Full Cost Breakdown (pricing is up to 2 years old, sometimes delivery is included, and sourcing from a couple of different places - your mileage may vary!):
Base, floor: £595.76
- 2x Tarps £19.98
- 1x Bulk Bag MOT Hardcore £57.60
- 5x 1x6" 3.6m Gravel Boards £19.20
- 1x 2x2" 4.8m Treated timber for Gravel Board posts £4.76
- 10x 150x500mm PVC Vent Pipe (Concrete Piers) £29.39
- 1x 25kg bag General Purpose Cement (Concrete Piers) £3.83
- 2x 25kg bag Sand (Concrete Piers) £4.06
- 4x 25kg bag Ballast (Concrete Piers) £8.11
- 1x 600g bag of concrete fibres (Concrete Piers) £6.50
- 8x 600mm Rolled Edge Restraint Strap Twist (Concrete Piers to Joists) £11.81
- 8x 50x150mm 3m C16 Treated (Joists) £57.60
- 3x 50x150mm 4.2m C16 Treated (Joists) £30.24
- 12x 50mm 305mm Leg Joist Hangers (Joists) £14.32
- 113 linear metres 25x38mm Battens (Insulation) £40.68 (also used for bulking out studwork to fit insulation)
- 6x 1.2x2.4m sheet 50mm Polystyrene (Insulation) £59.99
- 5x 1.2x2.4m sheet 18mm Shuttering Ply (Floor) £112.50
(there was also some weed fabric under the hardcore, but I had that anyway)
That got me to this point:
Studwork, insulation: £670.45
- 4x 75x100mm 4m C16 (Front/Rear Floor/Top Plates) £43.20
- 16x 75x100mm 2.4m C16 (Front/Rear Studs, Noggins) £103.68
- 63 linear metres 47x100mm C16 (Side Floor/Top Plates, Side Studs, Noggins) £100.23
- 2x 47x150mm C16 (Door Lintel) £11.52
- 18x 1.2x2.4m sheet 9mm OSB3 (Sheathing) £183.17
- 40x 0.6x1.2m sheet 120mm Kingspan equivalent £184.96 (from Seconds & Co - absolute bargain!)
- 1x 1x50m Vent 3 light (Breather Membrane) £29.99
- Expanding foam, cleaner (insulation gap filler!) £13.70
Roof: £645.45
- 9x 47x145mm 4.8m timber (Rafters/Purlins) £133.68
- 1x 50x150mm 3.6m timber (Purlins)
- 8x 50x100mm 2.4m timber (Curb)
- 4x 25x150mm 2.4m timber (Front/Rear Fascia) £56.46 (for this and the 2 above)
- 8x 600mm Rolled Edge Restraint Strap Twist (joining Rafters to Top Plates) £11.81
- 5x 1.2x2.4m 18mm Shuttering Ply (Roof) £112.50
- 1x 5L Firestone Water Based Adhesive (EPDM) £56.50
- 1x 2.5L Firestone Bonding Adhesive (EPDM edges) £39.90
- 5.4x4.95m Firestorm Premium Membrane (EPDM - 500mm overlap on sides) £234.60 (note this stuff is heavy!)
That got me here:
Glazing: £289.30
- 4 Double-glazed windows/sealed units, (incl replacement unit for one I broke!) £82.00 (from Facebook)
- Glazing Packers £12.99
- Double-glazed French Doors £120.00 (from Gumtree)
- Timber (to make Window Frames for long sealed units) £55.00
- UPVC window glazing tape £5.33
- 150mm x 10m Window/Door flashing Tape £13.98 (I think I bought the wrong stuff though)
Getting there:
Cladding: £1,011.97
- 110 linear metres 19x140 British Western Red Cedar, Grad A/B pack (Cladding!) £554.40 (from Code 6 Timber)
- 20 linear metres British Western Red Cedar (Door/Window Trim) £57.60 (from Code 6 Timber)
- 12 linear metres British Western Red Cedar (Corner Posts) £63.00 (from Code 6 Timber)
- Delivery of the above £102.00 (from Code 6 Timber)
- 122 linear metres 25x38mm Battens (Battens/Counter Battens) £54.82
- 600 Stainless Steel Torx 3.5mm x 45mm Screws (for Cladding) £37.10
- 200 Stainless Steel Torx 4.0mm x 50mm Screws (for Battens) £28.53
- 2x 2.5L Treatex Cedar Oil £102.53
- 1x 85mm x 30m Insect Mesh £11.99
Nearly...
Electrics: £1,018.58
- 50m of 10mm 3-core SWA (Armoured Cable) £295.00
- 12.7mm² Diameter SWA Cable Cleats (for Armoured Cable) £4.80
- BG 10 Way Metal Dual Split Consumer Unit c/w 1 x 80A & 1 x 63A RCD's c/w 10 MCB's £68.40
- 6242Y 6.0mm² Grey Twin & Earth Cable 50m Reel (Power) £61.20
- 6242Y 1.0mm² Grey Twin & Earth Cable 50m Reel (Lighting) £16.20
- 13 Amp 2 Gang Switched Metalclad Socket c/w 2xUSB sockets (with surface box) £22.74
- 13 Amp 2 Gang Switched Metalclad Socket (with surface box) £52.67
- 2 Gang 2 Way Metalclad Switch (Light Switch) £4.79
- 13A 2 Gang DP Switched Outdoor Socket - IP66 £15.54
- 6w LED Fire Rated Downlight - Daylight (Exterior Lighting) £40.80
- Brushed Chrome Bezel for LTCD6 LED Downlight (Exterior Lighting) £4.56
- Infinity 30w PIR Motion Sensor LED Floodlight (Exterior Lighting) £31.42
- 600x600 40W LED Panel Light (Interior Lighting) £51.60
- Mounting Frame for LED Panel Light (Interior Lighting) £36.00
- 70cm/90W Tube heater £49.49
- 2 ft guard (for Heaters) £38.38
- Electrician: install new fuse board, wiring all new circuits; supplied 4 x 20a MCB fuses; wire in 10mm, 3-core SWA cable into main fuse board in house; supplied 50a MCB fuse (Labour/Parts) £225.00
There were some extra bits and pieces, small amounts of timber, tools, guttering, etc. but I don't have a breakdown of them.
Physiotherapy for a bad back, caused by lifting the EPDM onto the roof myself, is also excluded! :shock:
Grand total of £4,231.50
Given that I saw similarly sized garden offices available on EBay for £12K+, sometimes without groundworks/base, little insulation or only basic electrics, I think that's not bad!
