Builders' language unravelled......Dry Rot

What is Dry Rot? Again, we’re not talking about that unsightly black mould – even though this is very harmful!

Dry Rot terminology is confusing as it implies decay occurring without the presence of moisture.   But in fact 'Dry' refers to the 'dry' wood that we use in the construction of our houses - opposed to “wet” wood - the wood in living or newly-felled trees.  Most homes have some wooden structures.  Even if they are made of brick - the basic structure being the frame – is made of wood.  The trim on most houses is made of wood.

Dry rot is the decay of the timbers used in the construction of the house. It is caused by a fungus which changes the composition of the wood, making it brittle. The fungus does require an elevated moisture content of 28-30% in order to start the growing.   Both continued dryness and continued saturation with water will encourage dry rot.  Window sills are a prime target for this fungus – see pictures below.

The first step in handling dry rot is to correct the condition that led to the initial growth of the fungus.  Eliminate the cause of dampness in the area and increase ventilation to the site. 

In most cases this is not possible, so you need to repair or replace the wood that was weakened by this fungus growth.

Signs of Dry Rot

Outside:   Warping or swelling of weather board; bubbling or lifting of paint; ends of fascia boards are soft or crumbling; any wood with areas of softness where a screwdriver can be pushed in easily.

Inside:  Water spots on walls, ceilings or carpets; discoloration of vinyl floors, carpets or under sink shelves; warping of flooring (usually in kitchen, bathroom or laundry); crumbling of gib-board on walls or ceilings.