Timber defects

Question 1

How can you measure moisture in timber?

Answer 1

With a moisture meter

Question 2

What level of moisture is acceptable in timber?

Answer 2

5 to 12% normal

17% is acceptable

at 35 - 50% wood is susceptible to rot and mold

Question 3

What are the 3 main timber defects

Answer 3

Dry Rot

Wet Rot

Insect Attack

Question 4

What are the difference between dry rot and wet rot

Answer 4

Dry Rot
- Wood shrinks and splits into large cuboidal cracking.
- The wood is liking in weight
- Crumbles under touch
- Dull brown colour
- Mycelium is often visible
- Grey when wet and yellow or purple when dry

Wet Rot
- Darkened timber
- Soft and spongy texture
- Mycelium growth
- Damp smell
- Linear cracking

Question 5

What moisture content would you expect to see for both dry and wet rot?

Answer 5

Dry rot - 20% Moisture

Wet rot 50-60% or higher

Question 6

What conditions does dry rot like?

Answer 6

Moisture - 20%

Temperature - 20c

Poor Ventilation

Nutrient source

Question 7

What conditions does wet rot like?

Answer 7

High moisture content

Damp

Poor ventilation

Nutrient source

Indoor temperatures

Question 8

Explain the Lifecyle of dry rot

Answer 8

Spore
Appear as fine orange brown dust

Hyphae
when in contact with wood will produce hyphae, which allow fungus to grow

Mycelium
hyphae turn into a mass of mycelium.
can grow over significant lengths

Fruiting body
The fungus create a fruiting body, which is a wee mushroom
this pumps out spores

Question 9

What are the remedial measures to dry and wet rot?

Answer 9

To locate and eliminate the sources of moisture

Promote rapid drying

Remove rotten wood

In some cases a surface application of fungicidal fluid

structural support measures if required.

Question 10

The ends of the joists in a timber floor built in an external wall
have been seriously affected by dry rot. How will you recognise this type of rot and what action would you take to
resolve the problem?

Answer 10

• Wood shrinkage and cracks of a cuboidal manner
• grey mushroom coloured skin, with yellow and purple/violet
• white fully mycelium

Timber should be propped if required.

Fully understand extend of outbrake

plaster in contact with the dry rot needs to be removed and masonry treated with a sterilizer or biocide

Any affected timbers should be removed, including approx. 300mm to 450mm beyond, and replaced with pre-treated timbers

Any other timbers at risk should be treated with a chemical biocide

areas should be kept dry and heated to ensure timbers dry out.

Question 11

You are surveying a deflected timber floor in an early 19th
century building. What are the causes and methods available
to deal with this if the client requires a level floor?

Answer 11

• Confirm the cause of the deflection whether this is due to:-
  o Notching.
  o Rot.
  o Insufficiently sized joists.
  o Insufficient centres.
  o Overloading.
  o Deterioration of sleeper walls.
• Confirm if the issue can be remedied and whether the timber floor can be retained.
• There may be a potential to:-
  o Supplement the timber joists.
  o To overboard.
  o Remove and replace with suspended timber floor.
  o Install an alternative solid floor.

Question 12

What are the signs of an infestation

Answer 12

wood worm
pin holes