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Garden room project · Ark Design Build

Thermowood garden office

A 5m × 3.5m Thermowood-clad garden office in Kent, with sliding doors and high windows on the back wall.


Published 1 June 2019 · Updated 23 October 2026 · 3 minute read · Written by The Garden Room & Annexe Guide

Thermowood clad garden office
Ark Design Build  5m × 3.5m, Thermowood

Ark Design Build recently completed this Thermowood-clad garden office in Kent. Working on a bespoke basis, they tailor both the design and specification to meet their client’s needs.

In this case, the 5m x 3.5m building is clad externally with Thermowood, a popular choice for garden offices. Often more affordable than Larch or Cedar, it offers similar long-term durability.

Thermowood is produced by treating Scandinavian softwoods at very high temperatures-between 180 and 230 degrees Celsius. This process doesn’t involve chemicals, making Thermowood an eco-friendly alternative to chemically treated wood. Additionally, at the end of its lifespan, Thermowood can be disposed of in the same way as untreated wood.

Unlike Larch and Cedar, which are relatively knot-free, Thermowood showcases the natural grain and knot patterns of the wood. When newly installed, it has a honey-yellow to brown colour, which depends on the treatment temperature. The higher the temperature, the darker the shade. Judging by the colour used by Ark Design Build on this project, the wood was treated at the higher end of the temperature range.

Thermowood can be stained or painted but also looks beautiful when left to weather naturally. Like Larch and Cedar, it will gradually age to a silver-grey patina.

At a glance

  • Size: 5m × 3.5m.
  • Built for: A home office.
  • Construction: Turnkey, from foundations to final electrical connections.
  • Finishes: Thermowood outside; plaster and a wooden floor inside.
  • Company: Ark Design Build, with Cat6 data cabling as standard.

Part of our garden office guide →

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The company

A turnkey project

Ark Design Build offers their garden offices on a turnkey basis, managing the entire process from installing the foundations to final decoration and electrical connections.

The layout of this office was customised to suit the client’s needs. Sliding doors were installed on one side of the front wall, while rectangular windows were placed high on the rear wall.

Inside, the room has been plastered and decorated. The addition of a wooden floor creates a light, modern space.

A light modern room has been created
The interior
Electrics

Data cabling installed as standard

Ark Design Build includes Cat6 data cabling as standard in their garden offices. Many other companies treat this as an extra feature. Hardwired Cat6 cabling is the most effective way to extend a reliable internet connection to a garden office.

Planning something similar?

Learn more about Ark Design Build

Ark Design Build operates in Kent, East Sussex, and parts of Essex. To learn more about creating a garden office, contact the Ark Design Build team on 07896 196 718 or email them at contact@arkdesignbuild.co.uk. Visit www.arkdesignbuild.co.uk to explore more of their work.

Visit Ark Design Build More Ark Design Build projects
More projects like this Garden offices 10–20sqm garden rooms
Read the guides What garden rooms cost Permitted development What is a garden room?

Published 1 June 2019 · Photographs courtesy of Ark Design Build.

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