Timber Frame Walls Research Articles

Towards rational decision-making on repointing to mitigate moisture damage in building envelopes: A probabilistic study

Repointing is a prevalent maintenance practice in Northern Europe aimed at mitigating moisture-related damage in brick masonry buildings. Although commonly used, evidence of its effectiveness is limited. This study assesses repointing's role in reducing damage risks by conducting a probabilistic hygrothermal analysis of two wall types: timber frame walls and masonry cavity walls. Results indicate that repointing could reduce the mold index in timber frame walls and moisture content in the autoclaved aerated concrete (AAC) layer of masonry cavity walls, particularly in walls with visible defects. However, its impact is minimal on walls without significant deficiencies. Moreover, the study suggests that repointing, given its labor-intensive and costly nature, may not always be the most judicious maintenance strategy. It recommends a selective repointing approach, suiting the specific conditions and needs of the wall based on its location, orientation, and existing state, rather than a blanket application across all façade sections.

Hygrothermal performance of timber-framed walls in Turkey – Long-term monitoring

The increasing energy consumption emphasizes the urgency of sustainable building practices. Worldwide, there is a tendency towards local, natural, durable, and recyclable materials like timber. Furthermore, timber's excellent thermal insulation and natural hygroscopic properties enable it to efficiently regulate indoor humidity levels, ensuring stability and comfort. In Turkey, timber construction declined significantly in the 20th century due to the shift towards vertical reinforced concrete, however, recent years have witnessed a renewed interest driven by earthquake concerns and global inclination. Despite this resurgence, timber construction practices are still limited, and the hygrothermal performance of exterior walls in both restoring traditional timber buildings and constructing new ones is often disregarded. Furthermore, there is a lack of scientific research in this area. Understanding the hygrothermal behaviour of these structures is essential for meeting modern energy efficiency standards. This study evaluates the hygrothermal performance of prevalent practices in timber-framed constructions in Turkey. Long-term monitoring in a full-scale test cabin exposed to real climatic effects provides insights. Findings indicate the exterior plywood sheathing on the North-west facing walls being more susceptible to moisture, particularly when the indoor relative humidity is elevated. South-east facing walls are better at drying, but air barrier membrane slows down drying. Timber cladding with ventilated cavity offers improved protection but its high exposure to rainfall in North-west, and solar radiation in South-east, implies potential performance degradation over time. Installing suitable vapour retarders and additional exterior thermal insulation particularly to the North-west facing walls could possibly reduce risks associated with moisture, as well as preventing thermal bridges.

Impact of different water penetration criteria and cavity ventilation rates on the risk of mold growth in timber frame walls with brick veneer cladding

The present paper investigates the impact of different water penetration criteria on the risk for damage in a common type of building envelope in Nordic countries, timber frame walls with brick masonry veneer. The studied walls are evaluated based on one damage criterion, the risk of mold growth. The study investigates several parameters: water penetration criterion, type of moisture source (uniformly distributed or point source) and its position in the wall assembly, air change rate (ACR) (representing different workmanship scenarios), wind-driven rain (WDR) coefficient, and locations (Gothenburg and Rensjön, with different average annual rainfall and temperature). Two criteria on how to implement water penetration are compared: a) a commonly accepted reference model that assumes one percent of all wind-driven rain deposited on the façade to penetrate the clay brick cladding, and b) a new criterion stating that 3.8% of WDR penetrates when the water content of the brick veneer cladding is above 90% of its saturation capacity. The simulation is done for a thirteen-year period with WUFI Pro and WUFI 2D. The results indicate the greater importance of implementing water penetration compared to ventilation in cavities. Further, the findings suggest that the moisture source’s location significantly impacts the mold growth risk. The results also show that the choice of the WDR coefficient affects the risks, which suggests that this factor needs accurate quantification for hygrothermal analyses. The results in this study suggest that an effective measure for the design/maintenance of such walls should incorporate: a) limiting the amount of water penetrating through the cladding, particularly stopping water from reaching the sensitive elements, i.e., timber studs, b) removing extruded mortar stemming from poor workmanship, if any, which may act as a capillary bridge.

Hygrothermal performance of corners and floor junctions of timber-framed exterior walls: a simulation study

Corners and basement junctions of different timber-framed walls were studied by computer simulation using Delphin 5.8.3 software. Wooden cladding and brick veneer were compared with each other, as well as different wind barrier solutions. Both internal and external corners were studied, first assuming them airtight and then modelling an air leak. Simulations were performed both in present and future climate conditions. According to the results, the walls with wooden cladding and brick veneer had a big difference in their hygrothermal behaviour. Mould index rose considerably after construction in sole plate of brick clad wall, even if the plate was originally dry. Wet sole plates dried up very slowly. Almost all corner junctions of walls with wooden cladding performed well when there was no air leak. Corners of brick clad walls were more problematic. With an air leak, all studied walls developed considerably high mould indices, underlining the importance of building airtightness.

Experimental evaluation of the out-of-plane behavior of a traditional timber frame with mud and rubble infill wall strengthened by a polypropylene band mesh on one side

The structural integrity of traditional Chinese village residences may be compromised due to inadequate connections between the timber frame and infill walls, coupled with the weak cohesiveness of clay mud. Among the various damage mechanisms resulting from earthquakes, the out-of-plane collapse of infill walls is a recurrent and significant concern. The goal of this research is to investigate the feasibility and effectiveness of a polypropylene (PP) band mesh reinforcement approach for a traditional timber frame with mud and rubble infill walls. The ultimate goals are to prevent out-of-plane collapse, improve the collaborative performance of the structure, reduce seismic vulnerability, and safeguard the architectural heritage of traditional dwellings. With careful consideration of their aesthetics, the study centers on timber frames with mud and rubble infill walls strengthened by a polypropylene (PP) band mesh and cement mortar on one side. A series of experiments were conducted based on out-of-plane cyclic one-way tests of four full-scale specimens. Different loading surfaces and reinforcing PP grid sizes with and without window openings were investigated to characterize the out-of-plane behavior of the reinforced hybrid walls. The damage evolution, failure modes, force–displacement curves, out-of-plane profile characteristics, stiffness, strength, and energy dissipation were described. All the reinforced walls exhibited marked improvements out-of-plane lateral capacity, with enhancements of approximately 120% and 162%, and stiffness increases of approximately 105% and 200%, compared to the unreinforced walls. The minimal out-of-plane displacement observed on the reinforcement side was also accompanied by significant increase in integrity and ductility.

Shaking table tests on single-bay timber-framed wall specimens with fired brick and adobe block infills and mortise-tenon joints

In-plane uniaxial shaking table tests were carried out on full-scale single-bay timber-framed masonry wall specimens characteristic of Ottoman-period mansions in mainland Greece. The posts were connected to the sill-beam with cylindrical mortise-tenon joints. Two infills were investigated: solid fired clay bricks with lime-cement mortar and adobe blocks with earth mortar. Both specimens proved able to withstand significant base accelerations up to 1.0 g with little damage, exhibiting rocking behavior, with the post tenons lifting up from the mortises due to exceedance of friction at the contact surfaces. The earth material specimen presented higher uplift, top displacement and acceleration. A short comparison with static monotonic and cyclic tests is also presented.

Probabilistic hygrothermal assessment of various timber frame wall compositions

The market share of timber-based buildings is growing in Europe, due to their advantages concerning CO2 emissions and embodied energy. Regrettably, timber frame constructions are susceptible to moisture damage, and their proper design is thus crucial, with specific emphasis on the ratio of the vapour diffusion resistances of the weather barrier and vapour barrier. While some rules-of-thumb are available, these commonly do not consider climatic aspects nor moisture buffering, and hence do not guarantee optimal solutions. This study targets general guidelines, for various European climates and wall compositions. As this requires numerous simulations, a convolutional neural network is applied, performing over 135,000 simulations, covering 96 wall compositions and 54 European climates. The walls’ performance is evaluated via mould index and condensation amount. The results reveal that defining one single criterium to avoid moisture damage is impossible and hence that climate-specific guidelines are needed. It is also noticed that moisture buffering plays an important role in avoiding condensation run-off, much more than the vapour diffusion resistances of weather and vapour barriers. Finally a matrix is defined with the criteria to avoid moisture damage, depending on climatic conditions and wall composition. The key result is that either the insulation material or the weather barrier must provide moisture buffering. Furthermore, each climatic condition and cladding type yields a different criterion for the required vapour diffusion resistances of weather and vapour barriers.

Measured Impact of Material Settlement in a Timber-Frame Wall with Loose Fill Insulation

Loose-fill thermal insulations in timber-frame structures are designed to provide efficient thermal protection with the ability to fill intricate details. In a previous study, we detected several air cavities formed in timber-framed wall samples filled with loose-fill mineral fiber insulation. This discovery led us to retrofit the walls by adding appropriate insulation, thus enabling us to evaluate the importance of proper amendment. This paper focuses on a wall fragment with an 80 mm high air gap at the top and a 30 mm high cavity in the middle of the wall height. The following paper compares data collected before the discovery and after the replenishment (refill of air gaps with additional insulation), evaluating potential thermal performance improvement. We were able to quantify the impact of these defects on the external wall exposed to realistic conditions. Based on temperature and relative humidity measurements, the results show significant advancement in the middle of wall thickness with an 8 °C and 45% difference. The results show that although this defect did not directly affect the energy balance of the building, it significantly increases the risk of mold growth due to thermal bridging.

Sound Isolation Performance Assessment of Traditional and Retrofitted Timber-Framed Dwellings

This study focuses on sound isolation performances of original timber-framed interior wall and floor components in traditional-framed dwellings in Turkey and 19th century mud-brick samples used as infill within the timber frame. The acoustical ramifications of some retrofits proposed in the contexts of minimum intervention and refunctioning the traditional dwellings are assessed in reference to the relevant standards. Field measurements show that sound isolation performances of the original timber-framed wall and floor are ineffective. The results of this study show that acoustical retrofits applied on the original wall keeping its wood lath and mud-brick infill are about 5–7 dB in the weighted sound reduction index (RW) and are more effective than those applied on the reconstructed wall. Sound transmission loss values of 50- and 100-mm-thick authentic mud samples are 22–38 and 30–43 dB, respectively, between 125 and 4,000 Hz. The sound absorption coefficient at mid frequencies and the noise reduction coefficient of 50-mm-thick mud samples are 0.28 and 0.23, respectively. These results signal the importance of keeping traditional construction techniques of wall and floor during retrofits to improve the sound isolation performance. Adobe mixtures similar to the 19th-century mud-bricks can be of guidance for the production of innovative soundproofing earth-based building materials.

Numerical Analysis of the Racking Behaviour of Multi-Storey Timber-Framed Buildings Considering Load-Bearing Function of Double-Skin Façade Elements

The paper presents an innovative approach in the modelling of multi-storey timber-framed buildings, where double-skin façade elements (DSF) are additionally considered as load-bearing wall elements against a horizontal load impact. The mathematical model with a fictive diagonal element developed for timber-framed wall elements with classical oriented strand boards (OSB) or fibre–plaster sheathing boards (FPB) is upgraded for DSF elements. The diameter of the fictive diagonal is determined with either experimental results or numerically obtained results using the time-consuming FEM model with elastic spring elements, which simulates the bonding line between the timber frame and both glazing panes. In the second part of the study, the numerical analysis of a specially selected three-storey timber-framed building was performed using the developed mathematical model with fictive diagonal elements. Two alternative calculations were performed with the DSF elements as non-resisting and racking-resisting wall elements. It was demonstrated on the selected case that the racking resistance (R) of a building can essentially increase up to 35% if DSF elements are considered as resisting wall elements. As a secondary goal of the study, it is also important to point out that by using DSF elements as racking-resisting elements, the distortion in the first floor essentially decreased. It is demonstrated on the selected numerical example that this torsional influence decreased notably (by almost 18%) when the load-bearing DSF elements were used for seismic excitation in the X direction. Therefore, such an approach can open new perspectives in designing multi-storey timber-framed buildings with a more attractive and dynamic floor plan and structure.

Defensive Buildings of the Bakalskaya Culture (The Staro-Lybaevskoe-1 Settlement in the Forest-Steppe Trans-Urals)

Purpose. The purpose of this article is to evaluate defensive potentialities of the Middle Age population in the Trans-Urals. The main task is to reconstruct the exterior of the fortified areas and the necessary amount of work.Results. The defensive buildings of the Staro-Libayevskoye-1 fortified settlement were used. It has been established on the terrace of the Middle Tobol river and had the 5-angle form, size 65 × 75 m and a simple rampart-and-ditch line with two approach gates. This square was used for habitation twice in Middle age epoch. Apparently, large earthworks were not carried out due to the features of the relief, which had a height difference of 2 meters; considering the wooden wall and the ditch depth. Based on the analysis of the archaeological finds and the cultural layer, we established that in the early period of the Bakalskaya culture (4th – 5th centuries) the settlement was encircled with timber-framed wall and the terrace slope possibly played a role of a berm. The inhabitants created a defense line minimum of 5.5–6 meters in height. We assume that there was exacerbation of social and local conflicts, and the population sought to prevent these conflicts by strengthening defense. The Ustyug-1 synchronous cemetery testifies to the existence of a constant military threat, such as attacks by migrants and conflicts with the use of weapons. Later, in 8th – 10th centuries the settlers used traditional methods and created a new earthen wall. It was built two times wider, then earlier, using pre-existing land cultural layer. The settlers abandoned the laborious movement of soil from the ditch to the height of the wall. For greater protection, they equipped the earthen rampart with timber-frame structures and created a barrier 5.5 meters high.Conclusion. Concluding, we suggest that a dangerous military situation persisted during this period, as evidenced by samples of weapons and a cemetery in the settlement. The study also revealed a trend towards increasing labor costs for fortifications construction.

Light timber framed wall under fire: Effect of the load and cladding

Light Timber Frame Walls are made of solid timber elements and are usually protected by cladding materials (gypsum). This investigation finds the effect of different load levels and cladding systems on the fire resistance. The timber frame structure is made with three studs and two rails, and will be analysed with two different protection levels. The computational model includes the thermal analysis under standard fire and a sequential mechanical analysis with time increments. Both, thermal and thermo-mechanical models are validated against experimental results developed in the reduced scale and full scale. The timber frame structure is deemed to have failed when it is no longer supporting the test load. The results are also compared with the failure criteria used for the experimental tests. The timber frame is deformed and all simulated models attained the global bucking instability mode, with studs moving to the outside of the furnace, due to the effect of load and charred layer. The fire resistance of a double-layered light timber frame wall is higher than a single-layered, and both decrease with the load level. This ability is reduced by 46%, on average for all load levels, when using only one gypsum layer. A new formula is proposed to determine the fire resistance, based on the load level and cladding systems. The fire resistance of the specimens with two layers of gypsum plates decreases faster than the specimens with one layer of gypsum, with respect to the increase of the load level.

Numerical analysis of timber frame wall filled with hemp concrete

This paper presents a numerical study of the lateral load-carrying capacity of hemp concrete as infill material in timber frame walls. The parameters that significantly affect the lateral resistance of hemp walls were investigated. For this purpose, vertical stud timber frame walls measuring 2.5 m in height and 1.2 m in length were used as the benchmark to validate earlier experimental work. A numerical study of three timber walls filled with hemp concrete was conducted to assess the effect of wall length on the lateral load-carrying capacity of hemp concrete. Three vertical stud timber frame walls with a standard height 2.5 m and different lengths (1.2 m, 1.6 m and 2.4 m) were investigated using Abaqus software. This study confirms, firstly, that the length of a timber wall plays a significant role in the lateral load-carrying capacity of hemp concrete. Secondly, the contact and bonding between the hemp concrete and timber wall have a significant effect on the lateral load-carrying capacity of hemp concrete as infill material in timber frame walls. It was clear, from the numerical results, that increasing the length of the wall significantly increases the contribution of hemp concrete to lateral resistance. Good contact and bonding between the hemp concrete and the timber elements also increase the lateral strength of the hemp wall.

The impact of wooden studs on the moisture risk of timber frame constructions

Since timber frame constructions can help to reduce CO2-emissions and lower the embodied energy of buildings, the market share of timber-based buildings is growing across Europe. Unfortunately, timber frame constructions are found to be susceptible to moisture damage, such as interstitial condensation, mould growth and wood rot. To avoid moisture damage, a correct design of the wall composition is crucial, with special emphasis on the ratio between vapour resistance of wind and vapour barrier. Given that experimental investigations are time-consuming and expensive, numerical tools are common to assess the hygrothermal behaviour of building components. And although timber frame constructions are inherently two- or even three-dimensional due to the embedded wooden elements, most often, 1D-simulations focussing on the basic configuration with insulation between wind and vapour barrier are conducted. This paper investigates to what extent neglecting the embedded wooden elements influences the risk assessment of the wall. Three different wall configurations have been considered and their hygrothermal response, as predicted by 1D- and 2D-numerical simulations, are compared. Variability of the exterior climate is included by using four distinct different climate regions. Contrary to common assumptions, buffering of moisture in wooden elements does not always lower the risk on moisture damage, but might even increase it. While the predicted risk on mould growth was found to be similar between 1D and 2D-simulations, the opposite was found for the risk on interstitial condensation. Mainly for cold climates and wall configurations with hardly any other hygric buffering capacity, levels of interstitial condensation were found to be significantly higher when taking the wooden elements into account in the numerical simulations. Hence, care should be taken when assessing the reliability of timber frame walls based on 1D-simulations only.

Analysis and enhancement of the new Eurocode 5 formulations for the lateral elastic deformation of LTF and CLT walls

This paper analyses the analytical formulations for the lateral elastic deformation of Light Timber Framed (LTF) and Cross-Laminated Timber (CLT) shear walls according to the new Eurocode 5 (EC5) proposal. Finite Element (FE) models and the Standard predictions are compared by emphasizing the role of each deformation contribution. A total of 1830 comparisons between analytical and numerical estimations are carried out by exploiting the Application Programming Interface of SAP2000 to modify the FE model parameters automatically. The parametric analyses proved that the numerical and analytical predictions are pretty consistent. Furthermore, in both LTF and CLT shear walls, the estimates for in-plane shear and rigid body sliding are in excellent agreement. Conversely, the analytical formulas for kinematic rocking are generally conservative for LTF and monolithic CLT shear walls, with an approximate 18%–19% discrepancy. The analytical expressions of the upcoming EC5 perfectly match the numerical model for segmented CLT shear walls under lateral forces and no vertical load. However, the presence of the vertical load determines a significant bias. Additionally, the predictions for bending deformations are not in good agreement. Therefore, the paper discusses possible enhancements for the equations proposed in the next generation of Eurocodes for the rocking deformation of segmented CLT walls to better conform with FE predictions.

Experimental investigation of the behavior of traditional timber mortise-tenon T-joints under monotonic and cyclic loading

• Monotonic & cyclic tests on traditional cylindrical mortise-tenon timber T -joints. • Great displacement capacity but also severe pinching in hysteresis loops. • Significant difference in force capacity if tenon under shear or bending. • Behavior also influenced by inherent material variations, construction etc. Monotonic and cyclic tests on cylindrical mortise-tenon timber T-joints typical of Ottoman-period mansions in mainland Greece were carried out, aiming towards a better understanding of such connections and their influence on timber-framed wall seismic performance in numerical and experimental investigations. Configurations from the head and foot of posts were tested so that the tenon was under either combined bending and shear, or pure shear. The two types of loads led to significantly different hysteretic behavior, force and energy dissipation capacity of the examined joints. Joints with gap and under push–pull out load were also tested.

Effects of spatial augmented reality assistance on the efficiency of prefabricating timber frame walls

ABSTRACT Assistance systems have the potential to support workers in various assembly tasks. Especially in mass customized prefabrication, the correct objects need to be selected and positioned accurately. Using conventional paper plans as assembly guidance, skilled workers need to spend precious time carefully reading plans for the individually designed elements. Augmented reality (AR) systems can help to integrate information for assembly tasks directly into the work environment, which should improve time efficiency and error rates. However, AR systems are often not ergonomic or accurate enough (e.g. smartglasses) or expensive (e.g. laser projectors). In the present study, the effect of a simple projection based spatial augmented reality (SAR) system was studied for building prefabricated wall elements under laboratory conditions, using printed CAD drawings as reference. Each subject built a timber frame wall element with dimensions close to reality. Using the SAR system, the completion times were reduced by nearly 50%, the error rate of subjects with a low experience level decreased and the reported task load measured according to the NASA raw task load index using the SAR system was significantly lower.

Fire performance analyses of modular wall panel designs with loadbearing SHS columns

Modular Building Systems (MBS) are still in the phase of developing its popularity in the industry, with emerging novel designs. Initially, MBS walls and floors had been highly influenced by the Light-gauge Steel Frame (LSF) designs made of Cold-Formed (CF) steel studs, either as loadbearing or non-loadbearing types which have been extensively researched all over the world. However, recently the MBS practice in the industry tends to incorporate Square Hollow Section (SHS) steel columns for their improved structural performance and convenience at the manufacturing stage despite of the limited research knowledge in terms of the Fire Resistance Level (FRL). Moreover, catastrophic failures and fatal accidents are common with steel-based structures in case of a fire. Hence, the fire performance of loadbearing modular walls with SHS columns have been identified as a critical research gap. Firstly, Finite Element Models (FEM) were developed for the original modular wall, a Light-weight Timber Frame (LTF) wall and some LSF walls. The FEM analyses results very well matched with the full-scale experimental results so that the FEM techniques were confidently used to study the effect of variables chosen based on material availability options, cost reduction and construction practice. Structural and Insulation FRLs have been evaluated for the chosen parametric walls, where the produced graphs of structural and insulation FRLs can be referred to determine the adequate thickness of column sheathing and the Insulation Ratio (IR) respectively. The choice of non-loadbearing stud type can be evaluated against other limitations related to energy, cost and construction practice.

Timber-Framed Wall Construction in Mansions of Mainland Greece during the Ottoman Period

ABSTRACT Two Ottoman period mansions in central Greece featuring timber-framed masonry walls and exhibiting many similarities in their construction are examined and several defining attributes are traced, connecting their structural system with that of similar buildings in mainland Greece. These buildings consist of a stone masonry ground floor, while the upper storey construction is a combination of stone and timber-framed masonry. The materials typically incorporated in such structures are presented. Details are given on the connections of timber elements. These buildings were constructed in seismically active areas, and have frequently been subject to earthquake strong motions, with the observed damages presented herein. The purpose of this investigation is to understand the load-bearing system of the mansions and its response under earthquake actions. The findings can later be used for further research of these structures.

A Sustainable Approach to Build Insulated External Timber Frame Walls for Passive Houses Using Natural and Waste Materials

This paper presents structures of timber-framed walls designed for passive houses, using natural and waste resources as insulation materials, such as wool, wood fibers, ground paper, reeds (Phragmites communis), and Acrylonitrile Butadiene Styrene (ABS) wastes. The insulation systems of stud walls composed of wool–ABS composite boards and five types of fillers (wool, ABS, wood fibers, ground paper, and reeds) were investigated to reach U-value requirements for passive houses. The wall structures were designed at a thickness of 175 mm, including gypsum board for internal wall lining and oriented strand board (OSB) for the exterior one. The testing protocol of thermal insulation properties of wall structures simulated conditions for indoor and outdoor temperatures during the winter and summer seasons using HFM-Lambda laboratory equipment. In situ measurements of U-values were determined for the experimental wall structures during winter time, when the temperature differences between outside and inside exceeded 10 °C. The results recorded for the U-values between 0.20 W/m2K and 0.35 W/m2K indicate that the proposed structures are energy-efficient walls for passive houses placed in the temperate-continental areas. The vapour flow rate calculation does not indicate the presence of condensation in the 175 mm thick wall structures, which proves that the selected thermal insulation materials are not prone to degradation due to condensation. The research is aligned to the international trend in civil engineering, oriented to the design and construction of low-energy buildings on the one hand and the use of environmentally friendly or recycled materials on the other.