Timing of move from one PPR to another

We are currently living in our primary residence which we own.

But we plan to start building a new PPR. But we want to build this new PPR very slowing as a self build so we can try to come up with some of the cash needed before taking out a mortgage.
We do not want to sell our current house until we are ready to move which could be a few years down the line.

Now I know that we have One year within to sell our original PPR and after our new PPR is ready. This will avoid having to pay Captial Gains Tax.

My question is what is meant by "ready". Is it when the engineer signs off the snag list to say the house is now habitable or is it at roof level. Or whne we move in? I just need to know when the timer starts ticking.

PPR

The new house will never be your PPR untill you take up residence there.
The old house will stop being your PPR when you move out with the proviso that for the last year of ownership you will be deemed to have occupied that house for PPR purposes regardless.

have I picked this up right

So If we stay in our current PPR until our new PPR is ready to move into (which can be as long as we take to get it ready) we will not have to pay cgt on the sale of our current PPR.

But say for example if we are living in our current house and our new house is ready . But due to jobs etc (we are moving 4 hrs down the country) we must stay in our old PPR for sometime before the move.
Will this mean we are liable for tax on the new home we built?

Re: have I picked this up right

You can only have one PPR at any time. So before you occupy the new house it is not your PPR.
If for eg you never moved into your new house then if you sold it you would pay CGT.
If you hold it for a number of years and it is your PPR for only some of those years then you apportion the gain over the 2 periods of ownerships and pay CGT on the non PPR period

Re: have I picked this up right

But say for example if we are living in our current house and our new house is ready . But due to jobs etc (we are moving 4 hrs down the country) we must stay in our old PPR for sometime before the move.
Will this mean we are liable for tax on the new home we built?

If you own a second house in addition to your PPR then it is implicitly an investment property in which case there will be CGT (on some portion of the eventual resale gain if it subsequently becomes your PPR) and/or stamp duty (e.g. investor rates of stamp duty on the purchase - not sure how this applies to a self build) implications. I think that the question of when the second house is deemed to be "ready"/habitable remains unanswered here and I can't answer it myself.

not to sell

Hopefully our new PPR will be for life. So we are not worried about being taxed on the sale of it.

But I as you said the question reamins unanswered about the "readiness" of the new house.

Re: not to sell

The question of when the house is ready is not relevant in your situation because as long as you continue to occupy your existing PPR then that continues to be your PPR even if you leave your new house completed and unoccupied for several years.
Only if you were planning to sell your new house would it be relevant and unless you had rented the house for a period
there should be no issue