How can we help you?

Send us a message
Search for contacts here
Find a contact
Look for a job at Stora Enso.
Get a job
Sylva rib panels by Stora Enso

Rib Panels

Building new visions with Rib Panels

Rib Panels are mass timber products that can be used for long-span floors and roofs where high load-bearing capacity and low self-weight are required. Stora Enso offers two types of Rib Panels: made from CLT combined with GLT (glulam) or from LVL.

Photo: GBL architectes

What are Rib Panels?

Our ready-to-install Rib Panels consist of flat wood panels bonded together with supporting ribs, using structural adhesives that deliver outstanding strength and performance.

Why Rib Panels by Stora Enso?

Open and flexible floor plans require long-span components to reduce the amount of load-bearing walls and columns. Rib Panels are ideal for spans over 6m, with impressive strength and structural performance.

All Rib Panels by Stora Enso are CE-marked, meaning they meet the European Economic Area's high safety, health, and environmental protection requirements. Precision cut Rib Panels minimise the need for remedial work for the elements to fit in place, speeding up the building process.

Rib Panels that are customised and delivered just-in-time (JIT) are part of our Sylva™* kit, where they can be used in Sylva Floors and Roofs.

*Sylva™ by Stora Enso is currently only available in Europe and Australia.

Technical product description

CLT Rib Panels by Stora Enso are made by bonding a CLT panel and GLT (glulam) ribs with a high-strength adhesive. For outstanding performance, our CLT Rib Panels are made from strength-graded boards. This means we have pre-sorted the wood based on its strength, stiffness, density, and appearance for optimal use.

CLT rib panels by Stora Enso 

 

Our LVL Rib Panels are made from LVL, combining LVL S, where all the veneers run in the same direction, and LVL X, where veneers are regularly spaced at right angles.

LVL rib panel by Stora Enso technical product description 

The structural bond between the components in Rib Panels by Stora Enso reduces the supporting structure’s depth and optimises the volume of timber material. This gives Rib Panels an advantage over traditional mechanically fastened Rib Panels where the components are simply screwed together. This makes it possible to:

  • achieve longer spans with the same structural depth (the total height required to achieve a certain structural performance), or
  • lower structural depth at the same span

As the only manufacturer with both CE-marked CLT- and LVL Rib Panels, Stora Enso holds European Technical Approvals (ETA) confirming that all Rib Panels by Stora Enso meet the required European health, safety, and environmental protection standards.

Image gallery

ANSES ANMV Headquarter, Javené, France
ANSES ANMV Headquarter, Javené, France
Photo: Guillaume M, Architect: DLW Architectes Developer: ANSES ANMV
Les Jumeaux - Parc Racine², Villeneuve d'Ascq, France
Les Jumeaux - Parc Racine², Villeneuve d'Ascq, France
Partner of Stora Enso: Creation Bois, Developer: Aventim Immobilier, Architect: GBL architectes

Key benefits of designing and building with Rib Panels

  • Prefabricated and lightweight panels allow for rapid workflow from delivery to assembly

  • Rib Panels by Stora Enso use wood in the most efficient way possible—yield more m² with less raw material

  • Floors and roofs made from Rib Panels allow for flexible floor plans that can be easily repurposed for changing needs

  • Less need for beams and load-bearing walls gives more architectural freedom

  • Insulation can be integrated into the structural layer of an LVL Rib Panel

  • The space between the ribs of CLT Rib Panels can be used to route services or other installations

  •  CLT Rib Panels have natural fire-resistant properties and even the structural elements can be left exposed for a beautiful visual surface

Applications

Sylva CLT Rib Floors and Roofs

How Sylva CLT Rib Floors and Roofs are best used in a building

Sylva CLT Rib Floors and Roofs are a great fit when the building project requires:

  • Exposed wood in ceilings
  • Optimal space utilization with installations such as sprinklers or lighting, acoustic panels and decorative elements
  • Medium to long spans
  • Fire resistance without the need to add protective cladding

*Sylva™ by Stora Enso is currently only available in Europe and Australia.

CLT rib panel by Stora Enso application

 

Sylva CLT Rib Floors and Roofs are an effective and economical solution for long spans due to their excellent material efficiency. They are available in visual quality, which means it is possible to leave ceilings and soffits exposed. With Sylva CLT Rib Floors and Roofs, it is not necessary to clad the ribs with e.g. gypsum board to meet national fire regulations as the timber structure can remain stable for up to two hours when exposed to a fully developed fire.


Building types

Suitable for residential, office and school buildings with medium to long spans of 6–13m. If longer spans are required, Sylva LVL Rib Floors and Roofs are recommended.

Sylva LVL Rib Floors and Roofs

How Sylva LVL Rib Floors and Roofs are best used in a building

Sylva LVL Rib Floors and Roofs are the ideal choice when the building project requires:

  • Optimal material efficiency
  • Medium to very long spans
  • Lowest possible weight
 

LVL rib panels by Stora Enso

LVL Rib Floors and Roofs are even more material-efficient than CLT Rib Floors and Roofs because they have the lowest weight yet the highest stiffness, load-bearing capacity, and dimensional stability. Due to their high material efficiency and lightweight nature, LVL Rib Floors and Roofs can also be more economical than CLT Rib Floors and Roofs. They can reach longer spans and are well-suited for roof applications with spans between 6–20 m.


Building types

Optimal for residential, school buildings and industrial buildings. LVL Rib Floors and roofs are recommended for spans of 6–20 m.

Product range and features

Product types

CLT Rib - type Open

The top panel comprises a CLT type L panel with GLT ribs structurally bonded to the underside.

CLT rib panel type 1

 
Standard variants
Length: 6–13 m
Height: 280–640 mm
Width: 2.45 m
 
* Please contact your local sales representative if a non-standard variant is needed.
CLT rib panel front view with measurements
Sylva CLT Rib Floors

T1 [mm]

B [mm]

H2 [mm]

S

160

200

240 280 320 360 400 440 480 520 560
R30 80L3s

160

H280-80L3s H320-80L3s H360-80L3s H400-80L3s H440-80L3s H480-80L3s H520-80L3s H560-80L3s H600-80L3s H640-80L3s ~800 mm
R60 100L3s

160

H260-100L3s H300-100L3s H340-100L3s H380-100L3s H420-100L3s H460-100L3s H500-100L3s H540-100L3s H580-100L3s H620-100L3s
R90 120L3s

200

H400-120L3s H440-120L3s H480-120L3s H520-120L3s H560-120L3s

CLT Rib - type Closed

Rib panel comprising of a top and bottom CLT type L panel with GLT ribs structurally bonded in between.
 
The addition of the bottom CLT panel further increases the product's fire and structural performance. This allows for a maximised possible span or decreased structural depth. *
 
* Please contact your local sales representative if you are considering CLT Rib- type Closed.

CLT rib panel type 2

 CLT rib panel front view with measurements
 

LVL Rib - type Open

Rib panel with a T-shaped cross-section comprising an LVL X top panel and LVL S ribs structurally bonded together. 

LVL rib panel type 1 perspective

Standard variants

Length: 6-20 m
Height: 336–636 mm
Width: 2.4 m
 
* Please contact your local sales representative if a non-standard variant is needed.
LVL rib panel type 1 front view
Sylva LVL Rib Roofs

T1 [mm]

B1 [mm]

H2 [mm]

S

LVL Grade X S 200 240 300 360 400 450 500 600
R0 24 51 H224-X24 H264-X24 H324-X24 H384-X24 H424-X24 H474-X24 H524-X24 H624-X24 600 mm
>R0 Handle with gypsum boards (see ETA)
Note - T1 thickness is after calibration sanding which removes 3mm of material.
Sylva LVL Rib Floors

T1 [mm]

B1 [mm]

H2 [mm]

S

LVL Grade X S 200 240 300 360 400 450 500 600
R0 36 51 H236-X36 H276-X36 H336-X36 H396-X36 H436-X36 H486-X36 H536-X36 H636-X36 600 mm
>R0 Handle with gypsum boards (see ETA)
Note - T1 thickness is after calibration sanding which removes 3mm of material.

LVL Rib - type Semi-open

Panel with an I-shaped section comprising a top panel made from LVL X, LVL S ribs and an LVL S bottom tension flange all structurally bonded together.
 
The addition of an LVL S flange to the bottom of the ribs improves the structural performance of the product and can be used to decrease structural depth* or reach even longer spans than with the open type.

LVL rib panel type 2 perspective

Standard variants
Length: 6-20 m
Height: 284 – 584 mm
Width: 2.4 m

LVL rib panel type 2 front view with measurements

 
Sylva LVL Rib Roofs

T1 [mm]

B1 [mm]

B2 [mm]

T2 [mm]

H2 [mm]

S

LVL Grade X S

S

200 240 300 360 400 450 500 600
R0 24 51 300 48 H272-X24-S48F H312-X24-S48F H372-X24-S48F H432-X24-S48F H472-X24-S48F H522-X24-S48F H572-X24-S48F H672-X24-S48F 600
>R0 Handle with gypsum boards (see ETA)
Note - T1 and T2 thickness is after calibration sanding which removes 3mm of material.
Sylva LVL Rib Floors
T1 [mm] B1 [mm] B2 [mm] T2 [mm]

H2 [mm]

S

LVL Grade X S

S

200 240 300 360 400 450 500
R0 36 51 300 48 H284-X36-S48F H324-X36-XS48F H384-X36-S48F H444-X36-S48F H484-X36-S48F H534-X36-S48F H584-X36-S48F 600
>R0 Handle with gypsum boards (see ETA)
Note - T1 and T2 thickness is after calibration sanding which removes 3mm of material.

LVL Rib - type Closed

LVL Rib comprising of a top and bottom panel made from LVL X with LVL S ribs structurally bonded in between.

The additional lower LVL X panel further increases the product's fire and structural performance. It also maximizes the possible span and the potential to decrease the structural depth.

LVL rib panel type 3 perspective

Standard variants

Length: 6 -20 mm

Max height: 284 - 534 mm

Width: 2.4 m

 LVL rib panel type 3 front view with measurements

* Please contact your local sales representative if a non-standard variant is needed.

* Structural depth means the total height required to achieve a certain structural performance or how thick the load-bearing part of the floor needs to be.

Sylva LVL Rib Roofs

T1 [mm]

B1 [mm]

T2 [mm]

H2 [mm]

S

LVL Grade X S X 200 240 300 360 400 450 500 600
R0 24 51 48 H272-X24-X48 H312-X24-X48 H372-X24-X48 H432-X24-X48 H472-X24-X48 H522-X24-X48 H572-X24-X48 H672-X24-X48 600
>R0 Handle with gypsum boards (see ETA)
Note - T1 and T2 thickness is after calibration sanding which removes 3mm of material.
Sylva LVL Rib Floors

T1 [mm]

B1 [mm]

T2 [mm]

H2 [mm]

S

LVL Grade X S

X

200 240 300 360 400 450
R0 36 51 48 H284-X36-X48 H324-X36-X48 H384-X36-X48 H444-X36-X48 H484-X36-X48 H534-X36-X48 600
>R0 Handle with gypsum boards (see ETA)
Note - T1 and T2 thickness is after calibration sanding which removes 3mm of material.

Surface qualities

CLT Rib Panels

 
CLT Rib Panels are available in three different surface qualities depending on your requirements. Due to the product's manufacturing process, only the bottom CLT panel or the GLT ribs are available in Visual quality. Please note that closed variants are not available in Visual quality.
 
Visual (VI)*: The best possible surface quality for when the floor will be exposed and part of the interior design of the building. Commonly used in public buildings, schools, or homes.
  • CLT panel - Visual quality
  • GLT rib - Visual quality
 
Industry visual (IVI)*: A surface quality suitable for leaving exposed, but not with the absolute toughest visual requirements. Suitable for when the CLT will be exposed in industrial buildings for example.
  • CLT panel - Industrial visual quality
  • GLT rib - Visual quality

Non-visual (NVI): Suitable for when the CLT rib panel is not visible or will be covered over with gypsum, plasterboard, or any other material.
  • CLT panel—Non-visual quality
  • GLT rib—Industrial quality
 
View CLT surface quality chart

 

* Please note that due to the manufacturing process, the dimensions of the ribs increase when using visual quality GLT vs industrial quality.
 

LVL Rib Panels

LVL Rib Panels are currently not available in visual quality.
 

Reference projects

Les Jumeaux - Parc Racine
Photo: GBL Architectes

Les Jumeaux - Parc Racine²

 Villeneuve d'Ascq, France
Learn more
Hylte mill
Photo: Stora Enso

Stora Enso Hylte mill

Hyltebruk, Sweden
Learn more

Browse over 500 wooden buildings and get inspired

Explore references

Technical product data

Key data

CLT Rib Panels

Service class Service class 1 and 2 to according to EN 1995–1–1
Product certification CE marked with ETA-20/0893
Strength class According to ETA-20/0893:
CLT panel according to ETA: C24
GLT ribs: GL 20h – GL 32h and GL 20c – GL 32c
Moisture content 11 % ± 3 %
Wood species Spruce (pine or fir also possible)
Typical density ~490 kg/m³. Please note a different density may be declared depending on the need (structural design, transportation, erection etc.)
Reaction to fire class Euroclass D–s2, d0
Resistance to fire, charring rate According to ETA–20/0893 Annex 4, Fire performance classified according to EN 13501–2
1. Open CLT rib, REI 90
2. Open CLT rib with gypsum board ceiling structure, REI 90
3. Closed CLT rib, REI 90
4. Closed CLT rib with gypsum board ceiling structure, REI 120
 
Airtightness CLT is airtight according to EN 12 114
Thermal conductivity of CLT panel 0.12 W/(mK) according to ETA–20/0893
Water vapor resistance 50 (dry) to 20 (wet) according to EN ISO 10456

LVL Rib Panels

Service class Service class 1 and 2 to according to EN 1995–1–1
Product certification CE marked with ETA 18/1132
Moisture content 10% +/- 2% when leaving mill
Wood species Spruce
Mean density 510 kg/m³ (LVL S and X)
Reaction to fire class Euroclass D–s1, d0
Resistance to fire, charring rate

According to ETA 18/1132– Annex 2, Fire performance is classified according to EN 13501–2

1. Open LVL rib single fire board ceiling structure, up to REI 30
2. Semi-open LVL rib with double fire board ceiling structure, up to REI 90
3. Semi-open LVL rib with triple fire board ceiling structure, up to REI 120
4. Semi-open LVL rib with double fire board ceiling structure, up to REI 120

The LVL X panel on the lower side of LVL rib panel by Stora Enso – closed type (or inverting a non-closed type) may be used as a non-load-bearing protection for the rest of the LVL rib panel cross-section or as a load bearing part of the structure in the design of the resistance to fire.

LVL material charring rate - According to EN 1995–1–2, Table 3.1

Airtightness LVL has adequate airtightness according to ETA 18/1132
Thermal conductivity 0.13W(mK) according to ETA 18/1132
Water vapor resistance Wet cup 70 μ
Dry cup 200 μ
 

Adhesives and emissions

CLT Rib Panels

Stora Enso manufactures CLT panels with formaldehyde-free PUR and EPI adhesives. GLT ribs used in our range are classified as E1 or have no formaldehyde content when bonded with PUR adhesive, according to EN 15425. The adhesive used in the manufacturing of the CLT ribs to attach the GLT rib to the CLT panel is a one component PUR adhesive as defined in EN 15425. The overall class of the product is E1.
 

LVL Rib Panels

The LVL X and S panels that make up the components of Sylva  LVL rib panels are bonded together with structural weather-resistant adhesive. The adhesive is cured in the LVL product and no longer reacts once it is in its solid state. As a result, LVL meets the requirements of class E1 (EN 717-1) with formaldehyde emissions <0.1 ppm. The ribs are bonded to the top panel and flanges using a formaldehyde-free PUR adhesive, so the product’s overall class is E1.
 

Fire performance

CLT Rib Panels

CLT Rib Panels have natural fire-resistant properties thanks to the unique charring properties of wood. Many people assume wood is not safe in a fire, but when exposed to heat, timber goes through a thermal breakdown process and a layer of char forms on its surface.
 
Wood has around a 10–12% moisture content, depending on the building's internal atmosphere. When timber ignites, the moisture evaporates, and the charring process begins. This charred layer acts as a natural insulator which protects the inner core. The surviving structure in the uncharred inner core remains relatively unaffected, maintaining its structural strength and stability for up to two hours when exposed to a fully developed fire. Our CLT Rib Panels therefore easily meet all fire regulations.
 

LVL Rib Panels

A building using Sylva LVL rib panels can be designed to protect against fire and reach fire resistance limits up to REI 120. This can be achieved by using protective layers such as fire boards on open/semi-open Sylva LVL rib panels or using a closed panel and letting the lower LVL X panel act as a non-loadbearing protective layer.If anything above R0 for open and semi-open LVL Rib Panels is required, they must be protected by a suspended fire protection system. 

Closed LVL Rib Panels can possess inherent fire resistance using the lower LVL X panel as a protective, non-load bearing layer for the remaining LVL Rib Panel. For more information on inherent fire resistance see section above on CLT rib fire performance.

 

Tolerances

CLT Rib Panels

Depth
 Rib height ≤ 400 mm   -2 / +4 mm
 Rib height > 400 mm  -0.5% x [height] / +1% x [height]
Width  +/- 2.0 mm
Length  +/- 5.0 mm
 
 

LVL Rib Panels

 Depth  Rib height ≤ 300 mm   ± 2 mm
 Rib height > 300mm, ≤ 600 mm  ± 3 mm
 Rib height > 600 mm  -0.5 %x[height] / +1 %x[height]
 Width  ± 2 mm or ± 0.5 %
 Height  ± 5 mm
 

Dimensional stability

CLT Rib Panels

 
Because CLT Rib Panels are cross-laminated, the effects of swelling and shrinking from changes in moisture content are minimized. Standardized values are:
 Direction/Component  % of shrinkage or swelling per % moisture change
 In plane direction / CLT Panel   +/- 0.02-0.04
In thickness direction / CLT Panel-GLT ribs  +/- 0.24 
 
 

LVL Rib Panels

Changes are not anticipated in normal conditions for LVL Rib Panels. When necessary, the dimensional change of the product due to the change of moisture content can be calculated as follows:

Direction  Direction % of shrinkage or swelling per % moisture change
 LVL-S LVL-X
 In plane direction  +/- 0.30   +/- 0.44
In thickness direction  +/- 0.31   +/- 0.33
 
 

Calculatis: a state-of-the-art timber design tool

Start designing with Calculatis

Sustainability

Emission comparison between a Sylva Rib Floor and Concrete

Compared to manufacturing a concrete floor, a Sylva Rib Floor has a significantly smaller carbon footprint CO2 equivalent (eq.). * In addition, the rib floor acts as carbon storage. While the floor locks in the CO2 eq., new CO2 is absorbed by replanted trees.

 Emission comparison CLT rib panel by Stora Enso


 Emission comparison LVL rib panel by Stora Enso  

The compared wall structures are as follows:

 

Hollow-core concrete floor

Concrete floor buildup 

-Screed 20 mm

-Glass wool insulation 25 mm

-Concrete 50 mm

-Reinforced steel

-Hollow core concrete slab 265 mm

 

Sylva Rib Floor (CLT /LVL)

Sylva CLT Rib Floors buildup

Sylva LVL Rib Floor

 

-Screed 50 mm

-Rock wool insulation 50 mm

- CLT/LVL rib panel 360 mm

-Gypsum 12.5 mm

 

Assumed building:

- European office/residential building, 10,000 m²

 

The dataset used for this comparison:

- Build-ups - typical European, equivalent build-ups from One Click LCA®—automated life cycle assessment software.

- Sylva CLT rib panel - Stora Enso data from the international EPD® system.

- Sylva LVL rib panel - Stora Enso data from the international EPD® system.

- Other materials—generic data from One Click LCA.

____________________

* Product stage CO2 eq. emissions per m²—the greenhouse gas emissions associated with materials and construction processes up to practical completion modules A1-A3. Excludes the CO2 sequestered in the installed products at practical completion.

 

An efficient way to use wood for floors and roofs

The amount of wood used per m² can be reduced by up to 40% by using a CLT rib floor and up to 70% by using an LVL rib floor instead of a massive CLT floor.

The example below shows a massive CLT floor and an equivalent Sylva CLT rib floor spanning 8 m in a residential building.

 

Massive CLT panel

 CLT by Stora Enso 

0.26 m³ of wood per m² floor

 

Sylva CLT Rib Floor

CLT Rib Panel by Stora Enso

  

0.16 m³ of wood per m² floor

 

Sylva LVL Rib Floor

LVL Rib Panel type 1

0.07 m³ of wood per m² floor

 

Documents and certificates

Documents

Related products and services

Navigate this page

Quick links