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Convert single storey extension to two storey extension.

Hi all
I'm buying a house with a single story extension to the back. The extension measures 5m x 5.5m and is 5.5m high. The vendor tells me it was built with adequate foundations to convert to a two-storey extension in future if required - which is what I intend to do.
Could anyone provide a ballpark figure on how much it might cost to convert the existing extension to a two-storey one on the same footprint, assuming the foundations are strong enough?
Also, do you think the resulting space would be big enough to get two kids bedrooms in, maybe even a toilet and washbasin somewhere too? (I realise the bedrooms might need to be interconnected to fit two in).
Finally, to complete the work, would it entail taking down the ceiling of the existing extension, or could you literally build on top without disturbing it?
Thanks for any help you can provide.

4 Answers from MyBuilder Extension Builders

Best Answer

Top of my head without taking into account what finishing you would require. You will be looking at about £20,000 for the extension. You would most likely have to replace the ceiling. You will be opening it up to build.


Answered 26th Feb 2013

Gareth, can't see a problem getting 2 rooms and a toilet / shower room. A Jack and Jill en-suite may be a good idea, something to think about. Regards Danny Marks ( D Marks Contractors )


Answered 6th Aug 2013

Hi Gareth,
Is the extension already build up at 5.5 m high? You can obtain easily 2 bedrooms as Mark is mentioning, they will be slightly longer or wagon kind of look but for kids is pretty comfortable considering in the future you can have the partition separating the bedrooms removed and achieve a single pretty massive bedroom with an en-suite or toilet/shower room. The foundation of the existing extension can be easily checked for depth and width, all you need is a surveyor to have a look at it or easier and more cost effective, hire a tradesman or a labourer to dig outside on the side of the rear facing wall, a whole in the ground to check the depth. Ceiling will most probably have to be replaced, build a new floor which will become ceiling bellow, that way you can reassure a proper sound proofing as well as proper strong floor.

Regards, Radu@EXLO


Answered 12th Feb 2016

Most likely possible. you will need to arrange a visit to the site first. I noticed the above suggest £20k to do the work. I dont see that happening so be weary.

wishing you the perfect build.



Answered 13th Feb 2019

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