21 Terracotta rainscreens
An external wall from the tool's Masonry walls group. With the layers below it has a U-value of 0.28 W/m²K, is 387.5 mm thick, and has about 70 kgCO₂e/m² of embodied carbon.
- U-value
- 0.28W/m²K
- Overall thickness
- 387.5mm
- Embodied carbon
- 70kgCO₂e/m²
- Fire
- A2 or better
Against the Building Regulations
| New home in | U-value limit | This build-up, 0.28 |
|---|---|---|
| England | 0.26 W/m²K | Misses by 0.02 |
| Wales | 0.18 W/m²K | Misses by 0.10 |
| Scotland | 0.17 W/m²K | Misses by 0.11 |
These are the limits for a single element in a new home. In England a new home usually needs better figures to pass the whole-house target, about 0.18 for walls. All UK U-value limits.
Section, drawn to scale
Layers, outside to inside
| # | Layer | mm | λ, W/mK | R, m²K/W | kgCO₂e/m² | Fire class |
|---|---|---|---|---|---|---|
| 1 | Terracotta rainscreen tile outside the ventilated cavity: not counted | 30 | 1 | – | 27.4 | A1 |
| 2 | Ventilated cavity behind cladding outside the ventilated cavity: not counted | 40 | – | – | 0 | – |
| 3 | Mineral wool rainscreen slab | 150 | 0.035 | 4.286 | 11.5 | A1 |
| 4 | Dense concrete block | 140 | 1.13 | 0.124 | 28.0 | A1 |
| 5 | Unventilated cavity or dab gap | 15 | – | 0.171 | 0 | – |
| 6 | Plasterboard | 12.5 | 0.21 | 0.060 | 3.5 | A2-s1,d0 |
| Total, with surface resistances | 387.5 | 4.900 | 70.4 |
U-value worked out to BS EN ISO 6946 from the total resistance, plus 0.080 W/m²K of corrections for fixings, gaps or brackets. Carbon is stages A1 to A3 for the layers.
Moisture and rain
Free of interstitial condensation No condensation in any month (Heathrow (London), 1 in 10 year). Surface factor 0.93 (needs over 0.71 and at least 0.75).
Rain: Zone 2 of max 4 for exposure zone 2 (moderate).
Other masonry walls
Figures come from the Build-up Atlas's own calculation, with generalised values for typical products, for an England new home with default settings. They are indicative, for design and teaching: check the manufacturer's declared values and the current regulations for your project. Rules and standards last checked 21 October 2026.