Interior Doors Explained - We look at Different Types of Interior Doors Including Their Sizes, How to Measure Them and How Door Liners are Used

Summary: In this guide we explain the different types of interior doors and where you should use them in the home including information on flush doors, panel doors, glass and glazed doors and panel and brace doors. Find out where each type of internal door should be used and what style and design type they suit, what common sizes of interior doors are available in, how to measure and interior door and also find out what door liners and door sets are and how they are used.

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Sizes of Interior Doors

When it comes to what size interior doors you will need, this very much depends on the age of your property. Most more modern houses should all feature similar size door frames and thus doors to fit them. In most cases the door size will be around 762mm wide by 1981mm high or 2'6" x 6'6".

In the table below you will find some common door sizes. These sizes are for a single door:

Metric mm (W X H) Imperial Inches/Feet (W X H)
915 x 2134 36 x 84 (3' x 7')
864 x 2083 34 x 78 (2'10" x 6'10")
838 x 1981 33 x 78 (2'9" x 6'6")
762 x 1981 30 x 78 (2'6" x 6'6")
686 x 1981 27 x 78 (2'3" x 6'6")
610 x 1981 24 x 78 (2' x 6'6")

As said, this will really depend on the age of your property, older properties tend to have slightly varying sized door frames that in most cases may not be square. Due this, it is very important you measure your door frame correctly so that you know exactly what size door you need.

If you can't find a regular sized door to fit then you may need to have one custom built. The majority of door manufacturers will offer this service as will most joiners and carpenters.

How to Measure an Interior Door

As your door may have been shaped slightly to fit the frame it needs to sit in it is very important that you measure the existing door in several places. Use the image below for guidance:

Measuring an existing door for replacement

How to measure an existing door to find out what size new door you need

It is also important that you measure the thickness of your door as if your new replacement door is thicker than your old one then you may have to start adjusting hinge positions and door stops etc.... rather than just replace the old door with the new.

When it comes to the thickness, most doors will fall under one of the following:

  • 35mm
  • 40mm
  • 44mm - Doors this thick are normally fire doors as they must be at least 44mm thick

Door Linings and Door Sets

In most cases you will already have a door lining installed. This is basically the frame that fits into the opening in the wall that the door is hung on. Typically, these linings come in two different types:

  • Door lining - A door lining normally comes as a 3 piece kit - 2 side timbers (or jambs) and a top timber (head). The top timber slots over the 2 side timbers to form the frame that is then installed within the opening. The most important thing to ensure when fitting a door lining is to ensure that it is absolutely square - more information on this can be found here
  • Door lining fixed together and squared up

    Door lining frame fixed together and squared up using supports

  • Door set - A door set is basically an all-in-one kit that features an assembled and squared up lining frame with a door fixed to it, hinges and all! The door also comes complete with all the door furniture already installed. The idea is that the entire set can be installed into the opening in one go without the need to fit all the components individually, a great idea but not always suitable as it relies on the fact that you have open is square so may not be suitable in some older properties
Different parts of a door and liner

The different parts that make up a completed door and lining frame

Types of Interior Doors

Interior doors or internal doors as they are sometimes known come in a variety of finishes ready for any room and due to this there is a huge range of different styles and types of interior door available today but pretty much all will fall under one of four different types:

Flush Interior Doors

Flush doors are simply doors with a completely flat surface on both sides. They can be bought "pre-finished" or ready to paint.

Available for both the interior and exterior, most merchants and DIY sheds have a range of flush doors which offer simplicity with a great finish. This type of door tends to be the most common door type found in more modern and contemporary properties as their clean, flat design tends to compliment a more minimalist look.

One of the best features of these types of doors is that you can reduce them in size, add to them and due to their popularity as they now feature on most modern and new build properties, many after market products can be purchased such as locks and other furniture, all available in many different styles and for many different applications.

Flush doors can come in solid format which is a door made of solid wood or hollow format which is lightweight and comprised of two layers of thin timber separated, usually, by a lightweight card honeycomb core.

Solid flush doors are usually used as firecheck doors of which more information can be seen in our firecheck doors project.

Flush door

Flush door

Panel Interior Doors

Panel doors are doors which are divided into panels set back from the door face. There can be any number of panels and they can form any number of patterns.

Panel doors can be made out of timber sheets set into a timber frame structure or by fixing pressed hardboard sheets onto the frame of the door itself.

Although in the past they were not regarded as very stylish and often their appearance was rather bland, today this has changed as there are a huge range of styles available including half single glazed and also in a huge range of colours and material types and due to this they now tend to be one of the most popular.

Panel doors can also be bought to conform to firecheck safety standards and come in different varieties of timber.

Panel doors need not have square panels and many interesting shapes can be moulded and formed to create this style of door. They are also available with glass panels as can be seen below.

When it comes to using glass panels in doors, please ensure that any glass used is safety glass. Check this before purchasing.

Panel door

Panel door

Panel door with reinforced glass pane

Panel door with reinforced glass panel

Glass Interior Doors

Glass doors allow plenty of light to play around the home. In most cases they come with full, easy fitting instructions and will fit into a standard door frame as long as its corners are square.

If your door frames are not of a standard size, glass doors can also be made to measure.

When purchasing glass doors please make sure they are constructed from at least 8mm toughened glass to BS 6026 standard.

The range of styles and finishes can vary but in most cases doors can be bought with either a sandblasted or a smooth finish. The sandblasted finish is shown in the image below.

If you are looking to update and give your property that modern and contemporary feel then glass doors are a very good choice and are well suited to this style.

Frosted glass swinging door

Frosted glass swinging door - Image courtesy of archiexpo.com

Framed Ledge and Brace Interior Doors

Ledge and brace doors are extremely fashionable and most commonly found in cottages and period properties as they are able to give a real "cottagy" and traditional feel. Obviously your interior decor and style of house will have to complement this style of door, unless you are decorating from scratch in which case you can design around your doors if you are going for that more traditional feel.

Again, as above, they are available in a variety of styles and finishes even solid oak.

Normally constructed using a Z-shaped frame with tongue-and-groove interlocking boards attached, they can be quite heavy in weight but this can depend on the thickness of boards used.

Due to their construction they are normally very strong and hardwearing and can also be planed and shaped to fit pretty much any door way. They are prone to quite a lot of movement however.

Framed ledge and brace door

Framed ledge and brace door

Now that you know all you need to know about the types of interior door and their associated items such as door liners etc.... all you need to do now is go and make your purchase in your chosen style. Once you have your door you will then need to hang it - information on how to do so can be found here.

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