I am beginning to think that something is very wrong here. Thermal insulation between floors of a single dwelling? Certainly, I cannot think of this requirement, and the BRegs are being rewritten at this moment so this is not something yet present. Ask Building control where and what this is. The envelope of buildings is the controlled thing, and any stairs will make this idea completely redundant anyway unless there are thermal doors top and bottom.


Now the Electrics.

From your description, I assume that the existing property has a single ring serving both floors, in the ceiling void of downstairs. Please advise if this is not the case. You wish to extend it to provide all the power for the extended property. I ask why, I would expect a new circuit at least for the kitchen. Is the ground floor solid? If so run a new circuit in a chase in the walls for downstairs. You will have a plasterer, it is easy to repair. I suggest another circuit for the kitchen only, same installation method, you have to chase the walls anyway so a bit more length is no problem. How will you feed the cooking appliances? It sounds as though the whole conversion/extension is a DIY job. Fine, not a problem, except you will need an Electrical Installation Certificate from a competent source (person) to get the BR completion certificate.


Asking here for a design is OK too, except that we only give advice on the regulations, not a final design. Plenty of ideas here (that is why the forum has members) but ideas are never the complete answer, or the design. Ask the Building Inspector about this inter-floor insulation. I have never seen it. Keep asking until he shows you the regulation which requires it. I have suggested an alternative method, much better than 200mm of Rockwool between floors. This will be thermally better, and much easier on the labour front, both the electrician and labourer and Boss will cost more than you putting up some nice slabs and 1 plasterboard. The loss through the joists makes 100mm useless, so overall only 100mm.


I may have drawn some incorrect conclusions from your data presented. Fair enough, present the real situation, why you want to do A or B is important. I am sure that you will then get the best free advice available.

As I got interrupted I missed the last post. You could do as you say but it is quite a lot of work, reduces the insulation u value of the floor, and will be very difficult to change and test in the future. This is much more than you seem to suggest, it would help if you describe the whole design, including how you intend to cope with partP of the Building Regulations. I trust the BI has told you about that too.

Regards

David CEng.

I am beginning to think that something is very wrong here. Thermal insulation between floors of a single dwelling? Certainly, I cannot think of this requirement, and the BRegs are being rewritten at this moment so this is not something yet present. Ask Building control where and what this is. The envelope of buildings is the controlled thing, and any stairs will make this idea completely redundant anyway unless there are thermal doors top and bottom.


Now the Electrics.

From your description, I assume that the existing property has a single ring serving both floors, in the ceiling void of downstairs. Please advise if this is not the case. You wish to extend it to provide all the power for the extended property. I ask why, I would expect a new circuit at least for the kitchen. Is the ground floor solid? If so run a new circuit in a chase in the walls for downstairs. You will have a plasterer, it is easy to repair. I suggest another circuit for the kitchen only, same installation method, you have to chase the walls anyway so a bit more length is no problem. How will you feed the cooking appliances? It sounds as though the whole conversion/extension is a DIY job. Fine, not a problem, except you will need an Electrical Installation Certificate from a competent source (person) to get the BR completion certificate.


Asking here for a design is OK too, except that we only give advice on the regulations, not a final design. Plenty of ideas here (that is why the forum has members) but ideas are never the complete answer, or the design. Ask the Building Inspector about this inter-floor insulation. I have never seen it. Keep asking until he shows you the regulation which requires it. I have suggested an alternative method, much better than 200mm of Rockwool between floors. This will be thermally better, and much easier on the labour front, both the electrician and labourer and Boss will cost more than you putting up some nice slabs and 1 plasterboard. The loss through the joists makes 100mm useless, so overall only 100mm.


I may have drawn some incorrect conclusions from your data presented. Fair enough, present the real situation, why you want to do A or B is important. I am sure that you will then get the best free advice available.

As I got interrupted I missed the last post. You could do as you say but it is quite a lot of work, reduces the insulation u value of the floor, and will be very difficult to change and test in the future. This is much more than you seem to suggest, it would help if you describe the whole design, including how you intend to cope with partP of the Building Regulations. I trust the BI has told you about that too.

Regards

David CEng.