All processes
PRC.03 · Construction Process

CLT (X-LAM) Timber Structure

A CLT structure is not built: it is assembled. The real work already happened at the factory, at cutting; on site remain the precision of the first wall, the right screws in the right places, and one true rule — timber must never touch concrete nor stay wet while standing still.

System
prefab, dry
Weight vs RC
~ 1/5
Carbon
stored
Assembly
days

Overview

TAV. 00

A CLT (cross-laminated timber) structure uses large solid-timber panels as load-bearing walls and floors. It is a prefabricated, dry system: panels arrive cut to the millimetre and are assembled in days, cutting time, noise and waste. For the same performance it weighs a fraction of concrete, stores carbon instead of emitting it, and offers timber comfort and aesthetics that are hard to match.

The site score

TAV. H
NOT TO SCALE0 of 4 layers in place

The detail of the craftfrom model to schedule

01Weeks before · at the factory

Design and prefabrication

BIM modelling and CNC cutting of the panels in the factory, with pre-arranged holes and joints.

Why it is done this wayIn CLT the drawing IS the construction: every hole, joint and services route is born in the model and CNC-cut. On site you don't cut: you only fix what the survey didn't see.
CNC · millimetric cuttingun modello · shared BIMrilievo · of the real pour
In handBIM modelassembly scheduleslifting plan
The mistake that costs dearlyReleasing to production without surveying the real pour: a kerb two centimetres off is paid for by every wall that lands on it.
Site supervision checkConsistency between model, schedules and drawings; assembly and lifting plan approved (weights, centres of gravity, lifting points).
"In CLT, mistakes are made at the desk and seen at the crane."site notebook — editorial synthesis
The beats — with site daysbeat 1 of 5

click a beat · arrow keys ← → walk the site · dashed pauses are the chemistry at work

Time that doesn't wait

The dry site

TAV. G1

No water in the processes means no chemical waits: the CLT score has no dashed pauses. The risk moves entirely to logistics — crane, deliveries, weather — and to the desk, where mistakes are born.

The flip side: such a fast site does not forgive improvised logistics. An idle crane is CLT's "dead time" — prevented at beat 01, not on site.

The rule that rules

Water is the only enemy

TAV. G2

Timber tolerates rain that runs off and dries; it does not tolerate rain that stands. Three points decide everything: the base separated from concrete, horizontal joints that drain, panel ends covered at day's end.

It applies to storage too: panels raised off the ground, spaced, covered yet ventilated — a clinging tarp that condenses is standing water as well.

How it ages (and what betrays it)

TAV. P
PIEDE MARCIOdecay at the wall base → timber in contact with concrete or missing membrane (beat 02)
VITI SBAGLIATEseismic behaviour off-design → undeclared "equivalent" substitutions (beat 03)
PASSI DI SOPRAaudible footsteps between floors → screed not decoupled or missing strips (beat 04)
SPIFFERI INVISIBILIworse consumption and comfort than designed → incomplete tapes closed too early (beat 05)
PANNELLI IMBARCATIgaps and warping appearing on site → uncovered storage and repeated wettings (beat 02)

Questions from the site

TAV. Q
Doesn't timber burn?

It burns predictably: solid timber chars at a known rate and the charred layer shields the section's core, which is designed exactly that way. That is why a well-sized CLT wall keeps bearing for a long time even in fire — details and protections matter, as always.

What if it rains during assembly?

A brief wetting that can dry out is no drama: the enemy is water standing in horizontal joints and panel ends. Hence: fast sequences, sheets at day's end, and an envelope closed early.

How long does assembly really take?

For a two-storey house the panels go up in days, not months — the most photogenic phase and the shortest. The real site time stays in foundations before and finishes after.

Do you still need external insulation?

Almost always yes: the panel alone insulates little. Wood fibre is the natural companion — summer phase shift and vapour permeability in order — and the envelope can close as rendered ETICS or a ventilated facade.

Materials involved

TAV. M

Reference regulations

5 norms

Informational links to the regulatory framework. Always verify the current text on the official source.