I'd trust an experienced installer much more than a store salesman. That installer could be a handy man, carpenter, or an employee of a company---construction/door/remodeling.

The way to size for a replacement door like you have is to accurately measure the rough opening. That means removing the interior trim to access the actual RO.

Standard installation calls for a rough opening 2" wider/taller than a standard door---the RO for a 34" wide/80" tall door will be 36" wide and 82" tall. That allows for the necessary shimming to install the door plumb and level. If the person/company doing the framing is also installing the doors, that RO can be smaller, since the people should be able to do the framing better so is does not need a lot of shimming. But, that seldom happens.

Now, the age of the home has nothing to do with the door sizes. Any size custom door can be built. If the doors available are smaller, you will have to make whatever changes in the trim will be necessary to use a smaller door---or order the correct size. But, as I outlined above---1/2" clearance on each side is half the normal distance---I cannot imagine having a problem with the trim and any gaps in exterior/interior wall treatments.

We make our entry systems to the unit size of the existing unit and finish with 2 1/2" wide trim to cover old paint lines, etc. A perfect fit, everytime. The rough opening means nothing to us. What matters most is the finished look!

It is not uncommon to find entry doors varying in unit sizes. Yes! That new door may very well be narrower than your existing unit because it may have a thin jamb. Our jamb thickness sizes can be 3/4" to 5/4"..depending on the application.

Should i go to a place that specializes in doors?
What do you think?

Call a professional door installation company, not Lowes. That installer is working for the lowes-t fee. He's hardly motivated to do a precision fit. That is why he's preparing you for a disappointment!

BTW, a replacement door is installed in the existing jamb. A new construction, full wood frame door is installed in the rough opening.

Michael

I'm another vote for a professional door installer and not Lowe's. If you have an odd sized opening, I'd recommend someone who really knows what they are doing - you may end up needing custom doors.

There's no reason that the interior and exterior moldings could not be switched out so they would reach the siding and the interior parameters. I don't think I've ever used the brick molding that comes with the doors. I have them include it with the door but tell them not to attach it to the jambs.
Have the carpenter install the door and then install the exterior covering you need to get to the siding. Then have them cap the wood with aluminum so you don't have to paint it. With the interior, apply the size molding you need to cover any raw areas. This is common practice in replacing a door. Any company that can't do it, don't hire them.
Ron

I don't understand. Do the jams need to be replaced? You don't want to order a "door system" if you don't need it. If the jams are ok, or can be repaired, just replace the doors. When you remove the outside molding, you also tear out the flashing, and you want to avoid this IMO. If a place only does prehung doors, then find a real installer.

A replacement door removes 1 1/4" from the door width (clearance). Be careful. There may come a day that something wont' fit inside or outside w/o removing the steel L frame of the replacement door.

Michael

If you scribe and cut a door to fit the existing jams, how do you loose 1 1/4"?

Lowe's uses subcontractors for installation. This sub-contractor can be a company that specializes in doors or just some joe working out of his truck. Either way they have the sub-contractor come out and measure the opening and check everything out. Atleast they do for garage doors. I personally have not been impressed by any of the installations I have ran into where I live. All the work has been sloppy and have even saw some doors hung completely wrong. I would have a reputable company come out and give you a bid.

If you scribe and cut a door to fit the existing jams, how do you loose 1 1/4"?

A replacement door comes with steel L frame that is inserted on to the existing jamb.

You're talking about a door slab, modified to fit an existing jamb. Two different things.

Question: Where do you think you'll find a steel entry door which is pre-hinged to fit an existing jamb?

Michael

This is all academic now. I doubt if the guy is reading this anymore, but I must apologize. I can't find anywhere the man mentions a steel door. I must have missed it.

I freely solicit opinions from others with direct hands-on experience but based on the description of the doors (fornt entry with side lights and a french door set), then $3000 for the doors, installed and finished sounds about the lowest that someone could get the job done and still get a quality door with a quality installation. I'd expect the estimates to be higher here in the Boston area.

I'll explain how I hung the last door I did. I used to do work for Zalez Construction when they needed special items done. They asked me to hang a front door. It was a 4/0 front door. I did not want to remove the stucco molding for 3 reasons. 1. The weather stripping was kerfed into the jam and door, a small channel in the jam and a bead in the door. Good system I didn't want to change. 2. I didn't want to remove the stucco mold because I would have to pull out the flashin with it and there were no signs of water damage. 3. It's hard to make an invisible repair in stucco that doesn't crack and I don't like to cover the repair with wide molding. I checked the jam and the only damage was cosmetic. I had a solid core v/g douglass fir door. I cut a piece of 1/2" MDF to fit in the opening as close as possible then scribed around the door using a piece of 1/2" scrap as the width and marked where the three hinges were. I laid the MDF on the door and registered my scribe marks and used a straight edge to make the cut lines. I have a circular saw kind of straight edge guide that I made. I cut to the center of the line. Then I used my adjustable hinge guide to cut the hinge mortises. I removed the interior molding and cut away the drywall behind the hinges and used some 1/4" and 1/8" peices of wood I had made as shims and support behind the hinges. I put the hinges against the jam and predrilled with a vix bit. I attached the hinges to the door and had a Zalez guy help me lift the door into the opening and hang it with two screws in each hinge. I wanted about a 3/32" gap so I scribed for that, removed the door and planed it to the marks where needed and smoothed out any saw marks on the edge. I kerfed a channel in the door for the metal bead for weather stripping along all four sides. I marked where the holes for the lockset needed to be and used my Porter Cable jig to drill the holes and mortices for the lockset. I installed the lockset and did whatever tweeking needed to be done. Whatever cosmetic repair needed to be done, like refinishing the threshold and sanding, bondoing and painting the jam, ect. was left to Zalez. I was paid $200 for the job. I don't know what Zalez paid for the door or what they charged their customer. All I know is he liked the work, shook my hand and said nice job. Good enough for me. I installed the door this way because IMO using this wide molding to cover up your work on the front of the house doesn't look good. I charged $200 to Zalez. Subsequently, a couple of weeks later, the home owner asked me to do some more work for him. I told him he would have to talk to Zalez. That happened alot but I didn't think it would be fair for me to do that. I may have missed a step or so. I retired 5 years ago and try not to do that kind of heavy work anymore. I mostly repair and make furniture.