Is building an extension on the existing footprint of our house cheaper?
Anonymous user 23/02/2024 - 3.26 PM
Is building an extension on the existing footprint of our house significantly cheaper than building beyond the existing footprint?
To the side of our house we have a single storey garage and utility room. We are looking to extend our house to add a bedroom upstairs and an additional downstairs room. My question is, would it be significantly cheaper building on the existing footprint, i.e. converting the garage to a room and building the additional room on top of the garage utility room cheaper than extending beyond the existing footprint as you don’t have to demolish what is there are re-do the foundations?
Are you a tradesperson and able to answer this question?
Yes it would be cheaper because you don't have to do all the ground works as long as the existing concrete foundation s are deep enough. A trail hole may has to be dug to inspect this.
Existing footings are the main issue in this case.You would have dig trial holes and get local authority ie building control to inspect.
Answered1 September 2019
2
Anonymous user
There is no simple answer to this question. It depends on when the property was built and it was built in pre-1970s it is unlikely that the existing foundation would be sufficient to support another floor above. There are few solutions so support the new floor above the garage but the cost are high and sometimes it is not possible to use any of the alternatives.
Before the build could start you have to also consider the planning permission as it is very likely you would need one (area dependant).
One way or the other the trial holes would have to be made alongside existing garage to expose existing footings. Structural engineer would be able to advise you on the possible solutions based on the existing foundation.
The process is simple if you have done it before but I would recommend to engage professional builder with sufficient experience to help you out.
I can pretty much guarantee that you will be required to lay new strip foundations for a 2 storey extension.
Structural engineer will specify what is required then trial holes to see if existing is suitable, it won't be.
