Many homeowners of existing homes built since the 1970s and current new home construction will need to know what is required to replace or install their exterior doors. Since this is a site for Do-It-Yourselfer’s (DIY) we will limit our discussion to residential housing in the USA only.
So we have to be clear here from the outset that when it comes to residential homes there is no “standard exterior door size” as there are homes built recently along with homes built over 50 years ago. These older homes can be a real challenge when replacing the door as almost certainly they will have to have a “special order” door that is not a common exterior door in today’s construction guidelines.
It would be in your best interest if you have an older home in the USA to work with a qualified and vetted remodel expert to measure, help you choose the door and have them install it. For the purposes of this article, we will discuss the rough opening and door sizes of modern homes using pre-hung doors that can be easily ordered through any DIY home improvement store.
There are modern codes requirements that are now followed and can be the guidelines for your new or replacement exterior doors. It would be best to check your local building codes and state building codes. For example, here is a list of different codes for your research:
- International Building Code (IBC)
- International Residential Building Code (IRC) for one or two-family residential buildings
- National Fire Protection Association
- Americans with Disabilities Act
- Your own state and local municipality ordinances
With that being stated, we will now look at the common standard exterior door sizes in use today for residential housing. We will look at the sizes and layout of the dimensions of these exterior doors. Let’s start with the exterior door single door only.
How To Measure Standard Exterior Door Sizes
Typical single exterior doors should be what are known as a 36 x 80 door. Some of the side or back doors may be smaller in width down to 32 x 80. We will see what that means down to the measurements needed. For now, let’s discuss the 36 x 80 single pre-hung doors.
The nominal door width is 36 inches. The nominal door height is listed as 6/8 which is 6 feet 8 inches or just 80 inches. Since these doors are pre-hung with the door jamb frame, the actual size of the pre-hung door is 37 ½ inches by 81 5/8 inches. Notice that the width is 1 ½ inch wider than the actual door and the height is 1 5/8 inches higher than the actual door. Keep this in mind.
We now have to get to the rough opening size measurements. In other words, the “before any door is installed” entrance area has to be larger than the size of the pre-hung door. The rough opening size is the construction size with the side lumber (studs) and header. For the 36 x 80 exterior doors, this rough opening will need to be 38 ¼ inches by 82 1/8 inches. As you can see, the standard exterior door size rough opening is a full 2 ¼ inches wider than 36 inches and 2 1/8 inches higher than 80 inches. Keep this in mind.
If you are using brick mold openings the dimensions would be 40 inches by 82 7/8 inches. As you can see when using brick molding the opening width is 4 inches wider than the door itself and 2 7/8 inches taller than the door itself. Keep this in mind.
So assume here now you are working with new construction or replacing an existing door you will need to measure the rough opening size. You may have to remove the trim pieces to get to this measurement on existing doors. Here is how to determine the rough opening size for your home.
- For the rough opening width, you will measure between the studs at the top than at the center and then at the bottom. You will need to take the smallest of those three numbers as your width.
- For the rough opening height measure from the floor up to the bottom of the header on the left and right sides of the opening. Use the smaller of the two measurements.
These two measurements are your rough opening size. If you have something other than 38 ¼ inches x 82 1/8 inches (or extremely close) you may not be able to shimmy your way through this. You may have to choose a different size door or go to a special order door. Time to call in the professionals!
There are several good reasons other than the obvious of fitting the pre-hung door into the rough opening that this opening has to be larger than the pre-hung door itself.
- You need the extra room to make sure that the installed pre-hung door can be properly plumbed and squared.
- Door manufacturers have slightly different sizes for their pre-hung doors so you will need the extra room to fit most manufacturers.
- You need the extra room because doors expand and contract with the changing temperatures and seasons. It is not a large number, but it is enough that a tight fit will create problems during this expansion and contraction.
We could give you a nice chart of the different door sizes but the chart may vary slightly by manufacturer. So let’s go with a formula that you can use no matter what door size you have.
- Rough Opening Width Size = Nominal Door width + 2 ¼ inches (or + 4 inches if using brick mold).
- Rough Opening Height Size = Nominal Door Height (80 inches) + 2 1/8 inches (or + 2 7/8 inches if using Brick Mold).
So what about if the opening is for a double door or a single door with one or two sidelights or even an upper transom? These, of course, add to the rough opening measurements. So let’s explore these additional options.
For a 72 inch double door (this is two 36 inch doors) the basic pre-hung size will be about 74 inches by 81 5/8 inches. The rough opening size is 74 ¾ inches by 82 1/8 inches. If using brick molding the rough opening is 76 ½ by 82 7/8 inches! As you can see, the principle of the larger opening is the same, it is just that the rough openings compensate for the two doors.
Sidelights typically come in 12 inches or 14 inches in width. So a single 36-inch door with two 14 inch sidelights is a nominal 64-inch width. The height is the same as with a single door. The pre-hung unit size will be about 67 ½ inches x 81 5/8 inches. This puts the rough opening size 68 ¼ inches x 82 1/8 inches. If using brick molding the rough opening is 70 inches by 82 7/8.
Now if you add a top transom it is typically an additional 12 inches added to the height of the door and even more complicated when the transom is not a rectangular shape but a half-circle or oval shape. This creates even more additional rough opening measurements which may be the very reason to call in a professional to get the job done correctly.
So the best standard exterior door sizes are in width from 36 inches to 42 inches and for double doors they are from 72 inches to 84 inches. The height of these entryways are typically 80 inches but can be as much as 84 inches to even 96 inches. In each of these situations, you have to add the extra amounts as discussed above to get to the rough opening size.
The proper exterior pre-hung door is based on even more factors. The standard jamb width is 4 5/8 inches. However, there are times when the jamb is wider and you will need to order a jamb extension for your standard pre-hung door.
In addition, you will need to know the swing and handing. This means is the door going to be a left or right in-swing and this determines where the door handles should be placed.
Then there is the insulation factor of the material used for the door. This means is it wood or vinyl or composite or even steel clad. It is a hollow-core or solid core? Which type of door will hold up under the stress of weather? What style of door will add beauty to your home? These are all additional factors you need to consider when choosing that perfect new exterior entry door for your home or new construction.
You will serve yourself well if you choose a door manufacturer or DIY home retail box store and get the full rough opening chart from them for the particular doors that you are looking to install or replace. This was just an introductory article to help you understand all the variables needed for the standard exterior door size for your new home or even existing home.
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