A Self-Build Garden Office: A Different Kind Of Project

I’ve always been into DIY. In the past, I’ve helped renovate houses, been handy with a paint brush and even tried my hand at a bit of carpentry.

The current house has also benefited from my DIY work as well, adding an ensuite wetroom shower room to a bedroom, painting, decorating, tiling and so on.

In the summer, the back garden, as small as it is, is a lovely place to be. We have a small garden laid to lawn, flower beds and a patio area.

Overall, it’s a pretty standard mid terraced house in a lovely part of Harrogate that we’ve injected a bit of love and attention into.

One area that was a bit of a disappointment for the back of the garden.

There was a boundary hedge separating the adjoining gardens that surround us, a shed (that I turned into a heaven for tools) and rough plants and vegetation.

It was a bit of an eye sore, especially with a neighbours breeze-block wall in full vision.

So I was thinking of ways to improve it.

At the same time, I found that working in the house was becoming a problem of sorts.

I never had a dedicated office so the usual distractions and inconveniences constantly plagued my ability to concentrate on my work.

So as we neared the end of 2016, I took the opportunity, whilst ‘work work’ was quiet, to challenge myself to build a dedicated garden office.

Off-the-shelf garden offices

In the summer, I was walking around a show and there were a few companies selling these garden offices and drawing in quite a crowd.

They had electric, were insulated, dry-walled inside and had a basic solid floor, then clad in this thin exterior log lap.

This was the best at the show and the prices started from £15k for a 12sqm room.

I spoke with one of the companies and they said the cost covers itself by the value it adds to the house, but I couldn’t see anyone spending a lot of time in one to be honest. You’d hear everything outside as they were very tin-can like.

I also looked at off-the-shelf solutions online that I could potentially invest in and build myself. For a DIY build, I’d be looking at a starting price of about £8.5k, then about £2k for the extra bits such as extra sockets, windows and so on.

I’d need to prepare the area. This included putting down footings, hiring an 8-yard skip, clearing the area, removing 6m x 4m of topsoil down about 12-15 inches and taking off time from work to do it, or bringing in help to do it all. This was a few more grand on top of the building price I’m sure.

Then I’d still need to furnish it, heat it and get electricity to it.

So I challenged myself to plan out a full self-build and build it all myself.

Planning Permission, Building Regulations and Permitted Development

As a DIYer, planning this build was pretty daunting for me.

I had no idea about whether I could even do it.

Do I need planning permission? Who do I ask? How long does it take? What does it cost? What if they say no? What if they said YES? What if……

Then there was building regulations.

After a lot of research, speaking with the local council, reading about “Permitted Development”, I was confident I had the green light to just push ahead and start planning for the “Big Build”.

In short, I had certain restrictions to fit within in order to bypass planning and build under Permitted Development. Things such as the max height of the building, proximity to the boundary, use of the building and so on.

Planning for me took weeks. I needed to pick the right materials, stick to a budget, get the best prices, bring in trades at the right time to help keep the schedule on track.

I bought squared paper, sharpened my pencil and started measuring up.

A quick overview of how I built my garden office

I didn’t compromise at all on materials, but I did seek out the best deals.

The Base

The base sits on about 10 8×8″ posts cut about 600mm into the ground and cemented in.

So as I write this, I’m now working in our new, high spec garden office.

The sub frame was 4×2″ c24 timber with Celotex insulation boards in between the joists.

Then OSB3 exterior boards on top.

Each joist cross section with the studs is supported on slabs to the ground to help make it solid.

I could park a tank on that base now. The other option was to set a solid concrete hard core base but it was extra cost to me and I didn’t need it with the way I built it.

The Walls

The walls are 4×2″, insulated, OSB3 boarded, house wrap membrane and log lap cladding. I was planning on Cedar cladding, this beautiful channeled stuff but it was working out about £1500 which I couldn’t justify, so I spent £300 on the log lap.

I haven’t clad the back as no one sees it so it’s just the OSB board which is coated in thick black bitumen that I painted on. I still need to fit guttering to the run off on the roof and maybe into a rain catcher.

The Roof

The roof is 6×2″ so I could fit insulation, downlighters and so on.

It makes the difference and makes the whole building solid.

The roof covering is a one piece EPDM rubber membrane from Rubber4Roofs.co.uk.

I didn’t need the extra plastic kerbs that stop the rain falling off the sides as I battoned the sides and laid the rubber around it.

It’s easy to lay and fit, just follow their videos.

I fitted the two skylights and the roof covering in a day, about 5 hours just before it got dark.

I opted not to show the rubber membrane on the sides and instead cover with cladding for a tidy finish, but you could as it looks nice.

The Doors

The doors were from Flying Doors.

They came in a few pieces and were pretty easy to fit, even just by me by myself.

I just left a 3mx2.1m aperture in the timber building and when they came, they fitted perfectly (thank heavens!).

I’m very much looking forward to welcoming in 2017 in a new, purpose built garden office – total bliss!


Inside I fitted electric underfloor heating that comes on a self adhesive roof.

You just roll it out to cover the floor area.

The next part is you need to set the heating in a kind of self leveling screed.

That cost almost the same as the underfloor heating and needed two separate layers to fully cover the heating mat.

Once both layers are down, you can’t see the underfloor heating and it’s both level and solid.

Then the rest is the plastering, skimming, painting, skirting, flooring (and breathable underlay) and the second fix electrics.

Materials and Costs

Cost wise, there’s a few things I needed to pay for that weren’t materials, such as the electrician, plasterers, nail gun hire, deliveries; that all added up.

I sourced tradesmen on Trusted People.

I got immediate responses and the best quotes, plus they could come and do the work immediately and when convenient for me.

I hired the nailgun from Jewsons and the time I had it I could have bought a new one. I couldn’t have done it without that nail gun.

Adding everything up, this cost less that the original pre-fab garden office I initially looked at on the Dunster House website.

Main materials included:

  • Timber and OSB3 boards
  • Insulation
  • Doors (double-glazed)
  • Skylights (triple-glazed)
  • Roof membrane and materials
  • Sparky, lights, switches, armoured cable
  • Plaster, materials, plasterboards, skimming

The rest makes up the rest of the cost.


In short, I worked on this project for about 6 weeks before I had it water tight.

I’m now about 9 weeks into it and I’m finished.

It’s finished now apart from a few finishing touches, a sofa delivery and no doubt a fancy rug.

So as I write this, I’m now working in our new, high spec garden office.

Image Gallery

Below are some images of “The Big Build”.

Gary Hartley

Gary Hartley is The Floating Frog. A seasoned freelance web designer with skills in UI/UX, CRO design, WordPress, branding, PSD-HTML conversions and more. Got a project you need to start or take to the next level? Please, get in touch!