The document contains 14 figures and provides information about different types of timber found in Tanzania. It discusses 4 main types - Mpingo, Mkongo, Mvule, and Mninga. It describes each timber's characteristics and potential uses. The document also covers the characteristics, defects, seasoning, and preservation of timber. It discusses mechanical and physical properties, types of seasoning including natural and kiln seasoning, common defects, and preservation methods like oil treatments.

1. i
LIST OF FIGURES
Figure 1: Mpingo (African Blackwood)................................................................................................2
Figure 2: Mkongo (Pod Mahogany) .....................................................................................................2
Figure 3: Mvule(African Teak)............................................................................................................3
Figure 4: Mninga(East African Padauk) ...............................................................................................3
Figure 5: Natural seasoning.................................................................................................................8
Figure 6: Kiln seasoning .....................................................................................................................8
Figure 7: Electric kiln .........................................................................................................................9
Figure 8: Radial shake.......................................................................................................................10
Figure 9: Heart shake........................................................................................................................10
Figure 10: Cup shake ........................................................................................................................11
Figure 11:Star shake .........................................................................................................................11
Figure 12: Rind gall..........................................................................................................................11
Figure 13 : Wall formwork................................................................................................................15
Figure 14 :stair form work.................................................................................................................15

2. ii
Table of Contents
LIST OF FIGURES ................................................................................................................................. i
CHAPTER ONE....................................................................................................................................1
1.0 INTRODUCTION ...................................................................................................................1
1.1 DIFFERENT TYPES OF TIMBER FOUND IN TANZANIA...............................................................1
1.2 HARDWOODS/CONIFEROUS.................................................................................................1
1.3 SOFTWOODS.......................................................................................................................1
1.4 DIFFERENT TYPES OF TIMBER FOUND IN TANZANIA...............................................................2
1.4.1 MPINGO (AFRICAN BLACKWOOD).........................................................................2
1.4.2 MKONGO(Pod Mahogany) ..........................................................................................2
1.4.3 MVULE(African Teak).................................................................................................3
1.4.4 MNINGA(East African Padauk)....................................................................................3
CHAPTER TWO ...................................................................................................................................5
2.0 CHARACTERISTICS OF TIMBER...............................................................................................5
2.1 INTRODUCTION ...................................................................................................................5
2.2 MECHANICAL PROPERTIES....................................................................................................5
2.2.1 Stress strain relationship...................................................................................................5
2.2.2 Compressive strength.......................................................................................................5
2.2.3 Tensile strength ...............................................................................................................6
2.2.4 Bending strength..............................................................................................................6
2.2.5 Shear strength .................................................................................................................6
2.3 PHYSICAL PROPERTIES..........................................................................................................6
2.3.1 Density and specific weight...............................................................................................6
2.3.2 Moisture movement.........................................................................................................6
2.3.3 Swelling...........................................................................................................................7
2.3.4 Heat conductivity.............................................................................................................7
2.3.5 Sound conductivity...........................................................................................................7
2.3.6 Resistance to action of acid and alkali................................................................................7
2.4 SEASONING OF TIMBER........................................................................................................7
2.4.1 Advantages of timber.......................................................................................................7
2.4.2 Types of Timber Seasoning................................................................................................8
2.4.3 Natural seasoning.............................................................................................................8

3. iii
2.4.4 Artificial seasoning...........................................................................................................8
2.4.5 Water Seasoning:.............................................................................................................9
CHAPTER THREE ...............................................................................................................................10
3.0 DEFECTS OF TIMBER...........................................................................................................10
3.1 INTRODUCTION .................................................................................................................10
3.2 Defects due to abnormal growth ........................................................................................10
3.3 Defects due to conversion..................................................................................................12
3.4 Defect due to seasoning.....................................................................................................12
CHAPTER FOUR.................................................................................................................................13
4.0 TIMBER PRESERVATION......................................................................................................13
4.1 INTRODUCTION .................................................................................................................13
4.2 OIL TYPE PRESERVATIVE.....................................................................................................13
4.3 ORGANIC SOLVENT PRESERVATIVES....................................................................................13
4.4 ACETIC ANHYDRIDE TREATMENT ........................................................................................13
4.5 WATER SOLUBE PRESERVATIVES.........................................................................................13
4.6 Methods of applying preservatives .....................................................................................14
4.7 DIFFERENT USES OF TIMBER IN CONSTRUCTION..................................................................15
4.8 Challenges of using timber in construction..........................................................................16
5.0 CONCLUSION.....................................................................................................................17
6.0 REFFERENCE............................................................................Error! Bookmark not defined.

4. 1
CHAPTER ONE
1.0 INTRODUCTION
Timber refer to the wood used for the construction work in fact the word timber is
derived from an old English word TIMBRIAN which mean to build, on the other hand
timber is material delivered from trees high plant gymnosperm and angiosperm division.
Hundred year timber has been used as building material in the country, timber as the
building material it used for varieties structural work such as trusses for roof
construction, beam, column, railway bulk and bridges structural element. Timber can be
highly being durable when properly treated been the case proper understanding of nature,
limitations, properties of timber is required in order have a good safe timber structures
1.1 DIFFERENT TYPES OF TIMBER FOUND IN TANZANIA
There several types of timber found in the country, they names given as results of the trees
names such as mninga , mpodo, mvule and Mpingo. Timber used for engineering works is
divided into two classes
1.2 HARDWOODS/CONIFEROUS
These are dicotyledonous plants characteristically with broad leaves, these tree give non
resinous wood, the timber obtained from these trees are strong along and across fibers it
is also flexible, Strong and tough capable of bearing tension, compression or shear.
Examples of hardwood found in Tanzania are Mninga(East African padauk),
Pangapanga, and Msenjele (African lignum vitae) which are normally found in Eastern
South of Tanzania.
1.3 SOFTWOODS
Softwood is wood from gymnosperm trees such as conifers. Softwood is the
source of about 80% of the world's production of timber, with traditional centers of
production being the Baltic region. Softwoods are not necessarily softer than hardwoods.
In both groups there is an enormous variation in actual wood hardness, with the range in
density in hardwoods completely including that of softwoods.

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1.4 DIFFERENT TYPES OF TIMBER FOUND IN TANZANIA
1.4.1 MPINGO (AFRICAN BLACKWOOD)
Mpingo is one of the most expensive timbers in the world and is preferred wood of the
musical instrument trade because of its high density, fine texture and exceptional
durability. Due to unsustainable extraction the tree is threatened with commercial
extinction, but a sustainable trade is possible, providing a secure long term future for both
woodwind musicians and communities who live around the forests where it grows and
they are found in the southern part of Tanzania .
Figure 1: Mpingo (African Blackwood)
1.4.2 MKONGO(Pod Mahogany)
Although prized locally, pod mahogany is rare in international trade. Small quotas for the
species restrict its application to specialist markets. The most suitable sectors for development
are: (1) musical instruments, particularly in the manufacture of guitars and xylophones, and (2)
furniture, where it could be used to substitute marabou, bubinga and/or rosewood. FSC 100%
supplies of pod mahogany could also be used to replace doussie, merbau and bubinga in the
construction, household and consumer goods, and flooring sectors (depending on the volumes
required).
Figure 2: Mkongo (Pod Mahogany)

6. 3
1.4.3 MVULE(African Teak)
African teak has strong dark brown hardwood resistant to termites and is
used for construction, furniture, joinery, paneling, floors and boats. The tree can be used
in the control of erosion. It makes a good shade tree and is useful as a roadside tree in
urban areas. It grows rapidly, can be coppiced and is ready for cutting after about fifty
years. The tree is nitrogen fixing and the leaves are used for mulching.
Figure 3: Mvule(African Teak)
1.4.4 MNINGA(East African Padauk)
East African padauk is already used to manufacture flooring, furniture, construction
materials, household and consumer goods, and musical instruments. It is easily worked and
versatile which, together with the large quota available, permits its potential entry into numerous
sectors, including large scale and structural applications (subject to the dimensions required).
FSC 100% stocks could be pitched as a supplement or alternative to current supplies and similar
species in all of the existing industries, as well as in the manufacture of windows and doors,
musical instruments and boats and yachts.
Figure 4: Mninga(East African Padauk)
i. The system is not expensive to be implemented into offices.
ii. It offers good records keeping in form of images because it has the memory card for
storage purpose.

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iii. It provides enough evidence in lawsuits this is due to fact that the system is capable of
saving the image of the victim.
iv. It is easy to do the maintenance and repair

8. 5
CHAPTER TWO
2.0 CHARACTERISTICS OF TIMBER
2.1 INTRODUCTION
The principal characteristics of timber with which specifiers may be concerned on are
strength, durability and finished appearance however timber can be characterized based on the
following
2.2 MECHANICAL PROPERTIES
Engineers, architects and carpenters must be well versed with the mechanical properties of
timber. In order that the engineer may properly design columns and beams for various parts
of wooden structures, he must be thoroughly conversant with the strength and stiffness of the
available classes of timber. The architect must not only appreciates the beauty of various species,
the relative ease with which each may be worked, the tendency to shrink, warp, and check; but
he must likewise be prepared to proportion joints and rafters to carry the imposed loads without
excessive deflection. The wheelwright must understand how the toughness and strength of his
axles, spokes, and shafts are influenced by species, rate of growth, density, and defects. The
carpenter and the craftsman must also have knowledge of the mechanical properties of wood
in order that they may work it to best advantage. The mechanical properties of timber that
need elaboration are as follows.
2.2.1 Stress strain relationship
Wood has three principal axes, longitudinal, radial and tangential along which properties are
fairly constant. Since wood is a noni tropic material, it has three values of modulus of elasticity
varying by as much as 150 to 1, three shear moduli varying by 20 to 1, and six Poisson’s ratios
varying by 40 to 1. There is no sharply defined elastic limit in wood but there is a proportional
limit. However, the stress-strain diagram in any direction is fairly straight over a considerable
range before it gradually curves off. It is a ductile material.
The relative stress-strain curves for direct tension, direct compression and bending stress
intensities parallel to the grain in Fig. 4.22 show that in both, direct compression and bending,
the proportional limit is in the vicinity of 65 to 75 per cent of the ultimate strength
2.2.2 Compressive strength
When subjected to compressive force acting parallel to the axis of growth, wood is found to be
one of the strongest structural material. Columns and posts are, therefore, often fashioned of it.
However, compressive strength perpendicular to fibres of wood is much lower than that parallel
to fibres of wood. When wood is subjected to compression parallel to the grain, it may fail
through collapsing of the cell walls or through lateral bending of the cells and fibres. In wet

9. 6
wood and in the hardwoods, which are composed of thick-walled fibres and vessels, incipient
failure is due to bending of the individual fibres. In cross-grained pieces, the failure is likely to
take place through shear parallel to the grain.
2.2.3 Tensile strength
When a properly shaped wooden stick is subjected to tensile forces acting parallel to the grain
it is found to have greater strength that can be developed under any other kind of stresses.
Indeed, the tensile strength of wood parallel to the grain is so great that much difficulty is
encountered in designing end connections so that the tensile strength of a piece can be
developed. Therefore, wood tension members are rarely used. Tensile strength parallel to the
fibres is of the order 80.0 to 190.0 N/ mm2 . However, wooden parts restrained at their ends
suffer from shearing stresses and crushing which wood resists poorly, and cannot be extensively
used in structure working under tension
2.2.4 Bending strength
Wood well withstands static bending, owing to which it is widely employed for elements of
buildings, e.g. beams, slabs, rafters, trusses, etc. The initial failure of long beams of uniform
width is indicated by a wrinkling of the overstressed compression fibres, much like the failures
which occur in compression prisms. Final failure of such beams is generally in tension. It is
accompanied more or less by snapping as the individual fibres begin to break when the
maximum load is reached. Very dry specimens sometimes fail very suddenly intension before
any wrinkling of the compression fibres is noticeable. Short deep beams fail by horizontal shear
suddenly, and this is more common in well-seasoned timber of structural sizes than in green
timbers or in small beams
2.2.5 Shear strength
Wood has low shearing strength of 6.5–14.5 N/mm2 along the fibres. Resistance of wood to
cutting across the fibres is 3 to 4 times greater than that along the fibres, but pure shear generally
does not take place since the fibres are also subjected to crushing and bending.
2.3 PHYSICAL PROPERTIES
2.3.1 Density and specific weight
All the physical properties of clear wood are related to its density, which varies directly
with the apparent specific gravity. The true specific gravity of wood is approximately equal for
all species and averages 1.54, whereas the specific weight and apparent specific gravity vary
with density of wood. The percentage of moisture in the wood has a very large effect upon the
specific weight and hence true comparisons of this property can only be made on dry specimens
2.3.2 Moisture movement
Water is found in three portions of wood: (1) it constitutes over 90 percent of the
protoplasm in the living cells; (2) it saturates the cell walls; (3) it fills, more or less

10. 7
completely, the pores of the life less cells. Timber is liable to shrink or swell with the
movement of moisture. This movement is not the same in all the directions.
2.3.3 Swelling
Is the capacity of wood to increase both its linear and volumetric dimensions when it
absorbs water. Swelling of wood along the length of fibres ranges from 0.1 to 0.8 per
cent, 3 to 5 per cent in the radial direction and 6 to 12 per cent in the tangential direction
2.3.4 Heat conductivity
Is quite low and the coefficient of heat conductivity along the fibres is 1.8 times greater
than that across the fibres and averages 0.15 to 0.27 K cal /mh°C. As the bulk density of
wood increases and its moisture content decreases, the amount of air entrapped inside
cavities decreases, the effect being greater heat conductivity of wood.
2.3.5 Sound conductivity
The velocity of sound in wood is 2 to 17 times greater than that in air and as such wood
may be considered to have high sound conductivity
2.3.6 Resistance to action of acid and alkali
Wood is not affected by weak alkali solution but decays in an acid medium (pH< 4).
2.4 SEASONING OF TIMBER
As fresh timber which is obtained from trees contains about 30 to 40 % sap or moisture.
This sap is very harmful for the life of a timber. Therefore, it is necessary to remove that sap by
applying some special methods. All those methods which are used for removing the sap from
timber are collectively termed as seasoning of timber
2.4.1 Advantages of timber
 It has reduced weight,
 It is strong and durable
 It has resistance to decay or rot
 It takes high polish
 It is easier to work
 Its life is more.

11. 8
2.4.2 Types of Timber Seasoning
 Natural Seasoning,
 Artificial Seasoning,
a. Kiln Seasoning,
b. Chemical Seasoning,
c. Electric Seasoning,
 Water Seasoning
2.4.3 Natural seasoning
In the air seasoning or natural seasoning or natural drying, seasoning of timber, timber is
dried by direct action of air, wind and sun. In this method, the timber logs are arranged one over
the other, keeping some space or distance between them for air circulation of fresh air.
Generally this type of seasoning requires few months to over a year, this is very slow process.
Figure 5: Natural seasoning
2.4.4 Artificial seasoning
 Kiln Seasoning:
In kiln seasoning timber is placed in a chamber with some special heating arrangement.
In this process one thing should be kept in mind that heating system should be under
control, otherwise timber will be crack or wrap. The time required for this seasoning is 3
to 12 days. This is quick process
Figure 6: Kiln seasoning

12. 9
 Chemical Seasoning:
In chemical seasoning carbon dioxide, ammonium carbonate or urea are used as agents
for seasoning, those are applied in dry state, the inter surface of timber dries first than
outer side. This ensures uniform seasoning. The time required for this seasoning is 30 to
40 days
 Electric Seasoning:
In this method electric current is passed through the timber logs. The time required for
this seasoning is 05 to 08 hours
Figure 7: Electric kiln
2.4.5 Water Seasoning:
In water seasoning, timber logs are kept immersed whole in the flowing water. The sap
present in timber is washed away. After that logs are taken out from water and are kept in
open air, so water present in timber would be dried by air. The time required for this type
of seasoning is 2 to 4 weeks.

13. 10
CHAPTER THREE
3.0 DEFECTS OF TIMBER
3.1 INTRODUCTION
Defects can occur in timber at various stages, principally during the growing period
and during the conversion and seasoning process. The defects in the wood as shown in Fig.
4.4 are due to irregularities in the character of grains. Defects affect the quality, reduce the
quantity of useful wood, reduce the strength, spoil the appearance and favor its decay.
3.2 Defects due to abnormal growth
Following are some of the important defects commonly found in wood due to abnormal
growth or rupture of tissues due to natural forces.
I. RADIAL SHAKE
These are similar to the star shakes and occur in felled timber when exposed to
the sun during seasoning. Radial shakes are generally irregular, fine and
numerous .In this many splits are appeared
Figure 8: Radial shake
II. HEART SHAKE
Occurs due to shrinkage of heart wood, when tree is over matured. Cracks start
from pith and run towards sap wood. These are wider at center and diminish
outwards.
Figure 9: Heart shake

14. 11
III. CUP SHAKE
Appears as curved split which partly or wholly separates annual rings from one
another. It is caused due to excessive frost action on the sap present in the tree,
especially when the tree is young
Figure 10: Cup shake
IV. STAR SHAKE
Are radial splits or cracks wide at circumference and diminishing towards the center of
the tree. This defect may arise from severe frost and fierce heat of sun. Star shakes appear
as the wood dries below the fiber saturation point. It is a serious fault leading to separated
log when sawn
Figure 11:Star shake
V. RIND GALL
Characterized by swelling caused by the growth of layers of sapwood over wounds after
the branch has been cut off in an irregular manner. The newly developed layers do not
unite properly with the old rot, thereby leaving cavities, from where decay starts.
Figure 12: Rind gall

15. 12
3.3 Defects due to conversion
Conversion is the term used to describe the process whereby the felled tree is converted
into marketable sizes of timber. Conversion defects are basically due to unsound practice in
milling or attempts to economize during conversion of timber. A wane occurs in timber which
contains, on one or more faces, part of the bark or the rounded periphery of the trunk. This
reduces the cross sectional area, with consequent reduction in strength in the parts affected.
Excessive slope of grains may also be classed as a conversion defect when conversion has not
been done parallel to the axis of the trunk.
3.4 Defect due to seasoning
These defects are directly caused by the movement which occurs in timber due to
changes in moisture content. Excessive or uneven drying, exposure to wind and rain, and poor
stacking during seasoning can all produce distortions in timber. These defects result in loosening
of fixings or disruption of decoration, or both. The common types of seasoning defects are
checks—longitudinal separation of fibres not extending throughout the cross-section of wood,
splitting—separation of fibres extending through a piece of timber from one face to another ,
warp age—consists of cupping, twisting and bowing.

16. 13
CHAPTER FOUR
4.0 TIMBER PRESERVATION
4.1 INTRODUCTION
Timber preservation generally refers to the application of treatments (chemicals) to
timber to stop the attack of woodworm, fungal decay (wet rot/dry rot) and to protect it from the
effects of dampness. Alternative methods of timber preservation can be employed without the
use of chemicals, these could be to introduce a physical barrier (such as a membrane) between
the timber and a source of moisture or even something as simple as increasing the airflow around
timbers can prevent or arrest the causes of timber degradation. The following are the preservative
methods
4.2 OIL TYPE PRESERVATIVE
Applied over outside of exposed timber, give unpleasant smell and are not suitable when timber
is to be painted. The types in use are creosote, carbolinium, solignum etc. with or without
admixture with petroleum or suitable oils having a high boiling range.
4.3 ORGANIC SOLVENT PRESERVATIVES
Preservatives Insoluble in Water) consists of toxic chemical compounds, e.g. pentachlorophenol,
benzene-hexa-chloride, dichlorodiphenyl trichloro-ethane (D.D.T) and copper naphthenate.
These are dissolved in suitable organic solvents like naphtha, or in petroleum products such as
kerosene, spirit, etc. The treated timber can be painted, waxed or polished.
4.4 ACETIC ANHYDRIDE TREATMENT
Is used for protection of veneers, plywood and light lumbers against decay by acetylation. They
are treated with acetic anhydride vapor, which minimizes swelling and improves resistance to
decay and attack by insects
4.5 WATER SOLUBE PRESERVATIVES
Are odourless organic or inorganic salts and are adopted for inside locations only. If applied over
outside surfaces, the salts can be leached by rainwater. Examples of leachable (3A-water soluble)
type of preservatives are zinc chloride, boric acid (borax), etc. Zinc chloride, sodium fluoride and
sodium-penta-chloro-phenate are toxic to fungi. These are expensive and odourless (except for
sodium-penta-chloro-phenate). Benzenehexa-
chloride is used as spray against borers. Boric acid is used against Lyctus borers and to protect
plywood in tea chests.

17. 14
to compile data. However, such standardized answers may frustrate users. Questionnaires are
also sharply limited by the fact that respondents must be able to read the questions and respond
to them.
4.6 Methods of applying preservatives
Before applying preservatives, the timber should be completely seasoned. There are
some important
methods of applying timber preservatives which are given below.
 Painting and dipping method
 Pressure process or full cell process
 Empty cell process
Painting and dipping method:
This is the most common method in which the preservative material is applied by
means of a brush several times. The timber is also immersed in a tank full of liquid
(preservative material). In both types the penetration hardly exceeds 1/16’’. The duration
of immersion and temperature of solution is increased the penetration rate.
Pressure process or full cell process:
In this process, the timber is placed in an air tight chamber, from which air is
withdrawn by creating a vacuum. The cells are full emptied to receive preservative
material. After that preservative material is pumped under pressure of 100 to 200 psi and
at a temperature of 120degreeF. As the timber contains required quantity of preservative
a low vacuum is maintained to remove excess preservative. Such a timber is generally
used in case of piles in salt water and railway sleepers.
Empty cell process:
This method is similar to the full cell process but initial vacuum is not to be
maintained and no attempt is to be made to remove the air from cells. The preservative
material is applied under pressure of 200 psi

18. 15
4.7 DIFFERENT USES OF TIMBER IN CONSTRUCTION
i. wood frame work construction
In certain part of the world such as Scandinavian countries, houses will be entirely built
of timber because it is suitable for climatic conditions.
Elsewhere, house builders can choose to support the house by wooden frames or stud
walling. Roof Truss rafters are made entirely of wood and timber shuttering can be
chosen for concrete work; in addition some construction plans require a massive bearing
beam that will balance structure
Figure 13 : Wall formwork
ii. outdoor features construction
Construction of commercial and some private projects will also include exterior work.
Outside features such as patios and decking will be made of wood. Additionally, garden
architects will require timber for raised plant containers and fencing, while garden shed
and garages are often constructed of timber.
iii. used in decorative works
The most visible use of timber is displayed in the finishing process of a construction
project. Stair case, door frames, skirting and floor boards as well as boiler, mater and pipe
boxes are wooden. Custom-built cupboards are also mostly wooden as are fitted kitchen
appliances
Figure 14 :stair form work
iv. Glued wood components e.g., beams, trusses, arches, frames and roofs of buildings and
Installations are very effective in chemically aggressive media because their service life
is 1.5 times greater than that of steel or reinforced concrete. However, the use for wood

19. 16
should be economically justified and the possibility of replacing it with prefabricated
concrete, asbestos cement, gypsum, plastics and other items should be carefully
considered.
v. The use of fibreboard, ply-boards in building practice provides a substantial saving both
in capital investments and running costs. The economy is provided, in the first place, by a
more complete utilization of raw materials for the manufacture of building materials and
items. The use of boards made of pressed wood shavings in dwelling house construction
has a great economical effect. Currently, wood waste is utilized to manufactures polymer
and cement based fibreboard and wood shavings board. This also allows manufacturing
materials of better physical, mechanical and decorative properties than wood.
4.8 Challenges of using timber in construction
Safety from Fire
 To provide an environment for the occupants inside or near a building that is
reasonably safe from fire and similar emergencies.
 To provide reasonable safety for fire fighters and emergency responders during
search and rescue operations.
Safety from Structural Failure
 Provide a high confidence of a low probability of structural failure resulting in
local or global collapse, or the creation of falling debris hazards that could
threaten life.
 Provide a high confidence that the structure will be capable of resisting regularly
occurring loads and combinations of loads without significant damage or
degradation.
Shrinkage and Swelling of Timber
 Timber is a hygroscopic material. This means that it will adsorb surrounding
condensable vapors and loses moisture to air below the fiber saturation point.
Safety during Building Use
 Provide an environment for the occupants of the building that is reasonably safe
during the normal use of the building.

20. 17
5.0 CONCLUSION
In modern building practice, timber and other wood product are extensively useful and normal
they are used for walls and floors of buildings, carpentry and graded plank items, as well as
prefabricated standard wooden cottages. This high usage of timber has brought great growth of
economy of a country also growth of cities and town . A great quantity of wood is consumed in
building and installation work for making piles, poles, various load-bearing components
formworks, scaffolds. Currently, wood waste is utilized to manufactures polymer and cement
based fibreboard and wood shavings board. This also allows manufacturing materials of better
physical, mechanical and decorative properties than wood.