Conservatory upgrade

[Extension-novices]

Looking for some advice, have a 2.70m x 4.25m conservatory with 80cm high brick walls and then glazed to a polycarbonate roof. On recommendation of builder looking to upgrade by using a timber frame to add structure for two large windows [approx 1.30cm each] rather than all 4m of length glazed and timber frame with grp roof. Do I need building regs as no longer considered conservatory if it has a solid roof? Looking to keep external door in place so doesn’t become part of the house. Keep reading about 75% glazing but not clear if this is the case in this instance.
On that would building regs expect structural engineer calculations that walls/ foundations in place could hold new structure if they were needed or can I just upgrade, anything has got to be better surely!
Thoughts appreciated before I knock the monstrosity down

 

[^woody^]

You are describing an extension so most likely should require approval.

Use of the room will also be a factor.

All typical b/regs for extensions will apply, but the existing structure that will remain could have a visual check for suitability.

 

[Mister Banks]

I have just had my conservatory roof replaced with a solid roof, building control were involved but the inspection was very brief.