Whether it’s a new build or a home renovation project, doors are always an important feature. Get them right and you instantly improve ‘curb appeal’ outside as well the beautifully finished interior. But there’s more to selecting the right ones than most people think.

With external doors, you need to consider a number of factors such as security, severe weather and protection from termites. What materials will be best? What are the best different wood types? And interior doors present their own set of considerations. Both, however, have one vital factor to keep in mind; selecting the correct size.

This guide takes a look at standard USA door sizes as well as some of the issues associated with them.

 

International Residential Code

Not many people will be aware that the size of their doors is regulated by the IRC. It is a set of rules to be followed in the design and construction of residential properties. This is usually enforced at a state level and was put in place to ensure that buildings complied with health & safety recommendations. Because of this, USA door sizes tend to be fairly standard, at least meeting the minimum dimensions as per the code.

 

Standard Exterior USA Door Sizes

In the USA, the standard height for an ‘entry door’ is 80 inches. The width will generally be 30, 32, or 36 inches, with a thickness of 1 3/4 inches. However, due to changes in building regulations, your door may not necessarily match these measurements – particularly if your home is more than a few decades old. Confusingly, although there are standard door sizes, this does not mean that all doors will be standard.

The type of material can also affect the dimensions of a door. The height of fibreglass or steel doors, for example, is set at 6 ft 8 inches, and 8 ft.

It is imperative to get a good fit for your front door, as a poorly fitting one may cause security issues as well as letting the weather in!

Ideally, once you measure the door you will discover that it is a standard size. If so, replacements are easily available from hardware stores or home improvement centers. But don’t be disheartened to discover that your door is ‘non-standard’. Take your measurements along to a local Home Depot or similar, and they will be certain to help you find the right one – though it may cost you a little extra.

 

Standard Interior USA Door Sizes

For ‘passage’ doors, the standard minimum height is also expected to be 80 inches, with standard widths of 24, 28, 30, 32 and 36 inches. The standard thickness should be 1 3/8 inches, although this changes 1 3/4 inches if your door exceeds 36 inches in width or 90 inches in height. For doors that are required to allow assisted access, the minimum width is 36 inches.

Closet doors these days generally have a height of 96 inches and width of 30 inches, but those in houses built pre-1990 may have very narrow widths – as little as 18 inches.

The IRC, however, stipulates that the minimum size for interior passage doors (any door that allows movement from one room to another) to be at least 80 inches (6 ft 8 ins) and between 28 to 32 inches wide. This doesn’t apply to closet or bathroom doors.

Interestingly, the code does not appear to stipulate the size of bedroom doors, though it may make sense to go with a standard size unless you are happy to incur the extra cost of bespoke units.

 

Measuring your door correctly

If you’re choosing the replacement door (or doors) yourself, it is best to have precise figures to limit the possibility of buying the wrong size.

 

Exterior doors

For exterior doors, you may be required to provide four different figures:

  • The door ‘slab’ size – the slab is the actual door itself, apart from any other fittings or frames.
  • The rough opening – this relates to the space between the wall studs to which the door unit will be attached.
  • The masonry opening – this is the measurement from brick to brick on the outside edge of the opening.
  • The unit size – this figure can be calculated using the rough opening and masonry opening figures, and relates to the frame on which the door slab will be hung.

Measurements should be taken from top to bottom and at about three points from side to side.

 

Interior doors

Measuring your interior doors should be a simpler task than the exterior ones (unless you are replacing the frame as well, in which case you will be required to follow the steps for exterior doors) though it still needs to be as accurate as possible.

Assuming that you are replacing only the ‘slab’ itself, then simply record the height, width and thickness of your existing door. It is a good idea to also note down the dimensions of the frame to compare against your other figures, and to take at least three measurements across the width. from the top, middle and bottom. Not all doors (or frames) are perfectly rectangular, so it might take some minor adjustments to get a perfect fit that will function properly.

If you are replacing double doors, then you must be extra-cautious when measuring! The standard height for these remains at 80 inches, though there is no standard width, the most common ones being 60, 64 and 72 inches.

French doors fall into the same category as ‘passage’ doors, with the standard dimensions of 80 inches by 36 inches – especially so for French doors that lead to the exterior. They will most likely be 1 3/4 inches in thickness.

 

The process of selecting your new doors need not be a chore – in all probability, your existing units will conform to the standard sizes and replacement will be straightforward. If, however, they are non-standard, all is not lost! Most outlets and suppliers are only too willing to help you find the perfect doors to enhance your home.