Exterior door measures 35.5" wide. I assume this is a nominal 36"
door? Or, a bastard size acquired by developer when the home
(A neighbor's door is 31.5" wide which I would assume qualifies as
a 32" door]
Thank you, that's exactly the answer I was looking for. I.e.,
that doors aren't like "dimensional lumber": nominally a particular
size (e.g., 2x4) but, in actual fact, somewhat smaller (1.5x3.5).
Seeing ours at 35.5, checking a neighbor's (different floor plan,
different building construction, different "nominal size" door)
seemed a quick way to the truth.
I'll bring a tape rule with me tonight and ask friends if I can
measure theirs to see if the pattern extends to all homes in the
neighborhood (the area was developed in two very distinct time
periods), all homes of particular styles/floorplans, all homes by
a particular *builder* (I think three different developers were
A sample size of TWO (out of two examined) undersized doors
isn't very conclusive...
That will tell me what they *sell* but won't explain why the two
doors I observed (different homes, different widths, different
construction techniques) are "off". I would find it hard to
swallow that an architect drafting (at least) two different plans
had to resort to trimming 1/2 inch off of doors in each case.
Did *he* not know what standard door sizes were?
If I can't buy a 35.5" door, then I'll have to alter the frame
to accommodate the slightly wider door (a fair bit of work).
On Monday, February 29, 2016 at 10:36:32 AM UTC-5, Don Y wrote:
You didn't say if you were looking for a pre-hung door or just a slab
or a slab and a separate jamb.
Whenever I have ordered pre-hung doors I gave them the RO measurements
and they told me the maximum size door that will fit that RO. Since the
doors are pre-hung, they use the RO measurement to determine the size,
factoring in the width of the jamb.
Granted, I haven't bought a door from a home center, I go through a
local contractor supply house where I know sales person. In any case,
the RO measurement is a better number to use than the width of an
existing door. I'd be surprised if even a home center staff didn't
ask for that measurement. Once you know that options based on that
number, you can decide the best course of action.
For the basement steel door, the custom size I needed (height-wise) was
way more than I wanted to spend, so I ordered the next taller size,
slapped a metal cutting blade in my circular saw and let the sparks fly.
That was the point of *asking* -- instead of surveying the entire
Bob's upthread assertion that *his* door is 36 inches suggests
either *his* is the oddball (being EXACTLY "as advertised")
*or* mine at 35.5 -- and neighbor's at 31.5 -- are the oddballs!
I find it hard to believe that an architect (multiple architects?)
drafting plans for different homes (floor plans, construction techniques,
etc.) would be off by 1/2 inch "more than once".
So, did the builder (or, ONE of the builders in this subdivision)
get a deal on oddball doors? Did the carpenters and masons
screw up reading the plans? Have door dimensions changed over
the years? etc.
Now, it's a "local" *puzzle*! I'll have to see how extensive the
"problem" is among my other neighbors' homes (I walk past all of
them each day; I *don't* drive to Home Depot every day!)
I venture none of the above...as another noted, doors are spec'ed by RO
and nominal dimensions; the various manufacturers have always had
slightly different precise measurements on prehung units.
I suspect if you'll measure you'll find the finished opening into which
the door fits is precisely 3-0 or whatever the nominal is and the door
slab itself is undersized to match the particular weather-stripping
system in use.
Built-in-place door frames and jambs generally will have a full-size
door slab and the opening will then be somewhat larger than nominal to fit.
Tract housing, even more "up-scale" than just starters 40-50 years ago
likely was using prehungs rather than custom-built even then although if
there's a significant time between the two and the earlier is '50s or
so, chances go up on custom framing.
On Monday, February 29, 2016 at 1:46:19 PM UTC-5, dpb wrote:
Thank you for joining the RO discussion. I'm not sure why that isn't the
*only* thing being discussed. Trying to find a slab to just drop into an
existing jamb may end up being more work than just buying a pre-hung
door, with modern weather stripping, etc. At a minimum the options for a
slab that fits are going to be more limited than the vast selection of
Modern doors are always about 1/2" narrower than their listed size.
There has to be some gap around the door, and that 1/2" is your gap. The
INSIDE of the frame is the listed size (32" 34" 36", etc).
If you're replacing an entire door and frame, you need the OUTSIDE
measurements of the frame, an you make your rough opening about 3/4"
larger, so you can align the frame and apply the shims.
Some OLD doors were the actual listed size, but not always....
(Of course back then, the frames had to be 1/2" bigger than the listed
You seem to be giving information out about what you want to know, and why,
Your original post was,
"Exterior door measures 35.5" wide. I assume this is a nominal 36"
door? Or, a bastard size acquired by developer when the home
But later posts seem to indicate that you want to replace your existing
door. And, I think you may have also mentioned that you want a metal door
for the replacement.
I mention this because if there is something specific that you want to do,
it may help to state that. But, if your question is just the curiosity
question that you originally posted (and you are not asking because you want
to replace your existing door), then the responses and answers would be
When I have investigated the possibility of replacing an exterior door in
two different older homes, I encountered some of the same issues that you
are encountering. In both of my situations, I thought the doors were
36-inch doors. Basically, when I measured the opening for each door, I came
up with a 36-inch opening. But, when I measured the actual width of the
existing doors, they came up as less than 36 inches wide -- around 35 1/2 or
35 3/4 wide.
Then, when I went to look at doors for sale (just the door slabs
themselves -- not prehung doors with the frame included), I kept coming up
with doors that were 36 inches wide. That meant that if I bought a new
wooden door, it would be 36 inches wide and I probably would have to trim it
slightly to make it fit in the existing door frame opening. If I bought a
metal door, it would be a problem because trimming 1/4 inch off of the width
of a metal door would not be a viable option (I don't even know if it is
doable at all).
So, that means that my two options are to:
1) buy a 36 inch wooden door and trim it slightly to fit the existing
2) buy a prehung metal door and replace the existing door and frame entirely
(which meant more work, dealing with the having to remove the existing trim
and frame around the original door etc).
I think that means that the answer to your original question is that, yes,
nominal 36 inch exterior doors on older homes were often only nominally 36
inches and were in reality about 35 1/2 or 35 3/4 inches wide to fit into a
36 inch wide opening.
Meanwhile, one of my possible exterior door replacements would have involved
a door that is 84 inches high -- not the typical 80 inch high doors that
they make now. That would have meant ordering a custom size door. And,
since I would be ordering a custom size metal door anyway, I thought that
may mean that I could order a custom metal door that was 35 3/4 inches wide
and 79 3/4 inches high to fit the existing opening. I never did check to
see if I could order a special size metal door with those exact
dimensions -- partly because I didn't have the heart to buy a metal door
that I only hoped would fit the existing opening correctly.
In the end, I wound up not replacing either door -- at least not yet. I
repaired one existing door and I just left the other one (the 84 inch high
door) as is and didn't replace it.
Those were my experiencing with this issue in case it helps.
You can, yes. You'll possibly not like the pricing options that go with
I was lucky in TN that there was a local manufacturer in Knoxville who
did the job for me for what I thought was quite reasonable -- replacing
a wood slab in basement block wall with 4" veneer field stone outside
84" is a standard height so you're not as far out in left field as you
might think but if you were to try to fit the door in existing opening
you've got more than just the actual width/height to deal with--you've
got the number, size and location of hinges, height/setback of the
lockset, whether there is/isn't additional deadbolt, etc., etc., etc., ...
Miss any one of those details and you're possibly hosed...or at least
have customizing to deal with.
We've had top go that route with some of our larger windows. While
painful, if you're already spending a kilobuck on a window, it's not
as distressing to have to spend a bit more to get what you truly
[OTOH, a generic $100 steel door doesn't want to turn into a $500
special order with 6 week delivery times, shipping charges, etc.]
Because this is EXACTLY what I want to know. I've learned that providing
context just invites endless questions that avoid the question being
asked (Why do you want to do that? Why do you want to do it THAT way?
Why are you obsessing over some trivial issue? Why is this explanation
so LONG?? etc.)
I asked the question in much the same way someone ignorant of dimensional
lumber standards might ask, "Why are my 2x4's 1.5x3.5?"
Had someone said "Two by four are NOMINAL dimensions -- just like 36 inches
is a NOMINAL door dimension", I then would have known that I just need to
buy a 36" door and it WILL fit in place of the 35.5" door that I have.
See above. That would inevitably have invited:
- what form of home construction
- interior or exterior
- why do you want steel instead of wood or fiberglass?
- will you need to cut a pet door *through* the door?
- why not install a WINDOW instead?
Reducing the question to one of "is a 35.5 inch door ACTUALLY what is
advertised as a 36 inch door" eliminates all of that discussion.
Exactly. And, I've taken the initiative to not ASSUME that my "sample of
one" was representative of ALL such doors -- by walking to neighbor's
house and measuring their door (knowing that their house is constructed
differently, different door size, etc.). I.e., if THEIR's is also
"half an inch undersized", it starts suggesting that this is a question
of nominal dimensions being used in place of exact dimensions.
(e.g., people will freely mix discussions of 2x4's (nominal sizes) with
32" and 36" doors -- who's to say the 32/36 isn't also a nominal dimension?)
The same sorts of problems apply to prehung doors as well -- except now you
have to contend with the frame, brickmold, etc.
Those are my choices, as well (restricting the discussion to JUST the
door -- lest folks want to comment on other unrelated issues that I
am not asking about!)
?? 79.75 for an 84 inch door?
The costs of custom -- for a door that is NEVER USED -- are just silly!
So, if doors actually ARE 36 inches, then I have to plan on making
the opening fit the door.
If I'm going to do THAT, then there are other options that I can
bring to bear on the problem that I wouldn't have exercised if I
could just install a "drop-in replacement".
Thanks, it basically confirms what I'd feared. Silly to talk to
the millworks folks about it as they'll just offer to sell me a
Short answer seems to be, take a tape with you and measure the doors.
Since we started here I have been measuring all the doors I see and
the answer I come up with is there is no standard.
I have anything from "right on" to a 1/2" smaller and one that is
about 1/4" smaller (steel door so I know it wasn't modified).
My guess is that manufactures make doors for standard rough openings
and the thickness they choose for the jam determines the actual door
I am curious how building inspectors deal with clear opening sizes for
accessible routes since even a full size door is smaller because of
Nope as I told you some several responses above...they build to a RO and
the final interior opening turns out to be what it is--the two of -1/2"
and -1/4" are pretty common for width but the length (height) is also
dependent upon those factors plus how they design the threshold.
If you're trying to order a door slab to fit an existing opening, see
above as well, there's a whole lot more besides just the exterior
dimensions to worry about, especially if you're talking steel, not wood,
where field modification is much more of a trick...particularly things
like number, size, placement and setback of hinges, hole locations, etc,
etc., etc., ...
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.