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Environmentally Friendly Wooden Housebuilding

     Having over 80 years of experience in the industry, our company, Heban, located in Tuchola managed to move into an previously uncharted territory, namely, that of building eco-friendly wooden houses. Drawing on the most up-to-date Scandinavian technology coupled with my own personal experience, I offer you an idea for not only healthy but also energy efficient timber frame houses.


     Wood, as the most natural construction material, has been used for ages because of its everlasting esthetic value and economic properties. Our company has managed to come up with other arguments which will certainly convince you to, at the very least, take wood into consideration in your own projects. First and foremost, the amount of wood required for a traditional roof frame in a brick house is just slightly smaller than the same amount of material used to create the whole house frame for a house of the same dimensions. Moreover, thinner exterior walls lend themselves to a greater total living area compared with a brick house; e.g. a 100 m2 one-storey wooden house is comparatively “bigger” inside by 10-12 m2 when compared to a similar brick house. It allows for a much greater total living area.

     Energy efficiency is an advantage as well. The combination of wood’s natural properties with modern insulation materials creates surprisingly favourable exploitation costs.

     Wood is dried and seasoned in our own plants, thus, bringing down its moisture content to 14-16%. Next, efficiently performed planing is responsible for its increased fire and moisture resistance. Such raw material does not require any impregnation (with the exception of wooden foundations which are pressure treated only with approved preservatives). Wooden components of the roof (joists, rafters, roof sheathing etc.) are cold soaked with environmentally friendly liquids until they are almost completely fire resistant. Timber framing draws on building materials of small dimensions but extremely high level of durability. As a result, light wooden house-frames are made of highly durable materials which make them applicable for detached houses, terraced houses or semi-detached houses up to five storeys.

     Our exterior walls are made of wooden frame and filled in with insulation materials providing not only thermal insulation but soundproofing as well. The exterior is covered with panelling or plasterboard. Siding is made of horizontal or vertical boards which were treated not only with fire and fungus resistant preservatives but an insecticide as well. Alternatively, it can be covered with styrofoam and a layer of stucco. The interior walls are also filled with mineral wool and both in the kitchen as well as in the bathroom are additionally covered with a layer of moisture resistant plasterboard. The roof is covered with metal shingles. All of the above are complemented by high quality door and window frame carpentry made of glue laminated lumber. Our glazing has U factor values of 1,1 while the whole building has U factor values well below 0,20. As a result, the annual utility and exploitation costs are extremely low, thus, making the building not only environmentally friendly but affordable as well.

Grzegorz Gołuński, CEO of Heban

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Timber Frame House Building and Glue Laminated Lumber

Timber is a completely natural, renewable resource characterised by its dense, organic structure. Due to its durability and longevity as a primary building material, it has been used for ages by humans. Moreover, it is an environmentally friendly material which can be obtained with only the slightest energy expenditure in the process of its production.

 


As a hygroscopic substance, timber provides an efficient moisture content maintenance which, in turn, creates favourable living conditions. What is more, timber is well known for its thermal conductivity which allows one to built thermally efficient dwellings without compromising any of  its mechanic properties.

 

These as well as other properties of timber have led to its common application as the primary building material in house framing. Its early application in the construction process sheds light on the quality as well as the utility of the object in question. The most common building material applied in house framing is pine timber which is widely used in the creation of walls, partitions, ceilings and roofs. Apart from using elements made of solid wood, engineered wood has also found its place as well (i.e. glued laminated timber).

 

Our research was mainly driven by the normative standards of classification which, unfortunately, are not always used in practice. In 2003, a fully European norm was introduced in Poland, namely, the PN-EN 338:2003 ‘Construction Timber. Durability Grading’ which outlined twelve classes of quality timber (from C14 to C50- based on its resilience to bending). On the other hand, glued laminated lumber should follow the PN-EN 1194:2000 ‘Wooden Constructions. Glued laminated Timber. Durability Grading and Its Characteristics’. It outlines the normative classification system for glued laminated timber based on the durability of the material in question (GL 24, GL 28, GL 32, GL 36).

Based on our research of both physical as well as mechanical characteristics of wood, we managed to match each sample to its corresponding class (as outlined in the above mentioned norms).

 

 

wykres_2

Durability classification according to the PN-EN 338 norm

Research Results:

  • Increased diameter of the raw material leads to an increased share of heartwood. However, this can only be observed up to a diameter of about 35 cm (after which any progress in the heartwood growth comes to a definitive halt).
  • The average density of the ring growth allows us to classify the material used as ‘narrow’. It is due to its average share of latewood (around 32%).
  • Our research, performed on ‘life-sized’ pine samples (as used in house framing), has yielded interesting results by proving the superiority of PU HB polyurethane glue. Urea-formaldehyde resin adhesives obtained slightly lower results.
  • Glued laminated timber shows a range of mixed mechanical properties depending on individual characteristics of the materials used in the production process. As a result, it is imperative that an extremely demanding quality control should be observed. Moreover, the production process should pay close attention to the creation of proper cross sections in the manufactured construction elements. All of the above have an important impact not only on the mechanical properties of glued laminated elements but more economic material management as well
  • The normative timber classification standards used in Poland require a complete overhaul of the system as they are too sophisticated. It seems like the system could be altered to accommodate the European norms which clearly describe and designate grade C timber.
  • There is a necessity for a change in the current standards which would clearly describe and designate grade C timber which can be applied to Polish house framing.
  • The construction elements made of pinewood obtained from Bory Tucholskie (designated to be used in making both solid and glu-lam pieces) fulfill all of the necessary requirements. Both the mechanical as well as physical characteristics of the material in question point to its wide ranging application in house framing.

Grzegorz Gołuński

Timber is a completely natural, renewable resource characterised by its dense, organic structure. Due to its durability and longevity as a primary building material, it has been used for ages by humans. Moreover, it is an environmentally friendly material which can be obtained with only the slightest energy expenditure in the process of its production.

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The Quality of Glued laminated Pinewood Components for House Framing

   In our research, we have clearly defined the quality of pinewood elements used in house framing. Our work has also encompassed the comparison of both the quality as well as durability characteristics of the material in question in relation to proper normative classification standards (including dimensional differences). For comparative purposes, we have contrasted our results with samples made in accordance with the existing norms. A decrease in resilience to static bending and a lower tensile modulus were observed (in comparison to the research done on smaller samples).


WIERUSZEWSKI MAREK, GOTYCH VIKTOR, HRUZIK GINTER J., GOŁUŃSKI GRZEGORZ

Summary:

The Quality of Glued laminated Pinewood Components for House Framing

1. Introduction

Wood, as one of the oldest building materials known to man, is the only one that is fully renewable. In order to compete with other construction materials, the producers of timber have to conform to the ever increasing expectations concerning the quality of all products involved. The classification of timber (helpful in the design of wooden constructions) is another matter altogether.

There is a range of classes which are applied in the process of durability grading of construction timber. The newest European norm, the PN-EN 338:2003 ‘Construction Timber. Durability Grading’,  outlines twelve classes of quality timber (from C14 to C50) based on its resilience to bending (from 14 to 50 MPa). According to the EN 338: 1995 or PN-EN 338: 1999, Polish classification of timber grading corresponds with the European one as follows: K21 ≈ C24, K27 ≈ C30, K33 ≈ C35, K39 ≈ C40. The amendment to the PN-81/B-03150 norm confirms that other classes are not applicable to the Polish conditions (W. Dzbeński, P. Kozakiewicz, S. Krzosek 2005).

        On the other hand, glued laminated lumber should follow the PN-EN 1194: 2000 ‘Wooden  Constructions. Glued laminated Timber. Durability Grading and Its Characteristics’. It outlines the normative classification system for glued laminated timber based on the durability of the material in question (GL 24, GL 28, GL 32, GL 36). Glued laminated timber is a type of structural timber product composed of several layers of dimensioned timber glued together.

Young’s modulus is defined as the ratio of uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. Along with its increase, an increase in the technical value of construction materials can be observed. The anisotropy of wood leads to a range of characteristics in terms of the tensile modulus in all planes (radial, longitudinal, tangential). The modulus can be determined using a range of tests. However, the examination of the tensile modulus in static bending is the most commonly used and is a basis for the comparative analysis of the material.

 

2. The goal, methodolgy and the description of the tests carried out

The main goal of our tests was to determine the quality of the obtained construction elements made of pinewood used in house framing. The research encompassed the comparison between durability as well as quality of the material in relation to the correct classification standards and its subsequent compliance with the dimensional classification of the construction elements.

 

          In order to correctly classify the construction elements, a number of glued laminated samples was obtained in two different sets. The first one consisted of 30 samples divided into groups of 10 with the following dimensions: 40x72mm, 40x100mm, 40x120mm. The second one consisted of 45 samples divided into groups of 15 with the following dimensions: 40x72mm, 40x96mm, 40x120mm. The first batch of samples, labelled as the A group, was glued using the polyvinyl acetate JOWACOLL 102 20 with the JOWACOLL 195 30 sealant (5%). The second batch of samples, labelled as the B group, was glued using the AKZO NOBEL EPI 8055 glue with the 1992 isocyanate sealant (15%).

 

3. Description of the tests arried out

 

The examination of resilience to static bending of both construction elements and solid samples was carried out using the DM 2214 testing machine. All samples were subjected to tensile testing.In order to maintain a range of comparative results of the tests carried out, a constant value in the gauge of supports in proportion to the relative thickness of the elements examined (12/1) was maintained.

 

        Young’s modulus was designated based on the results obtained in static bending. All tests were carried out on the DM 2214 machine according to the PN-63/D-04117 ‘Physical and Mechanical Properties of Wood. The Designation of the Tensile Modulus in Static Bending’. All readings had a potential margin of error of 0,01 mm. All samples were initially put under the pressure of 100 N which was subsequently increased by 500 N.

 

Comparative analysis

Density, as the most basic physical characteristic of the material closely connected to its structure, reflects the mechanical properties of wood. The characteristic density of each layer of the elements was shown in the tables 1 and 2.

 

Tabela 1 The average density of layers used in the production of group A construction componenets

 
Cross section(mm)

40x72

40x100

40x120

Layer

ζ [kg/m3]

Layer

ζ [kg/m3]

Layer

ζ [kg/m3]

1(G)

529

1(G)

554

1(G)

526

2

520

2

490

2

542

3(D)

511

3

557

3

520

   

4(D)

516

4

501

       

5(D)

515

Average of Density

520

 

529

 

521

 
Tabela 2 The avarage density of layers used in the production of group B construction components.
 

Cross section (mm)

40x72

40x96

40x120

Layer

ζ [kg/m3]

Layer

ζ [kg/m3]

Layer

ζ [kg/m3]

1(G)

556

1(G)

531

1(G)

544

2

519

2

519

2

529

3(D)

551

3

514

3

524

   

4(D)

529

4

499

       

5(D)

540

Average of Density

542

 

523

 

527

 
The highest average density (542 kg/m3) was observed in group B components with the cross section of 40x72 mm. The lowest average density (520 kg/m3) was observed in group A components with the cross section of 40x72 mm.
 
Another factor contributing heavily to the applicability of pinewood is its density of ring growth. According to the research data (e.g. Kollman’s), narrow annual growth is a reflection of the highest quality timber. The PN-82/D-94021 norm takes into consideration the average width of rings as the main criterion in designating the classification of construction timber. The average annual growth observed in the layers used in the production of construction components is shown in the tables 3 and 4.
 

Tabela 3 The avarage width of annual ring growth observed in the layers used in the production of group A componenets.

Cross sections (mm)

40x72

40x100

40x120

Layer

[mm]

Layer

[mm]

Layer

[mm]

1(G)

1,95

1(G)

1,51

1(G)

1,85

2

2,09

2

2,51

2

1,74

3(D)

1,76

3

1,57

3

1,82

   

4(D)

2,03

4

2,33

       

5(D)

2,05

The avarage width of annual growth

1,93

 

1,90

 

1,96

 

Table 4. The average width of the annual ring growth observed in the layers used in the production of group B components.

Cross section (mm)

40x72

40x96

40x120

Layer

[mm]

Łata

[mm]

Łata

[mm]

1(G)

1,62

1(G)

1,90

1(G)

1,73

2

1,85

2

2,26

2

1,83

3(D)

1,57

3

1,84

3

1,86

   

4(D)

2,03

4

2,41

       

5(D)

1,71

Avarage

1,68

 

2,01

 

1,91

 
The highest average width of the annual ring growth was observed in the group B components with the cross section of 40x96 mm (2,01 mm). The lowest average width of the annual ring growth was observed in the group B components with the cross section of 40x72 mm (1,68 mm). The width of rings in all our samples falls between 0, 3 mm and 5,3 mm.
 
On the hygroscopic plane (i.e. from 0% to 30%), an increase in the moisture content of the material in question leads to a decrease in its durability. It is caused by a spread of micelle when water is soaked up by the cell membrane.For the components with the cross sections of 40x100(A) mm, 40x120(A) mm, 40x96(B) mm, the average moisture content of layers was 10% and for 40x72(A) mm, 40x72(B) mm, 40x120(B) mm the moisture content observed was 11%.
 
For comparative purposes, all solid samples (in the tests carried out) were obtained according to the PN-68/D-4103 norm. All durability values (in static beniding) obtained are shown in tables 5 and 6.
 
Table 5. Resilience to bending observed in group A. 
  1. Rg15 [MPa]

Modulus

min

average

max

Bulk

53

77

97

Tensile

51

66

90

Shear

50

81

97

 
Tabela 6 Wytrzymałość na zginanie próbek modelowych próby B
 
  1. Rg15 [MPa]

Modulus

min

average

max

Bulk

49

71

90

Tensile

53

59

85

Shear

47

79

93

 

The samples with the lowest average resilience (66 and 59 MPa) were obtained from the middle layers of both (A and B) groups. The highest average resilience (81 and 79 MPa) was observed among both groups as well. The highest resilience value for a single sample was 97 MPa and the lowest 47 MPa.

Resilience to static bending is one of the most commonly applied tests which has direct influence on the design of wooden constructions of all shapes and forms. The tests performed have outlined particular values in terms of the resilience to static bending for ‘life-sized samples’ which are shown in tables 7 and 8.

Table 7. Resilience to static bending observed among group A components. 

Cross section(mm)

  1. Rg15 [MPa]

Min

Average

Max

40x72

25

39

48

40x100

24

35

55

40x120

27

29

31

 

Table 8. Resilience to static bending observed among group B components. 

Cross section (mm)

  1. Rg15 [MPa]

Min

Average

Max

40x72

23

40

55

40x96

23

36

50

40x120

26

34

45

 
Construction elements possessing the width of 72 mm have achieved the highest average values in our resilience tests (39 and 40 MPa). Our components with the width of 120 mm obtained the lowest average values in terms of resilience (29 and 34 MPa). The lowest values recorded (23 MPa) were obtained by the 40x72 (B) mm and 40x96(B) mm samples. However, the highest result (55 MPa) was obtained from the 40x100(A) mm and 40x96(B) mm samples.Some of the lowest values recorded were caused by the delamination of samples which was observed mostly at the adhesive joints.
 
The average values of the tensile modulus observed (i.e. the main quality of the material used in the classification of construction timber for individual construction components) are shown in table 9.
 
Table 9.Tensile modulus for ‘life-sized’ E samples (MPa) 

No.

Cross section [mm]

40x72(A)

40x100(A)

40x120(A)

40x72(B)

40x96(B)

40x120(B)

1

8595

8141

10926

11523

10244

10441

2

12484

10483

9738

10360

10889

9704

3

10572

10900

10959

9814

12036

9923

4

9098

9328

10012

12415

11676

9080

5

12471

9249

11494

9967

10554

10749

6

12007

9340

10909

8651

11701

10982

7

9718

11415

9797

12356

13288

9687

8

9319

9586

10847

10625

12573

8731

9

9560

10173

9883

11499

11370

10381

10

10621

7845

10851

12104

12142

9013

11

     

11488

10418

9496

12

     

11434

12341

9732

13

     

10411

11988

10533

14

     

11863

11326

10090

15

     

12145

9752

9623

avarage

10444

9646

10541

11110

11486

9878

 
The highest average value (11486 MPa) was recorded among the 40x96(B) mm samples and the lowest (9646 MPa) among the 40x100(A) mm. The highest value recorded for a single samples was 13288 MPa while the lowest was 7845 MPa. The average value per samples was 10518 MPa.

4. Conclusion

 Based on the tests performed, the following conclusions were obtained by the researchers:

1. The average moisture content of the layers used in the production process of construction elements falls between 10 and 11% which is according to the standards of PN-81/B-03150.01.

2. While testing the resilience to static bending, the following results were obtained: the lowest of 47 MPa and the highest of 97 MPa. The average value for each moduli fell between 58-81 MPa. The results obtained are much lower than those observed by Wanin (87 MPa) or Göhr (88 MPa).

3. Based on the most characteristic results obtained in the resilience to static bending for individual components (Fm,g,k = 17 MPa), it can be observed that the data gathered is insufficient to correctly classify the samples according to the PN-EN 1194-2000 norm. On the other hand, when taken into consideration, only the average values for solidwood samples can provide meaningful means of classification for 40x72 mm A and B samples. The others would be classified as follows: 40x100 mm A and B(construction elements)- MKS class; 40x120 mm A and B(individual components)- MKG class.

4.  The average value of the tensile modulus obtained (E= 10518 MPa), for both A and B samples, is too low to classify them according to the PN-EN 1194-2000. Moreover, the results observed for individual components are way lower than those observed by Leontiev for solidwood (E= 12200 MPa). The values required for proper classification of glued laminated timber were not achieved.

5. The low values of both the tensile modulus as well as the resilience to static bending were mostly caused by the delamination observed at the adhesive joints.

6. An introduction of the strictest quality control procedures (in terms of both the location as well as the positioning of layers used in making glued laminated lumber) may substantially increase not only the quality but the durability of individual components as well.

5. Bibliography

Dzbeński W., Kozakiewicz K., Krzosek S. : Wytrzymałościowe sortowanie tarcicy budowlano-konstrukcyjnej. Warszawa 2005, str. 16-18.

Kollmann F., Cöte W.A., 1968: Principles of wood science and wood technology. Solid wood – part I. Berlin-Heidelberg-N.York.

Krzysik F., 1978: Nauka o drewnie. PWN. Warszwa.

PN-63/D-04117, Fizyczne i mechaniczne własności drewna. Oznaczanie współczynnika sprężystości przy zginaniu statycznym.

PN-68/D-4103, Fizyczne i mechaniczne własności drewna. Oznaczanie wytrzymałości na zginanie statyczne.

PN-81/B-03150,  Konstrukcje z drewna i materiałów drewnopochodnych.

PN-81/B-03150.01, Konstrukcje z drewna i materiałów drewnopochodnych. Obliczenia statyczne i projektowanie. Materiały.

PN-82/D-94021, Tarcica iglasta konstrukcyjna sortowana metodami wytrzymałościowymi.

PN-EN 408:1998, Konstrukcje drewniane. Drewno konstrukcyjne lite i klejone warstwowo. Oznaczanie niektórych właściwości fizycznych, mechanicznych.

PN-EN 384:1999, Drewno konstrukcyjne. Oznaczanie wartości charakterystycznych właściwości mechanicznych i gęstości.

PN-EN 1194:2000, Konstrukcje drewniane. Drewno klejone warstwowo. Klasy wytrzymałościowe i określenie wartości charakterystycznych

PN-EN 338:2003, Drewno konstrukcyjne. Klasy wytrzymałości.

  

Wood, as one of the oldest building materials known to man, is the only one that is fully renewable. In order to compete with other construction materials, the producers of timber have to conform to the ever increasing expectations concerning the quality of all products involved. The classification of timber (helpful in the design of wooden constructions) is another matter altogether.

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Timber Frame House Bilding and Glue Laminated Lumber

     Wood is the most organic out all resources available to man. Apart from stone, it is one of the oldest and the noblest building materials. Its hygroscopic properties guarantee healthy living conditions, thus, creating the environment favourable for those suffering from allergy. These and other properties of wood have contributed to its application as the most commonplace building material.


    

At the beginning of the XXth century, English settlers brought the method of timber framing to North America. Since then, the method based on utilizing light timber frame has taken roots in American culture. It is said that an Englishman- William Manning was the first who, in the early XIXth century, created the archetype of what later became known as the timber frame construction (Szwedzkie budownictwo 2007). Over the years, the technology was constantly passed on and improved as the next generations wanted to create a design which would be appealing to the majority of future homeowners and, at the same time, relatively cheap ande easy to build. The intense economic boom coupled with the extremelly pragmatic worldview held by American citizens have standardised timber frame house building.

     The application of new finishing materials was also guided by the new standards. As a result, the system is based on a light and durable wood-frame construction filled with insulation and covered with high quality sheathing. In the end, the American “Timber-Frame” house building system was born.

     The economic transformations (which have taken place in Poland in the last years) along with expansion in trade, new technologies and building materials have had an enormous effect on the growing popularity of timber frame house building. Due to a range of creative ideas, the industry has begun producing much smaller wooden elements while, at the same time, keeping extremelly high levels of their durability.

     The idea of laminating timber with glue broadens the ability of applying small dimension wooden components in timber frame house building even further. The origins of engineered wood can be traced as far back as the XIXth century. Glue laminated timber has an ever growing group of proponents due to its durability as well as high quality of the application-specific performance.

     ‘Heban’ applies wooden frames made of glue laminated timber in its process of making prefabricated, energy efficient timber frame houses.

      Based on the standardised requirements, the production process starts with drying and seasoning of the material in question. The goal here is to bring its moisture content down to 10-14%. As soon as drying is over, a quality check takes place where all imperfections are being sawn off. Later on, the material undergoes mortising which allows us to make the so-called ‘finger joints’. After mortising, all elements are glued together and, later, are put through a surface planer in order to achieve a uniform overall thickness of 24mm. Moreover, the elements are then glued again in order to obtain the desired dimensions and mortised. The above mentioned technology allows us to produce wooden pieces which are characterised by countless advantages over solid wood.

     Przeprowadzone kolejne badania pod kierunkiem Prof. dr hab. Gintera Hruzika z Mechanicznej Technologii Drewna przy Uniwersytecie Technologiczno - Przyrodniczym w Poznaniu potwierdzają celowość zastosowań drewna klejonego w budownictwie szkieletowym. Na konferencji naukowo-technicznej, która miała miejsce w Tucholi, 20go kwietnia br. prelegenci  przedstawiali wyniki swoich prac badawczych. Wyniki pokazały, że kluczowe znaczenie podczas produkcji klejonego drewna konstrukcyjnego mają: rodzaj zastosowanego kleju, utrzymanie odpowiednich warunków podczas samego procesu klejenia oraz dobór drewna przeznaczonego do tego procesu.

     This production process has been thoroughly researched under the auspices of Prof. Ginter Hruzik who represents the school of applied sciences at the University of Natural Sciences in Poznań. The findings of the research support the idea that glue laminated timber is ideal for timber frame house building. During a conference which took place on the 20th April 2009 in Tuchola, all researchers highlighted the importance of paying attention to such variables as the type of the glue applied, proper environmental conditions during the production process and the quality of the timber used.

The detailed description of the above mentioned research will be published during the 7th annual conference entitled ‘Wood and Engineered Wood in the Housebuilding Industry’ which is organised by ZUT in Szczecin.

Other crucial properties of glue laminated timber are as follows:

  • geometric and dimensional stability- glue laminated timber has an extremely high ability to retain its shape when exposed to prolonged stress
  • durability - wood as a natural resource is very durable when exposed to ‘aggressive’ conditions (as opposed to steel and concrete). As a result, it has wide ranging applications in environments of extreme moisture or high salt content (e.g. coastal towns and villages)
  • fire resistance - glue laminated timber (when planed correctly) is very fire resistant. In case of heavy fire, the exterior of the wooden construction gets charred, thus, protecting the interior which, in turn, is extremely important when it comes to the preservation of load bearing properties of the building
  • energy efficiency - wood, as a building material, can be applied in a range of climates both hot and cold. This is possible to its natural ability to block heat rather than radiate it
  • natural beauty as well as other aesthetic factors - wood, as one of natural resources known to man, has a broad range of colours, structures and textures available. As a result, the inhabitants of wooden structures usually highlight the aesthetic properties of wood as creating not only comfortable but also relaxing living conditions. In some cultures, the application of glue laminated timber is a sign of prestige
  • affordable costs - the application of glue laminated lumber in house building leads to lower production as well as transportation costs. Lighter timber frame creates a smaller load for the load bearing components. Moreover, thinner walls lead to a much greater total living area (around 10%)
  • eco-friendliness - as opposed to steel frames, glue laminated timber does not require constant maintenance or renovation. Furthermore, the glues used in the production of glue laminated timber are not toxic

      These (along with a range of other factors) have made glue laminated timber the most widely applied building material. It is commonly used in the most daring projects (i.e. sports halls). However, due to its wide ranging properties, it has gained popularity in timber frame house building.
Grzegorz Gołuński
Tuchola, June 2009   

The above article was slightly changed and published in ‘Gazeta Przemysłu Drzewnego’ which is a leading publication in our industry

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