Capital expenditures include a variety of things that can happen in a house, like roots inside your sewer system, that are not considered regular maintenance. Depending what you put in your calculations that amount can flactuate. The only reason Im saying that is dont try to calculate with so much precision your cap ex dollar amount because thats going to be a lot of times off.
For example a AC unit might have 15 year life span, but because a repair was too much I replaced a unit in 9 years but got some credit for the old unit. That was a new cost of $2350 with a 10 year warranty. The roof when I bought the property had at least 10 years of life. For that property before I bought it I did my calculations with a 10% cap ex.
On another property that I had rehabbed everything, I calculated 5%. Of course if there is deferred maintenance I will consider it in my initial offer, when analysing comps.
To answer the roof question a new roof today depending what you install can have up to 35years warranty. A roof that was installed 2004 I would calculate that it has around 8-10 years of life.
