Load-bearing Wall in Porous Clay Block
A wall that carries, insulates and breathes with a single material: the porous clay block is the single-leaf answer to nZEB — but it forgives very little at the joints.
Overview
TAV. 00Porous clay traps millions of micropores in the body that slow heat down: a 38–45 cm block carries the floor and reaches the required transmittance at once, without external insulation. The single-leaf wall simplifies the site and gives mass and inertia — but it lives or dies at the joint: thermal mortar on the beds, vertical tongue-and-groove dry-butted, no through voids. Every open gap is a thermal bridge the single leaf cannot recover elsewhere.
The site score
TAV. HThe detail of the crafta millimetre here, a centimetre at the eaves
The starting course
Setting out on the kerbs and laying the first course on a levelling mortar bed, checking level and square around the whole perimeter.
You lay the first course with the level in hand and your hurry in your pocket: the whole wall sits on it.site notebook — editorial synthesis
click a beat · arrow keys ← → walk the site · dashed pauses are the chemistry at work
The point of the single leaf
A wall with three jobs
Carry, insulate, breathe: in porous clay the three jobs live in the same material. The price of that simplicity is that there is no other layer in which to fix a mistake.
Schematic. The choice between them is not about quality but strategy: the single leaf simplifies the site and concentrates risk at the joints; the layered wall spreads functions and risks across more interfaces.
Where the heat is lost
The map of thermal bridges
In a well-built single leaf the wall is not the problem: the problem is where it stops. Ring beam, lintel, base and window reveals matter more than a few extra centimetres of thickness.
The four circled points are to be solved in design, not on site: once the ring beam is cast, correcting it costs ten times as much.
How it ages (and what betrays it)
TAV. PQuestions from the site
TAV. QIs a single leaf really enough for an nZEB?
With the best-performing blocks and 38–45 cm thicknesses, yes in most Italian climate zones — but only if the thermal bridges at ring beams, lintels and base are solved. That is where the single leaf wins or loses, not in the field of masonry.
Can I put external insulation over porous block?
Yes, and in cold zones it is often worth it: a thinner block plus a thin external insulation. Choose a breathable insulant, though, or you cancel the clay's ability to regulate moisture.
Why must blocks be sawn?
Because a clean cut preserves the vertical tongue and the internal ribs. A block broken with a hammer loses its profile, no longer butts up, and forces you to fill the gap with mortar — that is, to create a thermal bridge.
How does it behave in a seismic zone?
There are specific reinforced-masonry systems, with reinforcement in the vertical holes and mortar beds, designed as a load-bearing structure. It is not a laying variant: it is a structural choice to be sized in design.