timber defects

Question 1

how does water naturally and artificially affect timber?

Answer 1

natural - rain, snow frost, dew, ground water, solubility, absorption

artificially - condensation, leaks, splits

Question 2

how do mechanical processes affect timber naturally and artificially?

Answer 2

natural - applied loads, wind loads, impact, abrasion

artificial - impact, abrasion, vibration and applied loads

Question 3

how do biologial and human processes affect timber?

Answer 3

biological - fungi, plants, insects and animals

human - abrasion, mechanical damage through fire use, fire vandalism and applied loads

Question 4

What is moisture content?

Answer 4

The ratio of the weight of water to the weight of the moisture content.

Question 5

At what percentage moisture content is timber susceptible to insect and fungi attack?

Answer 5

20% and above

Question 6

What type of material is timber?

Answer 6

timber is hygroscopic

Question 7

Timber is a hygroscopic material. What does hygroscopic mean?

Answer 7

Wood is a hygroscopic, meaning it is a material that absorbs water

Question 8

What impact does excessive notching have on the strength of wood?

Answer 8

reduces the strength of wood causing structural issues and reducing load bearing capacity of the joists

Question 9

what potential defects effect timber in house construction?

Answer 9

overloading 
natural defects within the timber itself - knots, resin pockets, weak and short grain, waney edge
fungi 
wood boring insects 
water / moisture

Question 10

Which organisms attack timber and why?

Answer 10

fungi and wood boring insects attack timber for food and moisture

Question 11

what is the life cycle of fungi?

Answer 11

fruit body
spores
germination
mycellium

Question 12

what is white rot?

Answer 12

wood develops fibrous consistency
tends to become lighter in colour
cracking in mainly along the grain

Question 13

what is brown rot?

Answer 13

cuboidal cracking

wood becomes darker becomes dry and crumbly

Question 14

what is the difference between wet and dry rot

Answer 14

all brown rots and white rots are know as wet rot

serpula lacrymans is known as dry rot

Question 15

what is the life cycle of wood boring insects in timber?

Answer 15

larvae tunnel into wood, eating it
pupa forms 
adult emerges through exit hole 
after emerging, adult mates and lays eggs 
larvae eggs hatch and process repeats

Question 16

what is the most common insect attacking buildings? how big are adults?
how big are exit holes?

Answer 16

common furniture beetle
adults size 3-5mm long
exit holes about 1-2mm diameter

Question 17

what are characteristics of the house longhorn beetle relating to timber

Answer 17

causes relatively severe damage
limited to some home counties
up to 24mm long
oval shaped exit holes 6-10mm diameter

Question 18

what are characteristics of the death watch beetle relating to timber?

Answer 18

commonly associated with historic buildings
usually only attacks damp decayed timber
adults 6-9mm long
round exit holes 3mm diameter

Question 19

What factors must be dealt concerning insect attack?

Answer 19

changes in environment may cause insects to die out
inertial treatments are intended to kill existing attack and leave a layer of poison against future attack
adverse effects of treatments on humans and other creatures need to taken in account

Question 20

what are the size of upper floor timber joists dependant on?

Answer 20

expected loading
spacing between joists
required span

Question 21

why is timber in houses the most suitable material?

Answer 21

it is readily avaialable
it is relatively cheap 
it is easy to cut and shape 
fixings are easy 
timber is relatively easy to repair or alter

Question 22

what factors affect the risk of damage by timber pests?

Answer 22

the natural durability of the species of timber
the food value of the timber
adverse environmental conditions - moisture content of timber
the protection afforded through any treatment by chemical preservatives

Question 23

how are some timbers naturally resistant to fungi attack?

Answer 23

this durability is determined by the presence in the tree of naturally occurring substances which are toxic to fungi

Question 24

How what are advantages and disadvantages of preservative chemicals relating to fungi attack?

Answer 24

can reduce the risk of fungal or insect attack

there are financial and environmental costs that come with their use

Question 25

Where does attack of wood by fungi and wood boring insects typically take place?

Answer 25

takes place in area of the wood that are damaged or dead area

Question 26

What is the difference between hardwood and softwood?

Answer 26

refers to botanical differences between broad leaved trees. (hardwood) and confierous (softwood)