The next stage after foundations was to build the sub-structure to support the main super-structure.  Due to the raft foundation slab, we only had to build one course of blockwork to support the timber structure.

We decided to build the timber frame on-site ourselves as opposed to buying a pre-fabricated timber kit.  For us this gives a cost saving due to the free labour aspect and buying the materials at cost price.

I would only advise doing it this way if you have got free or low-cost labour since the time taken to build on-site is far longer than ordering a kit from a manufacturer.  Paying for a contractor to build-it on site for you may also add up to the same as a pre-fab option.

Nowadays there is also the option of buying a pre-insulated kit giving you peace of mind that every single void in the external wall is filled with insulation (like a closed panel injected system) and reducing on-site installation time.