The solution:
Where space allows, the creation of an additional bedroom to a property can be a relatively straightforward proposal. However, there are always cases where it is not as clear cut. The house in question presents an unusual layout where the internal spaces are split over four levels. The floor plan is also unbalanced as the garage emerges around four metres forward of the principle elevation.
Where it might be obvious to extend over the existing garage, it would be difficult to achieve in this case due to the layout. Furthermore, creating a second storey over the garage would likely cause planning issues due to the vertical mass, which could be construed as incongruous in the overall street scene. And although extending over such a structure can be an economically sound decision, there will be an impact on the existing foundations; if they are too small, they would require underpinning, which can be prohibitively expensive. Instead, rebuilding from the ground up may provide a better alternative where the current foundations are not suitable. A structural engineer can advise and should be sought early in the design process.
In this instance, I suggest the garage be relocated to help bring aesthetic balance to the building while allowing for an extension above. It could be suggested that an extension to the rear of the garage could be a better alternative for an additional bedroom, but it would only exacerbate the issue of an unbalanced house. The aim is to help the owner realign the property, and will likely help in the future when it comes to sell the house.
In order to achieve the extra room, upstairs, bedroom one has had to be reduced in size to allow for passage to the new master suite. However, given the generous space provided by this fourth bedroom, this small sacrifice ultimately benefits the property.
Working on the basis that it would cost around £1,800 per square metre to create two floors of about 25 square metres, a scheme like this would likely need a budget in the region of £90,000.