Bespoke Arched & Round Windows

Formfönster

Name: Formfönster – Custom geometric timber windows and heritage profiles for demanding architecture
Brand: Formfönster

Bespoke geometric timber windows for every architectural angle and historic facade. At our Lenhovda factory, we have manufactured round, arched, and Gothic windows since 1994. We are also unique in Sweden in serial-manufacturing these complex curved geometries in solid European oak.

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Halvrundt Formfönster träfönster med solfjäderspröjs på skandinavisk träfasad

Factory & OriginLenhovda, Småland (founded 1994)

Core CompetenceRound, arched & Gothic windows

Timber SpeciesSlow-grown Swedish pine, ash & solid oak

Thermal & StandardsTriple Argon U=1.0 W/m²K · SS-EN 14351-1

HERITAGE & ENGINEERING

Artisanal woodcraft and industrial precision in Småland

Timber selection and authentic heritage joinery

Curved window profiles demand uncompromising raw material stability. Arches and circular sashes exposed to changing Nordic seasons can warp if the timber is not meticulously selected. Formfönster utilizes carefully graded slow-grown Swedish Scots pine with high heartwood content and solid European oak, kiln-dried to a controlled moisture equilibrium of 12 ± 2 %.

Dense annular ring growth provides natural resistance against moisture ingress and fungal decay. In historic conservation projects, we recreate original fanlight muntins, historic profiles, and drip sills in strict compliance with the Swedish Planning and Building Act (PBL 8:13 and 8:17).

5-axis CNC kinematics and industrial robotic finishing

To merge historic geometry with modern airtightness, all profiles are milled on 5-axis CNC machining centers directly from digital CAD models. The sash radii, tenons, and rebates are cut to sub-millimeter tolerances, ensuring that triple-glazed insulating units with Argon gas and warm-edge spacers sit perfectly tension-free.

Following assembly, windows enter our automated finishing line. Multilayer industrial robotic coating seals the end grain and joints against weather degradation. While classic Swedish off-white NCS S 0502-Y is standard, our automated system accommodates any NCS or RAL shade.

SYSTEM OVERVIEW

Product portfolio and technical systems

SYSTEM 01

Argon Arched (Half-Round Windows)

Arched energy window featuring triple-glazed Argon, warm-edge spacer, and factory drip sill.

Performance: U-value 1.0 W/(m²·K) with Argon gas and low-E coatings
Sizing: Standard -20 mm deduction (e.g. module 8x4 delivered 780x380 mm)
Timber: Premium Swedish pine standard, solid oak or ash optional

SYSTEM 02

Argon Circular (Full Round / Bullseye)

Full-round timber window with balanced frame symmetry and high thermal insulation.

Performance: U-value 1.0 W/(m²·K), Class 4 airtightness per EN 12207
Dimensions: Diameters from Ø400 mm up to Ø1400 mm in fixed configuration
Finish: Robotic coating in NCS S 0502-Y or custom RAL/NCS shades

SYSTEM 03

Argon Arched with Fanlight Muntins

Period-accurate turn-of-the-century window with radiating fanlight bars for listed buildings.

Heritage Profile: Authentic molded muntin profiles approved by conservation officers
Glazing: Continuous high-performance triple glazing behind historic joinery lines
Installation: Designed for historic reveal depths in stone, brick, or timber walls

SYSTEM 04

Decorative Blind Arched Window (Cold Attic)

Cost-effective decorative arched window in moisture-resistant HDF for cold attics and gables.

Glazing: 4 mm single glass bedded in sealant with profiled timber glazing beads
Dimensions: Delivered with -10 mm fitting tolerance (8x4 delivered 790x390 mm)
Casings: Complete with 12 mm interior casing and 22 mm exterior architrave

DECLARATION OF PERFORMANCE

Laboratory verified performance and tender specification

Property	Test Standard	Classification / Value	Notes
Thermal Transmittance (Uw)	EN ISO 10077-1	1.0 W/(m²·K)	Triple-glazed Argon with warm-edge spacer
Air Permeability	EN 12207	Class 4	Highest standard testing class
Watertightness	EN 12208	Class 9A / E750	Unbroken sealing around entire curved radius
Resistance to Wind Load	EN 12210	Class C3	Tested for exposed Nordic coastal conditions
Acoustic Insulation (Rw + Ctr)	EN ISO 717-1	34 dB (up to 40 dB)	Acoustic laminated glass optional

AMA Hus NSC.112

Timber windows and window doors in historic environments

Windows manufactured by Formfönster (Amawood AB). Executed with curved sash and frame geometry in Swedish Scots pine or solid European oak. Sashes and frames with heritage profiles per architectural drawings. Glazing: triple-glazed unit with Argon gas and warm-edge spacer, U-value 1.0 W/(m²·K). Finish: factory painted NCS S 0502-Y.

QUESTIONS & ANSWERS

Technical inquiries for architects and structural engineers

How do I calculate ordering dimensions for round and arched windows?

Formfönster products are supplied with a standard 20 mm deduction from nominal modular wall openings. A nominal 800x400 mm opening (module 8x4) receives an outer frame measuring 780x380 mm to allow a 10 mm caulking and adjustment perimeter.

Can Formfönster windows be crafted in solid European oak?

Yes. Formfönster is unique in Sweden in serial manufacturing circular and arched windows in solid European oak. Oak provides exceptional rot resistance and can be supplied either painted or treated with clear preservative oil.

Are your windows approved by municipal heritage conservationists?

Yes. We frequently supply listed and historic properties. Båg profiles and muntins are engineered with historical radii and we provide comprehensive CAD cross-sections for planning and building conservation applications.

Which paint coating systems and colors are available?

Standard finish is classic Scandinavian white NCS S 0502-Y. Our automated robotic spray line accommodates all NCS and RAL color specifications, as well as dual-color finishing (different interior and exterior colors).

Geometric & Round Window Division

Formfönster Order & Technical Engineering

Our design engineers and production managers at the Lenhovda facility review your architectural drawings, perform thermal U-value calculations, and provide dimensioned manufacturing packages.

Call the Factory: +46 474 218 00 Email: info@amawood.se

Manufacturing Plant & Delivery:
Amawood AB / Formfönster
Vagnvägen 10, SE-364 42 Lenhovda, Sweden

Project Support

Request CAD & Specifications

Attach your drawings (PDF/DWG/STEP) for complimentary technical review and tender documentation.