Property Renovation – Flat Roof vs Pitched Roof

If you are considering building an extension, one of the decisions you will need to make is whether to opt for a flat roof or a pitched roof. Both have their merits and will depend on several factors including your budget, the desired look of your home and the height of your extension. At SDA Build London, we have constructed both kinds of roofs. These are some of our observations.

Flat Roofs are generally cheaper and quicker to build than pitched roofs. This is simply because, they are structurally less complex. Whilst flat roofs have the reputation of being less resilient and have a lower ‘shelf life,’ new techniques and materials such as Asphalt, EPDM and fibreglass have mitigated this lack of durability label.  Avoid using single ply or rubber membranes for the roof as even a small puncture can cause leaks which are difficult to locate and repair.

From an aesthetic stand point, flat roofs are not pleasing to the eye, but can be ‘beautified’ by creating a balcony or a roof garden with hard-wearing plants for low maintenance.

Usually flat roofs have a lower ceiling, making the space seem smaller. However, with the addition of roof lights or lanterns, the perception of space and light can be created.

Top Tip: Make sure your builder knows what he’s doing. Whist your flat roof is essentially flat, it must be at a slight angle for efficient drainage. The last thing you want is pooling water on your roof which, over time, will cause your flat roof to bow.

Pitched Roofs are prettier, no doubt, however, they are more expensive to build due to the greater complexity involved in their structure. As a result, choosing a pitched roof over a flat roof will increase the cost and timeframe of your project.

With pitched roofs your ceiling can be higher giving your extension a sense of space and light, especially if you add Velux windows. Pitched roofs traditionally have a longer life span than flat roofs as they are deemed to be more weather resistant, have better drainage and have traditionally been built with more durable material.  With water draining off immediately, the wear and tear on these roofs is less than their flat roof counterparts.

From an insulation perspective, we have found that pitched roofs provide better insulation than flat roofs, impacting your energy bills in the long run. The building envelope is responsible for around 25-35% loss of energy within a building. Pitched roofs are built to allow natural ventilation between the outer layer and the building, preserving energy.

Top Tip:If you have a pitched roof that faces the direction of maximum sun, think about fitting solar panels, adding to the energy efficiency of your property.

The choice between a flat roof or a pitched roof for your extension depends on a variety of factors not least planning department and building regulation considerations. We recommend discussing your objectives and budget with your architect and builder before reaching a conclusion, because every property is different. An experienced builder will be able to assess your property and make recommendations on what’s best for your specific project.

Give us a call on 0208 191 7595 for a FREE Property Refurbishment Assessment or email us at to arrange a visit. A member of the SDA Build London team will come out to assess your property, discuss your needs and scope of work required and make recommendations of what we believe can be done and add the most value to your home.