The Journey of a Garden Annexe

Garden Annexe Pitched Roof

A Garden Annexe

The Starting Point

Site clearance and levelling.

The JointKit system does not require concrete foundations or bases, but uses a ground support system based on the established SureGreen paver products.

The hydraulic lift of a trolley jack enables the frame to be raised in a controlled way to get the frame members exactly level.

From the highest point in the centre back the height of each joint was established. Each of the joints of the base frame have slightly differing heights off their ground support slab.

This demonstrates another advantage of the JointKit system, that a totally levelled site is not essential.

Complete Upper and Lower Frames and Floor Joists

Once the base was level, the vertical pillars and the top ring were bolted into place and the floor joists assembled into the frame using 400mm centres.

Finally 100mm insulation was fitted between the floor joists.

The lower and upper rings were constructed with the JKlam process which the joints are designed to accommodate, using 18mm birch ply flitch plates 5mm less than the depth of the beams.

The ply flitch plates can be seen in the photo on the right and were glued and bolted between two lengths of treated timber.

In the bottom frame 145 x 45mm timber was used while in the top frame the flitch plates were glued and bolted between 195 x 45mm timber to provide a room with a clear span of 4.8m.

Fitting the Roof

With the insulation the floor was fitted over the joists. The flooring was specified as moisture resistant, but like any chipboard product doesn’t take too kindly to being soaked.

Once the roof is on the building can be made watertight and the studwork for the external walls erected. In this instance the studwork was built off the floor.

The fall to the roof was created by using firring pieces fitted to the tops of the rafters. Lifting 18mm OSB  onto the roof rafters was interesting on such a sloping site(!). The roof boards were quickly fitted and the initial waterproof layer installed.

Erect the External Wall Studwork

While erecting the upper frame the clients considered that the mass of the building was too great, and decided to reduce the height by cutting down the vertical pillars by 150mm. This still left 2.3m internal ceiling height.

This highlights the flexibility of the JointKit solution and the late change was easily accommodated.

The floor now provided a flat surface to work off and the building was protected by tarpaulins from the worst of the weather allowing the external wall studwork to be erected. The timber was 145 x 45mm to allow for maximum insulation.

The roof was then completed by fixing the made-to- measure rubber roofing.

Finish Roof, Prepare for Final Cladding

The first task was to insulate the roof prior to the final item, the rubber fitted roof cover.  Shown is the 100mm insulation being  fitted  into place,  followed by the rubber roofing material.

The building was then clad in 11mm OSB boarding, followed by the vapour barrier membrane.

Finally, the doors and windows were installed. All that remains outside is to fit the larch cladding.

This is the final stage of making the building watertight so that the internal fitting out can begin.

This also marks the end of the JointKit phase, with internal fitting out of the completed shell able to start.

Customer Testimonial – Garden Annexe

“We discovered Joint Kit through their stand at the National Self Build and Renovation Centre in Swindon. It immediately struck us that this was the system to use for our garden room as we had never constructed anything like this before. Peter was able to assist in finalising the design, drawings and calculations. He then provided some initial tuition, along with an intervention at a critical point, which gave us the confidence to build our garden room without recourse to a professional joiner”. 

Contact Us

Phone : 01892 669971

Mobile : 07887 998033

JointKit Ltd, 

4 Clock House Court,

Beacon Road,


East Sussex,