davezawadi (David Stone):

I am beginning to think that something is very wrong here. Thermal insulation between floors of a single dwelling? 


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.

 

Thanks David for your very detailed reply.


This is acoustic insulation to satisfy part E. There is an argument that it doesnt apply to extensions, but the water here is muddy and both local planning control's ascertion is that it does, as does the independent building control company that I am using for the build (licenced). Being completely honest I am quite pleased that there will be acoustic insulation present as with 3 boys in the house whose version of 'no running in the house' seems to be the complete opposite there may be significant benefit from it!


The extension itself is a project managed professional job. I am only tackling some aspects of it myself - agreed with the team performing the majority of the work. I do not have the skills for the majority of the work, or at least to do it to the standard required and the speed required. We wouldnt cope with the roof half off for 2 months while I did it, but a week is do-able!  I would class myself as a pretty well read DIYer when it comes to both the plumbing and the electrical works. I am reasonably bright, have been through the on site guide and read IET Wiring Regulations: Electric Wiring for Domestic Installers and a couple of other books to understand the theory behind the regulations. Other hobbies involve electronic and microcontroller design mostly for RC model aircraft which involves similar basic principles. I am doing this work because I want to rather than have to - I enjoy the learning and understanding that comes with it even though I will not be using it professionally (Im a surgeon by trade). It would of course be a lot simpler to leave this headache to someone else and pay them for their time, and will indeed be paying someone competent to provide the relevant certificate for building control.  I appreciate that I will not be able to do the job as efficiently as someone with formal training, but with enough care and attention and research I should be able to do the work to an acceptable standard - and if not I will be pulled up on it quite quickly. I hope that helps with where I am coming from on this - not an arrogant 'its easy I can do that' but more a 'I enjoy learning how to do this and it gives me satisfaction to know that I have made some of our home work and work safely'.


So back to your post:

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.


Not quite. The existing property has two 32 Amp ring final circuits on 2.5mmT&E. The first supplies both floors at the front of the property (Study, Kitchen excluding cooker, hallway on GF, hallway on FF, one bedroom). The second supplies both floors at the rear of the property (Living room, two bedrooms).

Lighting is by 2 x 6 Amp radial circuits on 1mm2 T&E, one per floor.

The existing cooker is supplied by a 40 Amp radial on 6mm2 T&E



The extension is at the rear of the property, and two stories. The old kitchen becomes a 'snug' which seems to be the in word for another small living room. No changes need to happen to the front of house ring final to meet new demand (demand will actually reduce).


The old living room becomes the kitchen, the extension the new living room. Upstairs there is the addition of an extra bedroom and ensuite, although the layout changes and existing socket points no longer have a wall to be attached to so will need to be moved.


I am at the point of drawing up the design. preliminary calcs suggest that I could do the whole rear of the house on a single 32 Amp ring final, but in reality I suspect use will push beyond this at times and would rather have the certainty of being well within spec rather than on the edge and risk several thousand pounds of corrective work.


I'm on call tonight, but let me post up the design and calcs once I run through them and then I welcome the scrutiny. Im not expecting people to do this work for me, but a gentle nudge or more if I am going off piste. As a quick summary current plan (in my head) is to replace the rear of property ring final with 2 x ring finals one for each side of the house. cooker will be supplied by a 40 Amp radial as previously but on 10mm2 T&E (this is already in but of course not connected). Part P will be dealt with through the electrician who will be inspecting and the building control company I am using.


Once again thanks for your help

davezawadi (David Stone):

I am beginning to think that something is very wrong here. Thermal insulation between floors of a single dwelling? 


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.

 

Thanks David for your very detailed reply.


This is acoustic insulation to satisfy part E. There is an argument that it doesnt apply to extensions, but the water here is muddy and both local planning control's ascertion is that it does, as does the independent building control company that I am using for the build (licenced). Being completely honest I am quite pleased that there will be acoustic insulation present as with 3 boys in the house whose version of 'no running in the house' seems to be the complete opposite there may be significant benefit from it!


The extension itself is a project managed professional job. I am only tackling some aspects of it myself - agreed with the team performing the majority of the work. I do not have the skills for the majority of the work, or at least to do it to the standard required and the speed required. We wouldnt cope with the roof half off for 2 months while I did it, but a week is do-able!  I would class myself as a pretty well read DIYer when it comes to both the plumbing and the electrical works. I am reasonably bright, have been through the on site guide and read IET Wiring Regulations: Electric Wiring for Domestic Installers and a couple of other books to understand the theory behind the regulations. Other hobbies involve electronic and microcontroller design mostly for RC model aircraft which involves similar basic principles. I am doing this work because I want to rather than have to - I enjoy the learning and understanding that comes with it even though I will not be using it professionally (Im a surgeon by trade). It would of course be a lot simpler to leave this headache to someone else and pay them for their time, and will indeed be paying someone competent to provide the relevant certificate for building control.  I appreciate that I will not be able to do the job as efficiently as someone with formal training, but with enough care and attention and research I should be able to do the work to an acceptable standard - and if not I will be pulled up on it quite quickly. I hope that helps with where I am coming from on this - not an arrogant 'its easy I can do that' but more a 'I enjoy learning how to do this and it gives me satisfaction to know that I have made some of our home work and work safely'.


So back to your post:

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.


Not quite. The existing property has two 32 Amp ring final circuits on 2.5mmT&E. The first supplies both floors at the front of the property (Study, Kitchen excluding cooker, hallway on GF, hallway on FF, one bedroom). The second supplies both floors at the rear of the property (Living room, two bedrooms).

Lighting is by 2 x 6 Amp radial circuits on 1mm2 T&E, one per floor.

The existing cooker is supplied by a 40 Amp radial on 6mm2 T&E



The extension is at the rear of the property, and two stories. The old kitchen becomes a 'snug' which seems to be the in word for another small living room. No changes need to happen to the front of house ring final to meet new demand (demand will actually reduce).


The old living room becomes the kitchen, the extension the new living room. Upstairs there is the addition of an extra bedroom and ensuite, although the layout changes and existing socket points no longer have a wall to be attached to so will need to be moved.


I am at the point of drawing up the design. preliminary calcs suggest that I could do the whole rear of the house on a single 32 Amp ring final, but in reality I suspect use will push beyond this at times and would rather have the certainty of being well within spec rather than on the edge and risk several thousand pounds of corrective work.


I'm on call tonight, but let me post up the design and calcs once I run through them and then I welcome the scrutiny. Im not expecting people to do this work for me, but a gentle nudge or more if I am going off piste. As a quick summary current plan (in my head) is to replace the rear of property ring final with 2 x ring finals one for each side of the house. cooker will be supplied by a 40 Amp radial as previously but on 10mm2 T&E (this is already in but of course not connected). Part P will be dealt with through the electrician who will be inspecting and the building control company I am using.


Once again thanks for your help