Forest Xtend 3.0+ Insulated Garden Office 2.98m x 2.9m (97mm SIP)

The Forest Xtend 3.0+ (XTEND3.0PHDBUN) is a SIP-built insulated garden office measuring 2.98m x 2.9m externally (approximately 9ft 9in x 9ft 6in). Internal floor space is 2.65m x 2.15m enough for a proper home office setup with room to spare.

The walls are built from 97mm SIP panels 75mm polystyrene insulation sandwiched between two OSB sheets giving a total wall thickness of 177mm including cladding and cavities. Unlike many rivals, the floor (108mm SIP) and roof (122mm SIP) are fully insulated too. External cladding is 15mm kiln-dried tongue and groove timber. The roof is covered with 1.2mm EPDM rubber membrane rated for 50 years.

Double-glazed UPVC double doors (1500mm x 1950mm) are secured by a 7-point multi-lock with Ultion three-star barrel. Two full-length double-glazed windows flood the interior with natural light and both open at the top for ventilation. 28mm wall battens and 45mm roof battens leave cavities ready for electrical wiring and recessed lights. The building is fully usable year-round.

With a 15-year structural guarantee, A-rated 28mm double glazing and an energy efficiency rating of 78 (category C) this is a serious work-from-home building. UK-made. Free delivery to most addresses.

The Xtend 3.0+ uses SIP construction throughout. Each wall panel is 97mm thick 75mm polystyrene insulation between two OSB sheets giving a total wall build-up of 177mm including battens and cladding. The 108mm SIP floor and 122mm SIP roof extend that insulation to every surface. External cladding is 15mm kiln-dried tongue and groove timber. The roof is covered with 1.2mm EPDM rubber UV-stabilised and rated for 50 years. Glazing is 28mm A-rated double-glazed safety glass in uPVC 5-chamber frames. Wall battens create a 28mm cavity for cable routing and 45mm roof battens allow recessed lighting.

Structure: SIP panels with 75mm polystyrene core between OSB sheets. External cladding: 15mm kiln-dried tongue and groove timber. Internal lining: MDF with vertical beaded profile, pre-primed. Floor: 108mm SIP panel left unfinished. Roof: 122mm SIP panel with 1.2mm EPDM rubber membrane. Doors and windows: uPVC 5-chamber frames with 28mm A-rated double-glazed safety glass.

A solid level base is required before delivery or installation. A concrete slab or level paving is suitable. The base is not supplied the buyer arranges and pays for ground preparation. No flooring is included; the SIP floor panel is left unfinished for the buyer to cover with carpet, laminate or similar.

The building arrives flat-packed as pre-cut modular SIP panels. All fixtures, fittings, anthracite grey exterior fascias and a step-by-step installation guide are included. Forest also provide two how-to videos online. Two or more people are recommended for assembly. The pre-cut panels are designed for straightforward self-build without specialist tools.

Forest offer a professional installation service carried out by expert fitters. A solid level base must be in place before the installation date. Installation does not cover electrics or any other accessories. Contact Forest Garden directly to arrange and confirm availability in your area.

Forest do not supply an electrical service. The building is wired-ready 28mm wall battens create a cable routing cavity and 45mm roof battens leave space for recessed lights. A qualified electrician must carry out all electrical installation work.

Treat the exterior timber on assembly and every year after using a product such as Sikkens Cetol HLS Plus, Restol Wood Oil or Osmo Country Colour. Annual treatment is required to maintain the 15-year structural guarantee. The EPDM roof is maintenance free. Internal MDF walls are primed and can be repainted with standard interior emulsion as needed.

The internal floor space is 2.65m x 2.15m roughly 5.7 square metres. That fits a full-size desk with monitor, a storage unit and a second chair comfortably. It works well as a single-person home office or a focused creative studio. The space is tight for a sofa but works for a compact hobby bench or a small exercise bike. Full-length windows and double doors make it feel larger than the footprint suggests. It is fully insulated so it works as a year-round office without the need for heavy heating.

Most garden offices fall under permitted development in England if they are single storey and used as ancillary to the main house. This model has a 2400mm eaves height and 2500mm ridge height which typically sits within the permitted development thresholds. Rules differ in Scotland, Wales and Northern Ireland. Always check with your local planning authority before you build this is not legal advice.