Horizontal flue is the most common style in UK homes

While the horizontal flue is the most common style in UK homes, vertical flues are also available. Vertical flues exit through the roof, and are more expensive than horizontal flues. They are less likely to become blocked and less likely to attract birds' nests. However, vertical flues are not as easy to install. This is because they are longer and require more room. It is important to note that both horizontal and vertical flues have their own benefits.

The ideal length of a flue varies according to the length of the boiler. Ideally, the length of a flue should be as short as possible, as long flues can hinder access to the boiler. A flue that is too long can cause exhaust fume leakage and ineffectiveness. It can also endanger household members, so it's essential to check the length of the flue with a qualified heating engineer.

When installing a boiler, it's important to remember that the flue needs to be accessible to the boiler and the heating system. A horizontal flue kit is usually installed on the internal side of the external wall. A vertical flue should exit through the roof, and it should be able to produce steam when it's working. A vertical flue kit is usually more expensive than a horizontal flue kit. It's also more complicated to install, so it's recommended that you hire a roofing contractor.