The flat roof, the white rendered walls, the steel windows and the clean lines. The art deco villa (funkisvilla) from the 1930s is architecture with conviction — inspired by the Bauhaus movement and modernism’s ideals of light, air and functionality. But 90 years after construction, many art deco houses are struggling with the same problems: moisture in the flat roof, cold bridges in the slender structure and windows that do not retain heat.
Here is an overview of what to expect — and what it costs.
What defines the art deco villa?
Art deco houses (functionalist architecture) were built primarily in the 1930s–40s. They differ markedly from the traditional brick villa:
- Flat roofs. Concrete structure or timber with roofing felt. The most vulnerable part of the house.
- Rendered facades. White or light-coloured render over masonry. Elegant, but requires maintenance.
- Steel windows. Slender profiles with large glazed areas — but massive cold bridges and poor insulating capacity.
- Cubic form. Clean lines, no roof overhangs. This means the facade is more exposed to driving rain.
- Open floor plan. Revolutionary for its time — living room and dining area in one space, large windows facing the garden.
- Terraces and balconies. Integrated into the architecture as outdoor living spaces.
- Minimal insulation. One-and-a-half brick masonry without a cavity — poor insulation by current standards.
What does it cost?
New flat roof: 100,000–250,000 DKK Flat roofs have a shorter service life than pitched roofs. New SBS-modified roofing felt lasts 25–40 years. The concrete structure beneath must be checked for moisture and cracks. Insulation on top (warm roof solution) gives the best result — 150–300 mm EPS or XPS with new roofing felt on top.
Facade renovation: 80,000–200,000 DKK Rendered facades crack and flake over time. New render with reinforcement mesh and surface treatment. Colours should often match the original — especially for listed buildings.
Window renovation/replacement: 80,000–250,000 DKK Original steel windows can be renovated with new weatherstripping and secondary glazing (cheapest, preserves the appearance). New slim-line steel windows with energy glazing cost 8,000–20,000 DKK each, but recreate the original look with modern performance.
Insulation: 50,000–200,000 DKK Internal insulation with vapour barrier is typically the only option in art deco houses without a cavity. 50–80 mm internal insulation reduces room size, but gives noticeable comfort improvement. The ceiling is insulated from above with 200–300 mm mineral wool.
Moisture remediation: 50,000–200,000 DKK Flat roofs, absent roof overhangs and rendered facades without drip details make the art deco villa prone to moisture. Correct drainage, new roof drains, and repair of cracks in render and foundation are often necessary.
New heat source: 60,000–150,000 DKK Many art deco houses have radiator systems that work well with heat pumps or district heating. Underfloor heating in bathroom and kitchen as a supplement.
Preserving the architecture
The art deco villa has a strong architectural identity. A renovation that ignores it destroys the value of the house — both aesthetically and financially:
- Preserve the slender proportions. External insulation makes windows deep-set and the facade thick. Internal insulation preserves the appearance.
- Preserve or recreate the steel windows. Plastic windows in an art deco villa are an architectural disaster. Slim-line steel windows or renovated originals are the way forward.
- Preserve the flat roof profile. A pitched roof on top of an art deco villa destroys the proportions. Insulate and renew the flat roof instead.
- Preserve the colours. White and light facades are part of the expression. Contrast colours on doors and windows are typically dark — green, black or dark blue.
Many art deco villas are listed or conservation-designated. Check the SAVE value and any listing conditions before you begin.
Which art deco villas are most at risk?
Houses with original flat roofs. If the roof has not been renovated in 25+ years, it is high on the priority list. Check for damp patches on the ceiling and moisture in exterior walls at the roofline.
Houses with untreated render. Render without regular maintenance absorbs water like a sponge. Cracks at window corners and the base of the wall are classic entry points for moisture.
Houses with unchanged steel windows. Without secondary glazing, original steel windows lose enormous amounts of heat — and condensation on the inside is unavoidable in winter.
Houses with added extensions. Many art deco houses were extended in the 1960s–70s with additions that break the original architectural language. These extensions are often built to a lower standard than the original.
Budget and grants
The art deco villa costs more per m² to renovate than the average house — specialist materials (steel windows, specialist render) and conservation considerations cost extra. But property values are also higher — a well-renovated art deco villa in a good neighbourhood is among the most valuable detached houses in Denmark.
Energy companies provide grants for insulation and heat pumps — regardless of house type. The BoligJob scheme provides a tax deduction for labour costs on energy improvements. See Sparenergi.dk for current rates.
For listed buildings, the Danish Agency for Culture and Palaces (Slots- og Kulturstyrelsen) can in some cases provide grants for restoration. Contact the agency early in the process.
Timeline
A comprehensive renovation of an art deco villa typically takes 4–8 months. This is longer than for a type house — because specialist craftsmanship (steel windows, render work, flat roof flashings) requires experienced firms with often longer lead times. Plan early and choose contractors who have experience with houses from the period.
The most common mistakes in art deco renovation
- Plastic windows. Destroys the slender proportions and reduces the property value. Use slim-line steel or restore the originals.
- External insulation. Makes the facade thick and the windows deep-set. Does not preserve the elegance of the form. Internal insulation is better.
- Pitched roof. Adding a pitched roof to an art deco villa is like adding a moustache to the Mona Lisa. Repair the flat roof instead.
- Wrong render type. Cement render on original lime mortar walls traps moisture. Use lime or silicate render.
How to move forward
The art deco villa is one of the most characterful house types in Danish architecture. It deserves a renovation that understands its qualities and respects its architectural language. Start by mapping the condition of the house — especially roof, moisture and windows — and draw up a plan that balances technical needs and architectural integrity.
If you have a traditional brick villa instead, many of the same principles apply — but with different structural details and typical weaknesses.
Sources: Bygningskultur Danmark, Bolius — 1930s houses, Danish Agency for Culture and Palaces