Log yard storage as inventory with a use-by date

Logs waiting in the yard are inventory, and wood is a perishable inventory. The portal's log supply and air-drying articles give the biology, the methods, the time limits and some costs. The existing Academy course on log quality and storage covers the defect side; this lesson treats storage as a logistics decision: how long, at what cost, with which exit date.

The biological window

The Bavarian LWF leaflet 7 "Rundholz" (November 2025) states that damaging organisms need oxygen and water, available at moisture contents of roughly 20 to 30% up to about 120%. Above 120% oxygen is too scarce; below 30% there is no free water. So the strategy is to keep logs wet (excluding air) or to dry them quickly below 30%, ideally below 20%. Temperature sets the speed. In a Latvian roundwood study, first blue stain appeared after 50 to 70 days at an average daily temperature of +6 degrees C, 30 to 42 days at +10 and 17 to 23 days at +18. These are logs, not boards, but the pattern is a warning for spring.

Dry storage

In-bark dry storage works only for a few weeks for winter-felled wood. Spruce must leave before the bark beetle flight (March or April, depending on weather) or sit at least 500 m from conifer forest. Piles belong on shaded, wind-sheltered sites beside truck roads, on supports, secured against rolling, at most 4 m high, with logs at most 7 m from the road centre. Debarked dry storage needs the opposite: ventilated, dry, warm, unshaded. The LWF cites 1 to 3 years for debarked spruce, and debarking costs about 8.50 euro per Fm (long wood) and 12.50 euro per Fm (short wood) in Bavaria, 2025. Logs debarked before storage are not attacked by bark beetles, horntails or longhorn beetles.

Wet storage and sprinkling

Lutze (LWF, 2014) states that sprinkling needs 50 mm of water per day (one millimetre equals one litre per square metre, so 50 litres per square metre per day) and a water-law permit, with practice of 3 to 6 years for spruce, at least 2 for pine and about 2 for beech; opened beech must be sawn within 1 to 2 days because of grey oxidation. The 2025 LWF leaflet gives about 0.7 l/s per 1,000 Fm in interval operation, a minimum economic size of 1 ha per 15,000 Fm, and total cost of 18 to 20 euro per Fm per year, of which operation is 3 to 4 euro and freight about 80%.

Worked example (own calculation). 0.7 l/s is 0.7 x 3.6 = 2.52 m3/h per 1,000 Fm. A 15,000 Fm site therefore needs 15 x 0.7 = 10.5 l/s while running. At 18 to 20 euro per Fm per year, holding 15,000 Fm costs 270,000 to 300,000 euro per year. For spruce kept 3 years the cost is 54 to 60 euro per Fm, assuming the annual figure applies each year. The 2014 and 2025 documents use different units and reference areas and should not be compared directly. Neither states sprinkling start and stop temperatures or pile height; take these from the local permit.

Wet storage has a use-by date

Engesser (WSL; 2003) reported that after the 1999 storm Lothar the only fungus able to attack properly sprinkled wood was honey fungus (Hallimasch). Sprinkling had been seen as suitable for 4 to 6 years after the 1990 storm Vivian, yet first decay appeared sporadically after the third year in Germany, after about 3 years at Swiss sites, a 25,000 m3 spruce pile in Vaud was dissolved just under 3 years after the storm, and the worst case began after 2 years. Attack is almost only in sapwood, so small logs lose most value. Fruiting bodies on logs suggest faulty sprinkling or already infested wood.

This turns storage into a schedule: record the felling date and the sprinkling start date for every pile, and plan outflow inside the 2 to 3 year window where honey fungus was seen. The portal's inference is that a large part of the German salvage stock had to be processed by about 2024 to 2025; no source documented what actually happened.

Key points

• Decay needs air and water; keep logs above about 120% moisture content (wet) or dry them below 30%, ideally below 20%.
• Dry in-bark storage lasts weeks; spruce must be gone before the bark beetle flight.
• Sprinkling: about 0.7 l/s per 1,000 Fm, 1 ha per 15,000 Fm, 18 to 20 euro per Fm per year (Bavaria, 2025); 15,000 Fm needs about 10.5 l/s.
• Honey fungus decay appeared after 2 to 3 years in sprinkled spruce; plan outflow inside that window.
• Record felling and sprinkling start dates; they define the use-by date.