Docsity
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Docsity AI
Docsity AI
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search for your university

Find the specific documents for your university's exams

Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

Timber lecture Notes, Lecture notes of Construction management

Makerere UniversityConstruction management

Lecture notes on Timber as a construction material

Typology: Lecture notes

2018/2019
On special offer
30 Points
Discount

Limited-time offer

Uploaded on 08/28/2019

BENERT
BENERT 🇺🇬

4.3

(4)

6 documents

1 / 49

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
MAKERERE UNIVERSITY
P.O Box 7062 Kampala
COLLEGE OF ENGINEERING, DESIGN, ART AND TECHNOLOGY
SCHOOL OF BUILT ENVIRONMENT
DEPARTMENT OF CONSTRUCTION ECONOMICS AND MANAGEMENT
Date: September - 03 - 2018
CONSTRUCTION MATERIALS (CMG 2108)
GROUP FOUR
TIMBER PART II
S/N
Name
Registration No.
Course
Signature
1
ARIHOONA BENERT
17/U/21110
CM
2
KYAMUWENDO RUTH
17/U/5564/PSA
CM
3
WASSWA VICENT MUTABAZI
17/U/1230
CM
4
ACHAL DANIEL
17/U/2021/PSA
QS
5
GGITA JOSEPH
17/U/4071/PSA
QS
6
KIRONDE ELVIS NKATA
17/U/5234/PSA
QS
7
MUKONYEZI SHEILA
17/U/1825
QS
8
SEMUKUTU EMMANUEL KIRETA
17/U/9977/PS
QS
9
KASULE DAVID
17/U/358
QS
10
AINEMBABAZI CHRISTINE
17/U/2294/PS
LE
11
CHEPTOEK KERINE
17/U/3886/PS
LE
12
KANYESIGYE RACHEAL
17/U/4638/PS
LE
13
TUSIIME EMILANIA
17/U/10633/PSA
LE
14
NASASIRA ELIZABETH
17/U/8817/PSA
LE
15
AREMWAKI GILBERT ERAIJAH
16/U/108
LE
Lecturer’s name: Mr. Semanda Julius
Year Two Semester One
ACADEMIC YEAR 2018-2019
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff
pf12
pf13
pf14
pf15
pf16
pf17
pf18
pf19
pf1a
pf1b
pf1c
pf1d
pf1e
pf1f
pf20
pf21
pf22
pf23
pf24
pf25
pf26
pf27
pf28
pf29
pf2a
pf2b
pf2c
pf2d
pf2e
pf2f
pf30
pf31
Discount

On special offer

Partial preview of the text

Download Timber lecture Notes and more Lecture notes Construction management in PDF only on Docsity!

MAKERERE UNIVERSITY

P.O Box 7062 Kampala

COLLEGE OF ENGINEERING, DESIGN, ART AND TECHNOLOGY

SCHOOL OF BUILT ENVIRONMENT

DEPARTMENT OF CONSTRUCTION ECONOMICS AND MANAGEMENT

Date: September - 03 - 2018

CONSTRUCTION MATERIALS (CMG 2108)

GROUP FOUR

TIMBER PART II

S/N Name Registration No. Course Signature

1 ARIHOONA BENERT 17/U/21110 CM

2 KYAMUWENDO RUTH 17/U/5564/PSA CM

3 WASSWA VICENT MUTABAZI 17/U/1230 CM

4 ACHAL DANIEL 17/U/2021/PSA QS

5 GGITA JOSEPH 17/U/4071/PSA QS

6 KIRONDE ELVIS NKATA 17/U/5234/PSA QS

7 MUKONYEZI SHEILA 17/U/1825 QS

8 SEMUKUTU EMMANUEL KIRETA 17/U/9977/PS QS

9 KASULE DAVID 17/U/358 QS

10 AINEMBABAZI CHRISTINE 17/U/2294/PS LE

11 CHEPTOEK KERINE 17/U/3886/PS LE

12 KANYESIGYE RACHEAL 17/U/4638/PS LE

13 TUSIIME EMILANIA 17/U/10633/PSA LE

14 NASASIRA ELIZABETH 17/U/8817/PSA LE

15 AREMWAKI GILBERT ERAIJAH 16/U/108 LE

Lecturer’s name: Mr. Semanda Julius

Year Two Semester One

ACADEMIC YEAR 2018- 2019

TIMBER PART TWO NOTES

i | P a g e

TIMBER PART TWO NOTES

TIMBER PART TWO NOTES

 - 9/3/
  • 1.0 CONVERSION OF WOOD Table of Contents
    • 1.1 Felling
    • 1.2 Sawing of Timber
      • 1.2.1 Considerations while sawing up a log
      • 1.2.2 Factors that determine the type of cut.................................................................................
    • 1.3 Ways of Timber Conversion
      • 1.3.1 Radial sawing (rift cut)
      • 1.3.2 Tangential sawing (slash cut)
      • 1.3.3 Comparison between slash cut and rift cut
    • 1.4 Methods of Conversion.................................................................................................................
      • 1.4.1 PLAIN SAWN
      • 1.4.1.1 Advantages of plain sawn
      • 1.4.1.2 Disadvantages of plain sawn
      • 1.4.2 QUARTER SAWN METHOD
      • 1.4.2.1 Advantages of Quarter Sawn
      • 1.4.2.2 Disadvantage of Quarter Sawn
      • 1.4.3 RIFT SAWN
      • 1.4.3.1 Advantages of Rift Sawn
      • 1.4.3.2 Disadvantage of Rift Sawn
  • 2.0 SEASONING OF TIMBER
    • 2.1 Reasons why seasoning is done
    • 2.2 METHODS OF SEASONING
      • 2.2.1 NATURAL SEASONING
      • 2.2.1.1 Air seasoning.
      • 2.2.1. 2 Water seasoning.
      • 2.2.1.3 Advantages of Natural seasoning.
      • 2.2.1.4 Disadvantages of natural seasoning.
      • 2.2.2 ARTIFICIAL SEASONING
      • 2.2.2.1 Methods of artificial seasoning
      • 2.2.2.1.1 BOILING
        • 9/3/
      • 2.2.2.1.2 KILN SEASONING ii | P a g e
      • 2.2.2.1.3 CHEMICAL SEASONING
      • 2.2.2.1.4 ELECTRICAL SEASONING
      • 2.2.2.2 Advantages of artificial seasoning.
      • 2.2.2.3 Disadvantages of artificial seasoning.
  • 3.0 SPECIAL TIMBER PRODUCTS
    • 3.1 Different forms of industrial timber:
      • 3.1.1 Veneers
      • 3.1.2 Plywood...............................................................................................................................
      • 3.1.3 Laminated Boards.
      • 3.1. 4 Fibre Boards
      • 3.1.5 Impreg Timbers
      • 3.1.6 Compreg Timbers
      • 3.1.7 Hard Boards.........................................................................................................................
      • 3.1.8 Chip Board
      • 3.1.9 Block Board
  • 4.0 TIMBER PRESERVATION
    • 4.1 Types of methods used in preserving timber
      • 4.1.1 Definition of a preservative;
      • 4.1.2 Requirements of a wood preservative................................................................................
    • 4.2 Chemicals used for Preserving Wood
      • 4.2.1 Oil-soluble salts
      • 4.2. 2 Water-soluble salts
      • 4.2.3 Volatile base salts................................................................................................................
    • 4.3 Methods of Preservation of Timber
      • 4.3.1 Brushing Application
      • 4.3.2 Spraying Method
      • 4.3.3 Dipping Application
      • 4.3.4 Open Tank Application
      • 4.3.5 Pressure Application
  • 5.0 GRADING OF TIMBER
    • 5.1 STRUCTURAL GRADING. - 9/3/
    • 5.1.1 Machine stress grading. iii | P a g e
      • 5.1.1.1 Advantages of using the machine stress grading method
      • 5.1.1.2 Disadvantage of using the machine stress grading method
    • 5.1.2 Machine proof grading,...........................................................................................................
      • 5.1.2.1 Advantages of using the machine proof grading method.
      • 5.1.2.2 Disadvantages of using the machine proof grading method.
    • 5.1.3 Visual stress grading................................................................................................................
      • 5.1.3.1 Advantages of using the visual stress grading method.......................................................
      • 5.1.3.2 Disadvantages of using the visual stress grading method.
    • 5.1.4 Quality Control.
    • 5.2 APPEARANCE GRADING.
    • 5.2. 1 Types
      • 5.2.1.1 Select grade.........................................................................................................................
      • 5.2.1.2 Standard grade.
      • 5.2.1.3 Character grade...................................................................................................................
      • 5.2.1.4 Factors that may affect appearance of the timber include;
  • 6.0 STORING OF TIMBER
    • 6.1 Storing of timber on the site
  • 7.0 APPLICATIONS OF TIMBER
    • 7.1 Structural
      • 7.1.1 Architectural roof trusses
      • 7.1.2 Framing
      • 7.1.3 Packaging
      • 7.1.4 Portal frames.......................................................................................................................
      • 7.1.5 Shear walls
      • 7.1.6 Structural Insulated Panel Systems (SIPS)...........................................................................
      • 7.1.7 Structural timber poles
    • 7.2 Interior and exterior....................................................................................................................
      • 7.2.1 Doors
      • 7.2.2 Flooring
      • 7.2.3 Joinery
      • 7.2.4 Rails and Balustrades
      • 9/3/
    • 7.2.5 Cladding iv | P a g e
    • 7.2.6 Decking
    • 7.2.7 Fencing
    • 7.2.8 Retaining wall
    • 7.2.9 Stairs....................................................................................................................................
  • 8.0 CONCLUSION
  • 9.0 REFERENCES

TIMBER PART TWO NOTES

1.2 Sawing of Timber

After felling, trees are cut into convenient lengths that can be used in construction and can easily

be transported from place to place

They are first air seasoned for some period and then cut into transportable sizes

1. 2 .1 Considerations while sawing up a log

1. Taper ; this is the difference in size between two ends of the log. This affects how a log

needs to be cut up.

2. Size of planks or boards needed. The size of the board required will affect the method of

cut to employed.

3. Any heart rot or shakes(cracks) in the wood would also affect the method of cut and

whether the log is to be converted or not.

4. How round the log is. Irregular shapes of timber will be more complicated to convert as

this will affect the method or machinery to be used.

1. 2 .2 Factors that determine the type of cut

1. Type of sawing machine; some methods are so bulky that heavy machinery needs to be

employed.

2. The condition of the log; defected timber will call for more special cuts. For example the

box hearted.

3. Economy; the method of cut to be used will depend on its cost

4. The size of the log; some methods of conversion are wasteful that smaller logs will need a

different approach.

5. The wood species; some species give different aesthetics with different types of cuts. For

example, the oak species has ray flecks which may appear appealing

6. The end use of the resulting timber; structural timber will need to be more stable. So, the

rift cut will be more fancied for timber that is to be used for such purposes.

TIMBER PART TWO NOTES

1.3 Ways of Timber Conversion

There are two ways of timber conversion;

1. Radial sawing or rift cut

2. Tangential sawing or slash cut

1.3.1 Radial sawing (rift cut)

This is where timber is sawed such that the annual rings meet the wider face of the timber at an

angle greater than 45^0

TIMBER PART TWO NOTES

1.4 Methods of Conversion

There are three main methods of timber conversion namely

1. Plainsawn/ slash/ through and through method

2. Quarter sawn method

3. Riftsawn method

TIMBER PART TWO NOTES

1.4.1 PLAIN SAWN

Plain sawn is the most common way a log is sawn, perhaps because it is the most inexpensive way

to convert logs into timber. It also produces the most recognizable type of wood figure: the

distinctive ‘cathedral arches’, so perhaps this also explains its prevalence.

Plain sawn oak, showing 'cathedral arches'

Looking at the end of a board of flat-sawn timber, you will see that the annual growth rings are

around 30 degrees or less to the face of the board; this is often referred to as tangential grain, as

the cuts are made on a tangent to the circumference of a log.

While it may be the most efficient means of conversion and produce the most familiar grain

pattern, flat-sawn produces the least stable timber. This is because timber is hygroscopic: it

expands and contracts with changes in seasonal humidity. But it is also anisotropic: it has different

properties depending on the direction or orientation of the grain—it’s not the same in all

directions—and one of the areas where this property is most clearly seen is in dimensional stability.

As a rule of thumb, movement across the tangential plane is twice that of the radial plane. So,

when this plane is the largest surface, as with flat sawn timber, the board will more susceptible to

seasonal movement.

That was a bit technical, but suffice to say that flat-sawn solid timber is not to be used on wide,

unsupported surfaces. Working with veneer avoids this problem, but that's a topic for another day.

Visually, flat-sawn timber is appropriate for when a stereotypical ‘wood’ look is desired. It also

TIMBER PART TWO NOTES

1.4. 2 QUARTER SAWN METHOD

As we can see from the diagram, quarter sawn material is cut from quarters of the log. This reveals

a different face for the boards, giving straight grain, and the end of a board shows growth rings at

60 - 90 degrees to the face of the board.

When quarter sawn, species such as oak will display spectacular figure know as ‘ray fleck’. This

is the intersection of the tree’s medullary rays (which transmit sap within a tree) with the face of

the board, and will be more prominent the closer the growth rings are to 90 degrees to the face of

the board. That got a bit technical again, so let's focus on the fun bit: how quarter sawn surfaces

look.

Quarter sawn oak, beautiful rays dancing across the surface.

TIMBER PART TWO NOTES

As well as oak, ray fleck is also seen in species such as sycamore, beech and London plane. Quarter

sawn London plane is known as Lacewood due to its striking figure. I think it is just as beautiful

as any exotic imported timber, and it grows right here in London. I source it from the streets and

parks of our city, and a proud to promote its use as a high-value resource.

Quarter sawn material is more stable than flat-sawn, but is less efficient and therefore more

expensive. It will give straight grain, which is desirable in many modern aesthetics, as well as

producing spectacular ray fleck in particular species.

Quarter sawn material that shows ray fleck is a great way of introducing visual texture into a piece.

It can also provide emphasis, and in the case of pronounced examples, a real focal point of a space.

1.4.2.1 Advantages of Quarter Sawn

  • Smoother surface due to less distinct grain
  • Decreased expansion and contraction on the plank’s width
  • Twisting, cupping, and warping resistance
  • Ages evenly over time
  • Chances of surface checking are significantly reduced
  • More resistant to moisture penetration
  • Enhanced paint retention

1.4.2.2 Disadvantage of Quarter Sawn

  • The cutting operation is much more complicated and involves more waste.
  • The boards are rather narrow.
  • It is an expensive method

TIMBER PART TWO NOTES

offered a man-made product, describing it as Swiss oak. Very rare Swiss oak. Client and designer

left happy.

1.4.3.1 Advantages of Rift Sawn

  • Ideal for custom furniture makers to use for table, chair and other straight pieces
  • The most dimensionally stable cut of lumber available
  • Unique, linear appearance on both sides of the lumber planks
  • Rift sawn lumber is dimensionally superior to both plain sawn and quarter sawn lumber.

1.4.3.2 Disadvantage of Rift Sawn

  • They produce the most waste.
  • Rift sawn lumber will cost more per board foot than either quarter sawn or plain sawn

lumber.

TIMBER PART TWO NOTES

2.0 SEASONING OF TIMBER

Seasoning of timber is the process by which moisture content in the timber is reduced to required

level. By reducing moisture content, the strength, elasticity and durability properties are

developed. A well-seasoned timber has less than 15% of moisture content in it.

2.1 Reasons why seasoning is done

1. Reduces weight and this saves transportation costs.

2. Makes it fit to receive painting

3. Makes it workable

4. Maintains its shape and size

5. Increases stability

6. Makes it burn easily when used as fuel

7. Reduces the tendency of cracking and warping

8. Imparts hardness, stiffness, strength and resistance to electric shocks.

9. To increase durability by protecting it from fungi, insects, and other causes related to

moisture content.

2.2 METHODS OF SEASONING

1. Natural seasoning

2. Artificial Seasoning.

2.2.1 NATURAL SEASONING

Natural seasoning is the process in which timber is seasoned by subjecting it to the natural elements

such as air or water. Natural seasoning may be water seasoning or air seasoning.

2.2.1.1 Air seasoning.

In the process of air seasoning timber logs are arranged in layers in a shed. The arrangement is

done by maintaining some gap with the ground. So, platform is built on ground at 300mm height

from ground. The logs are arranged in such a way that air is circulated freely between logs. By the

movement of air, the moisture content in timber slowly reduces and seasoning occurs. Even though

it is a slow process it will produce well-seasoned timber.

TIMBER PART TWO NOTES

2.2.1.2 Water seasoning.

Logs are placed in a river with thicker ends pointing upstream. A number of logs are tied together

and anchored to a standing tree or to a rock to see that it is not carried away by the water. The sap

contained in the timber is washed way out over a period of 2- 4 weeks and replaced with ordinary

water. The timber is then stacked in a dry place and it takes comparatively less time for the logs to

dry. The logs can also be placed in stagnant water if running water is not available. In this case,

the water should be replaced every week.

Compared to air seasoning, this method takes a little time.

2.2.1.3 Advantages of Natural seasoning.

1. It requires low investment.

2. It does not require skilled labour

3. It's ideally suited to low and non-uniform market demand.

2.2.1.4 Disadvantages of natural seasoning.

1. It needs larger space for seasoning

2. The process is so slow; takes a period of two to four years.

3. As the control depend on natural air, there is no control on it.

4. Ends may dry first and split. Interiors may remain moist while exteriors dry very fast.

5. Moisture content can no be brought below a certain limit (16-17) percent.

2.2.2 ARTIFICIAL SEASONING

It has been developed of now days and its faster that natural seasoning. it takes 4-5 days to produce

a well-seasoned timber.

2.2.2.1 Methods of artificial seasoning

1. Boiling

2. Kiln

3. Chemical

4. Electrical

TIMBER PART TWO NOTES

2.2.2.1.1 BOILING

Seasoning of timber is achieved by immersing it in water for three to four hours. After boiling. The

timber is allowed to dry but however for large quantities of timber it is difficult to boil, so hot

steam may be passed over the timber to give good results. the timber is dried slowly .. This method

is effective but very costly.

2.2.2.1.2 KILN SEASONING

In this method, timber is subjected to hot air in an air tight chamber. Hot air circulates around the

timber to reduce the moisture content.

In such a kiln, carriages of timber move from one to the other end slowing.

Hot air is pumped from the discharging end so that temperature is higher at that end compared to

the charging end.

So as timber comes out the discharging end, sufficient moisture is removed.

In this method, seasoning is required on a large scale since investment costs are high.