TRJ CONSTRUCTION · YOUR BUILDING SPECIFICATION

What’s included
in your SIP building.

Understand the standard specification, choose the extras that matter to you, and agree a clear scope for your garden room or granny annexe.

Discuss your specification ↗
Thermowood-clad garden building with glazed doors

Thermowood-clad garden building with glazed doors

THE STANDARD STARTING POINT

Eight parts of a finished SIP building.

From the support below the floor to the final decoration, see what the standard specification covers.

Screw piles installed for a TRJ garden building foundation

01 · STANDARD SPECIFICATION

Screw pile foundations

Screw piles form our standard starting point for garden-building foundations. They can reduce excavation and concrete use where ground conditions and the structural design allow.

  • Standard specification describes 1,250mm-deep screw piles
  • Ground conditions and building-control requirements can call for deeper piles, up to 2,550mm in the stated options
  • A different system, such as a reinforced raft, may be priced as an extra

The site assessment determines the actual depth and system. Confirm groundworks and any extra costs in your quotation.

Foundation guidance ↗
SIP floor and wall panels during assembly

02 · STANDARD SPECIFICATION

Foam-injected SIP panel kit

The base, walls and roof are constructed using Structural Insulated Panels: a rigid insulation core between structural OSB board faces.

  • SIP panels for the floor, walls and roof
  • Foam-injected insulation within the panels
  • Panel connections and sealing coordinated with the design

The panels combine structure and insulation. The complete specification confirms thicknesses, openings and thermal performance.

Explore SIP construction ↗
Thermowood-clad garden building with glazed doors

03 · STANDARD SPECIFICATION

Standard external cladding

The standard external finish combines Thermowood at the front with fire-retardant boards to the sides and rear.

  • Thermowood timber to the front elevation
  • Fire-retardant boards to the sides and back
  • Side and rear boards painted Anthracite Grey, RAL 7016

Alternative finishes are available as upgrades and are agreed for your project.

Compare cladding options ↗
Flat-roof garden building with rooflight and external cladding

04 · STANDARD SPECIFICATION

EPDM flat roof

The standard flat-roof specification uses an EPDM membrane, black edge trims and a black gutter at the rear.

  • EPDM roof membrane
  • Black edge trim and rear gutter
  • A 350mm front canopy in the stated standard design

The stated membrane specification offers a 25-year warranty and expected service life over 60 years. Applicable warranty terms, product choice and installation requirements are confirmed for your project.

See the roof construction ↗
Garden building with full-height French doors and glazing

05 · STANDARD SPECIFICATION

uPVC doors and glazing

Standard joinery uses uPVC French doors with full-height fixed glazing at the sides, or an agreed combination.

  • uPVC French doors and fixed glazed frames
  • White, black or Anthracite Grey colour options
  • Configuration agreed around the building layout

Door sizes, glazing and the final arrangement are set out in the quotation. Aluminium and bi-fold options are listed below.

Discuss doors and windows ↗
Consumer unit and LED downlights for a garden building

06 · STANDARD SPECIFICATION

Electrical installation

The standard electrical package includes a separate consumer unit with RCD protection and basic lighting and sockets.

  • Up to 10m of armoured supply cable
  • House connection where the existing supply point is accessible
  • Consumer unit inside the garden building
  • Basic sockets and internal/external LED downlights
  • White plastic fittings in the standard specification

The supply route and existing installation must be assessed. Longer cable runs, difficult access or additional electrical work are discussed and quoted individually.

Plan your electrical requirements ↗
Finished white interior walls and ceiling in a garden room

07 · STANDARD SPECIFICATION

Internal walls and ceiling

Walls and ceilings are plasterboard-lined and skimmed to provide a smooth finished interior.

  • Plasterboard lining to the walls and ceiling
  • Skimmed finish
  • Dulux Vinyl Matt in Pure Brilliant White

The agreed scope confirms decoration and any changes to the standard finish.

Explore our building services ↗
Laminate flooring in a completed garden building

08 · STANDARD SPECIFICATION

Laminate flooring and skirting

Standard flooring is Howdens laminate, finished with painted MDF skirting.

  • Howdens laminate flooring
  • 100mm MDF skirting
  • Dulux Pure Brilliant White satinwood finish to the skirting

Discuss the available colours and finishes when agreeing your specification.

Discuss your floor finish ↗

BUILD AROUND YOUR NEEDS

Optional extras. A specification that fits you.

Our buildings are bespoke in shape, size and configuration. These upgrades are discussed separately and added to the agreed quotation.

Timber-clad garden building exterior

OPTIONAL UPGRADE

Premium external cladding

Upgrade the exterior with Western Red Cedar, full K-Render or Cedral fibre cement. Discuss the appearance, maintenance and complete wall build-up for your chosen finish.

Explore cladding upgrades ↗
SIP extension with wide glazed doors

OPTIONAL UPGRADE

Aluminium doors and windows

Choose aluminium joinery or bi-fold doors for a different frame profile and opening arrangement. The glazing, thermal specification and door dimensions are agreed individually.

Discuss aluminium joinery ↗
Composite decking outside a completed garden building

OPTIONAL UPGRADE

Composite decking

Create a finished entrance or seating area with composite decking in a choice of colours. Guide prices start from £195 per sqm; the quotation confirms the design, supporting platform, site work and applicable VAT.

Plan your decking ↗
Wall-mounted air conditioning unit inside a garden room

OPTIONAL UPGRADE

Heating and air conditioning

LG inverter air conditioning with Wi-Fi control is one option for heating and cooling. The stated compressor warranty is up to 10 years, subject to the selected product and terms. Haverland electric wall radiators with an electronic thermostat are another option.

Explore heating and cooling ↗
Garden studio roof and rooflight viewed from above

OPTIONAL UPGRADE

Sedum roofs and rooflights

Sedum roof options can be discussed where the design or planning brief calls for them. Velux fixed or electric rooflights up to 1,500 × 1,500mm are stated options, subject to stock, roof design and structural suitability.

Discuss roofs and natural light ↗
Fitted annexe kitchen with cabinetry and appliances

OPTIONAL UPGRADE

Bespoke annexe kitchens

Plan a kitchenette or fitted kitchen around the annexe layout, storage and appliances. Howdens is our main supplier; the design is developed with you and the agreed kitchen specification is included in the quotation.

Explore annexe kitchens ↗
Completed shower room and bathroom fit-out

OPTIONAL UPGRADE

Shower rooms and toilets

Standard shower-room packages have a guide starting price of £7,000 including VAT. Deluxe options can be discussed. Product choices and installation requirements are confirmed for each project.

Explore shower-room options ↗

What can the shower-room package include?

  • Aqua panels or wall tiles within the shower enclosure
  • Aurora Stone 1,200 × 800 × 40mm rectangular shower tray
  • Milton 1,200mm sliding shower door
  • Neo Modern basin tap and waste
  • Valencia LH 1,100mm combination unit with basin and round toilet
  • Extractor fan and waterproof surface LED light
  • 450mm electric towel radiator with thermostat
  • Triton 8.5kW electric shower
  • Waterproof laminate flooring

The stated standard option includes the building-control fee and up to 10m of gravity drainage in standard soil conditions. The route, levels and scope are assessed individually. Items may change with stock availability; replacement choices are agreed with you.

FROM YOUR FIRST IDEA TO THE FINISH

How to order your garden building.

Start with the way you want to use the space. The design, site assessment and written specification turn that brief into a project.

  1. Initial consultation

    Discuss the intended use, approximate size, location and the features you would like.

  2. Site survey

    Assess access, ground levels, drainage, services and potential installation constraints.

  3. Design and planning

    Agree the layout, materials, openings and specification. Establish the planning route for your proposal.

  4. Approvals and building regulations

    Confirm applicable planning and building-control requirements. The proposed use and site affect what is needed.

  5. Panel preparation

    Prepare the SIP components and other agreed materials around the approved design.

  6. Installation

    Deliver and assemble the building on the specified foundations. The programme depends on the size, access and project scope.

  7. Finishing and handover

    Complete the agreed electrics, plumbing, flooring and decoration, then review the finished specification and relevant documentation.

See the construction process in detail ↗

Choose what your space will become.

A workspace, leisure room or independent living space starts with the right brief. These photographs show more examples from the original specification page.

Garden room bar and leisure interior
Timber-clad garden building with a pitched roof
Garden studio with wide folding doors
Explore completed projects ↗

Questions about your specification.

What is included in the standard SIP garden-building package?

The standard guide covers screw pile foundations, a SIP floor/wall/roof kit, specified external cladding, an EPDM flat roof, uPVC joinery, basic electrical installation, finished plasterboard walls and ceiling, and laminate flooring with skirting. Your quotation confirms the final scope.

Are kitchens and shower rooms included automatically?

Kitchens and shower rooms are listed as optional additions in this guide. Granny-annexe specifications may include them within an agreed package; check the individual quotation for facilities, products and connections.

Can ground conditions change the foundation price?

Yes. The standard starting point is screw piles, but the required depth or foundation system can change after assessment. Deeper piles, a raft or additional groundworks are discussed and priced for the site.

What electrical connection is included?

The stated standard package includes up to 10m of armoured cable and a house connection where the existing supply point is accessible, plus the building consumer unit, basic sockets and LED lighting. The existing supply and cable route must be assessed.

Can I change the doors, cladding or interior finishes?

Yes. The building is bespoke and upgrades can be discussed, including premium cladding, aluminium joinery, decking, heating/cooling, rooflights, kitchens and shower rooms. The quotation sets out the selected specification and price.

Let’s make the specification clear.

Tell us your postcode, intended use, approximate size and preferred finishes. We’ll discuss the standard package, upgrades and the requirements of your site.

Request your tailored quotation ↗07966 800519