Workshop rebuild cost (insurance)

[monabri]

I'm trying to find info to provide to our insurers. We have a brick built "workshop" (1950s) , size 9.4m by 4.2m. It has a flat roof ( EPDM rubber covering). We already insure the rest of the property ( a shop with a flat above) but we thought we'd better add the workshop on to the policy as well as it hasn't been specifically noted on the policy. The workshop is separate but is within the bounds of the property/garden and is used for hobby woodworking. The only heating is by electrical heaters and there is no water supply. The insurers want to know what the rebuild cost would be...I have no idea ! Are there any online calculators that we could use to estimate rebuild costs?

[EssDeeAitch]

Depends where you live but in the Newcastle region, a domestic extension would be between £1200 and £1500/m2 and I would imagine that a workshop would be at the low end of this range.