Handling of CLT at the workplace
This information is an excerpt from the publication “Moisture-Safe CLT Construction Without Comprehensive Weather Protection” by Svenskt Trä, edition 1:2021. This information sheet does not cover moisture protection during the construction phase but only addresses storage and handling of CLT before installation. Good summary guidance for moisture-safe construction can be found in the same fact sheet mentioned above from Svenskt Trä.
Storage and Handling
CLT elements are manufactured with high precision and have a low moisture content when delivered to the construction site. To maintain these properties during the production phase, the CLT elements must be protected from precipitation, sunlight, dirt, and ground moisture. Plan deliveries according to the production pace so that intermediate storage at the construction site is as short as possible.
Packaging
When CLT elements are delivered, check that the packaging is intact and that the elements are free from soil and dirt. Damaged packaging is repaired immediately. If moisture has penetrated damaged packaging, the packaging must be removed to allow the CLT to dry out.
Cleanliness
Ensure that the CLT elements are free from chips, soil, and dirt. Do not place CLT elements where there is a risk of contamination from, for example, splashes from roof drips or traffic. Contaminated wood is more prone to growth as spores and nutrients are often present in dirt. Contaminated material is cleaned to minimize the risk of growth. If growth is detected, it can usually be removed with suitable cleaning agents or light sanding.
Placement and Loading
Choose a storage location with a flat surface where water cannot accumulate under the CLT elements. Asphalt or coarse gravel is a good base, as there is little risk of soil and dirt splashing up. The ground should also be cleared of snow. Do not place CLT elements where there is a risk of contamination, such as from splashes from roof drips or traffic. Ensure there are enough supports so that the CLT elements do not bend. Place supports 2000 mm apart, never more than 2500 mm, and at least 300 mm off the ground. If several panels are stacked on top of each other, align the spacers to avoid deformations.
Outdoor Storage
Cover the CLT elements in such a way that air can circulate and that there are no high temperatures or condensation. Try to ensure that the storage location is in the shade during spring, summer, and autumn. If panels are to be stored outdoors for a longer period when the risk of growth is particularly high, it should be ensured that the panels can be stored under a roof or preferably indoors to minimize the risk of condensation in the packages. If the packaging is completely sealed, the products can be stored outdoors for a short period.
Direct sunlight on unprotected CLT elements causes rapid drying of the surface, which increases the risk of cracks and moisture movements. From a static point of view, the cracks are insignificant, but cracks can increase the risk of moisture penetration during the assembly period.
