Full-fill cavity wall, DriTherm 32
Brick outer leaf, a 100 mm cavity fully filled with Knauf DriTherm Cavity Slab 32, aerated blockwork inside.
Layers, outside to inside
| Layer | Thickness | W/(m·K) | R |
|---|---|---|---|
| Brick (generic) | 102 mm | λ 0.77 | 0.13 |
| Knauf DriTherm Cavity Slab 32 | 100 mm | λD 0.032 | 3.13 |
| Aerated concrete block (generic) | 100 mm | λ 0.16 | 0.63 |
| Plaster (gypsum) (generic) | 13 mm | λ 0.51 | 0.03 |
Where this fits
The ordinary UK masonry cavity wall, insulated by filling the cavity rather than lining the room. It suits new build and a rebuilt outer leaf, where the cavity can be kept clean and the slabs fitted tight; it is the wrong answer for a wall exposed to driving rain without a proven full-fill detail, and it cannot be retrofitted to a cavity that was never designed to be filled. Because the slab is continuous between the leaves, the calculated U-value is close to what gets built — which is not true of a stud wall.
What the calculation assumes
Series calculation through continuous layers. Wall ties bridge the cavity and are not modelled; nor are mortar joints, lintels or reveals. Surface resistances are the EN ISO 6946 defaults for this element. This is an indicative figure for comparing constructions, not a compliance calculation.
Sources
- Knauf DriTherm Cavity Slab 32 — declared data · checked 2026-08-25
Change it, or use it
Open it in the calculator to swap a layer, change a thickness or solve for a target U-value — the result keeps its own URL, so a build-up you have altered is still something you can send to someone. Or take this one straight into the editor, where it arrives as a named wall type you can assign to the walls you have drawn: the thickness follows and the U-value comes with it. Nothing is assigned until you say so.