How to measure uPVC, vinyl, aluminium and wood sliding doors?

How to measure sliding door

Do you know what is the most common reason for clients complaints? If you have a little bit of experience for sure you can say that those are installation mistakes. How to do the sliding doors measurements well?

The rules of installation are the same for every material such as vinyl, upvc, aluminium or wood.

Let’s start with the measurement. The way of measurement is different in each of these three situations:

1. First situation: 

You install the door when the floor is done and there is no possibility of embedding the threshold in it.

You should measure the width of the door opening from right to left at 3 heights and choose the smallest dimension. Subtract 2cm from the left and 2cm from the right. In this way you have the width of the opening in the narrowest place minus 4cm.

Determining the height is a more difficult task. It all depends on the installation conditions.

You should measure the width of the door opening from right to left at 3 heights and choose the smallest dimension.

If the floor in the building is finished, and we cannot embed the threshold into the floor, we determine the patio door height from the floor to the lintel line, subtracting 2-3 cm for expansion joints.

The final height of the door will be about 2.5 cm (or an inch) lower than the height from the floor to the lintel at the lowest point.

Remember to order doors with the lowest possible threshold if you can.

For example, in Bifold door or HS sliding doors, you can order thresholds not embedded in the floor and meeting the criteria of a low threshold without barriers.

The final height of the door will be about 2.5 cm lower than the height from the floor to the lintel.

Let us show you this on example:

We have a window opening with dimensions declared by the investor as 400cm in width and 220cm in height.

It turns out that when measuring the width at the bottom – the real dimension is 398cm, in the middle – 400cm and at the lintel 401cm.

Therefore, our width is the smallest dimension: 398cm – 4cm which equals 394cm.

The height is similar: for the left jamb – 221cm, in the middle 223cm and for the right 224cm. We choose the lowest measurement  – 221cm – we subtract 2cm and set the door height as 219cm.


To order doors you should provide the following dimensions 394cm and 219cm. Always remember that the width is given first.

How to measure sliding doors - practical example.

It is more difficult to determine the correct height of the door when the building is under construction, and there is no physically finished floor yet –  the so-called level “zero”.

In this case you must require from the investor to indicate and mark on the walls where the floor level is planned.

Once you have determined the “zero level” of the finished floor (with tiles / carpet / plank or anything else) measurement is very simple, but there are two options again.

2.  Second situation:

You install the door with the threshold embedded in the floor, you can do measurements as follows.

Measure the height from level “zero” to the lintel at a minimum of 3 points. Then you subtract 2 cm from the lowest height obtained. And this is the height of your door from the threshold to the upper part of the frame.

REMEMBER! To order the door correctly – you must add the threshold height to this height – which, depending on the model, can be from 20 to 90mm!

You need to have those parameters:
1. The height of the opening from the lintel to the zero level.
2. Door model and threshold height, which will be embedded in the floor.
3. And height from the bottom frame to the zero level /(the lowest of 3 measurements).

The supplier will select a sliding door with an embedded threshold of optimal dimensions, and system profiles widening the frame or ground profiles, for example from XPS or styrodur.

To order the door correctly, you must add the threshold height, which (depending on the model) can be from 20 to 90mm!

To describe the measurement process accurately, we’ll use an example

In practice, the width at floor height is 401cm, at half height it’s 399cm and 400cm near the lintel. The door will therefore be 399cm – 4cm equals 395cm wide.

The declared height is 240cm. However, it turns out that in practice the finished floor will be 20 cm higher, than the current bottom jamb.

After marking it on the walls and using a laser level to measure in 3 places from the sideways, the dimension from the future level zero to the lintel is 221cm on the left, 221cm on the right and 219cm in the center.

The door will therefore be 399cm - 4cm equals 395cm wide.

The height from the threshold to the upper frame of the door will be 219 – 2 cm equals 217cm.

So as we choose corvision plus doors from Cortizo – the threshold is 6.9 cm The finished height of the shift is 217cm + 6.9cm threshold equals 223.9 cm 

The total size of the sliding doors will be: 395cm x 223.9cm

For this we choose system extensions to be embedded in the floor. 3 measurements from the level of the finished floor to the current one. 20cm on the left, 19cm in the middle and 21cm on the right.

So the extensions we need are 19cm-6.9cm threshold equals 12.1 cm  The whole measurement is written as follows: Window width: 395 cm Window height: 223. 9 cm + extensions profile 12.1 cm high.

Measure the height from level “zero” to the lintel at a minimum of 3 points.

3. Third situation

 If you install BiFold, Sliding door type having a threshold base set at floor height – measurement is much simpler.

You only need: measurements at 3 points in height from the zero level of the finished floor to the lintel. You subtract 2 cm from the lowest dimension and this is the height of your door.

 Extensions in 3 points, as in the previous example (the height from the finished floor level to the bottom jamb).

You give the lowest value to the supplier – as the dimension to which you should choose system profiles expanding the frame or ground profiles.

If you install BiFold, Sliding door type having a threshold base set at floor height - measurement is much simpler.

Let’s put it into practice

The hole declared by the investor is 400x240cm The finished floor will be 20 cm higher than the current height of the sill.

The situation with the width is identical to the previous example. The dimensions below are 401, 399 in the middle and 400cm in the top. Therefore, the width is 399-4cm = 395cm.

The size of the finished door is 395cm x 218cm.

What about height? With identical assumptions. From the future floor to the drive rail height: from the left: 221, right 221, in the middle 220cm. The door will be 220cm high – 2cm equals 218cm high. Thus, the size of the finished door is 395cm x 218cm.

It remains to choose the ground widening – we measure the height from the sill to the finished floor height (zero level) from the left 20, in the middle 19 and on the right 21 cm.

Therefore, we order extensions from the supplier up to 19cm, giving the following ordering parameters: Window dimensions: 395cm x 218cm + System extensions: 19cm.

about author

Voytech Stanowski

Founder and owner of, company from Poland that specializes in the export of windows and doors in the B2B segment.

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