Single storey extensionSingle storey extensions are an extension built on to a part of the house whereby one side (or more) of the extension adjoins the property, and there is only the ground floor plus any basement built to it.
Main considerations here must be the size of the extension, its impact upon neighbours, how the roof will work with the existing building and specifically whether the same type of roof covering as the existing can be used on the extension. Positions of flues, drains and excavations must all be considered.
In some instances planning permission will not be required for single storey extensions. Building Control Permission will almost certainly be required.
Two storey or multi-storey extensionA multi-storey extension can, like a single storey extension, also be built to any part of the existing building. However, with an extension of more than one storey the possibility of nuisance towards neighbours is much stronger. In some instances it may be possible to build what you want without requiring planning permission, but we would strongly advise that you get a letter from the Planning Department to cover this.
Over-structure extension (typically over-garage)An over-structure extension is, as it sounds, where you are extending over the top of an existing structure such as a garage, a kitchen, a living or dining room.
Unfortunately this is not as simple as many people think.
For example, many houses have only single-skin brickwork for garages. This is not sufficient to build over as the new brick and block work above is twin-leaf. The solution is either to dig down through the garage floor, install a new foundation and a new inner leaf, or to install block work 'piers' in the garage and fix a steel beam over the top of these.
Similarly, there is a potential problem if you are building over the top of a kitchen or dining room which has a twin leaf wall but was built in the 60's. Because the conditions of the foundations cannot be guaranteed it is generally necessary to dig a trial hole to investigate. In terms of planning permission and building control the rules about whether or not you need planning permission are far more difficult to define. In these instances it depends on distances to boundaries between neighbours, as well as aspect ratios and other factors, and you are well advised to seek specialist advice. Building Control Permission will almost certainly be required.
Are you looking to structurally extend, convert or alter your home?
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