Mechanical flashing waterproofs windows; caulk is a supplement.

"They both said that the replacement windows will stick out several inches from the window frame."

Huh? What do your current windows look like? Pictures? What window are they proposing to use?

Windows are ordered knowing your wall framing depth, siding thickness and interior finish so unsure why they would stick out? Sounds very strange to me.

Kind of need to see your application here. Something isn't quite lining up.

I am a home owner that is trying to get Vinyl replacement windows for my residential home. The current windows have the cheapest windows that the builder could find. My current windows fit flush on the outside and do not stick out.

How many ways are there to install residential windows? Or better yet what is the correct way to install residential windows. I would think that the windows manufacturers would have research this and came up with one specific way for installing their windows. What a concept!

Again, thank you for your help.

Depending on your exterior finish you can get windows that are recessed like in a brick home, you can have windows with brick mold that goes ontop of siding, you can have windows with a J-channel to accommodate vinyl siding, you can have windows built for a 2x4 wall or 2x6 wall or in some areas 2x6 with extra insulation because of a colder climate etc. etc etc. No house is the same therefore all windows are made to accommodate what you have. The window itself can be standard HOWEVER what is built around the window is not. So again if you want more help maybe you can help us and give us some pictures as well as what the window companies are offering.

Hire a reputable company that has a focus on replacement windows and you will be fine. if you hire some local ”pick up truck guy” that does everything, then I would be careful. With a reputable company, you dont need to be nearly as inquisitive. installing sheetrock to sheetock is also acceptable as long as they spray foam the outside perimeter.

I repeat:

"What do your current windows look like? Pictures? What window are they proposing to use?"

And then this one waiting to be answered:

"Kind of need to see your application here. Something isn't quite lining up."

I think you need to find someone who knows what windows and I have no clue why they stick out . We did all vinyl replacement windows in a 1905 house and they still fit the sapce no sticking out. Go to a good window shop and get good advice.