Extension foundations and existing slab

[oldkettle]

As I am looking for a way forward following the setbacks mentioned on the other thread, I wanted to get an idea about options for extension foundations and the existing slab replacement.

 

1. The bungalow has a traditional strip (or trench?) foundation. Is it possible to use a passive raft foundation for the extension? 

2. I want to dig out and replace the existing slab adding insulation and UFH. The questions here are

 a) Is it OK not to do the whole existing slab in one go? Ideally I'd want to leave the bathroom and possibly the kitchen for "stage 2". Are there significant technical disadvantages of this approach?

 b) How do the these replacement parts come together and how do they connect to the extension slab? any dangers / complications there? issues for UFH (no single loop)?

 

From some other threads (such as https://forum.buildhub.org.uk/topic/3726-how-to-deal-with-these-stones/) it seems the answer to 2a is "it's doable".

 

I understand overall this is not an ideal approach but I'd really want to start the process ASAP - I am not young enough to wait for another 3-4 years before moving forward. Yes, it will be somewhat more expensive and yes, it will have cold bridging, but as long as it is not dangerous for the extension's sole plate and just requires more insulation and/or more heat we can hopefully live with it.

 

Thanks in advance.