CLT panels from a manufacturer in Ukraine

What is CLT — cross-laminated timber

CLT (Cross-Laminated Timber) is a structural timber product made of kiln-dried softwood boards stacked at 90° to one another and bonded under pressure. The result is a massive panel with leading structural properties: high load-bearing capacity at minimal self-weight, excellent thermal and acoustic insulation, and resistance to seismic loads.

CLT is widely used across Scandinavia, Central Europe and North America for multi-storey (20+ floors) and modular construction. In Ukraine, Rezult was the first to launch industrial CLT production, making the material available without import dependency.

Rezult CLT panel types

Panel type	Use	Layers	Thickness, mm
Wall	Exterior and interior walls	3 / 5 / 7	80 – 280
Floor	Inter-floor slabs	5 / 7	140 – 300
Roof	Pitched and flat roofs	3 / 5	100 – 200

Exact thicknesses and formats for your project are confirmed with the production department — the range is expanding.

Rezult CLT specification:

• Species: spruce / pine (FSC® C134555 certified raw material)
• Adhesive: zero-emission melamine (E0) or polyurethane
• Lamella moisture: 8–14% (per ETA)
• Standard: EN 16351 (cross-laminated timber); ETA-21/0914 (CE marking)
• Strength grading: C24 per EN 338

Technical characteristics per ETA-21/0914

Values below are declared in the European Technical Assessment for Rezult CLT (ETA-21/0914 of 25 Nov 2021, EAD 130005-00-0304). These are material characteristics for design; the thicknesses and formats actually offered are in the section above.

Parameter	Value	Tolerance
Panel thickness (per ETA)	60–360 mm	± 1 mm
Panel width (per ETA)	≤ 3.50 m	± 3 mm
Panel length (per ETA)	≤ 18.00 m	± 3 mm
Number of layers	3 ≤ n ≤ 9	—
Consecutive layers with same grain direction	≤ 3 (for n ≥ 5)	—
Gap between adjacent boards in a layer	≤ 2 mm	—
Lamella thickness	20–43 mm	—
Lamella width	105–204 mm	—
b/t ratio, inner transverse layers	≥ 4:1	—
Moisture content (EN 13183-2)	8–14 %	≤ 5 % difference within a panel
Board strength class (EN 338)	≥ T10 or ≥ C16	—

Characteristic values for design

Property	C16 / T10	C24 / T14
Modulus of elasticity along grain E₀,mean	per EN 338	12,000 MPa
Bending strength f_m,k	k_sys · 16 MPa	k_sys · 24 MPa
Tensile strength f_t,0,k	16 MPa	19 MPa
Compressive strength f_c,0,k	20 MPa	24 MPa
Compression perpendicular f_c,90,k	2.5 MPa	3.0 MPa
Gross-section shear f_v,gross,k	3.2 MPa	4.0 MPa
Net shear in board joints f_v,net,k	8.0 MPa	8.0 MPa
Torsional shear at crossings f_v,tor,k	2.5 MPa	2.5 MPa
Rolling shear modulus G₉₀₉₀,mean	50 MPa	50 MPa
Density ρ_k — Scots pine	1.1 · 380 kg/m³	1.1 · 420 kg/m³
Density ρ_k — other softwoods	1.1 · 310 kg/m³	1.1 · 350 kg/m³

Panel design follows Annex 3 of the ETA: cross-section stiffness is determined by the mechanically-jointed beam method, with joint slip replaced by dᵢ / (G · b) (dᵢ — transverse layer thickness, G = G₉₀₉₀,mean).

Preliminary floor thickness selection

Indicative single-span floor spans for typical layups, residential load q = 2.0 kN/m². Calculated from the characteristic values of ETA-21/0914 (gamma method, Annex 3).

Panel	Dry floor	XPS 20 mm + 60 mm screed
CLT 100 (3 layers)	up to 2.9 m	up to 3.2 m
CLT 120 (3 layers)	up to 3.4 m	up to 3.7 m
CLT 140 (5 layers)	up to 3.8 m	up to 4.0 m
CLT 160 (5 layers)	up to 4.2 m	up to 4.5 m
CLT 180 (5 layers)	up to 4.5 m	up to 4.8 m
CLT 200 (5 layers)	up to 5.0 m	up to 5.1 m
CLT 240 (7 layers)	up to 5.5 m	up to 5.8 m

For office loading (q = 3.0 kN/m²) subtract approx. 0.2 m from the values above.

Why the screed gives longer spans. A floating wet screed adds mass, so the natural frequency drops. But it raises damping from ~1 % to 4 % and distributes point loads, so the EN 1995-1-1 vibration check moves to a milder regime: instead of a strict f₁ ≥ 8 Hz, f₁ ≥ 4.5 Hz with an acceleration check is sufficient. The gain from damping outweighs the loss from added mass.

Preliminary values for concept-stage thickness selection. Design spans are determined by calculation with the actual loads, support conditions and service class.

Where CLT panels are used

Modular and multi-storey construction. CLT enables buildings up to 8–10 floors and higher. Assembly is 30–40% faster than monolithic construction — a critical advantage for reconstruction and mass housing.

Single-family homes. Walls, floors and roof from CLT with factory precision. Minimal moisture on site, fast weather-tight enclosure.

Commercial and office buildings. Exposed timber structure as an architectural feature of LEED/BREEAM projects. A growing trend in Poland, Czechia and the Netherlands.

Reconstruction and recovery. CLT modules are a solution for fast construction amid shortages of traditional materials and labour — an active direction in Ukraine’s recovery.

CLT vs Concrete: comparison for specifiers

Parameter	CLT	Reinforced concrete	Brick
Self-weight	~500 kg/m³	~2400 kg/m³	~1800 kg/m³
Assembly speed	High (factory elements)	Medium	Low
Carbon footprint	CO₂ stored in timber	High emissions	High emissions
Precision	±1–2 mm (CNC)	Depends on formwork	Masonry
Fire resistance	R60–R120 (charring protects the core)	R90–R180	R120+

Rezult CLT and turnkey construction

Rezult manufactures CLT panels as a material. Design and turnkey construction with CLT is handled by the group’s CLT Rezult division: clt-rezult.com.