Cash our refinance tax deduction

Hi, 

I am thinking of a cash our refinance, pulling $200k out on top of a $500k outstanding balance. We will use it on various home improvement projects... the largest being an addition. My question is if we refinance now but don’t do the addition for another 8 months or so, can I still deduct all the interest of the $200k? Or do you only deduct on what I have actually paid thus far (ie arch fees, permits, but not construction?) we are trying to take advantage of the low interest rate which is why we are doing the refinance now... plus, it costs $ to do all the design work, etc!

Thanks!