shed rainwater. The fall needs to be between 1:40 and 1:80 and there are several ways to build it;
- Set the cross walls at different heights, although a fall built in this way may have an internal ceiling that slopes.
- Using battens (also known as firring strips) cut at an angle and placed on top of the roof joists.
- You can also cut a fall into the roof insulation. Many businesses prefer this option and it is often referred to as tapered insulation.
Why Choose a Flat Roof Design
A flat roofing design can have very many advantages. Some of them include the following;
- A Flat roof frees up internal space
- A flat roof gives you the freedom to plan interesting shapes beneath the flat roof without having to consider the way the roof is held up.
- A flat roof is highly flexible
- They can also be instrumental in keeping the internal temperature stable.
- Flat roofs eliminate the impression of bulk you get with a pitched roof, without having to compromise the internal space.
- They are also much cheaper to construct than pitched roofs and they need much less material.
How to Build a Flat Roof
The method you choose to build a fall will depend on how the flat roof is built. Generally, you have three options;
1. Build a Warm Roof
The simplest and most affordable option is to construct a warm roof. In this method, the roof insulation sits on top of the timber structure and then the roofing membrane is laid over the insulation. A warm roof is generally the preferred method from a construction perspective, but it will often result in a higher roof profile, which is not acceptable from a planning perspective.
2. Build a Cold Roof
In this option, the insulation is placed between the rafters, underneath the ply roof covering. It is the most common method on flat-roof extensions, but it is almost never used for new buildings.
3. Build a Hybrid Roof
There is also the option to build a hybrid roof. This is a form of a warm roof that also incorporates other elements into the design. There are some designs of hybrid roofs that call for a ventilation gap above a warm roof. This is meant to prevent any moisture build-up inside the structure.
It is very important to prevent moisture from getting trapped within the roof. Many designers undertake frequent risk analysis to ensure that any potential dew point is eliminated, although it is still up to you to ensure there is no leakages into the roof void.