German houses are solid on purpose. The default is Massivbau - the masonry tradition of brick, calcareous sandstone and concrete block, wrapped in insulation and render, roofed in tiles at a pitch steep enough to live under. Around that core sits a building culture that takes energy law seriously, tests airtightness with fans, and treats the attic as a future room rather than a place for boxes. For a renovator, the combination means heavy walls, honest U-values, and a rulebook that shows up early.
This guide covers the conventions that change planning most: how walls are actually built, what the render-and-insulation system does, why the roof is steep, and where the energy rules and the trades boundary sit. Practice varies by region, era and builder - everything here is typical, not universal.
German plans and trades work in metric: millimetres, square metres, cubic metres; cement comes in 25 kg bags. The typical wall is a monolithic sandwich - 17.5–24 cm masonry block + 12–20 cm insulation + 8–15 mm render outside, plaster inside. Roofs are steeply pitched (35–45°) in clay or concrete tiles, with the attic commonly converted to living space. Energy is law: the GEG sets targets for new builds and major renovations, and the Passivhaus reference is 15 kWh/(m²·a) heating demand with airtightness n50 ≤ 0.6/h. Supply is 230 V; fixed electrics and anything gas are professional work.
The Drawing Speaks Millimetres
German working drawings dimension in millimetres, exactly as in Austria, Switzerland and much of the continent: a room is 3600 wide, a door 1985 high, a windowsill 850 above finished floor. Room heights are commonly spoken of in centimetres - the classic new-build ceiling is around 2.50 m, with older flats running 2.60–2.80 and Altbau apartments going past 3.00 - but the drawing itself stays in millimetres throughout.
Two module habits matter for planning. Window and door formats follow a co-ordinated size grid (multiples of 125 mm), which is why replacement windows are ordered by nominal format rather than measured gaps. And block lengths are co-ordinated with wall lengths, so an extension designed to whole block modules generates a fraction of the cutting that an improvised dimension does.
Massivbau: The Solid-Wall Default
The structural default for German houses is masonry in one of three families: Ziegel (fired clay blocks, often precision-ground and glued), Kalksandstein (calcareous sandstone, dense and strong, common for loadbearing and party walls), and concrete block. Timber framing and prefabrication are respected and growing, but the detached-house default remains solid. There is no cavity in the Anglo-Australian sense - no air gap managing rain - because the wall's weather protection is the render, and the layers stack solidly outwards from there:
| Layer (outside → in) | Typical thickness | Job |
|---|---|---|
| Render (Außenputz) | 8–15 mm, often thin-coat over mesh | Weatherproofing, finish |
| Insulation (EPS or mineral wool) | 12–20 cm | Thermal break; glued, dowelled, or both |
| Masonry core | 17.5–24 cm | Structure, mass, sound |
| Plaster (Innenputz, often lime-based) | 10–15 mm | Interior finish |
The thickness that changes over time is the insulation: it is the dial the energy law turns, which is why a 1990s wall carries 8 cm, a 2010s wall 14–16, and a current ambitious build 18–20+. For the DIY planner, masonry means the usual consequences: heavy walls on strip footings or rafts, shelves hang from plugs drilled into block, and every pipe run is a chased channel through solid material.
Render Outside, Lime Inside
The outside face is a rendered system, and German practice is closer to factory chemistry than site mixing: multi-coat thin-coat renders over reinforcement mesh, with mesh strips bedded at every opening corner and material change, and the whole system specified by the insulation manufacturer so the layers are warranted together. The inside face is plaster, and in both new builds and renovations the classic material is Kalkputz - lime plaster - prized for buffering humidity and staying alkaline, with gypsum plaster the everyday mainstream alternative.
Site-mixed cement render still exists for garden walls, basements and repairs, and that is where the arithmetic runs in bags and cubic metres: cement in 25 kg bags (the German standard - double the count for nothing, unlike the 50 kg bags described in the South African guide), sand by the cubic metre or the 25 kg sack. The Render & Plaster Calculator speaks exactly that arithmetic, and the render and plaster guide covers the coat logic behind it.
Steep Roofs and the Attic Nobody Wastes
German roof pitches run steep by Anglo standards - commonly 35–45° for tiled roofs - and the steepness is not romantic: it sheds snow, weather-proofs tiles at their comfortable working angle, and creates the roof volume that German planning treats as a resource. The Dachausbau - the attic conversion - is one of the country's most standard renovations: insulation between and under the rafters, VELUX-style roof windows or cut-in dormers, and a staircase meeting escape-route geometry. Because the roof is engineered timber (rafters and purlins, often historically hewn beams in older houses), any conversion is a structural design exercise first.
The covering arithmetic matches the tiled tradition the Roofing Materials Calculator runs: tile counts per square metre of roof plane, ridge and hip pieces, underlay and counter-battens beneath. Clay and concrete tiles dominate; sheet metal and slate appear regionally, and flat roofs mark the modernist minority.
Energy Is Law: GEG, U-Values, Passivhaus
Where other countries' building codes set energy as one chapter among many, Germany runs a dedicated energy law - the Gebäudeenergiegesetz (GEG) - that sets primary-energy and transmission targets for new builds and pulls major renovations toward the same standards. Its practical fingerprints: walls, roofs and windows are specified by U-value (W/(m²K) - lower is better; the reciprocal of the R-values used in North America, a conversion the insulation guide covers), triple glazing is the ordinary choice on new windows, and heating systems are planned around the building's calculated demand rather than sized by tradition.
The reference point above the legal minimum is Passivhaus: space heating demand no more than 15 kWh per square metre per year, airtightness verified by blower-door test at n50 ≤ 0.6 air changes per hour, and comfort criteria that cap summer hours over 25 °C. A Passivhaus is built from unremarkable parts assembled obsessively - thick insulation, no thermal bridges, triple glazing, heat-recovery ventilation - and its influence on ordinary construction rules is the reason German detailing reads as fussy: the fussing was load-bearing.
Airtightness and Breathing Old Buildings
New-build Germany is wrapped in an airtight layer with taped joints, tested with the blower door, and ventilated deliberately - often with heat recovery - because a tight house must be ventilated on purpose. Old-build Germany is its opposite: the Altbau (broadly, pre-war construction) was built from lime plaster, timber floors and masonry that all expected to exchange moisture with the air, and sealing any part of that system carelessly - plastic paint, cement render, interior insulation - moves the moisture somewhere less visible. The dew-point risk of interior insulation is the classic case: done wrong, water condenses inside the wall where no one can see it until the damage is structural.
The renovator's rule that falls out: in an Altbau, prefer lime over cement, vapour-open over vapour-closed, and exterior insulation over interior wherever the facade allows. And before sealing anything, understand where the wall's moisture was going.
Electrics, Heating and the Trades Line
Supply is 230 V at 50 Hz with the Schuko plug, and the DIY boundary is the familiar continental one: plug tops, lamps and unplugged appliances for the householder; anything fixed into the wiring belongs to a qualified Elektriker, with the work documented. Gas work is professional without exception. Heating in existing stock is overwhelmingly radiators on a central boiler (increasingly heat pumps in new builds, where the energy law pushes hard), with underfloor heating the norm in new construction - a fact that matters to renovation planning because a converted attic or a new bathroom usually inherits radiator arithmetic rather than choosing freely.
German building administration is correspondingly formal: permits for structural changes, conversions and window replacements, inspections at defined stages, and a culture where the paperwork is part of the craftsmanship rather than an affront to it. Planning a German project means planning the approvals alongside the materials.
How This Site's Calculators Map to German Practice
Everything on this site is metric-first - millimetres in, square metres, cubic metres and litres out - the language German drawings and builders' merchants (the Bauhaus and Hornbach aisles) already speak. Four tools map especially well:
- Render & Plaster Calculator — site-mixed render and interior plaster arithmetic in 25 kg bags and cubic metres, for repairs, basements and garden walls.
- Attic Insulation Calculator — blown and batt coverage by area and settled depth; mind the U-value/R-value conversion the guide covers.
- Roofing Materials Calculator — tile counts per roof plane with pitch multipliers, for the steep-roof arithmetic.
- Tile Layout & Mortar Calculator — the wet-room standard that German bathrooms are, in metric formats from 100 × 100 up.
Common Mistakes
- Assuming a cavity. German walls are monolithic - there is no air gap to vent or bridge, and the render is the weatherproofing.
- Sealing an Altbau. Plastic paint and cement render over lime construction move moisture into the structure - the damage is slow and structural.
- Interior insulation as a weekend job. The dew point moves into the wall; it needs professional condensation analysis.
- Planning the attic as furniture. A Dachausbau is a permitted, engineered structural change - structure, escape route, insulation, in that order.
- Bag arithmetic across borders. German cement bags are 25 kg; recipes from 50 kg countries double the count.
Plan It With the Render & Plaster Calculator
A repair or basement render job carries three quantities: area, thickness and mix. The tools speak German units - millimetres and metres in, 25 kg bags and cubic metres out. Run the Render & Plaster Calculator for the mix, the Attic Insulation Calculator for the insulation depth, and the Roofing Materials Calculator for the tile counts.
Frequently Asked Questions
Why are German houses built from masonry?
Tradition plus physics. Solid masonry - the Massivbau tradition of brick, calcareous sandstone and concrete block - delivers the sound insulation, fire performance, thermal mass and century-scale durability that German building culture values highly, and the supply chain, trades training and financing norms all organised around it. Timber-frame and prefab construction has been growing steadily and is a respected alternative, but it remains the minority choice for detached homes. For a renovator the practical meaning: assume masonry until proven otherwise, and expect heavy walls, strip footings and plaster finishes.
What is a typical modern German wall made of?
A monolithic sandwich: a loadbearing masonry core of 17.5-24 cm block (brick, calcareous sandstone or concrete), 12-20 cm of insulation - EPS or mineral wool boards glued and mechanically fixed to the masonry - and 8-15 mm of rendered finish outside, with plaster on the inside face. No cavity in the Anglo sense; the layers sit in one solid buildup. The layer thicknesses are tuned to meet the energy-law U-value target for the wall, which is why insulation thickness is the number that changes between decades and climate ambitions.
What is the Passivhaus standard?
A voluntary performance standard that began in Germany: space heating demand no more than 15 kWh per square metre per year, airtightness verified by blower-door testing at n50 of 0.6 air changes per hour or better, and comfort criteria that cap summer overheating. It is achieved with heavy insulation, triple glazing, heat-recovery ventilation and obsessive thermal-bridge detailing rather than gadgets - and it has become the reference point that ordinary new-build energy rules are measured against.
Can I insulate an old German house from the inside?
It is the last resort, done only with professional design. Exterior insulation is the German default because it keeps the masonry warm and dry; interior insulation moves the wall's temperature swing into the structure and creates a dew-point risk inside the wall - moisture accumulating where you cannot see it, on a wall that was built to breathe with lime plaster. Where inside insulation is unavoidable (listed facades, boundary walls), it uses specialised capillary-active or vapour-permeable systems with condensation analysis, not off-the-shelf boards on a dusty weekend.
Can I convert my attic into living space?
Often yes - the Dachausbau is one of Germany's standard renovations, because steep roofs leave genuinely usable volume. But it is a permitted, engineered project, not a fit-out: the structure must carry the new floor and dormer loads (often requiring reinforcement of rafters and the floor joists), stairs must satisfy escape-route geometry, insulation moves into the roof plane between and under the rafters, and the windows and dormers need approval. Allow real time for the planning phase and expect the building authority to be part of the process - that is normal, not an obstacle.
Planning guidance only. GEG requirements, permit scopes and listed-building rules vary by state, municipality and property - confirm the current rules for your project, and treat fixed electrics and all gas work as professional territory.
Related MyHouseLogic Guides
- Render and Plaster: Coats, Mixes and Coverage — the arithmetic behind the rendered facade, in 25 kg bags and cubic metres.
- Home Project Basics for South Africa — the other masonry country: double brick, 50 kg bags, the contrasts that clarify both.
- Timber and Lumber Sizes Around the World — the regional mapping for the roof timbers a Dachausbau touches.
- Homes Around the World — the collection of regional measurement and planning guides.
- Field Guide library — every MyHouseLogic guide, each tied to a calculator.
The bottom line: German homes are solid masonry under render, steep roofs over convertible attics, and energy law in every wall dimension. Plan in millimetres, specify in U-values, keep old walls breathing with lime - and file the permits with the drawings, because the paperwork is part of the craftsmanship.