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Measuring for Interior Bifold Doors

Once you’ve established the space where the bifold door is going to be installed, you’ll need to take some measurements to ensure you purchase the correct one.

Firstly, you’ll need to vertically measure the wall in three places; the left, right and center of the wall. Secondly, you need to vertically measure the wall in another three places; the top, middle and bottom of the wall. Internal bifold door sizes vary immensely, so ensure you’re measuring with accuracy. If it’s an option, ask someone to help you with the tape measure.

We would advise measuring at least twice to ensure your figures are accurate. If you have a discrepancy between the sizes of more than 10mm then you have a crooked opening. This will need to be fixed before installing your bifold door as the door won’t hang properly.

Although a pain when it comes to fitting bifold doors, it can be fixed with shims (spacer).

Finally, you need to consider the ‘fitting tolerance’. This is the difference between the edges of the gap in the door and the edges of the actual door.

There needs to be a slight gap between the door frame and the wall frame for warping purposes.

Depending on the material that you use, warping may not be an issue for an internal bifold door, but usually, indoor bifolds are made from wood.

Wood expands and contracts in different temperatures and if moisture gets into the wood, the frame will expand and crack. Although your door is internal, these conditions are still relevant and the wood needs to be treated properly. If you haven’t allowed extra room for a fitting tolerance, the wood will expand without having the extra space to expand into and will become stuck and unusable.

In contrast, if you allow too much fitting tolerance, you’ll be left with a draught. Although not much of an issue for internal doors, if you’re separating a conservatory (which tends to be a pretty cold room in the colder months) from the rest of the house you’ll receive an unwanted draught through the openings.

The interior bifold door sizes, for warping, need to have a 10 - 15mm fitting tolerance to account for the wood expanding and contracting due to heat and moisture, and to prevent draughts. 10 - 15mm tends to be the sweet spot for a perfectly accounted for fitting tolerance.

Tools needed

The tools required for a perfectly measure bifold door are:

  • Tape measure - preferably one that measures in small measurements

  • Spirit level - if your measurements aren’t adding up correctly, use a spirit level to see whether the wall is crooked or not

  • Shims - you may need shims to even out your door if the wall is crooked

Now you know how to appropriately measure your internal bifold doors, check out our helpful guide on how to fit internal bifold doors and the essential step of how to fit bifold door handles

View our full range of internal bifold doors here and if you have any queries, our team is more than happy to help so get in touch.

In Summary

An internal bifold door is a modern and versatile way of opening and closing spaces. Adding bifold doors allow you to keep the space open, and light while still separating rooms and blocking out noise pollution.

Installing a bifold door is an excellent choice, however, if measured incorrectly, could result in the opposite effect and potentially damage the door and wall. By ensuring an accurate measurement, you can enjoy the process of picking a bifold door that suits your aesthetic and installing the door without any hiccups.

Taking the time to triple-check your measurements can be a tedious project but it’ll be more than worth it in the end!


Further Questions

What are standard internal bifold door sizes?

There are a range of different sizes for internal bifold doors; some are standard and some sit somewhere between standard and unique to the buyer. Considering the width of your wall, or the design and feel you want to create with the door, the width can vary quite a bit.

Typically, measuring for bifold doors is done in millimetres as the doors need to be as precise as possible to stop draughts and noise pollution. The main, standard sizes for internal bifold doors are:

  • 1905mm

  • 2130mm

  • 2370mm

  • 2820mm

What is the standard height of an internal bifold door?

Similarly to the width, there is a varying amount of sizes for the height of your bifold door. Due to wall height, the height of the door can differ a fair way from the ‘standard’. For most doors, however, the standard height is 2095mm.

What is the smallest opening for bifold doors?

The smallest opening for an internal bifold door is an individual door pane at 70cm. Smaller openings can be achieved however, if you’re using the door for walk-through traffic, any smaller, and the door could be unusable.

The maximum opening for a bifold door is 2.5 metres. Before introducing a large set of folding doors into your home, make sure you’ve considered how they’ll sit when the doors are open. The bigger the bifold, the bigger the concertinaed stack will be.

What size opening do I need for internal bifold doors?

The size of the opening is more about what you want, rather than what someone tells you. If you need advice, then please seek it; made to measure internal bifold doors may be the best option for you. 

However, think about the reasons why you’re installing the bifold doors in the first place. If you want to create the illusion of a larger area or bring in more natural light, then a larger set of bifold doors is the best option. If you want the bifold doors to add a modern twist to your home, and purely for use as a walk-through, then a smaller, two-paned door is ideal.

How much space is needed for bifold doors?

Interior folding doors can really be as small or as large as you like, whether you want a one person walk-through door or a whole wall made up of folding doors. The important thing to think about is that not only do you leave enough space between the frame, ceiling and surrounding walls, but you also give yourself enough space when you want to open the bifold doors.

As with external bifold doors, internal bifold doors fold back in a concertina fashion and are stacked at one end of the door track. Having three or more doors stacked up may take up too much room in your house. It’s important to think about the space around the doors and how it’ll look when they’re open.

What is the rough opening for a bifold door?

A rough opening refers to the size of the “cut-out” needed in the wall before any frames are installed. The rough openings for a bifolding door are typically between 609mm and 1828mm. But, depending on the type of wall you have, you may need to go with a slightly larger or smaller opening; a drywall opening for example, is usually 1244mm and 2082mm.

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