Forest Xtend 4.0 Garden Office

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The Forest Xtend 4.0 garden building is a 13ft x 11ft cabin-like structure that is substantial and designed to extend your living and working space into the garden, it's versatile with many uses as office, hobby space or studio.

Bright sunshine will stream through the extensive glazing to create a light filled spacious interior and the energy efficient design that includes the use of structural insulating panels within the walls, roof, and floor, meaning that the building is fully insulated and can be used at any time of the year, staying cooler in the summer and warmer in the winter. Additionally, for very warm days, the UPVC double-glazed door and windows can be opened for ventilation.

Tongue & groove cladding adds to the cabin's eye-catching presence on the exterior, the natural wood is kiln dried and needs no further treatment to last many years although it is possible to paint the wood if you think this enhances its appearance and your garden. The inside is also cladded with primed-MDF panels, ready to paint over in your preferred colour choice, making the inside personalised to your taste.

To waterproof the roof and ensure the cabin remains a dry welcoming environment, EPDM rubber is used instead of traditional roofing felt. There's no doubt this highly durable material is a superior choice as it will last for 50 years and is rot, blister, and tear-resistant. The Xtend 4.0 building is structurally guaranteed for 15 years and is manufactured in the UK.

Feature Highlights:

  • Modern-Design 13ft x 11ft Home Office Garden Building
  • Pre-Insulated To Stay Cooler In The Summer & Warmer In The Winter
  • Ready-to-Paint Inside & Out to Personalise To Your Taste & Use
  • UPVC Doors & Windows with Double Glazing Safety Glass
  • Super Thick 117mm Walls Combining SIPs Panels, Cladding & Cavities
  • Wall & Roof Cavity For Easy Installation of Lights & Electrics (Parts Not Included)
  • Guaranteed To Last with Forest's 15-Year Structural Guarantee

Structural Features:

  • Core Walls: 97mm Thick Structural Insulated Panels (SIPs)
  • External Cladding: 15mm Thick Timber Cladding Panels Cut To Size
  • Internal Cladding: 9mm Primed MDF Cladding Panels Cut To Size
  • Internal Floor: 97mm Thick Structural Insulated Panels (SIPs) with 11mm MDF Topper
  • Pent Roof: 100mm Insulation with EPDM 1.2mm Black Rubber Liner & Grey Fascias
  • Single Door: On The Front with 7-Point Lock & Ultion Three-Star Security Barrel
  • Windows: Two Fixed at Front & One ¼ Openable On The Side


  • Overall Height: 250cm (8ft 2ins)
  • Overall Width: 405cm (13ft 3ins)
  • Overall Depth: 342cm (11ft 3ins)
  • Base Width: 403cm (13ft 3ins)
  • Base Depth: 304cm (10ft)
  • Height To Eaves: 240cm (7ft 10ins)
  • Internal Height: 207cm (6ft 9ins)
  • Internal Width: 367cm (12ft)
  • Internal Depth: 268cm (8ft 10ins)
  • Door Opening Height: 195cm (6ft 5ins)
  • Door Opening Width: 75cm (2ft 6ins)
  • External Wall Cladding: 15mm
  • Internal Wall Cladding: 9mm
  • Roof Thickness: 122mm (100mm Insulation + 11mm Inner/Outer Boards)
  • Floor Thickness: 108mm (97mm SIP Panel + 11mm MDF Cladding)
  • Double Glazing Thickness: 28mm (4mm Pane, 20mm Air Gap, 4mm Pane)
  • Door UPVC: uPVC Reinforced 5 Chamber
  • Window UPVC: uPVC 5 Chamber
  • UPVC Colour: Anthracite Grey with White Interior
  • Weight: 2400kg
  • Brand: Forest
  • Model: XTEND4.0

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Xtend 4.0 Assembly Instructions

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Delivery & Installation Services

Home Delivered

Home Delivered (XTEND4.0HD)

Your new Forest product delivered directly to your home, ready for you to self-assemble in the garden. Full instructions and fixings are included with mostly pre-assembled parts for quicker assembly.
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Installed (XTEND4.0IN)

Includes delivery of your Forest product, followed by installation on a future day thereafter. This service is the assembly of the product and does not include base preparation or disassembling existing buildings. A flat, solid base area must be pre-prepared. Not available within areas excluded from home delivery.
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  • Home Delivered

£11,500.00 inc. VAT

Delivery Information

Fast Free Delivery within Mainland UK.
In some cases we can even deliver outside the mainland e.g. Channel Isles and arrange the VAT element for you. In all instances please contact us today for a personalised quote.

Delivery Period
Delivery will typically be made within 4 - 6 weeks but may be extended during busy times of the year. For larger products, the carrier will call and book in a convenient delivery date. For other products, a delivery date will be provided by email from the carrier, which will include a link to allow tracking online.

If you have purchased an installation service with us, available on selected Forest branded sheds, structures and buildings then this is completed after successful delivery of the product and is generally completed with 2 - 4 weeks following. After successful delivery, you will be contacted directly by the installers to book in an installation date. Please ensure that you have checked the delivery for all components and keep in a safe, dry place until the installation occurs.

Please note that this service is assembly only. It does not include laying bases or disassembling existing buildings.

Installation/assembly is excluded in the following postcodes BT, GY, HS, IM, IV, JE, KA, KW PA, PH, PO, TR, ZE, and any other offshore islands, highlands, or countries.

Vehicles We Use
Items will be delivered on larger lorries which can get to most places it's typically, a 7.5 ton lorry which is about the size of a dustbin lorry, this will depend on the item that is being delivered and should you have any concerns with restricted access to your property we ask you to contact us prior to placing an order.

Unloading Of Your Delivery
Due to the nature of this product, delivery will be made to the front of the property to the nearest location. Our drivers will not carry these items inside your home or back garden. When the item is delivered on a pallet, the pallet and packaging are non-returnable and the goods can only be manoeuvred on a flat and level surface (i.e. not a gravel driveway) by a pallet truck. On some occasions the driver will split the package to assist with manoeuvring of the item. Once you are happy, we will ask you to check the condition of the goods and sign for the delivery. Assistance with unloading may be required.

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