Many thanks to Wikipedia for this image. A good source of information, and a good cause to support financially and to contribute to with your writing and editorial skills.
In general, if you have never seen this Hitchcock classic, you must. Secondly though, I watch it over and over, trying to figure out the layout of the apartment, that is almost the only location you see in the entire movie. Must have been a cheap production except for her red dress.
I keep counting the steps that the actors make to determine distance. I estimate the size of the furnishings, but then give up because classic English furniture can be so different in scale from ours in the "States".
There is one long room in the movie. There is a rather monumental fireplace at one end with a door to the bedroom on the left side of it, and a large alcove for a highboy on the other.
On the other end of the room is a huge bay of French doors to the garden. They form a large bay that is curtained with heavy olive green velvet drapes.
The third(long) wall has a couple of built in book cases.
The fourth(long) wall has(from left to right) the door to the kitchen(which we never see much of), that could not be large, as it is behind the entry hall stairs...then there is a blank area with a bar/console table...next is the entry door...a second blank wall has a console table.
There are several distinct areas for living. Along the entry door wall there are only the console tables, but the area serves as a hallway from one end of the room to the other, though open to the room in all ways.
Facing the fireplace wall is a sofa with a sofa table behind it and a coffee table in front of it. Two comfortable chairs flank the fireplace.
There is an empty area next, which is where they set up a breakfast or dining table as needed. They would probably store it against the wall with the bookcases.
A desk stands in the bay of French doors, facing the rest of the room.
We never see the bathroom, but it is off the bedroom, behind the alcove to the right of the fireplace.
The bedroom is not large, but it has a square bay of windows along one wall, facing the street.
The entire apartment is a small space, but it has fabulous(Adam) period woodwork, high ceilings, and is very elegant despite its small dimensions.
The best I can do in this case is to adapt the size to modern furniture, and guess at the dimensions from there.
The room could have windows where the console tables are, but wall space is minimal in a small house, so, best to use the space for a couple of nice paintings. To make up for the lack of windows, this might be an ideal opportunity to put in a fabulous beveled glass door, or a French door...as long as you are not in the habit of running around in naught but your skin.
I will try to do a floor plan.
With just the most basic measurements, I would guess that the room could be about 18 by 24 feet. the bedroom is only wide enough for the door swing, two twin beds, a bedside table, and a wall about the same as the door swing wide....perhaps 14 feet at the most, by 11, and the bath would just fit into the 6 feet left over in the width of the main room.
That would only leave a little galley kitchen of perhaps 8 by 10.
That only leaves the bay window of the living area to figure in.
It may total only about 720 square feet of interior space, not including the bay window. Certainly even adding in the wall thicknesses and closets, you could squeeze the entire space into a 1000 square foot building....that just qualifies as a small house.
I have done a floor plan. The dimensions will not be there, and I have not put in the little bump outs in the walls that seem to make no sense. (They probably facilitate removal of sections of the wall for filming.) It is just a general idea about how the house works. I am thinking that it would make more sense symmetrically to reverse the bedroom and put the bath on the front of the apartment/house to balance off the kitchen. That leaves a little entry courtyard, and the north wall blank to save energy. These changes are only my own invention, of course, but I am not putting this post in to make a slavish copy, but to use the best parts of the subject to make a good house for you.
Another alternative would be to put a galley kitchen and bath along the bookcase wall, perhaps only five feet wide, to square off the building a bit and leave the north side utilitarian and insulating the main room from the north weather.
The fabulous detail work at the top of the walls in the room can be easily replicated by looking for LINCRUSTA. This is a linoleum like sheet that simulates carving or plaster work. The extreme height of the room makes it appear very large. In this case it was probably to facilitate dramatic camera work in the movie, but in a reasonable climate, or somewhere where the heating bills are not important, a high ceiling is a wonderful space maker.
Still another option would be to put a staircase behind the fireplace and make upstairs sleeping lofts or bedrooms....not too practical for the rooms, as the house would look like it was about to fall over on its side, but a loft would be good as would a storage space.
Please give me a break on this, I just finally decided to make a quick sketch of this and stop beating myself up about the dimensions and the size of the furniture. This was a ten minute sketch. It took more time to scan it in than to draw it. Watch the movie and understand my alterations. Also, add a good sized coffee table in front of the sofa...whoops!
Using 2x6x10 for framing the walls of this or any building will give a sense of space that you will not have with shorter walls. Having your walls framed very high also allows you to attach shed roof additions without the ceilings becoming very low at the eaves.
Make sure you draw a scale picture of your house and look at it critically, so it does not end up looking like Rapunzel's tower from the outside.