Existing outhouse, PP required??

We re planning to refurbish our terraced house in Dublin, and as there are no structural changes, no planning permission is required.

However, there is hallway, outside toliet and store that had been built a long time ago, but we were informed when we bought the house that there was no planning permission sought. I did not mind at the time, because it was literally coming to pieces.

However if it was refurbished it would make a lovely addition to the house for washing machine/dryer etc, outside toilet and store, plus saving much needed space inside.

My question however is in regard to the planning permission required for this. I am sure I have read before that if a structure was in place for a number of years, it did not need planning permission, provided there was no structural change?

Am I correct in assuming this and how long would that all important number of years be?

Ring the Planning department in your council
They will tell you right away. have the measurments for them when u call

If you stay under 40 sq meters and stay at back of house you won't need planning get more info