How much to do a Single Storey Rear Extension (3m x 5m)

[MrSplash]

Hi -

Myself and DW have recently put an offer on a Semi-detached 3bed property in Watford. We're looking to do a single storey rear extension (3m out x 5m wide). We have a budget of 25K and want to know if we can achieve this?

How long can an extension take to complete as we have a 5 month old. We can stay in our current property for 1 month, maybe 2 months maximum to complete as much work as possible in that time.

I doubt it. We have spent nearly 5k on drawing, structural survey, planning fees and building warrants.

And our extension is in the loft space so no foundations etc. A dormer window.. .9x12ft bedroom and tiny ensuite came in at 40k