The rafters are most likely too low...

http://www.constructionwriters.org/attic-and-loft-conversions/

I can’t speak for how universally common it is, bit in my last two houses, only part of the attic was accessible.

My entire attic is accessible and, believe me, when I'm finished and return back down, my back is sore from bending to avoid bumping my head around the edges.

The roof is the same height in the entire house, and it’s the part of the house that doesn’t have any vaulted ceilings, so the attic would have more room, that I have no access to. I wouldn’t care, but I’ve dealt with mold in previous houses, so I’m extremely vigilant when it comes to things like that.

I think that's your answer: "...it’s the part of the house that doesn’t have any vaulted ceilings..." The vaulted ceilings have taken place of where your attic floor would have been.

No, sorry if I wasn’t clear, the part that doesn’t have vaulted ceilings is the part I can’t access. It seems backward.

I would contact your builder.

My one story house had two pull-down stairs, one in the garage and one in a hallway, and you had to go to each set of stairs to access that half of the attic. Maybe there is another way to get to your in accessible attic.

Bruce

Depending on your square footage you may find this is a fire barrier, it is code in some places.

Depending on your square footage you may find this is a fire barrier, it is code in some places.

That is typical in multi family type dwellings, if this is single family home that is not likely the reason.

If it was like some mega mansion or something and in the city limits then 'possibly'.

It may be due to the roof design. The more crowns on the roof, need supports thus cutting down access to the attic?

I don't really know though... it's an oddity for sure.

Bruce, I thought there may be another entrance somewhere else in the house, as the one that I know of is in the ceiling in the garage, but I checked everywhere else in the house and there's nothing.

The house is just a normal size ranch house, so I don't think it would need an additional fire barrier. I'm going to be contacting the builders tomorrow to find out what's up with that, along with additional things. Thanks for all the suggestions, much appreciated.