Build your own insulated DIY garden office - self-build

Lists of materials, tools, timber and electrical gear needed for a self-build, DIY garden office or room that's insulated, cheap and outdoor

In 2017 I built a 6m x 5m garden office/room in a British garden. Here I’ll set out everything you need to do it yourself, including materials, tools and tips and tricks to keep things on track and to get the best bang for your buck/pound/euro.

The finished product is insulated (fibreglass and foil wrap around/above/below) for sound and heat, has been used as a cinema, trading room, yoga space, music room, gym and no doubt some others I’m forgetting. Having worked from home for well over a decade, coming up on two now, it far beats local office space, working inside the house or any other permutations I’ve tried over the years.

It cost me £3000 in materials and labour was basically me for 99% of the project, with help called in for holding up some framing, plasterboards and roof sheets. And electrics, of course, were done by a pro. It took 3 months of evenings and weekends flying solo, but I’m sure that anyone with a team and a well organised build could do it in a month, max.

At the end you’ll be able to grab the lists for timber purchases and prices, electrical items and click through to Amazon for the few key tools you’ll need.

Quick run-through of the process


  • Level ground. Leave at least 1m from boundary.
  • Cut ~30cm down to below frost line, add hardcore
  • Lay concrete blocks to support base
  • Layer of mortar + 2nd optional block to level them

Alternatives: piles, screw footings, anchors, concrete slab



  • 6x2in joists for strength, centres at 600mm for stiffness of floor
  • Pre-drill your timbers before screwing together
  • Galvanized/stainless screws, 100mm generally
  • Make sure everything’s square!
  • Remember to think of plasterboard/drywall on the inside of frame, so corners need an edge for boards
  • Centers at 600mm again


OSB outer

  • Wrap under frame to keep wind out (I used fibreglass insulation)
  • OR Celotex pressure-fit and membrane over top
  • 9mm/18mm OSB for shell outside of the frame
  • Tyvek or some kind of breathable weather membrane outside


Steel sheeting

  • Steel joist hangers on each end of the wall frame tops for secure fit
  • Close centres, 600mm again, for a strong roof and plenty for plasterboards to cling to
  • I used steel sheets, but you can also use EDPM rubber roofing for ease
  • If using steel, put silicon between overlaps to stop water creeping up
  • Overhang over deck if you make one - careful where you sit.


Front wall took twice as long as back 3 walls together

  • Front wall of frame can be built to house these
  • Double up on framing around doors and windows for strength


  • Needs planning early for socket locations, any distribution boards etc.
  • Electrician sign off at the very least!
  • Armoured cable in garden
  • Consider fibre between garden office and house, rare cases of blown switches over longer distances with voltage differences have happened


Insulation layers

  • Fibreglass cheapest, good R values and deadens sound
  • Rockwool cleaner to work with, better R value and sound deadening
  • Celotex good R, not as good on sound
  • Aluminium foil can seal the room and help further retain heat


Promax plastering!

  • Thinnest/smallest boards for ceiling (or cut the big ones in half!) - trust me on this
  • Scrim to bridge gaps and a whole heap of drywall screws
  • Promax plaster at £25 a tub - apply yourself! Needs a lot of energy but can be sanded back and finish is white


Weatherboard cladding

  • Nail on to battens screwed into OSB on outside
  • Weatherboard - cheapest, respectable
  • Steel cladding (back and sides) - cheap, strong
  • Cedar etc. - expensive but attractive (costs as much as rest of building)
  • Board and batten - painted, can be attractive


Laminate flooring

  • Laminate for a quick fit!
  • Skirting to tidy up, apply with no-nails adhesive or countersunk screws


Simple decking

  • 6m lengths, treated, screwed into front part of frame

Options for extras

I considered more fixtures like a stove, toilet and kitchen but the idea of running water and fire with young kids around made me put that on hold.

For heating I use an oil heater. On a timer for early morning, the office is warm when I get in and loses at most 1 degree C per hour (in snow/frost).

More to come

That’s a brief run through of what’s involved. I’ll add timber list, electrics/wiring list and tool list over time.

Thanks for reading.

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