Timber

Question 1

What is the advantage of timber?

Answer 1

its relatively light compared to its compressive strength
natural and renewable resource
sequesters carbon
light and easily prefabricated and transported
short lead time from sawn timber
can be engineered and re engineered at end of life

Question 2

disadvantages of timber?

Answer 2

variable material properties and is anisotropic
fire resistance/ fuel
shrinkage and movement over time
not suitable for tall buildings
slow to construct onsite
vibration governs long spans

Question 3

types of engineered wood?

Answer 3

CLT
CDT

Question 4

softwood v hardwood?

Answer 4

hardwood takes twice as long to grow
more durability
supports more life and habitat
broad leave and sheds every year
higher density 500 to 1000 kg/m3
ash, beech, birch, cherry, chesnut, oak

softwood grows fast
supports less life and ecosystem
neddles instead of leaves
lower density 400-600 kg/m3
douglas fir, pine, larch, spruce

Question 5

how does wood work?

Answer 5

roots extract water and minerals from the soil
draw them up the tree as sap
leaves absorb co2 and photosynthesis uses light to turn the co2 and water into cellulose and release oxygen
cellulose make new wood.

Question 6

makup of a treetrunk?

Answer 6

bark and bast
fibers
vessels

sapwood is the newer wood near the bark
heartwood is the older compressed innerlayers

Question 7

how much of timbers weight when felled is water?

Answer 7

about a half

Question 8

what is fiber saturation point?

Answer 8

its the point where moisture is down to about 30% and after this point further drying causes shrinkage in cells

Question 9

what moisture content can we get from air dried wood?

Answer 9

roughly 20% but its slow, take month or years
after this a kiln is required

Question 10

What moisture content can we expect from structural timber in comparison to joinery?

Answer 10

Structural 20%
Joinery 12%

Question 11

For example in oak, once the fsp is reached at 30%, how does it shrink?

Answer 11

longitudinal 0.1%
Radial 4.5%
tangential 8%

Question 12

How i timber graded?

Answer 12

C14 - C50 (12 classes)
C - Coniferous
14 - bending stress

D30 - D70
D - deciduous

Question 13

How do you know if timber is machine graded?

Answer 13

It has an M preceeding the C??

Question 14

How does machine grading work?

Answer 14

Via wood e modulus and measuring vibration

Question 15

What type of strength does wood have? and what does it mean?

Answer 15

Anisotropic, means its stronger in the direction of the grain
is 5-20 weaker against the grain

Question 16

what is wet rot?

Answer 16

wet rot is gound on wood with a moisure content of 40-50%
does not spread into adjacent timber

Question 17

What is dry rot?

Answer 17

Moisture content above 20% with poor ventilation and humid conditions
can spread to adjacent timber
hard to remove, mush change the environment

Question 18

What two insects are found in the uk that lay eggs in wood and eat their way out?

Answer 18

Boring weevil
Woodworm
larve hatch and eat their way out for up to 4 years

Question 19

types of wood preservation?

Answer 19

tanalising
pickling (accoya)
thermally modifyed wood

Question 20

what are panel products made from?

Answer 20

sheets
strands
fibers
particles

Question 21

what is plywood?

Answer 21

sheets laid perpedicular to each other
is the oldest manufacture sheet

Question 22

what is osb?

Answer 22

Oriented Strand board
strand of wood between 50-100mm long and 10-50mm wide
bonded under heat and pressure

Question 23

what is mdf?

Answer 23

non structural fibre board (medium density fibreboard)
interior use
high density = hardboard

Question 24

what is particle board?

Answer 24

chipboards
not structural
interior use only
poor durability needs a veneer

Question 25

what is wood plastic composite?

Answer 25

wood made by mixing wood fibres with thermoplastic

Question 26

types of engineered wood?

Answer 26

Glulam - up to 2m deep, 200 wide and 30m long

Question 27

what is kerto laminated timber?

Answer 27

Lvl - laminated vaneer lumber
kerto q - some layers cross laminated
kerto s grains run in the same direction
used for studs and i joists