U-value of a tile-hung wall

The tiles on a tile-hung wall don’t count in its U-value: BR 443 (§4.7.1) treats the space behind tile hanging as a well-ventilated cavity, so the tiles, the battens and that space are left out, and the outside surface resistance rises from 0.04 to 0.13. A 1930s tile-hung cavity wall — brick both leaves and a 50mm empty cavity — comes out at about 1.28 W/m²K, against 1.44 for the same wall below the tiles. Filled with 50mm of blown mineral wool it is about 0.54, inside the 0.55 Approved Document L asks of cavity fill. Re-hanging the tiles over 100mm of PIR on a 9-inch solid wall gives about 0.21, inside the 0.30 for external insulation.

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The build-up (outside → inside)

Clay plain tiles on 38 × 25mm battens (a well-ventilated space: disregarded)
102.5mm brick outer leaf (λ 0.77, BR 443’s outer-leaf value)
50mm unventilated cavity
102.5mm brick inner leaf
13mm plaster

Clay tiles on battens are entered as cladding outside a well-ventilated air space, so U-Monkey disregards them and uses an outside surface resistance of 0.13 (BS EN ISO 6946 §6.9.4; BR 443 §4.7.1, §4.7.3). The outer leaf behind the tiles is taken at BR 443’s outer-leaf value, λ 0.77 (§3): its protected value behind cladding, 0.56, is written for solid walls (§7), and one row shows it. A solid wall behind tiles is taken as protected. Screws through insulation behind re-hung tiles are U-Monkey’s “EWI screw fixings” preset (6 per m², stainless). The link opens as an existing cavity wall being filled, judged against Approved Document L’s 0.55 (2021 edition, Table 4.3).

Typical U-values for this construction

Specification	U-value (W/m²K)	Notes
1930s tile-hung cavity wall: brick both leaves, 50mm empty cavity	≈ 1.28	As pre-filled
The same, with the outer leaf taken as protected brick (λ 0.56)	≈ 1.20	BR 443 §7 gives the protected value behind cladding to a solid wall, not to an outer leaf
The same wall untiled (ground floor)	≈ 1.44	Outside surface 0.04
50mm blown mineral wool cavity fill (λ 0.040)	≈ 0.54	Meets 0.55 for cavity fill (0.540)
9-inch solid brick, tile-hung	≈ 1.57	A solid wall behind cladding: protected brick (BR 443 §7), its mortar joints counted (§4.2)
9-inch solid brick, tile-hung, brick at 0.77	≈ 1.77
9-inch wall re-hung over 100mm PIR, 6 stainless screws per m² through it	≈ 0.21	Meets 0.30; of the usual board thicknesses, 70mm is the thinnest that does (0.284)
9-inch wall re-hung over 120mm wood fibre (λ 0.041), screws as above	≈ 0.30	Meets 0.30, just: 0.296
Counted the wrong way: tiles and a still air space, outside surface 0.04	≈ 1.13	Understates the U-value by 0.15

Figures computed with the BS EN ISO 6946 combined method and BR 443 conventions — bridging, mortar joints in blockwork (and in solid brickwork where BR 443 §4.2 requires them) and the air-gap correction included — exactly as the pre-filled calculator works them out, with any pass or fail judged on the unrounded U-value. Indicative for the generic build-up shown: your products, thicknesses and (for floors) footprint will move the number, and that's what the calculator is for.

What changes the number

The tiles are cladding, not insulation. BR 443 takes the air behind tile hanging as well ventilated (§4.7.1), at the outside temperature, so everything outside it drops out, and because the cladding shelters the wall from the wind the outside surface resistance becomes 0.13 rather than 0.04 (§4.7.3); counting the tiles and a still air space instead understates the U-value by about a tenth. Behind the tiles the brick stays drier, but BR 443 gives brick its protected λ, 0.56, behind “an external insulation or cladding system” only in a solid wall (§7); for the outer leaf of a cavity wall its value is 0.77 “unless otherwise specified” (§3), and that is what U-Monkey uses here. Taken as protected, the wall would be 1.20. A solid 9-inch wall behind tiles does take the protected value. From there the usual routes apply. A 50mm cavity can be filled (0.54 with blown mineral wool at λ 0.040), and the tiles keep driving rain off the outer leaf, which is what tile hanging has long been used for. Stripping and re-hanging the tiles is the chance to put insulation behind them: on a 9-inch wall, 100mm of PIR gives about 0.21 with the screws through it, and 120mm of wood fibre about 0.30. Or insulate inside and leave the tiles alone.

Condensation and mould with a tile-hung wall

The empty 1930s wall fails U-Monkey’s surface-mould check — fRsi 0.69 against the 0.75 a home needs — as most uninsulated walls do; filling the cavity lifts it to 0.87. The filled wall gets a conditional pass in the BS EN ISO 13788 check: seasonal condensation against the back of the outer leaf, peaking at about 490 g/m² in March, that dries out over the summer — the usual Glaser result for a filled cavity. The check itself says it can’t settle this one alone: the result turns on the brick’s vapour resistance, which BS 5250 gives only as a wide range, and a Glaser calculation doesn’t model rain or the liquid moisture that brick carries, so its figures are indicative. Insulation behind re-hung tiles, PIR or wood fibre, passes with no condensation in any month: it keeps the whole wall warm. Keep the batten space ventilated and drained, with an underlay behind the battens.

Check this build-up for condensation — free

Opens pre-filled. The condensation verdict sits just under the U-value — tap it for the full month-by-month check, the surface-mould (f_Rsi) check included. If it isn’t a pass, How to fix it tests the usual remedies on your build-up — a vapour control layer on the warm side, a more vapour-open layer on the cold side, more insulation to warm the inside surface — and applies the one you pick in a tap, with Undo.

Need it in writing for Building Control? The full condensation risk analysis report is £25 +VAT (£30 inc VAT), or included on Monkey Pro Unlimited — see an example report (PDF), or read what building control expects the analysis to show.

It is a screening to BS EN ISO 13788 (the Glaser method), honestly labelled as one: it does not model air leakage, rain or moisture stored in materials, so for high-risk or heritage constructions a full hygrothermal simulation (BS EN 15026) is the right next step. Figures above use the app’s defaults — Manchester (Ringway) climate, humidity class 3 (dwellings with high or unknown occupancy), a 1-in-10 design year and, on a roof, the surface taken 2 K below the air for night-sky cooling — so pick your nearest weather station for your own build-up: the result can change from one station to another.

Next: check the junctions

A U-value covers the flat area of an element — but heat also escapes where elements meet, and at modern U-values those junctions can be 20–30% of a dwelling's fabric heat loss. Now you know your U-values, model the junctions with the free ΨMonkey psi value calculator (no subscription; PDF reports £25 +VAT a junction):

Or read thermal bridging explained to see how junction Ψ-values feed your SAP calculation.

Frequently asked questions

What is the U-value of a tile-hung wall?

Do I have to insulate when I re-hang tile hanging?

Possibly. The Building Regulations count the replacement of a layer of a wall as renovating it (regulation 2(1)), and renovating more than half of a wall’s area brings in the upgrade Approved Document L asks for — 0.30 for external insulation — so far as that is technically, functionally and economically feasible, with a simple payback of 15 years or less (regulation 23; Approved Document L, paragraphs 4.12 and 4.13). Whether stripping and re-hanging the tiles counts that way is for building control, so ask before you start; if it does, 70–100mm of PIR or about 120mm of wood fibre behind the new tiles is the usual answer on a 9-inch wall.

Is this calculator free?

Yes — building the element, reading the U-value, the compliance targets (including the Future Homes Standard), the condensation-risk screening check and the thermal-mass figures (decrement factor, time lag, κ) are all free in your browser, and the Building Control-ready PDF report is free too. No sign-up.

Does it follow the official calculation method?

Yes — the combined method of BS EN ISO 6946:2017 with BR 443 conventions, including timber bridging, mortar joints in blockwork (and in solid brickwork where BR 443 §4.2 requires them) and air-gap corrections, BS EN ISO 13370 for ground floors, suspended floors and basements, and ISO 13788 for the condensation screening check.

Other common build-ups

Walls

Roofs

Floors

Different build-up? See the full wall U-value calculator, or start from scratch in the main U-value calculator.

Need the wider compliance picture? U-values feed straight into SAP calculations — or let our New Build Compliance Pack handle the lot. Background reading: what U-values actually are, and why two calculators can give different answers for the same wall.