What is the minimum height of a raised deck terrace on pedestals?

If you only need a short answer:

• lowest adjustable pedestal: 10 mm – SPIRAL 10–17 mm,
• lowest support without adjustment: 2 mm – PAD-002 rubber shim,
• minimum terrace height with a 20 mm ceramic paver on a 2 mm shim: approximately 22 mm,
• minimum terrace height with a 20 mm paver on an adjustable SPIRAL pedestal: approximately 30 mm,
• minimum terrace height with decking boards on an aluminum joist: approximately 48 mm when using a 3 mm shim or approximately 55 mm when using an adjustable pedestal from 10 mm.

In practice, the exact height also depends on the type of surface, substrate, existing slopes, and the required leveling capability of the structure.

The lowest possible variants – examples:

• Support: 2 mm
• Surface / structure: ceramic paver 20 mm
• Approximate minimum height: 22 mm

• Support: 10 mm
• Surface / structure: ceramic paver 20 mm
• Approximate minimum height: 30 mm

• Support: SBR rubber pad 3 mm
• Surface / structure: ALU joist 25 mm board approx. 20 mm
• Approximate minimum height: approx. 48 mm

• Support: 10 mm
• Surface / structure: ALU joist 25 mm + board approx. 20 mm
• Approximate minimum height: approx. 55 mm

Important: the pedestal height is not the same as the height of the finished terrace. When designing, always calculate the entire layer system from the substrate to the top surface of the paver or board.

If by minimum height we mean the lowest height at which we still want to have the ability to adjust and level the terrace, the solution is the pedestal from the SPIRAL 10–17 mm series.

Its minimum height is 10 mm, and the adjustment range of the first model covers heights from 10 to 17 mm.

This is particularly important in places where the space between the substrate and the planned terrace surface is very small, but we still need the ability to correct height differences.

Most often when:

• the level of the finished terrace is very close to the existing substrate,
• the terrace surface needs to be matched to the threshold of the terrace door,
• the substrate has minor unevenness,
• there is a slope requiring correction,
• we need precise leveling of the pavers,
• the height of the structure changes across the terrace.

The last point is very important.

If, for example, we have a space from 10 mm at one end of the terrace to 16 mm at the other, a single pad with a fixed height will not solve the problem. An adjustable pedestal allows each support point to be set individually.

This is probably the most important part of the answer.

The client very often measures the distance:

from the existing substrate to the bottom edge of the terrace door threshold

and asks: "I have 3 cm here. Will a raised deck terrace fit?"

In such a case, the information that we have a pedestal with a height of 10 mm is not enough.

You need to calculate all layers of the structure.

In the case of a terrace with pavers, the simplest formula is as follows:

For point support on pedestals, appropriately prepared terrace pavers are used. A very popular solution is ceramic porcelain pavers with a thickness of 20 mm.

When designing, always check the declaration and guidelines of the specific paver manufacturer regarding the method of support.

Calculation:

20 mm + 2 mm = 22 mm

The theoretical minimum height of such a system is therefore approximately:

22 mm

that is 2.2 cm from the substrate to the top surface of the paver.

This is one of the lowest possible configurations for a dry-laid terrace.

This is where you need to be careful.

Standard thin ceramic tiles intended for adhesive bonding should not automatically be treated as pavers suitable for point support on pedestals.

With a raised deck terrace, the paver does not rest on a full bed of adhesive mortar. It is supported at specific points, so it must be intended by the manufacturer for such use and have adequate strength.

In practice, 20 mm thick porcelain pavers, designed specifically for outdoor applications and installation on pedestals, are very commonly used.

Therefore, you should not reduce the total height of the structure by using a random thin tile of 8, 9, or 10 mm intended for traditional adhesive bonding.

5 rules to ensure terrace pavers on pedestals won't crack.

Minimum height of a deck terrace with boards on joists

The situation is slightly different for terraces:

• wooden,
• composite,
• WPC,
• made from other boards mounted to joists.

Here, you need to add up three elements:

support + joist + board = terrace height

For example:

• SBR rubber pad – 3 mm,
• low aluminum joist – about 25 mm,
• deck board – about 20 mm.

Calculation:

3 + 25 + 20 = 48 mm

So, a very low deck terrace on joists can be about:

48 mm, which is just under 5 cm.

If, instead of a 3 mm support pad, we use a SPIRAL pedestal that starts adjusting from 10 mm:

10 + 25 + 20 &= 55 mm

we get approximately: 55 mm of total construction height.

In exchange for a few extra millimeters, we gain the ability to adjust the height of individual support points.

This often makes installation much easier.

In a very low terrace, there is a temptation to use the thinnest possible profile. This is not always a good direction.

A joist placed on pedestals is supported at points, and between the support points it transfers the loads acting on the terrace.

Therefore, it must have adequate rigidity.

In practice, aluminum profiles are particularly beneficial for low structures. In such applications, a profile with an appropriate height should be used—for example, around 25 mm or more, depending on its cross-section, support spacing, joist spacing, and the designed load.

So, the joist should not be selected solely based on its height. The final support spacing and allowable loads should be determined by the parameters of the system used.

And what about the slope of the substrate?

For very low terraces, the slope is extremely important.

Imagine a balcony where there is a 20 mm difference in height between one end and the other.

If there is 30 mm of space at the door, there may already be 50 mm on the opposite side.

Therefore, one should not answer the question:

"Which pedestal should be used?" based on a single height measurement.

Before selecting pedestals, at least the following should be measured:

• the lowest point of the substrate,
• the highest point of the substrate,
• the level of the planned terrace surface,
• the thickness of the chosen surface material.

Only then do we get the actual range of heights needed for the supports.

How to calculate the required pedestal height?

For pavers:

pedestal height = finished terrace level – substrate level – paver thickness

Example:

Distance from the substrate to the finished terrace level:

42 mm

Paver thickness:

20 mm

42 mm – 20 mm = 22 mm

So we need a pedestal that allows achieving approximately 22 mm in height.

At this point, an appropriate model from the SPIRAL series can be used.

pedestal height = finished deck height – board thickness – joist height

Example:

Available height:80 mm

Board: 20 mm

Joist: 25 mm

80 – 20 – 25 = 35 mm

So about 35 mm remains for the pedestal itself.

What to choose for a very low deck height?

A simple rule can be applied.

If the surface consists of 20 mm pavers, you need to consider support pads of fixed height, e.g., 2 mm, as well as possible thin leveling elements.

We can use a 20 mm paver and an adjustable SPIRAL pedestal from 10 mm.

A very low system is possible:

SBR rubber pad + low aluminum joist + deck board.

You can consider:

SPIRAL + low aluminum joist + board.

Don't design the terrace "flush"

Although mathematically we can achieve a minimum height of e.g. 22, 30 or 48 mm, in a real project it is good to leave some margin.

Construction substrates are very rarely perfectly level.

On site, the following may appear:

• local unevenness,
• slopes,
• waterproofing overlaps,
• drains and drainage systems,
• sheet metal flashings,
• level differences,
• installations running under the terrace.

Therefore, before purchasing structural components, it is worth taking height measurements at many points across the entire surface.

Raised deck terraces – installation systems and technology for professionals

A low terrace does not mean there is no space for water drainage

One of the common questions is also whether, with little space under the pavers, water will be able to drain freely.

In a raised deck terrace, water passes through the open joints between the pavers and then drains off the layer beneath the surface.

Therefore, it is important not only to raise the pavers, but also to properly prepare the substrate and ensure a path for water drainage.

Gap or joint on an external terrace - how to choose the right width?

How to build a raised deck terrace on gravel, grass, or concrete yourself?

The answer depends on what we mean by terrace height.

If we are asking about the lowest support element, we can go as low as:

2 mm – fixed-height support pad.

If we need an adjustable pedestal:

10 mm – SPIRAL 10–17 mm.

If we are interested in the entire terrace with a 20 mm ceramic paver:

• approximately 22 mm on a 2 mm support pad,
• approximately 30 mm on a 10 mm adjustable pedestal.

However, if we are building a terrace with boards on joists:

• approximately 48 mm with a 3 mm support pad + 25 mm joist + 20 mm board,
• approximately 55 mm with a 10 mm pedestal + 25 mm joist + 20 mm board.

Therefore, before choosing a system, it is worth answering four questions:

What is my total available height?

Will the terrace be made of pavers or boards?

Do I need height adjustment?

How large are the level differences on the substrate?

Only then can pedestals or support pads be correctly selected.

The lowest adjustable pedestal from the SPIRAL series has a range of 10–17 mm. It allows height adjustment from approximately 10 mm.

If mechanical height adjustment is not needed, fixed-height support pads can be used. The lowest solutions for pavers are approximately 2 mm.

Yes. With a ceramic paver 20 mm thick and a SPIRAL pedestal set at 10 mm, the total height of the structure is approximately 30 mm.

With a typical terrace paver with a thickness of 20 mm, this is very difficult, because the surface itself already takes up about 20 mm. When using a 2 mm support pad, the minimum system height is about 22 mm.

Using a 3 mm SBR rubber pad, an aluminum joist about 25 mm high, and a board about 20 mm thick, the structure can be about 48 mm. Exact values depend on the components used and the required support spacing.

You should not automatically use standard thin tiles intended for bonding as point-supported pavers. The paver must be designed by the manufacturer for this type of installation. In raised deck terraces, special porcelain pavers with a thickness of about 20 mm are very often used.

In such a situation, it is best to choose an adjustable system whose height ranges cover the entire surface. The SPIRAL series starts at 10 mm and allows you to continue adjustment in subsequent ranges.

You should determine the target level of the upper surface of the terrace, then measure the distance to the ground in several places and subtract the thickness of the paver or the thickness of the board and joist. This way you will get the actual height of the pedestals needed.