Site ext for effective period of planning permission

Hello,
Does anyone know the process of getting an extention to there planning permission in the case of a site with full planning on it that is going to run out.

I'll be under pressure to meet the minimum build requirements by the end date. I just want to be sure before I approach Galway planning office...

I asked engineer and he hadn't done one before? Its for Galway County.

Also what is the minimum build you have to have done with site/house to meet this deadline, heard different views on this...

Thanks...

As far as I know you just need to have it to floow level or even just foundations - a call to the council will answer