Wood Construction

Why is timber considered sustainable

renewable in 25-40 years

What's the issue with timber sustainability today

another enough is grown back

Key advantage of timber structurally?

high strength-to-weight ratio

Why is wood widely used in construction

Easy to mechanize, can be shaped into many forms, lightweight + strong

Current trend in timber use

less solid wood - more engineered wood products

What is natural wood made of

cellulose + lignin

What is the structure of wood?

Fibrous (long cells transporting water)

Why do ring form

Spring/summer - fast growth (wide thin cells)

When are rings more visible

In climates with strong seasonal variation

What is anisotropy in wood

properties depend on direction

Strongest direction in wood?

Longitudinal (along fibers)

What affects timber strength heavily

Angle between fiber direction and applied force

What is quarter sawn wood?

Cut perpendicular to rings (structural use)

What is backsawn wood

Cut tangentially (Decorative use)

Why does wood deform?

Moisture loss (shrink)

Softwood (Conifers)

easier to work, more stable, used in construction + finishes

Hardwood (deciduous)

Harder, more durable, used in structure + high quality finishes

Glue laminated timber (Glulam)

boards glued together to form larger sections

Properties of Glulam

large spans, can be curved, better fire resistance, less movement from humidity

CLT (cross laminated timber)

Glued perpendicular to each other

Properties of CLT

Does not allow bending, used for walls & slabs, (3 5 7 layers)

What is NLT

nail laminated timber (planks nailed together)

What is DLT

Dowel laminated timber (wooden dowels)

What is LVL (Laminated Veneer Lumber)?

Thin wood layers glued together - beams, cladding

What is plywood

Thin layers glued with alternating fiber direction, can form complex shapes

What is OSB

oriented wood strands + adhesive + pressure

What is chipboard?

Small wood particles + adhesive. Low structural strength & water resistance

What is fiberboard (MDF / HDF)

Wood pulp compressed into dense panels, homogeneous and good for marching (interior use only)

What damages wood biologically

fungi and termites (prevent = keep wood dry)

Why is drying important

lower humidity = better performance

Moisture levels in wood

semi-dry: 23%, commercial: 18%, dry: 13%, anhydrous: 0%

Oil finishes (open pore)

absorb into wood, allows breathing, high maintenance

Varnishes (closed pore)

create surface film, more durable, less breathable (acrylic, epoxy)

Wood-based insulation types

wood fiber panels, cork, wood chips

Fire performance parameters

R: structure resistance, E: integrity, I: insulation

What are traditional joints

Geometry based, sometimes without metal

Mechanical types

Nails / screws, bolts, bars, nail plates. LOW TENSILE STRENGTH PERPENDICULAR TO FIBERS

Rule for timber in contact with soil

Must be separated ~30cm to avoid moisture + pests

Uses of timber in construction

structure, facades, interior finishes

Parquet vs board flooring

Parquet: patterned, glued, more natural. Boards: floating, cheaper

Types of flooring

Solid wood, multilayered, laminated, synthetic

Timber Regulations

CTE DB-SE-M