How is depreciable value caluculated after BRRRR?

[Matt W.]

So I am in the beginning phase of my first BRRRR. Purchased for $60k aiming for $180 ARV and trying to keep my rehab to under 60k.

My question is how is the building value determined once all is said and done?

As I understand it, if the original building value was $30k and I spend $60k on the rehab, the new building value =$90k.

This leads me to a couple questions:

1. If the new total value is $180k and the land value is still $30k, why is the depreciable building value not $150k?

2. Let’s say for the sake of argument I were Super DIY Guy and could complete the same rehab for the just the cost of materials, say $20k. So now the only invoices I have are materials receipts, so 20k+ 30k original building value=$50k depreciable building value?? If so, have I screwed myself out of tax savings? However I should get to pocket the extra $40k I saved by doing it myself?

I know the first priority should be profitability and then worry about taxes, but I want to be smart. Thanks!