Wet Storage - Organising Storage and Removal of Timber
- Usually, the logs are piled with the butt end facing the road, and at
right angles with the road. This way, the desired roof profile with the water
running off to one side is achieved. Logs should be sorted by length and
- Cross sections need to be well covered by the irrigation water. A
uniform front side of the stack, ideally leaning backwards a bit, and clean
removal of the buttresses is required. Never should upper logs protrude further than the ones lower down.
This would create a rain protected dry area, where quality will be lost (see
- Generally, alternating stacking is not advisable, as water demand is
then higher and removal more complicated. Risk of Armillaria infection is
higher because the logs are more densely packed.
- Height of stacks should not exceed 4 metres.
- Timber should be sorted by length, diameter, tree species, quality, and
owner and stacked separately. Stacks should be marked visibly and durably (good
are wooden signs placed outside the irrigation zone, or structural separation)
(see Fig. 2).
have to be instructed correctly and comprehensively (Control stack
construction, give warnings where necessary).
Fig. 1: Disadvantageous: Vertical front side. Good:
Front side leaning backwards.
Fig. 2: Options for separating different
- Wet conservation can
only be successful where strict quality measures are used for classification.
- Homogenous lengths
are important. Protruding upper logs create rain protected areas where quality
is lost. After calamities, (softwood) long logs should not exceed the maximum
length capacity of regular timber lorries (in Germany 19 metres). This allows
for more variability regarding the transport mediums used.
- Size classes: Timber
for wet storage should be divided into two lots according to diameter class,
“up to 34 cm” and “35cm and over” (“up to diameter class 3a” and “3b and above”
in German classification).
- On larger sites, especially where timber from several forest owners is
stored on the same site, documentation of the whole processes is useful (stack
plans showing where the various lots are located, stack books containing
information on forest owners, volume of wood, timber quality, time of logging,
time of rolling in, start of irrigation,…).
Monitoring timber removal
Pic. 2+3: Photos R. Willmann
Documentation of removal of timber from wet storage sites has been
neglected frequently in the past. However, real-time data on state of removal
is necessary for superordinate controlling to deal successfully with matters of
markets and budget. An estimate on the current state of removal can be formed
by looking up sales from previous years. A sufficient overview can only be
gained by consistent accounting.
Timber quality at the time of rolling in
- Sufficient sap-wood moisture (min. 100%) is essential for quality
preservation. An average relative wood moisture of 120% is recommended. This
can only be achieved with green timber (speedy conversion and rolling in).
- Logs intended for wet storage must therefore not be stored temporarily
alongside the forest road. Immediate transport to the wet storage site is
- Measuring moisture of timber in life
conservation intended for wet storage can help decide whether putting the
timber in wet storage does still make sense, or if it needs to be brought to
market immediately after primary conversion.
- Chemically treated timber must not be put in wet storage.
between primary conversion and rolling in must be kept as short as possible.
Irrigation has to start immediately after rolling in.
Documentation of timber qualityt
- Only best quality timber is suited, low-grade timber must not be put
into wet storage.
of timber brought to wet storage should be documented. Delivery notes can be
issued by responsible on-site staff to raise timber quality state-wide. The
position of the storage supervisor should be strengthened. This could go as far
as entitling him/her to refuse to accept low quality timber and to issue a
protocol including the reasons for non-acceptance and a time-limit for
Risk of deterioration of quality
- Risk of deterioration of quality by fungi or insect infestation is
relatively low, even for perennial storage. Scientific studies showed that
essential technological wood properties are still within the usual range for
green timber after several years of wet storage.
- Ideal storage period for softwood is 2-3 years, in exceptional cases up
to 4-5 years. Hardwood (beech) should only be stored a couple of months up to
one year max.
- After three years of wet storage, commencing deterioration of quality by
Armillaria infestation has to be taken into account (see leaflet 2.6.8 “Wet
Storage – Armillaria infestation”).
of the sap-wood is a specific problem of longer storage over bark. The stains
are caused by tannins which enter the wood while dissolved in the irrigation
water or during the drying process. These discolourations are usually not very
deep, they can be removed from the wood once it is dried (planing, sanding,…)
and do not reappear.