It may seem that by reducing the size of the corners, you may increase the light into your extension or orangery. However you need to know about the 695mm rule. Any corners smaller than this will require additional structural calculations and in many cases additional support. One of our clients reduced the corners to 440mm externally without letting C.P. Architectural know and when queried by their Building Control Officer a new retro fit steel was required. This addition came as a shock to the client as the room was fully plastered! With advice from our engineers a steel angle and base plate was added to the smaller corners all of which needed to be plastered and screeded at an additional cost. Always work with your designer when changes are required we can advise on regulations for any alterations, and the earlier the better as these additions may need to be hidden within the fabric of the building.