How much for a 2 storey extension?

[Designzilla 10]

Due to the current housing Market we have been unsuccessful in selling our house so we have decided an extension is the way forward but we are not sure on costs, I have rung a few builders but no one is interested without plans and I don't want to waste money getting plans drawn up for builders to then turn round and say £100k because the estate agents have already told us on an estate we will be lucky to get back between a third and half what we spend.

 

I have drawn my own set of plans which are 4 1/2 meters out to the side of the house and 8 meters length of the house, the second floor however is the same as the ground floor plus going over the detached double garage which is at an almost 90 degrees to the house ie it would become a corner house. We would also like floor to ceiling windows going accoss the back of the house which will end up been around 12 meters and underfloor heating throughout the ground floor.

 

Can anyone help on this matter? If a 2 storey extension turns out to be too expensive we might have to consider a single storey.

 

Many thanks

[maccamac 10]

could be anything from 20,000 to 45,000 but its no good guessing with out plans itis like saying how long is a lenght of rope

[plansdrawn 10]

I can draw the plans for planning and building regulations for £700

[sc-uk 10]

We can draw plans too, PM has been sent