Pitched roof or Flat roof?
Over the years we are constantly being asked by our clients, which is better… a pitched roof or a flat roof? The answer is dependent on a number of factors and personal preference. In order to help you make this decision for yourself we have decided to create a comparison of the two roofing systems in several categories including cost, usability, durability and aesthetics.
Cost & installation
Cost is always a big question on anybody’s mind when planning a home development project. Maintaining a budget is essential in any project, whether it be a small £50k extension or a multi-million-pound new build, see our blog on maintaining budgets here. That being said, cost cannot be the be all and end all factor and the cheapest option is never necessarily the best.
With the two roof systems, the general theme is that a traditional flat roof would be the cheaper option when compared to a traditional pitched roof. Variables in materials for both can change this, for example a standing seam zinc flat roof would be considerably more expensive than a traditional tiled mono-pitched roof.
A cost to consider is the difference in potential glazing costs between the two roof systems. A flat roof can utilise much larger and bespoke glazing features such as large feature roof lanterns, which can come with an additional uplift in initial cost and fitting and labour cost when compared to an off the shelf pitched Velux rooflight. Roof lanterns may also require steelwork for support, as they increase roof loads, which would obviously come with additional structural engineer’s input/design, material and fittings costs. Taking glazing out of the equation, flat roofs are generally a cheaper option, as they require less materials and require less time & labour to install. It is essential that you choose a trusted and experienced contractor, who can provide you with the necessary guarantees on any roof works.
Usability & Practicality
Flat roofs and pitched roofs both have merits in terms of usability and practicality. Pitched roofs are generally the more popular of the two roofing systems when it comes to extensions. The pitched roof design allows for a vaulted ceiling within an extended space, this combined with the use of roof lights can add to an open plan layout and create a greater feeling of volume and make the space feel larger and more inviting.
Flat roofs on the other hand offer advantages of their own. Although glazing features add to the open plan feel of a vaulted ceiling, you are limited with the sizes and styles of available rooflights. Flat roof windows and lanterns offer a wide range of flexibility and can generally offer much larger glazing features, increasing the potential for natural daylight into your home and increasing the flexibility to create feature zones.
Flat roofs are sometimes the more practical option, with loft extensions for example, a flat roof dormer extension would maximise the usable head space compared with its pitched roof counterpart. In other instances, flat roofs are the only option, for instance, a large ground floor rear extension projecting circa 4 or 5 meters, with the requirement for natural daylight via roof glazing/windows would be limited to a 15 degree pitch, (maximin pitch set by the manufacturer), this often causes issues when considering existing first floor window sill heights, and ensuring that a new pitched roof does not clash with first floor windows. In these circumstances, a flat roof would obviously avoid this problem. It is worth noting that flat roofs also offer the possibility for an accessible outdoor space at first floor level with both PVC and GRP roof covering options.
Durability and maintenance
Pitched roofs offer the advantage of requiring very little maintenance, with a post autumn gutter cleaning advised and roof tile cleaning for aesthetics purposes every few years. Generally, as the materials used with a traditional pitched roof tend to be more robust than its flat roof counterpart, a pitched roof is the more durable of the two, but tile-based roof systems are susceptible to high winds.
One of the main downsides to flat roof systems is the requirement of general maintenance, it is recommended that you regularly check your roof, seasonally and after storms & extreme weather. Drainage cleaning is advised, and you must ensure your flat roof is free of any foliage, litter and debris regularly. It’s recommended that surrounding & over shadowing trees are regularly trimmed and maintained. Some flat roof materials such as EPDM (rubber roof) are susceptible to punctures and its strongly recommended to avoid foot traffic on the roof surface.
Although for most home extensions the footprint is modest, and this maintenance is not considered extremely time consuming. When considering large new build properties or commercial buildings the general maintenance can become quite a large task. To avoid this, you’ll see many buildings utilising a sedum “green” roof, which creates a plant-based ecosystem looking to retain and feed off rainwater and sunlight. This roof system not only removes air contaminants from the surrounding atmosphere, but also boasts minimal maintenance. A sedum roof does create more weight, additional costs and additional structure to take into account the weight, all of which needs to be factored into the decision making process. For more information on sedum roofs, refer to our blog “Designing with flat roofs“.
Something that is commonly mentioned and perhaps rightly so, is the possibility of pooling water and drainage failing on flat roofs. Although the name “flat roof” suggests just that, flat roofs are actually required to be installed with a minimum pitch of 1 degree, this along with regular maintenance, would eliminate the possibility of water pooling, providing the roof has been installed correctly. We always recommend that once works have been completed, your contractor carries out a water test to ensure no ponding is present and grades are sufficient to shed water to the required outlet.
Aesthetics and planning
Aesthetic appeal is again down to personal preference but also can be dependent on the property, older more traditional properties usually suit the more traditional pitched roof. Although, sometimes the contrast (if designed correctly) of a modern flat roof can be an appealing feature to the property’s external appearance. The modern flat roof comes in several different materials including EPDM, PVC and GRP, allowing for variations and a more tailored design to your personal preference. As mentioned previously, flat roof extensions allow for large rooflights and roof lanterns to be utilised as a stylish focal point to an extension.
Considering local planning departments planning policy, certain roof configurations are frowned upon and are unlikely to receive approval. For example, in conservation areas planning can be particularly fastidious. As previously mentioned, a flat roof dormer within a loft space offers a lot more practical & usable space than its pitch dormer counterpart, however in accordance with current planning legislation within a conservation area, a flat roof dormer extension can be seen as unsuited with the surrounding architecture and it would be difficult to receive planning approval.
In addition, flat roof first floor extensions, such as a side extension to an existing property, are frowned upon by local authorities, due to the fact that these designs are not in keeping with the existing properties character and features, and detract from the original design, which we are in total agreement with. By choosing the right designer for your project, there’s no reason why a carefully considered pitched roof design cannot easily be incorporated, that is in keeping with your existing property.
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