Non-poisonous timber protection
Practical Action
Protection of vulnerable surfaces
Surfaces of timber beams and columns which are cut across the grain are extremely
vulnerable to insect and moisture penetration. Problems are avoided by fixing protective
wooden boards or metal plates at the end of beams (Figure 4).
Wood surfaces in contact with the ground, or with other building materials that
accumulate moisture (e.g. concrete), are in constant danger of moisture and insect
penetration. Splashing rainwater and floods are additional hazards for wood components
close to the ground.
Therefore:
Wooden board
timber components should be
installed at a minimum of 30cm
above the ground;
timber columns should be fixed on
metal supports and never embedded
in concrete or masonry footings;
if necessary adequate resistance to
insect penetration should be
provided using metal plates
projecting at least 5cm (Figure 5).
Metal
cap
Figure 4: Simple ways of protecting end grain
Termite
groove
Steel
support
Metal
termite
shield
Poor detail:
Water is attracted
inwards and up
between the timber
elements
GOOD
VERY GOOD
Figure 5: Timber posts on concrete footings
Good detail:
Water drips off the
outer edges
Exclusion or quick removal of water
Wide overhanging roofs are essential where
rain occurs frequently. Eaves gutters help
Waterproof
membrane
to avoid the splashing of rainwater.
Timber wall elements with the grain
Termite
groove
running vertically drain water fastest. The
lower edges should be shaped so that
dripping water is discharged outwards and
not encouraged to find its way into joints
and openings (Figure 6).
To hasten the removal of any moisture
(from rain or condensed water) that
Figure 6: Timber wall cladding
penetrates timber components, air must be allowed to circulate on all sides. Provision
for ventilation gaps and cavities should therefore be made at the design stage of a
timber construction.
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