The complete home improvement magazine
Renovation expert Michael Holmes
Follow expert renovator Michael Holmes’ advice for how to find the space you need to extend.
Extensions come in all shapes and sizes depending on the amount and type of space you require. The most common type of extension is to add space at the rear, but it is also possible to add an additional storey by redesigning the roof or even by digging a new basement storey. End-terraces may also offer some scope for side extensions.
The most cost-effective away to add extra space is likely to be with a twostorey extension. This is because the cost of the most expensive construction elements, the groundworks and roofing, decrease as a proportion of overall costs the more storeys there are. Multi-storey extensions also sacrifice a small proportion of garden space than a single-storey extension. Using the roof space of any new extension will also help to reduce the average cost per m² of additional space.
Adding further storeys to an existing structure can also be cost-effective, although only if the existing foundations are capable of carrying the increased loading. Structures built after 1978 are likely to have been built with footings capable of carrying additional storeys. In all circumstances, unless evidence can be provided that the foundations meet the buildings regulations requirements, the existing foundations will have to be exposed for inspection for statutory building control purposes. If the foundations are not adequate, they will have to be improved, most likely by some form of underpinning. This can be expensive so other alternative ways to extend should also be explored and a comparison made to find the most cost-effective way to add more space.