Log supply for sawmills: measurement, sorting, storage and quality

A sawmill does not buy "logs". It buys a volume, a quality, a delivery date and a risk profile, and each is defined by a measurement rule, a grading rule, a storage condition and a contract clause. This article follows a log from the forest road to the saw line, looks at the 2018-2024 European bark beetle crisis, and ends with contracts and traceability. Every figure comes from a source opened during research, with region and year; calculations by the author are labelled "own calculation"; paywalled or unopened material is flagged in the text and in the closing sections.

Why measurement is a commercial question

Log volume is the base of nearly every payment in the wood chain. The Swedish regulation on log volume under bark (Biometria, version of 1 April 2025) states the principle: systematic errors must be insignificant, and for batches over 10 m3 the permitted batch deviation decreases as batch size grows (the document does not print the values). Random errors cancel in large batches; a systematic error never does.

Under the Huber-type formula of the German framework agreement, volume is proportional to the square of the mid-diameter. For a 30 cm log, one centimetre of diameter error is about 6.8% of volume (own calculation: 31 squared minus 30 squared, divided by 30 squared). A caliper that reads 1 cm high is a price change on the whole batch, which is why rules fix rounding conventions and require calibrated instruments for billing.

Measuring logs in Europe

Germany: mid-diameter and the Huber formula

The "Rahmenvereinbarung für den Rohholzhandel in Deutschland" (RVR) is a voluntary private agreement issued by the German forestry and timber industry councils (DFWR, DHWR). It was signed on 11 December 2014, has applied since 1 January 2015, and the brochure consulted refers to the 5th edition of 1 December 2023. It replaced the statutory Forst-HKS, which lost validity on 31 December 2008. It applies only when buyer and seller include it in the contract, in full or in part.

The RVR measures mid-diameter without bark at the middle of the log: one horizontal caliper reading up to 19 cm, two perpendicular readings from 20 cm, rounded down to whole centimetres. Volume is V = (pi/4) x d squared x L x 10 to the power of minus 4 (d in cm, L in m), in cubic metres solid without bark (Fm o.R.). Length starts at the middle of the Fallkerb (felling notch). Worked example (own calculation): a 30 cm mid-diameter, 5.00 m log is 0.7854 x 0.09 x 5 = 0.353 m3, reported as 0.35 m3.

Diameter classes run from D0 (up to 9 cm) through D1a (10-14 cm), D1b (15-19), D2a (20-24), D2b (25-29), D3a (30-34), D3b (35-39), D4 (40-49), D5 (50-59), D6 (60-69), D7 (70-79) to D8 (80 cm and above). The length allowance is 1% of order length, rounded up to whole centimetres, minimum 10 cm, and is excluded from volume. Section order lengths run up to 6 m; "Industrieholz-lang" is over 3 m and "Industrieholz-kurz" 1 to 3 m.

For stacked wood the RVR gives factors from Rm m.R. to Fm o.R. of 0.70 (1 m), 0.65 (2 m) and 0.60 (3 m), and for weight 1 t atro with bark equals 2.2 Fm o.R. for spruce and fir, 2.1 for pine and Douglas fir, 1.8 for larch, 1.5 for beech and 1.4 for oak. The brochure states that these are averages for internal and statistical use and must not serve as a sales measure. Own calculation: 100 Rm of 1 m spruce is about 70 Fm o.R. on the average factor. Source for this section: FNR, RVR brochure (2023).

Sampling and section methods

The FVA Baden-Württemberg leaflet 49/1997 (republished on waldwissen.net) describes three methods for short wood: the end-face method, the mid-diameter sample and the section stacked-volume method. The first two suit cases where total volume and a strength-class distribution are needed; the third where total volume, volume-average stem and mean mid-diameter suffice. All three can serve as sales, billing or control measures if written into the contract. The RVR (2023) restricts sampling for billing to exceptional cases (calamities, lost original data, disproportionate effort), by mutual agreement, and recognises only the end-face and mid-diameter methods for billing. The "Heilbronner Sortierung" could not be verified in an open source and is not described.

Sweden: sections, bark functions and stacks

The Biometria regulation (in force 1 April 2025) distinguishes m3to, a cylinder with the log's length and the under-bark top diameter measured 10 cm from the top end, from m3sub, the form-adjusted solid volume obtained by mid-point, top-butt, conversion-matrix or section measurement. Section measurement uses sections of at most 50 cm, summed, mainly with scanners approved by the authority (3D, shadow or X-ray). Under-bark diameter comes from bark functions Y = a + bX (Y double bark thickness in mm, X top diameter over bark in mm), for example y = 2.00 + 0.0153x for thin-bark pine in Norrbotten and y = 3.10 + 0.0496x for spruce in "Area 1". The tracheid method needs bark abrasion on at least 4% of the log surface; snow, ice, blue stain or long-term watering can stop it working. Volume from top diameter and conversion factors may not be used as a basis for payment.

For stacks (version of 1 January 2026) volume is m3sub, intended to match top-butt log measurement. The stack volume is the product of external dimensions multiplied by a wood-volume percentage; the document's example is 6.00 x 3.01 x 1.08 = 19.505 m3t, which at 55% gives 10.73 m3sub. Base percentages are 70% (spruce), 68% (pine), 66% (aspen), 65% (alder, oak) and 64% (birch, beech, ash), adjusted for bark, stacking, crookedness, snow and ice, logging waste, wood length and stack height. At storage sites stack height must be 100-300 cm with at least 1 m between stacks. The contrast with the German flat factors is instructive: the Swedish figure is built from the actual stack.

Austria and mill measurement

According to the Tyrol forest administration, Austrian round timber measurement follows Ö-NORM L1021 and the Holzhandelsusancen, and instruments for value-defining features must be calibrated. Two system types exist: MAWM (calibrated for mid-diameter, length, volume, taper and curvature) and RHMA (taper and curvature not calibrated). With "Werksübernahme" in the sales letter, the seller accepts electronic mill measurement and may attend the takeover; with "Waldabmaß" the seller bears the takeover costs. As a plausibility check the page gives about 25 Fm per trip for a truck with trailer carrying spruce or fir.

Staudenmaier (FVA, 2018) explains that mill measurement is contactless: length is the shortest distance between the ends, and diameter is simulated with a virtual caliper in two perpendicular planes after debarking. Harvester measurement could not be a sales measure in Germany at the time for legal and technical reasons, and only one photo-optical pile system (sScale, Dralle) was calibratable for pile-front area as of October 2018. These are 2018 statements; current approval status was not verified.

Poland: State Forests technical conditions

Public Lasy Państwowe documents (annex "Podział, terminologia i symbole", version mod2024, with blank order number and date) divide timber into large (W, minimum top diameter 14 cm without bark), medium (S, 5 cm) and small (M). Long logs (dłużyca) start at 6.1 m nominal length; logs (kłoda) run 1.0-6.0 m. Large-size classes are A (WA0), B (WB0), C (WC0) and D (WD, utility), plus WA1 (veneer), WB1 (plywood) and WC1 (poles). Mid-diameter is taken at half the length, and nominal length (used for volume) is distinguished from gross length; surpluses, reductions and end protection are excluded from volume.

The conifer large-size document specifies long logs of 6.1-14.0 m in 10 cm steps, produced in bark and measured piece by piece, with a 1% length surplus. Sweep limits are 1 cm per m (A), 2 (B), 3 (C) and 5 (D); internal and diffuse rot are allowed in no class; end-face blue stain is not allowed in class A; side stain is allowed up to 3 mm deep in some classes. The extracted tables were partly garbled, and volume formula, bark deduction and rounding rules are not in these documents. PN-D-95000 and the older WZ rules were not found in an open source, so nothing is quoted from them.

Measuring logs in North America

North American mills use board-foot rules that estimate sawn recovery from small-end diameter and length. The USDA Forest Service handbook NA-FR-15 (Ashley, 1989; internet version revised October 2001) prints these values for 16-foot logs; the Scribner and Doyle columns are headed "(tens)" and the scaling could not be confirmed unambiguously from the extracted text, so the values are shown as printed.

Source: USDA Forest Service, NA-FR-15 (US, 1989, rev. 2001), 16-foot logs.

For a 16 in. log, Doyle gives 20% less than International (own calculation), while at 30 in. the rules converge. Spelter (Journal of Forestry, June 2004) found in the abstract that the three rules generally underestimate true recovery, inconsistently, with the undercount growing sharply for smaller logs, and argued for cubic measurement. Only the abstract was readable; no recovery percentages are quoted. A price in "MBF Scribner" therefore cannot be compared with a European Fm o.R. without a size-dependent conversion agreed in writing.

Grading logs

EN standards

Visual quality classification of round timber sits in the EN 1927 series for softwoods and EN 1316 for hardwoods. Catalogue pages show: EN 1927-1:2008 for spruces and firs (Picea and Abies), with a route for unknown intended use and an informative annex for known use; Parts 2 (pines) and 3 (larches and Douglas fir) listed by national bodies; and EN 1316-1:2012 for oak and beech (sessile oak, English oak, European beech). Feature measurement is covered by EN 1309-3:2018, which for round timber serves appearance grading only and requires the method used to be stated. These standards are paywalled; class limits are not quoted, and a contract should name the part and edition.

National frameworks

The RVR classes are A (excellent, flawless or only insignificant defects), B (normal, few or moderate defects), C (normal, more frequent or stronger defects) and D (usable as stem wood but not meeting A-C), with a 3 m minimum section length for A and B; mixed grades such as B/C must be agreed. Poland uses a similar A-D ladder with quantified limits; Austria applies the Holzhandelsusancen unless the sales letter says otherwise. The letter schemes look alike but are not equivalent. Per the Tyrol page, when sorting is done on the mill system the buyer bears takeover costs, the seller may attend, and analysis systems under the Forst Holz Papier platform can reveal measurement errors, a good model for any contract.

Log yards, storage and what it does to wood

The LWF Bavaria leaflet 7 "Rundholz" (November 2025) gives the biological thresholds: damaging organisms need oxygen and water, available at moisture contents of roughly 20-30% up to about 120%. Above 120% oxygen is too scarce; below 30% there is no free water. The strategy is to keep wood wet or dry it quickly below 30%, ideally below 20%.

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 should be on shaded, wind-sheltered sites beside truck roads, on supports, secured against rolling, at most 4 m high, logs at most 7 m from the road centre. Debarked dry storage needs the opposite site (ventilated, dry, warm, unshaded); the LWF cites 1-3 years for debarked spruce according to various authors, and debarking costs about 8.50 euro per Fm (long wood) and 12.50 euro (short wood) in Bavaria, 2025. Insecticides are a last resort, from the annual BVL approved list.

Wet storage and sprinkling

Lutze (LWF, 2014; waldwissen 2016) states that 50 mm of water per day is required, a water-law permit is needed, and practice runs 3-6 years for spruce, at least 2 years for pine and about 2 years for beech; opened beech must be sawn within 1-2 days because of grey oxidation. Costs then were 13-15 euro per Fm in year one for sprinkling plus 2-2.50 euro per year, and about 15 euro per Fm for water storage (depth at least 2-3 m).

The 2025 LWF leaflet gives about 0.7 l/s per 1,000 Fm in interval operation, 1 ha per 15,000 Fm as the minimum economic size, spruce 3-6 years, pine at least 2, beech only months, and total cost of 18-20 euro per Fm per year, of which operation is 3-4 euro and freight about 80%. Own calculation: 0.7 l/s is about 2.5 m3/h per 1,000 Fm, so a 15,000 Fm site needs about 10.5 l/s while running, and yearly storage costs are about 270,000-300,000 euro. The two documents use different units and reference areas, so they 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; Wald Holz 2003) reported that after the 1999 storm Lothar the only fungus able to attack properly sprinkled wood was honey fungus (Hallimasch). Sprinkling had been considered suitable for 4-6 years after storm Vivian (1990), yet German observations showed first decay sporadically after the third year, Swiss sites after about 3 years, a 25,000 m3 spruce pile in Vaud was dissolved just under 3 years after the storm, and the worst case was onset after 2 years. It attacks almost only sapwood, so small logs lose most value, and infested logs lost much sapwood with the bark at debarking. Fruiting bodies of decay fungi on logs suggest faulty sprinkling or already infested wood.

Inside the wood

Grüll and Neumüller (Holzforschung Austria, 2021) note that several months of storage can damage pit membranes, greatly raising liquid uptake; bacteria can be responsible. The effect appears at coating as dark spots (their example is a pine window profile), with colourless impregnation as the first coat as remedy. Blue stain does not reduce strength, while early brown or white rot does, though nail-firm wood can often still be used structurally. Technical drying kills insects when the core stays above 55 degrees Celsius for several hours. Logs debarked before storage are not affected by bark beetles, horntails or longhorn beetles.

LWF describes blue stain as a blue-black discolouration, often in summer-felled wood, that rules out visual-grade use although technical properties remain. Bark beetle larvae can cause it, and wood-boring insects (timber bark beetles, longhorn beetles, wood wasps) open entry points for other pests. For appearance products this is a grading criterion, not just a storage metric.

The bark beetle crisis 2018-2024

A 34-country study (Patacca and co-authors, Global Change Biology, 2023, abstract) found about 43.8 million m3 of disturbed timber per year in 1950-2019 (likely conservative), bark beetles causing 17% of damage over the period and doubling their share in the last 20 years; disturbances averaged 16% of mean annual harvest in that time. The abstract gives no 2018-2020 values.

For Germany, Thünen Working Paper 244 (Zimmermann and Jochem, August 2024) lists damaged timber harvested per the federal statistics office at 31.9 (2018), 46.2 (2019), 60.1 (2020), 50.5 (2021) and 44.7 (2022) million Efm, 233 million in total. It cites Möhring and co-authors (2021): about 177 million Efm damaged in 2018-2020, price losses of 3.39 billion euro (26.31 euro per Efm), and spruce price losses of roughly 45%. The estimated cumulative forest storage stock of salvage timber in 2022 was 38.6 million Efm, at most 24.1 million after a trade-balance correction. Germany moved from an import surplus of 3.45-5.81 million Efm (2010-2017) to an export surplus from 2018, peaking at 6.97 million Efm in 2020, linked to demand from China; prices recovered from September 2020.

For the Czech Republic, Holzkurier (7 June 2024, quoting the Czech Statistical Office) reports damaged wood of 30.9 million m3 in 2019 (99% of harvest) and 33.9 million m3 in 2020 (98%), of which 26.2 million m3 bark beetle; 133.9 of 141.8 million m3 (94%) for 2018-2022; and in 2023 a harvest of 16.6 million m3 with 11 million damaged, 5.6 million of it bark beetle. This is trade press. The statistical office page showed for 2025 removals of 16,712,575 m3, of which salvage felling was 5,275,965 m3 (31.6%) and spruce 64.8%. Own calculation: the 2023 salvage share was about 66%, though definitions may differ between the sources.

ResourceWise (blog, 7 November 2022) reports sawlog price rises in local currency over about two years of roughly 90% in Central Europe, 70% in the Baltic States and 20% in Finland and Sweden; Czech and German sawtimber roughly doubled in 2020-2022. Oversupply of insect-damaged timber first pushed prices down; later degraded quality and a shortage of fresh sawlogs raised costs. Sawmills absorbed about 60% of the extra supply and exports about 40%. This is a commercial blog and indicative only.

Mill practice that follows from the sources: sort by age and condition on arrival, separate fresh attack from old galleries, debark early, dry technically above 55 degrees Celsius for insect-sensitive products, and write explicit blue stain, rot and gallery limits for salvage lots. A large part of the German salvage stock had to be processed by about 2024-2025 to stay inside the 3-6 year window; that is the author's inference, as no source documented what happened to the stocks.

Transport, moisture and weight

The RVR gives the oven-dry tonne for industrial and energy wood: oven-drying per DIN 52 183 on at least 100 g weighed to 0.1 g, scale accuracy 20 kg, range 50 t, weighing slips to the forest owner within 14 days. For stem wood the commercial basis remains volume. The FVA warns that sales lots can be mixed during transport, so lot marking and delivery slips are the base of traceability.

The Forest Products Laboratory Wood Handbook tables of green moisture and density could not be opened, so no green weight values are quoted. A mill contracting transport by weight should sample its own tonne-to-cubic-metre relationship by species and season, as the Swedish stack rules adjust for snow and ice.

Purchasing contracts and price formation

A log supply contract should fix: the measurement rule and its version; place of measurement and cost split (forest or mill); the grading standard, who grades, and the seller's right to witness; allowances and rounding; tolerance on volume; delivery period and storage responsibility; force majeure; and documents for traceability.

The most detailed open document on price formation is a Lasy Państwowe presentation of 17 September 2024 proposing 2025 rules. It is a proposal; the final text was not checked. It envisages two sales periods in 2025 (three in 2024); channels including offer sales through the Forest-Timber Portal, system auctions and internet auctions in e-drewno; an offer/system-auction pool split of 70/30 in 2024 and 75/25 in 2025; buyer ordering share of purchase history reduced from 100% to 75%; and permitted volume deviation of minus 10% and plus 5%. Offer evaluation weights price at 80% (2024) and 75% (2025), with processed-wood share, processing depth and, in 2025, purchase geography (10%) making up the rest. The deposit is 5,000-150,000 PLN, and false data lead to a 120-day block (2024) or a 730-day ban after a final court ruling (2025).

The structure matters more than the details: one volume channel for supply security, one auction channel for price discovery, and policy goals written into evaluation criteria. In the crisis the sawlog price was set by the balance of salvage supply and export demand; Thünen links the recovery from September 2020 to pandemic construction demand, exports and the Forest Damage Compensation Act. Index-linked price formulas are the usual protection at both ends of the cycle, but no open source quantifying their use was found.

Traceability

The European Commission states that the EU Deforestation Regulation, which covers wood, applies to large and medium operators from 30 December 2026 and to micro and small operators from 30 June 2027 (30 December 2026 for those already covered by the EU Timber Regulation). Simplification amendments came in December 2024 (Regulation (EU) 2024/3234) and December 2025. The page did not mention geolocation, so that element is not covered here; as dates have shifted before, check the page again before acting.

At the mill this means a chain of identifiers: the lot or stack number linked to delivery slip, supplier or felling area, felling date, species and measured volume, then carried through the sorting line and pile to the output batch. For storage the identifier should include felling date and sprinkling start, since they define the use-by date.

Checklist for a mill buyer

• Fix measurement rule, version, place and cost split in the contract.
• Name the grading standard and part, and give the seller a right to witness.
• Fix rounding and allowances (RVR: round down to whole cm; 1% length allowance, minimum 10 cm, excluded from volume).
• Check calibration status for billing instruments.
• Ask for felling dates; plan summer spruce in weeks unless sprinkled or debarked.
• Record sprinkling start dates and plan outflow inside the 2-3 year window where honey fungus was seen.
• Test permeability of long-stored wood before coating.
• Separate salvage lots in receiving and in the contract.

Sources used

FNR, RVR brochure (2023); FVA leaflet 49/1997 and Staudenmaier (2018) on waldwissen.net; Tyrol forest administration page; Biometria log-volume (2025) and stack (2026) regulations; Lasy Państwowe technical conditions (mod2024) and sales presentation (2024); USDA NA-FR-15 and Spelter (2004) abstract; SIS and BSI catalogue entries for EN 1927-1, EN 1309-3 and EN 1316-1; LWF leaflet 7 (2025); Lutze, Engesser and Grüll and Neumüller on waldwissen.net; Thünen Working Paper 244; Patacca et al. abstract; Timber Online (2024); Czech Statistical Office; ResourceWise (2022); European Commission EUDR page. Full links are in the sources field.

Limits of this article

• EN 1309-3, EN 1927 and EN 1316 are paywalled; only catalogue pages were read, so no class limits are quoted. EN 1309-2 was not checked.
• Heilbronn sorting, PN-D-95000 and the WZ rules could not be verified and are not described.
• Polish technical conditions were read as extracts with garbled tables; the 2025 sales rules are from a 2024 proposal.
• Spelter (2004) full text and Wood Handbook tables were not accessible; the NA-FR-15 scaling note is unresolved.
• Czech series come from trade press and a statistical office page with possibly different definitions; the ResourceWise price data are from a commercial blog.
• Sprinkling temperatures and pile height were not found; the two LWF water figures are not like-for-like.
• 2018 harvester and photo-optical approvals may have changed.
• EUDR dates were read on the Commission page on 26 October 2026 and have changed before; geolocation was not covered.
• This is an industry synthesis, not legal or contractual advice.