Identification and improvement of critical joints in CLT construction without weather protection

Kalbe, Kristo; Kukk, Villu; Kalamees, Targo

doi:10.1051/e3sconf/202017210002

Cited by 12 publications

(5 citation statements)

References 17 publications

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“…The moisture safety strategy of the ZEB Laboratory is found to align with these recommendations. Kalbe et al also measured wood moisture developments with similar findings to the present paper, with wood moisture levels quickly dropping once the building envelope was assembled [15]. In their two papers, Kalbe et al stress the importance of protecting end-grain edges of CLT panels during construction.…”

Section: Discussionsupporting

confidence: 76%

“…The moisture safety strategy contradicts Danish CLT guidelines [10], which specifically recommend using WPS during CLT construction. Kalbe et al describe an examples of CLT construction projects with and without the use of WPS [15,16]. The recommendations by Kalbe et al include a fast installation process and drying of moisture before wooden elements are covered.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Moisture safety strategy for construction of CLT structures in a coastal Nordic climate

Time,

Andenæs,

Karlsen

et al. 2023

J. Phys.: Conf. Ser.

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To reduce the carbon impact of new buildings, wood is seeing increased use as a structural material. Cross-laminated timber (CLT) and glue-laminated wood (glulam) elements allow the construction of multi-storey buildings. However, wood is vulnerable to moisture, especially when naked wood is exposed to weather during the construction process. This paper presents the moisture strategy employed during the construction of a four-storey CLT/glulam building in Trondheim, Norway. The building was constructed without the use of a weather-protective tent, requiring alternative protective measures. The construction of the main structure was scheduled to be as short as possible. Local protective measures were employed to protect the structure from rain and free water was removed after rain events. The project was closely supervised by the client, with particular care for moisture control. Moisture was regularly measured at 50 points throughout the building. No wooden surfaces were encapsulated until a wood moisture content below 15 weight-% was measured. The performance of the moisture strategy was evaluated using measurements of wood moisture, indoor climate, airtightness, and visual inspections. The wood moisture content quickly decreased as the building envelope was assembled, indicating that drying was well facilitated. In the first year after construction, gaps between the flooring and baseboards were observed, suggesting that the wooden elements have experienced some shrinkage. The moisture safety strategy is deemed to have been generally successful. The overall experiences were important in the development of new recommendations in the SINTEF Building Research Design Guides for CLT structures.

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Section: Discussionsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Moisture safety strategy for construction of CLT structures in a coastal Nordic climate

Time,

Andenæs,

Karlsen

et al. 2023

J. Phys.: Conf. Ser.

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“…There was surface drying in 1P sections, while the deeper parts stayed above 40% MC. This finding emphasised the importance of surface exposure to drying if a major wet event happens during construction and the possible limitation if the full surface of the panel is not exposed for drying [22,24,25,39].…”

Section: Discussionmentioning

confidence: 99%

Effect of Alternate Drying Techniques on Cross-Laminated Timber after Exposure to Free-Water Wetting

Shirmohammadi¹,

Faircloth²

2023

Forests

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Cross-laminated timber (CLT) panels are commonly used in mass-timber multistorey constructions due to their prefabrication, construction flexibility, environmental credentials and weight-to-strength ratio advantages compared to competing building materials. However, the long-term durability and service life of these mass timber panels require further understanding of their performance when exposed to free water. Wetting and drying trials were conducted by exposing Radiata pine (Pinus radiata) CLT sections to either free water (pooling on a single surface) or submerged water (all directions exposed) saturation, followed by either ambient or fan drying. The panels exposed to water pooling only reached MC above the FSP up to 40 mm of the panel depth. For submerged panels, the MC reached values above the fibre saturation point (FSP) at depths of 30 to 40 mm penetration on both panel faces. When comparing the ambient and fan-drying panel sections over the same time period, a less uniform MC profile was observed for the ambient drying, whereas the fan-dried panels fell below the FSP faster and with a more consistent MC profile. A complementary study was conducted on a standalone 3.0 × 3.0 m CLT room, where the room was wetted during a simulated pipe burst event. The moisture monitoring of wall and floor panels during fan drying of the room showed that an MC reduction from an excess of 40% to below 20% could be reached in less than 96 h for the panels’ surface; however, the middle sections of the panels dried slower than the surface sections. The CLT structure fan drying required a longer drying time than the CLT sections tested due to the closed sections (overlaps and connected faces) and a lower rate of airflow. The study of drying CLT sections highlighted the product reaching and maintaining MC higher than FSP points and the need for further drying applied to minimise long-term decay development. Further study is recommended to investigate the effects of closed sections (connected faces) and the duration of drying needed for semi-finished and finished buildings.

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“…One common measure to guarantee moisture safety on a construction site is to erect a temporary roof. Several types of moisture damages have been observed in wooden buildings constructed without a temporary roof (Kalbe et al, 2020(Kalbe et al, , 2022Liisma et al, 2019;Olsson, 2021). In ideal conditions the temporary roof can prevent accumulation of excess moisture of any kind because the building is protected from precipitation.…”

Section: Construction In Dry Conditionsmentioning

confidence: 99%

Moisture Safety in Prefabricated Roof Renovations: Causes and Strategies

Kodi,

Kalbe,

Kalamees

2024

sace

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Achieving carbon neutrality by 2050 requires extensive energy renovation of the existing building stock. In this study we focus on deep renovation with prefabricated insulation elements as a potential solution to attain the required renovation speed and volume. The use of such elements without a proper moisture safety strategy can, however, lead to moisture-related problems, including mould growth. Here we examine the causes of moisture and mould damage in a case study of a building that has been renovated to near-zero energy standards using prefabricated insulation elements. The study elucidates the reasons for the moisture damages detected and proposes two moisture safety strategies to improve the situation. The first strategy emphasizes the importance of ensuring dry construction conditions by either using a full temporary roof or avoiding rainfall during installation. The second strategy addresses localized water damage to the attic floor and involves the use of protective measures, active ventilation and a correct installation sequence. In the case of local moisture damage, the required amount of ventilation air flow during summer is 0.5–0.55 l/(s·m²). During cooler periods, heating is needed. The employed methods include modelling the case-study building with the IDA Indoor Climate and Energy software, as well as mould growth risk assessment based on temperature and relative humidity measurements. The results highlight the effectiveness of both strategies in preventing mould growth if applied correctly, and emphasize the need for thorough planning, moisture safety regulations and rapid response to ensure successful renovation with prefabricated insulation units. The study provides valuable information on moisture safety strategies for serial renovations with prefabricated elements. The existence and proper implementation of a moisture safety strategy is important for achieving the desired energy performance goals while maintaining building durability and occupant health, and it needs to be applied throughout the chain of site management: from the main contractor down to the skilled worker.

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Identification and improvement of critical joints in CLT construction without weather protection

Cited by 12 publications

References 17 publications

Moisture safety strategy for construction of CLT structures in a coastal Nordic climate

Moisture safety strategy for construction of CLT structures in a coastal Nordic climate

Effect of Alternate Drying Techniques on Cross-Laminated Timber after Exposure to Free-Water Wetting

Moisture Safety in Prefabricated Roof Renovations: Causes and Strategies

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