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The reference work for the carpentry trade: measurement, centre spacing, stairs, rafters and the boundary between geometry and structural calculation — explained so it can be used on site.
Articles
Become a carpenterGet started · 5 minThe carpenter raises the building's frame, closes it against wind and weather, and fits it out inside. It is a versatile, high-demand trade where you both work out geometry and work with your hands — and where the path from apprentice to journeyman is straightforward. Here is why you should consider the trade.The stair's going/rise relationship — Blondel's ruleGeometry & measuring · 10 minWhy 2·rise + going ≈ 61–63 cm, and how to derive the number of risers and the going depth from the floor height. Blondel's pace-measure rule is still the basis for a comfortable stair.Centre-to-centre spacing (cc) and number of membersGeometry & measuring · 8 minHow to count rafters, battens and posts correctly with the fence-post principle — and why there is always one item more than gaps when an item sits at both ends.Material consumption and wasteGeometry & measuring · 9 minHow to calculate the number of boards/sheets from an area — and why the waste allowance is never a fixed percentage, but depends on the room, the pattern, and the piece length.Concrete volume — calculate it, don't guessGeometry & measuring · 9 minHow to find the concrete volume for a foundation or slab with V = L · W · H, and why the waste allowance belongs there. Volume is pure geometry — strength and mix design belong to the project.Rafter length and roof pitch with PythagorasGeometry & measuring · 11 minThe rafter is the hypotenuse of a right-angled triangle — here is how to find the length and the pitch from the span and the rise, and why the sloping eaves overhang is always a touch longer than the horizontal dimension.Load-bearing timber structures — what geometry doesn't decideStandards & rules · 8 minWhy measuring and quantities are your job, while cross-section, span and centre spacing belong to the structural calculation per Eurocode 5 (DS/EN 1995) and the building regulations.Eurocode 5 and the Danish rulesStandards & rules · 8 minA practical overview of the standard set a carpenter encounters in load-bearing timber structures: Eurocode 5 with Danish amendments, load standards, material standards and building regulations — and what changed in 2024 and 2026.Sizing according to Eurocode 5 — ULS and SLSStandards & rules · 10 minWhat is ultimate limit state check (ULS), and what is serviceability limit state check (SLS)? Here are the central formulas from Eurocode 5 with DK NA:2024, the k_mod table and a worked example.Loads on truss structures — snow and windStandards & rules · 8 minSnow load 1.0 kN/m², wind speeds 24 and 27 m/s and roof shape factors — the specific figures from the DS/EN 1991 series that determine what your rafters and beams must carry.Fire in wood constructionsStandards & rules · 8 minWhy wood actually behaves predictably in fire — charring rate 0.65 mm/min for solid coniferous timber, R/REI requirements and what DK NA:2026 changes for CLT constructions.Moisture in wood structuresMaterials & properties · 9 minFiber saturation point ~28 % MC, tangential shrinkage 2.5–3.0 mm/m per % MC, vapour barrier placement and moisture technical requirements in BR18 and SBi-instruction 224.Energy requirements in BR18 — U-values and energy frameStandards & rules · 7 minU-value ≤ 0.30 for external walls, ≤ 0.20 for roofs and ground floors, energy frame 30 kWh/m²/year for dwellings — the concrete BR18 figures the carpenter needs to know, and how to calculate them.Quality assurance (QA) — receipt, process and final inspectionWork environment & quality · 7 minQA is mandatory for all load-bearing and climate-screening work. Here is the three-phase model from DI Building, what is checked when, and why photo documentation of hidden structures is crucial.The history of the carpenter trade — from guild to EurocodeThe craft's history · 7 minThe carpenter trade is one of the oldest building crafts and its development can be traced in the traces that can be documented: the guild period's master-journeyman-apprentice tradition, industrialisation's sawmills and factory-made materials, standardization of load-bearing timber according to Eurocode 5 and the building code, and today's timber frame and CLT construction. Here we stick to what sources can bear.Working environment, safety and wood dustWork environment & quality · 11 minFalls from height are the most common cause of death in construction, and wood dust is carcinogenic. Here are the binding rules for work at height, scaffolding, ladders and dust — with the specific figures from the Working Environment Authority that a carpenter must know to go home safely.Roof structure — underroofing, battens and roof coveringConstruction & execution · 11 minThe rafters are just the skeleton — the roof's tightness is determined by the roof underlay, battens and roof covering. Here are the roof underlay's DUKO classes, ventilation requirements, battens according to roof tile and the details at roof edge, ridge and penetrations where most moisture damage occurs.Windows and doors — installation and joint sealingConstruction & execution · 10 minA window is only as good as its installation. Here is the principle: weathertight outside and airtight inside, correct fastening and installation depth, joint tapes and the errors that cause thermal bridges, draughts and mould — the classic complaint cases.Joints and fittings in timber structuresConstruction & execution · 11 minSizing provides the cross-section — but how the timber is joined determines whether the structure holds. Here are the connection types, CE requirements for nails, screws and fittings (DS/EN 14592 and 14545), and the errors that make a joint the weak link.Drawing reading, measuring and markingGeometry & measuring · 10 minReading a working drawing and setting out accurately is the foundation for all other carpentry. Here are scale, plan-section-elevation, symbols, dimensions and module lines — and setting out on site with datum point, string line, laser and the 3-4-5 method.Façade cladding and ventilated timber facadesConstruction & execution · 10 minA timber façade is a rain screen, not a seal. Here are the cladding types, the ventilated cavity with batten spacers, timber durability and use classes (DS/EN 335 and 350), fixing allowing for movement, and the details where moisture otherwise penetrates.Light partition walls and plasterboard claddingConstruction & execution · 11 minA partition wall is one of the carpenter's daily tasks: a frame of wood or steel, clad with plasterboard and filled with insulation. Here are the frame types, single/double/staggered cladding, the connection with board format and c/c, fire and sound-insulating assemblies and the seals that determine whether the wall lives up to its promises.Beam layers, subfloor and timber floorsConstruction & execution · 11 minFrom loadbearing beam to finished plank: here is the floor structure, subflooring in chipboard and OSB, floating floors and floating timber floors, the three floor types (solid, parquet, laminate) and the moisture and movement rules that determine whether the floor stays flat and quiet for years.Sound insulation and acoustics in timber constructionConstruction & execution · 10 minAirborne sound (R'w) and impact sound (L'n,w) between dwellings are mandatory requirements in BR18 and DS 490, and they are met with carpentry decisions: double wall, offset framing, floating floor and decoupled ceiling. Here are the requirements, principles and the seals where sound otherwise escapes.Ground floor against earth — construction and radon protectionConstruction & execution · 10 minThe ground floor is the building's floor against the earth, and it must cope with three things at once: stop rising damp, insulate against the cold and keep radon out. Here are the layers from bottom to top, the capillary break layer, the insulation, the U-value requirement and the radon barrier according to BR18 (max. 100 Bq/m³) and SBi 233.Retrofit insulation and energy renovationConstruction & execution · 10 minMuch of the carpenter's work is renovation. Here is retrofit insulation of ceiling, sloping roof and external wall, the difference between internal and external insulation, the moisture trap internal retrofit insulation can create, and the tightened renovation U-values in BR18.Wet room — carpenter's substrate and wet room protectionConstruction & execution · 9 minIn a wet room, the carpenter builds back walls, floor structure with fall and board backing that must meet wet room regulations before waterproofing and tiles are applied. Here are the wet zones, requirements for rigid and moisture-resistant substrate, fall to the drain and the interface between trades.Wood structure, wood types and strength gradingMaterials & properties · 10 minBasic material science for the carpenter: softwood vs. hardwood, heartwood and sapwood, annual rings and knots, and how structural timber is strength-graded — visually or mechanically — and ends up in strength classes such as C18, C24, and C30 to DS/EN 338.