Working out area on a build?!?!?!

[angelboy]

When calculating the area for a build it's usually costed out at '£+++/sq m/ft' so if I were building a 2 storey with 100 sq m per storey then the area would be 200 sq m. If this costs say £800/sq m then the build should be £160,000.

Question: How is the cost/area worked out for a 2 and a 1/2 storey (basically a loft conversion)? Surely it wouldn't be a 300 sq m cost adding £80k for a loft conversion!

I need help understaning this.

 

[angelboy]

Does nobody know then?

 

[angelboy]

It this post in the wrong section?

 

[freddiemercurystwin]

If nobodies replied its because they don't know. As you say, it would be reasonable to assume that the cost of habitable accommodation in a loft would not cost as much as an additional floor, but it won't be much cheaper as all you're taking out of the build is the walls and ceiling and the roof itself may be more costly as you can't just use plain old timber trusses and you'll have rooflights or dormers for example. Its not an easy one to answer without more info tbh.

 

[angelboy]

Thanks for the reply.

I understand the additional factors, I just wondered if there was a rule of thumb that was widely used in these cases.