TRJ CONSTRUCTION · PROJECT PORTFOLIO
Waltham Cross Granny Annexe
An 8 × 5 m SIP garden annexe in Waltham Cross, with a lounge/gym area, separate office, kitchenette, shower room and LG heating and cooling.
THE PROJECT
From an idea
to a real space.
An 8 × 5 m SIP garden annexe in Waltham Cross, with a lounge/gym area, separate office, kitchenette, shower room and LG heating and cooling.
TRJ Construction built this bespoke garden annexe in Waltham Cross, Hertfordshire, creating a flexible space for work, relaxation and everyday use.
Size and layout
The signed drawing shows an 8 × 5 m building, giving an overall external footprint of 40 m². The layout combines a lounge/gym area with a kitchenette, a separate office and a shower room.
SIP structure and exterior
SIP panels form the floor, walls and roof. The order specifies screw-pile foundations with an increased-depth allowance, subject to the soil report, engineering and building-control requirements. Supporting beams were specified over the larger openings and for the main roof.
Vertical black composite cladding finishes the frontage. Fire-retardant boards with anthracite grey RAL 7016 render cover the sides and rear, with a rendered front canopy. The external build-up includes a membrane, battens and wall ventilation. An EPDM roof covering and black round guttering complete the roof.
Entrance and glazing
The composite entrance door measures 900 × 2,100 mm and is black inside and outside. The window specification includes a 1,800 × 1,050 mm front casement with two openers, two 1,200 × 1,050 mm casements and a 500 × 500 mm obscure-glass top-hung shower-room window. The main windows are black inside and outside; the shower-room window is white inside and black outside. Trickle vents, toughened glass and argon-filled glazing were specified.
Kitchenette and shower room
The order includes an allowance for kitchenette units and installation, with the final design and units to be agreed with the customer. The separate shower room includes a shower enclosure, WC and basin, extractor fan, towel radiator and surface-mounted LED light.
Interior, heating and services
The interior is plasterboarded and skimmed, with Howdens laminate flooring, white skirting and Howdens four-panel internal doors. The order allows for the customer’s final paint colour, applied by TRJ.
A 2.5 kW Wi-Fi-enabled LG inverter air conditioning unit provides heating and cooling, supported by a 1 kW Haverland wall radiator. The electrical specification includes seven double sockets, fourteen internal downlights, five exterior downlights, a separate shower-room LED light, additional ceiling roses and a fire alarm. An independent consumer unit with RCBO and surge protection, water and electricity connections, an outside tap and an exterior socket were included. Gravity drainage was the intended arrangement, with any pump requirement dependent on site checks.
CUSTOMER REVIEW · 5 STARS
Fabulous Garden Annexe with high level finish
“Before I hired TRJ Construction, I spoke to and reviewed many companies for my Garden Annexe. Many of them were on shaky financial grounds and used 3rd party postal and tel. numbers so be wary if you go elsewhere. Costi puts his name and his address to his work and that's because he's rightly proud of the end result. I highly recommend TRJ. Great skill level, very flexible and adaptable to my strange requests and a high level of professionalism. I'm delighted with the final finish.”
RKK · ★★★★★ · 12 September 2026
REAL PROJECT PHOTOGRAPHS
A closer look
at the build.
Explore photographs from this project using the rotating gallery. Use the arrows or pause the movement to study each view.
View the full photograph collection ↓Photograph 1 of 4 · Project photograph 1
THE PHOTOGRAPH COLLECTION
Details worth
a closer look.
Photographs recorded for this project. They may show different stages and views; the gallery is not a promise of a standard package.
View 34 more project photographs
YOUR NEXT PROJECT
Start with
your own brief.
Tell us how you want to use the space, where it will be built and which details you like from this project. We can discuss a layout and specification suited to your property.
Access, ground conditions, services, planning and building control requirements need to be assessed for your site. Dimensions, prices and timescales are agreed for the individual project.
