What KVH is
KVH stands for Konstruktionsvollholz — structural solid timber. It is not a separate material but softwood to an agreed quality: strength graded, kiln dried, with defined surfaces and limited defects. That turns grown timber into a component you can calculate and plan with.
The species used are usually spruce, fir, pine, larch and Douglas fir. Strength grading is done visually or by machine, in Germany mostly to DIN 4074-1. Kiln drying takes the material below 18 per cent moisture content.
Two versions exist: KVH-Si for exposed use, chamfered and planed, with tighter limits on knots, wane, cracks and discolouration. And KVH-NSi for concealed use, chamfered and levelled.
Finger jointing frees KVH from the length of the grown log. Preferred sections run from 60/100 to 120/240 mm.
Advantages
- Dimensionally stable. Controlled drying takes the movement out of the timber before it is installed. What arrives on site keeps its dimension.
- Far less cracking than undried construction timber. It no longer dries out in place.
- Usable without preventive chemical treatment when installed dry. Low moisture content removes the basis for fungi and insects.
- Calculable strength. The grade is the basis of structural design — unlike ungraded squared timber.
- Ready to install. Chamfered and planed or levelled, no reworking beforehand.
- Long lengths without joints through finger jointing.
- Suitable for exposed use in Si quality, without cladding.
Drawbacks
- Higher price than undried squared timber. Drying, grading and planing show up in the cost.
- Limited sections. Above 120 mm width reliable drying is no longer possible, and greater depths exceed what the trunk yields. It stops at 120/240 mm.
- Finger joints stay visible. In exposed positions that is a matter of taste, best settled beforehand.
- Not weather resistant. Spruce and fir have almost no natural durability. Without structural protection KVH is out of place outdoors.
- Bonded components. Finger-jointed KVH contains adhesive. Anyone aiming at clean separation at end of life must factor that in.
- Special sections and lengths are rarely in stock and extend delivery times.
Applications
KVH is the standard material for load-bearing components in dry, protected conditions:
- Roof structures: rafters, purlins, collar and tie members
- Floor joists in residential and office buildings
- Timber frame construction: studs, sole plates, head plates, the entire framework of panel elements
- Interior fit-out with exposed structure, in Si quality
- Substructures for wall and ceiling linings
- Roofed, fully protected structures such as carports
Where to avoid KVH
- Direct weathering and ground contact. Deck substructures, fence posts, free-standing pergolas — those need a durable species or proper protection, not KVH.
- Wet areas and permanently high humidity. Pools, wet rooms, unventilated basements.
- Large spans and heavy loads. Where the section would exceed 120/240 mm, glulam or duo/trio beams are the right product — there the section is created by bonding, not by the trunk.
- Curved or cambered beams. Shaping is impossible in solid timber; only glulam can do that.
- Planar components. Where a load-bearing plate or diaphragm is required, the route leads to cross-laminated timber, not to a stick frame.
- The highest visual demands. Where neither finger joints nor drying cracks are acceptable, heart-free stock or glulam is the better choice.