Is it necessary to glue or dowel terrace pedestals to the substrate?

No. In a typical raised deck terrace, adjustable pedestals do not require gluing or anchoring to the substrate.

A terrace on pedestals is essentially built as a floating structure. The pedestals are placed on a stable substrate, their height is adjusted, and then the following are laid on them:

• terrace pavers,
• joists and boards,
• or an aluminum substructure.

The weight of the surface, proper placement of supports, and edge restraints ensure that a correctly built terrace forms a stable structure without the need for drilling into the substrate.

This is particularly important on balconies, roofs, and terraces built over waterproofing, which we do not want to damage with mechanical anchoring. Solver explicitly states that the primary advantage of the solution is the ability to build a terrace without permanently fixing the pedestals.

However, there are situations where local gluing, anchoring, or other additional securing of the structure may be recommended or required.

These most often concern:

1. terrace edges without a permanent edge restraint,
2. installation of vertical fascia boards,
3. building a single step,
4. areas exposed to particular wind loads,
5. unusual or tall structures,
6. projects where additional fixing results from calculations or technical documentation.

Therefore, the correct answer is:

Terrace pedestals are standardly not glued or anchored. Additional fixing is used only where there is a specific need to stabilize the structure.

Typical paver terrace, surrounded by walls or edge restraint

• Adhesive / doweling: No

Terrace with decking boards on a properly constructed substructure

• Adhesive / doweling: Usually not

Pedestals standing on waterproofing

• Adhesive / doweling: We do not dowel through the waterproofing

Last row at the open edge of the terrace

• Adhesive / doweling: Additional stabilization may be recommended

Vertical bottom fascia board at the edge of the terrace

• Adhesive / doweling: We recommend stabilizing the edge pedestals

One step made using the bottom fascia board

• Adhesive / doweling: Yes – additional stabilization of the structure is required

Several steps

• Adhesive / doweling: A rigid AluDeck structure is better

Terrace particularly exposed to strong wind

• Adhesive / doweling: The solution should be selected during design

Structural design requires anchoring

• Adhesive / doweling: Yes, according to the design

With a properly constructed terrace, they should not move freely during use.

However, you must ensure:

• a stable and load-bearing substrate,
• correct pedestal spacing,
• proper alignment of pavers or joists,
• proper edge finishing,
• appropriate geometry of the entire structure.

A rubber shim can additionally:

• protect the waterproofing membrane,
• increase friction between the base and the substrate,
• improve acoustics,
• limit direct contact between hard elements.

→ Frequently asked questions (FAQ)

Gluing is not a standard procedure performed under every pedestal.

We use it locally when we want to limit the possibility of shifting specific points of the structure.

The most common cases are:

• pedestals at an open edge,
• pedestals under vertical bottom fascia boards,
• a single-step structure,
• an area particularly prone to shifting,
• a situation where mechanical anchoring is not possible.

The advantage of gluing is the ability to stabilize the element without mechanically penetrating the waterproofing membrane.

However, this does not mean that any adhesive can be applied directly to any membrane.

Compatibility must be checked:

pedestal ↔ adhesive ↔ substrate layer.

On the current Solver page, 3M 560 polyurethane adhesive-sealant is indicated as an example solution.

3M describes product 560 as a one-component polyurethane adhesive-sealant that creates a flexible and weather-resistant bond, intended among others for construction and outdoor applications.

However, the name of one product should not be treated as a universal answer for every terrace.

Before bonding, you should always check:

• the material of the pedestal base,
• the type of substrate,
• the type of waterproofing membrane,
• the adhesive manufacturer's recommendations,
• surface preparation,
• application temperature,
• curing time.

If the adhesive is to be applied directly onto the waterproofing membrane, the approval of the membrane manufacturer for contact with the given adhesive is particularly important.

Some wind-resistant systems use bonding or a special adhesive layer instead of penetrating the membrane. For example, the Windproof system by Eterno Ivica connects the pedestal to the substrate using a special butyl adhesive layer adapted to selected waterproofing membranes.

It cannot be said that one method is always better.

Provides very secure mechanical fastening, but requires an appropriate substrate.

It can be considered, for example, in the case of:

• a concrete structure without a waterproofing layer,
• a prepared structural element,
• a solution specified in the design.

The biggest limitation is the possibility of damaging the layers beneath the pedestal.

Does not require making a hole in the substrate.

It can be beneficial:

• at the edge of the terrace,
• near fascia boards,
• where we only want to limit the movement of the pedestal,
• when the substrate cannot be drilled through.

But the connection is only correct when the adhesive used is compatible with both materials.

A vertical fascia board is used to cover the visible space:

paver → pedestal → substrate.

Unlike a regular paver placed horizontally, the fascia board can also transfer loads acting laterally to the structure.

Therefore, the pedestals located at such an end should be properly stabilized.

In the case of a fascia board, the following are particularly important:

• stabilization of the outermost row of pedestals,
• proper fastening of the vertical element,
• maintaining proper expansion joints,
• ensuring water drainage.

How to install vertical elements covering the space under the terrace, the so-called fascia boards?

In the case of a single step made using a side finishing closure plate, we recommend additional stabilization of the pedestals.

This can be done by:

• mechanical fastening to a suitable substrate,
• or gluing, if this is a suitable solution for the layers below.

Current Solver system recommendations indeed provide for doweling or gluing the pedestals for such a single step.

The reason is simple.

A step is loaded differently than a regular terrace surface:

• the user presses on its edge,
• dynamic loads occur,
• horizontal forces appear,
• the same section is repeatedly and intensively loaded.

Therefore, a step should not be treated the same as a regular pedestal located in the middle of a terrace.

For a larger number of steps, a better solution is to create a rigid aluminum substructure AluDeck, instead of making a series of independent steps.

How to build stairs for a raised deck terrace?

Not always.

This issue is more complex because wind can primarily affect the surface, not just the base of the pedestal.

For particularly exposed terraces, the following must be taken into account, among others:

• building height,
• location,
• edge and corner zones,
• terrace height,
• paver format,
• paver weight,
• joint width,
• edge finishing method,
• the possibility of air getting under the surface.

Therefore, simply gluing the pedestal bases is not automatically a solution to the problem of pavers being lifted by the wind.

A system may be needed that connects:

substructure ↔ pedestal ↔ paver

or otherwise secures the entire structure.

Eterno Ivica, in its Windproof solution, creates exactly such a connection between the substructure, pedestal, and paver, showing that when it comes to wind uplift resistance, the entire system must be analyzed, not just the base fixing.

Solver also has separate solutions and recommendations for terraces exposed to wind uplift.

See also: Protecting a raised deck terrace from wind - how to prevent pavers from being lifted?

No.

The height of the pedestal alone does not automatically mean it must be anchored to the substrate.

However, with tall structures, the following become increasingly important:

• lateral stability,
• the geometry of the entire structure,
• loads,
• support height,
• potential bracing,
• the use of a subframe.

Instead of screwing every pedestal to the substrate, stability can often be achieved in many structures by interconnecting the elements above.

A good example is a subframe made of aluminum joists, which forms a rigid frame resting on the pedestals.

This is a completely different situation than having dozens of independent supports without any interconnection.

A terrace on joists – do the pedestals need to be fastened?

Similar to pavers – there is no such general requirement.

In the system:

pedestals → joists → boards

stability can primarily result from the connection of the entire subframe.

The joist should be properly attached to the element on the pedestal head according to the instructions of the given system.

However, this does not mean that the base of every pedestal must be screwed to the substrate.

In the case of the RAPTOR Solver series, it is explicitly indicated that the base has holes for fastening, but fastening the pedestal to the substrate is optional, and on waterproofing, mechanical attachment may even be inadvisable.

What should be the spacing of pedestals under terrace joists?

Why is it not worth gluing every pedestal "just in case"?

You might think:

"If gluing increases stability, then maybe it's best to glue all the pedestals?"

Not necessarily.

One of the fundamental advantages of a raised deck terrace is the reversibility and accessibility of the structure.

The pavers can be lifted.

The pedestals can be:

• adjusted,
• moved,
• replaced,
• reused.

You can also gain access to:

• the waterproofing,
• drains,
• installations,
• conduits running beneath the terrace.

Pedestal systems are valued precisely for, among other things, easy disassembly and reuse of components.

So there is little sense in giving up this feature by permanently bonding every element to the substrate if the structure does not require it.

Doweling into concrete – when is it possible?

If the pedestal stands on:

a solid concrete slab without a waterproofing layer at the fastening point

and the design requires additional securing, appropriately selected mechanical fastening can be used.

However, you must first determine what is actually beneath the base.

Beneath the visible layer of concrete, there may be:

• installations,
• heating conduits,
• insulation layers,
• drainage elements,
• reinforcement,
• waterproofing located deeper.

Therefore the rule:

"I have concrete, so I can safely drill"

is not always correct.

What to do if we cannot drill, but we need stabilization?

We have several options depending on the structure:

If the surfaces and the material used allow it.

A profile, parapet, wall, or other element can stabilize the terrace without interfering with the waterproofing.

Aluminum joists can be connected into a rigid frame.

Under wind load, solutions designed for the entire system may be required.

Therefore, a mechanical anchor in the base is not the only way to ensure stability.

It should be:

• load-bearing,
• stable,
• properly drained,
• free of loose debris.

If the situation requires it, apply an appropriate protective layer or rubber shim.

According to:

• the format of the pavers,
• the layout of the joists,
• the design of the surface.

Determine the target level of the finished surface.

The weight of the pavers or the entire substructure begins to stabilize the system.

It is the edges that require special attention.

Unnecessarily complicates installation and may damage the substrate layers.

This is a much greater potential risk than leaving a properly positioned pedestal without an anchor.

Not every adhesive properly bonds the materials used in the terrace, and not every one is compatible with the waterproofing membrane.

The opposite of over-fastening is completely ignoring edges, steps, and fascia boards.

When dealing with wind suction, the entire paving system must be analyzed, especially the possibility of pavers being lifted.

Pedestals are elements of a floating structure and standardly do not require permanent attachment to the substrate.

This is particularly beneficial on substrates with waterproofing, because we do not make unnecessary holes in the layer responsible for the terrace's tightness.

Additional fastening is considered primarily in special locations:

• at open edges,
• at vertical fascia boards,
• at a single step,
• in atypical structures,
• under special wind loads,
• if required by the design.

The most important rule:

CENTER OF A TYPICAL TERRACE

without gluing and without doweling

EDGES / FASCIA BOARDS / STEPS / SPECIAL CONDITIONS

additional stabilization if needed

So you should not ask only:

"Does the pedestal need to be glued?"

Better to ask:

"Does the structure in this specific location have sufficient stabilization without permanent fastening?"

No. In a typical raised deck terrace, pedestals are not glued to the substrate. Gluing can be applied locally in areas requiring additional stabilization.

There is no such general requirement. If the structure requires additional mechanical fastening and the substrate allows for drilling, appropriate anchoring can be used.

You should not accidentally puncture the waterproofing membrane. Any penetrations through the membrane must be resolved according to the design and requirements of the waterproofing system manufacturer.

A properly designed and constructed terrace is stabilized by the weight of the paving, the layout of the elements, and the edge restraints. The issue should be analyzed for the entire structure, not for an empty individual pedestal.

This can only be considered if the adhesive used is compatible with both the pedestal material and the specific waterproofing. The manufacturers' documentation for the materials should be followed.

With a closed, properly secured edge, this is not always necessary. With an open edge or with a vertical fascia board, we recommend additional stabilization of the outermost pedestals.

When constructing a single step using the fascia board system, it is recommended to permanently stabilize the pedestals through appropriate mechanical fastening or bonding.

Yes, in particularly exposed locations, a special solution to protect against wind suction may be necessary. In such a case, the connection of the entire structure – pavers, pedestals, and the substrate – should be analyzed, not just the anchoring of the pedestal bases.

Not as a general rule. A properly constructed joist substructure can stabilize the entire system without the need to anchor each base to the ground.

The terrace remains a demountable structure. You can lift the surface, access the waterproofing or installations, adjust the pedestals, or replace individual elements.