Large bay or extension?

How big can a square bay window be before it becomes an extension? What are the differences to planning/regs (if needed)? What differences need to be considered in actual construction?

I have sliding patio doors in an extended kitchen. This was extended sideways so the back of the house is still 'flat'.

A conservatory would be expensive to heat etc and I really wanted a larger footprint to the kitchen.

So could I have a 3' 'bay window' with french doors for example.

Be kind to me, I have no idea what is involved here but would like to have some insight before I start talking to builders etc.

Thanks

believe it or not, a 'bay' window will be classed as an extension no matter how small. it will be subject to b'regs.

Thanks for this.

Does this mean it needs foundations and a 'proper' roof even if I only go out 2'? There are two shallow steps out of the patio door at the moment, so I would need a floor too.

Is this beginning to sound like an expensive way of gaining an extra 2' x approx 8' on the kitchen? I just wanted some where to sit in 'daylight' if you see what I mean.

Sorry to sound dim, but I'm not sure what is involved here. I just like to have some understanding before I get any tradesmen in to give quotes.

Thanks again.

It will require full building regs - foundation depth will be subject to a site inspection, but will be close to the depth expected of typical extensions in your area.

Roof, floor and walls will require to conform to current insulation values

You will need planning permission if this projects nearer to the road than any other part of the elevation. But if at the back, then it will be permitted development - so no planning permission required (unless there are specific constraints on the property)

You will be looking at £3-4k

Thanks for the replies. I understand much more what is involved now.