Cross Laminated Timber. Q & A
Do you need to leave expansion gaps in CLT Panesl ?
Direct answer: Yes, you generally need to allow for movement gaps when installing cross-laminated timber (CLT) panels. Timber is hygroscopic, meaning it expands and contracts with changes in moisture and humidity. Proper detailing ensures panels don’t buckle, crack, or compromise airtightness and structural performance.
Why Expansion Gaps Are Needed
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Moisture movement: CLT panels can swell or shrink depending on ambient humidity. Even though CLT is more dimensionally stable than solid timber, it still moves across the grain.
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Avoiding stress build-up: If panels are installed tightly without gaps, seasonal expansion can cause warping, joint failure, or damage to finishes.
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Air and moisture control: Expansion gaps are often sealed with compressible tapes or membranes to maintain airtightness while allowing movement.
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Durability: Gaps prevent trapped moisture at junctions, reducing risk of decay.
Typical Detailing Practices
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Perimeter gaps: Small gaps (often a few millimeters) are left at wall-to-wall, wall-to-floor, and wall-to-roof junctions.
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Service penetrations: Openings for pipes or conduits should include clearance to avoid crushing or splitting.
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End grain protection: Exposed panel edges are sealed or taped, especially at expansion joints, to prevent water ingress.
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Airtightness tapes: Flexible tapes are applied over joints to accommodate movement while keeping the structure airtight.
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Manufacturer guidance: Each CLT supplier provides specific tolerances and installation manuals—these should always be followed.