budget garden room build

How to build the best budget insulated garden room

In this post I’m going to show you in detail how to build your own garden office for the least amount of money, whilst still making it as good (if not better) than a professionally built garden room. There are a few different ways to approach this project but I believe the following is the cheapest and most efficient method. When I say ‘efficient’, I mean this in two ways. Firstly, the most time effective construction method, and secondly, this building will be thermally efficient all year round.

Garden office BillyOh Kent finished

Cheap garden rooms are a great way to add space to your home, giving you somewhere you can work quietly without interruption. If like me you are on a budget then I hope my project will give you some inspiration to build your own. You’ll need a couple of weeks off work to complete the job but then you’ll have an extension to your home that will definitely add value, both to your lifestyle and to your property.

How much do garden offices cost?

Typically, a professionally built garden room measuring ~ 4m x 3m will cost in the region of £22,000. This includes the structure, insulation, house-quality doors and windows, electrical sockets, and lighting. My 4m x 3m insulated garden office with electrics cost me less than £6000. I don’t currently have house-quality doors and windows (just double glazing), but for about £3000 extra these could be added quite easily.

garden room build guide

As you can see, it’s quite easy to half the price of a garden room if you’re willing to build it yourself. I’ve written an in-depth guide on how to build your own garden office in another post. It includes a step-by-step guide to make things easier should you wish to try it yourself.

Whether you are looking to build a small garden office or a large garden room this post should give you a good idea of achieving it without spending a fortune.

How to build a cheap garden office or garden room

I don’t really like using the word ‘cheap’. It makes it sound as though this kind of building won’t last, or isn’t as good as an expensive building. That isn’t the case here. I prefer to call it a ‘cost effective’ garden room.

My insulated garden office is also known as a log cabin due to the style and construction method. Log cabins can make a great home office. The log cabin kit I purchased was easy to construct by myself and only took a total of 2 weeks to complete.

I’ve broken this article down into sections in an attempt to make it easier to follow.

Step one. The size of the garden office or room

First things first, you need to decide how big you want your office or room to be. The bigger you go the more expensive it will be. This post is based on my 4m x 3m room but this BillyOh garden room is available in a number of sizes up to 5.5m x 5m.

Start off by measuring your garden and working out what size building you can fit in the space. If you are building next to a neighbouring boundary try and leave at least a 50cm gap for building and maintenance access.

clearing garden for office
I have removed my old shed and am clearing space for the new office

There are certain building regulations you will need to stick to, to avoid lengthy and expensive planning applications. You can read these here if you are based in the UK. If you decide your garden room will go outside of these restrictions then you will need planning permission.

With the size now decided it’s time to think about the base.

Step two. Building the base

The base or foundation of your garden office is very important. It provides a level and secure footing for your building. The cheapest way to do this is to build a wooden frame using construction timber. You could also build a solid base using cement or paving slabs but this can be time consuming and might require heavy machinery.

base for garden office

My base was built using treated C24 construction timber (150x47mm). Footings were dug into the ground and fixed into place using Postcrete and additional support was added with some reclaimed breeze blocks. You can read the full guide here on my other post.

The base materials cost me roughly £250 from a local Travis Perkins which was very reasonable.

Step three. Electrics, part one

Now is a good time to think about your electric. You will need a qualified electrician for this part as it will need to be signed off. They will need to run an armoured cable from your house to the garden building. The cable will likely enter the structure from underneath which is why it’s good the get this ready before you start work on the main structure. Expect to pay about £400-£800 on this, depending on the location of your garden office.

garden office electrics
consumer unit for garden office

Step four. The main structure

For this part I purchased a garden office kit from Garden Buildings Direct. More specifically I purchased the Kent Garden Office 4m x 3m. There are lots of other prefabricated garden building companies out there but I decide to go with this one as I liked the style and most importantly the price. For only ~£3200 I purchased this building with the upgraded double glazing windows and doors, and 19mm flooring and roofing.

DIY garden office

This structure took me about 3 days to erect on my own. The instructions were pretty good and all the materials were included in the kit. These buildings don’t however include insulation, boarding or any of the internal electrical wiring. I will show you how to add these separately.

Step five. Finishing the exterior

I’ve added some decking around the front and one side of my building. It gives the building a nice finishing touch and makes the transition from outside to in much nicer. This cost another £140.

painting exterior of garden room

With the main structure and decking complete it’s important to protect all the wood with a good quality stain or paint. I used a decking stain and shed paint to finish mine but you can select whatever you prefer. My only advice here is not to miss this out. Get your wooden garden building protected as soon as possible.

garden office decking

Step six. How to insulate your garden office

The interior of you new building will get very cold in the winter without some insulation. It’s a good idea to insulate the floor, walls and ceiling to get the most efficient thermal protection.

insulate a garden office

I used a 25mm insulation board on the walls and ceiling and thermal underlay on the floor. All the boards were cut to size and carefully packed into a purpose built frame.

Electrics, part two

Now it’s time to complete the electrics. Hiring a qualified electrician to complete this is important. They will be able to add your desired number of sockets and lights and make sure everything is safe. Expect to spend between £300 and £600 for this work to be completed.

plasterboard interior garden office

With the electrics now in place you can return to insulating and boarding the interior. I used 12.5mm plasterboard to cover all the walls and hired a plasterer to skim them. The plasterer cost £250.


The floor was covered with thermal underlay and laminate flooring was installed. The ceiling had insulation boards fitted and finished with some softwood cladding.

For all the insulation, plasterboard, flooring and cladding I paid about £450.

Step seven. Finishing your garden room

The interior was then painted, some skirting added and finished with some furniture. The costs here will depend on your desired decor but expect to pay between £150 – £600 for all these finishing touches.

BillyOh Kent garden office interior

So there we have it. One fully functioning garden office or garden room that can be used all year round. Best of all, for a fraction of the cost of a professionally installed garden building.

Total cost for this self built garden office

Here is a breakdown of all the costs for each section of this build:

  • Base & decking – £390
  • Electrics – £1300
  • BillyOh Kent garden office – £3200
  • Interior (insulation, boarding, flooring, plasterer, etc.) – £700
  • Paint and wood stain – £110
  • Furniture – Not relevant for this post but something to consider in your build

Total cost for this garden office – £5700


I believe this is the cheapest way to build a garden office. But remember, a cheap garden office doesn’t have to be poor quality. My flat pack garden office (or prefab garden office) is the perfect way to build a very functional space for a fraction of the price. So, is this a cheap insulated garden office, or a low cost garden office? I prefer the later.

Even the smallest gardens can accommodate small garden rooms of some sort, you just might need to get a little creative with your planning and design. Finding the right building to suit your garden can be tricky but try one of these website for some of the best bargains around. They also offer free delivery!

Some of these suppliers also sell insulated garden rooms but they tend to be a little more expensive. To save the most money it’s best to do this yourself.

The good thing about the Kent garden office I purchased is that you can opt to have a storage unit on the side. This way you can have a garden office with a shed on the side.

With a little planning and thought you will have your garden home office up in no time. If you are looking to build your own garden office from scratch then take a look at mine here. It should give you some great ideas to achieve your very own bespoke garden room.

It’s also worth considering converting an existing summer house or shed into a garden office. Summer houses make great light spaces and can easily have insulation and power sockets added to them.

If you’re thinking of building an office in the garden then hopefully you have found this article useful. Take a look at some of my projects for some further garden office ideas:

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