How to build a garden office from scratch – on a budget

With many of us now working from home there’s an increasing need find a suitable space in which to work away from distractions and normal family life. Making a garden office in which we can switch off from the day to day home life to focus on work is important for a number of reasons. Whether it’s a segregated space away from the home or just some much needed extra space this guide should help you decide if building your own garden room is right for you. I’m targeting this post at those with some basic DIY skills and have a limited budget.

You won’t need to follow my instructions step by step as your space may differ from mine. Your design ideas, for example, might resemble a garden pod or garden office log cabin, but the principles are much the same with regards to the overall construction.

garden office build
Still a bit of work to do

Many of us have setup home offices within the house by moving around the general home layout and investing in suitable furniture but others are turning to their gardens to create that all important isolated, distraction free space. In this post I’d like to talk about how you can create your own garden office without breaking the bank. I’ll show you a step by step guide on how to build this with useful tips and common mistakes that can be avoided. If like me you’re on a budget then this will hopefully give you some great ideas to save money on both the construction and any tools that you might require.

Professionally installed garden offices of this sizes will cost on average £15,000 to £20,000 depending on where you live. You can get a beautiful garden office from garden rooms Essex if you have the budget available, but if not then I will show you how to achieve your own garden office by building it yourself for about £5000. In my build I am extending from an original shed I built a couple of years back. I will be showing you how I extended this structure and insulated the whole thing. The original structure cost me about £1200.

garden office build
It doesn’t have to look like a shed, if you’ve got the space 🙂

A DIY garden office isn’t for everyone and there are certain things you probably won’t be able to complete yourself, such as the electrics, but the structure itself can be achieved relatively easily with a few select tools, a little bit of research and some time. Time is an important factor here as you’ll need to dedicate about a full week in dry weather to complete the main structure. You’ll also probably need another two weeks to finish off the interior and aesthetic touches. I have completed my office in and around work. With this and the bad weather during winter it’s taken a little over two months so far.

If building your office from scratch isn’t quite right then you can always consider a flat pack office. All you’ll need is a suitable base and the rest is easy. Take a look at the great range of garden buildings from Robert Dyas.

Before you get started you’ll need to produce a plan and know a few basic building planning restrictions.

Planning permission

There are a few regulations in place that prevent you from building a structure that might affect your neighbours so be sure to check the UK planning portal before you get started.  Failing to follow these rules could mean that your lovely garden office will need to be taken down so make sure you stick within the guidelines. It’s also important to check your property deeds as there might be a covenant that prevents building works in specific areas.

Further more you can always check with your local planning department to double check these restrictions and get relevant guidance.  The following is a quick list of restrictions for outbuildings that are considered permitted developments.

  1. On designated land, outbuildings to the side of the house are not permitted development.
  2. Outbuildings are not permitted development within the grounds of a listed building.
  3. Outbuildings are not permitted development forward of the principal elevation of the original house.
    The term original house means the house as it was first built or as it stood on 1 July 1948 (if it was built before that date).
  4. Outbuildings and other additions must not exceed 50% of the total area of land around the original house. Sheds and all other outbuildings (see intro) and extensions to the original house must be included when calculating this 50% limit.
  5. To be permitted development, any new building must not itself be separate, self-contained, living accommodation and must not have a microwave antenna.
  6. Outbuildings must be single storey with a maximum eaves height of 2.5 metres and maximum overall height of 4 metres with a dual pitched roof, or 3 metres in any other case.
  7. If the outbuilding is within 2 metres of the property boundary the whole building should not exceed 2.5 metres in height.
  8. In national parks, the Broads, Areas of Outstanding Natural Beauty and World Heritage Sites the total area to be covered by any outbuildings more than 20 metres from ANY WALL of the house must not exceed 10 square metres to be permitted development.

Location planning

Grab a piece of paper, a tape measure and pop into the garden to start thinking about the ideal location for your new building. Consider the following factors:

  • Think about how level the ground is. Do you have a suitable flat space with which to start your construction or will you need to complete some ground works or build a suitable support frame?
  • Are there any obstructions such as trees, underground pipes or electrical wiring that need to be avoided or removed?
  • Which way will the office front and entrance face? Also, where does the sun rise and set as this might affect how you select the perfect location.
  • You’ll need access to all sides of the building so leaving a suitable gap between neighbouring boundaries is essential, not just for the construction but also for maintenance in the future. 50cm is probably the minimum.
  • Will you need a path to the front door? You might already have a suitable path but others might just have a lawn which isn’t ideal when going to and from the office as you’ll drag dirt and mud around, especially during the winter months.
  • Are you under a tree? This might not seem that relevant but my building is. During autumn the office is always covered in leaves from the trees which need to be removed. It’s not the best job and if not cleared can start to cause issues with the felt roofing.
  • Size. How big is your building going to be? Consider material sizes when planning your ideal space. Most sheet material comes in 2440x1220mm (8ft x 4ft) sizes so try and work to multiples of these sizes which will mean less cutting and less waste. Whilst it’s not essential to do this it will save you some time.
  • Electrics. How will you get power to your office. You’ll need a qualified electrician to install your electrics and costs can skyrocket the further you are away from the home. You’ll need armoured cable run between the house and your office which is expensive. It’ll need to be dug underground or fixed along a fence which can take up a lot of time.

Structural planning

Have a think about how you will construct your office including the roof, floor and wall designs. There are many different ways to achieve these so consider the following:

The floor & foundation

  • Plinth supports are the cheaper option and also provide slightly better water drainage. This option will however provide a void underneath your structure which allows vermin to nest and cold air to circulate which can affect thermal efficiency. This is the option I went for on my build due to time and budget restraints. I will talk you through this process below in my step by step guide.
  • Solid foundations will provide the most stable and long lasting support for your office but will also be the most expensive. Constructing this using concrete will provide a level and sturdy foundation with which to build on. You can watch this video to guide you through the process.
  • You may also wish to consider a patio base for your office which I built for a previous shed foundation. This is equally as effective as a concrete base but again is generally more expensive. You can read about this process in another post of mine here: Building a garden workshop

The walls

Structurally most walls will be the same but you will need to consider the type of insulation and cladding you prefer. An office without any insulation is going to be very cold in the winter months so think carefully about this stage. Consider one of the following or do your own research for the best insulation to use.

Insulation

For the insulation I decided to use Rockwool RWA45 (50mm) slabs because they offer both excellent thermal and acoustic properties. I wanted additional soundproofing as I use half of my office as a workshop for cutting and sanding my furniture. Thermal conductivity: 0.035 W/mK 

For extra acoustic soundproofing consider going for the Rockwool RW3 or RW5 but this application is best suited for sound/recording studios, not general office use.

For general thermal insulation consider:

  • Kingspan TP10 Insulation Board (2400x1220x50mm) – Expensive but these large boards are great thermal insulators, easy to cut and provide good coverage for larger wall cavities. ~£45 per board. Thermal conductivity: 0.022 W/mK
  • Kay Metzeler General Purpose Polystyrene EPS70 – (2400x1200x50mm) – The cheapest option but not a great acoustic insulator, and it’s not fire resistant. ~£16 per board. Thermal Conductivity: 0.038 W/mK
W/mK explained (The U-value)

The U-Value is the flow of heat through the building materials used to make up the building itself. This includes bricks, flooring, roofing and windows. The value is measured in watts at the rate of heat transfer. The lower the U-Value of a material the better insulator it will be.

Cladding

For the exterior walls you will again have a choice of many different types of cladding. Most will provide adequate protection from the elements so it’s really down to your preference on aesthetics.

On my first structure I used a log lap cladding as I like the look of it and it was a reasonably thick material (at 22mm). For the second part of the structure I decided to go for a slightly cheaper shiplap cladding and now prefer the look of this.

I purchased the shiplap cladding from B&Q. It has great ratings and is easy to work with. The boards come in 3m lengths and are 119mm x 14.5mm. This is a little thinner than the loglap but also a bit cheaper at £5.27 per board.

You can find the 22mm thick loglap cladding here

Here is the 38mm loglap cladding which is great for that little bit extra thermal and acoustic insulation.

The roof

What style roof are you looking to create? They all pretty much provide the same function but some may be easier to construct and maintain. I went for a dual pitched roof purely because I like the look of it.

Flat roof – This is probably the simplest construction and you’ll benefit from only requiring one side of guttering. You’ll need to do your own research if you want to build this style but this video is a good starting point.

Apex roof or dual pitched roof – You can follow my instruction below for this style roof. It’s not overly complicated and can be built in two different ways. Either with the rafters running longways, similar to that of the flat roof or upwards to the apex like my original design.

Consider how much over hang you want on the roof. A roof with a decent size overhang will provide more protection from rain than a small overhang. My roof overhangs on each edge by about 30cm which is a little more than most sheds but it protects the walls from the elements.

Materials

I’ll list all the materials I have used on my build but you may want to consider upgrading or downgrading some of these to suit your own requirements. For example, I went for a more expensive type of insulation that also acts as a sound barrier. I also selected a cheaper type of waterproof breathable membrane which you may wish to upgrade.

Why use a breathable membrane? A breathable membrane will offer weatherproofing against the elements whilst also allowing air to move freely between the barrier. This is required to prevent moisture build up within the structure, which causes damp and mould to grow, which we don’t want to happen.

Using reclaimed materials is always a good choice where possible to help bring down costs but finding the right ones can be challenging. Search Google for local reclaimed wood suppliers and visit them to see what you can get. Search Google for ‘wood recycling project’ to find your nearest recycling business. Here is the Bristol branch: https://www.bwrp.org.uk/

Materials List

These are the materials and costs for my project which was an extension of my original self built shed. I also insulated and boarded the existing shed/office so please make sure to complete your own calculations based on the size of your build. I’ve included all the links to where you can find the materials.

MaterialSizeApplicationQuantityCost
18mm OSB 3 board2440x1220mmFlooring4£82
9mm OSB 3 board2440x1220mmWalls and roof20£310
CLS studwork 2.4m38x63x2400mmFlooring, walls & roof40£100
CLS studwork 3m38x63x3000mmFlooring & walls8£54
Upvc french doors1190x2090mmDoors1£480
C16 stick timber95x45x3600mmRoof ridge1£9.39
C16 stick timber70x45x3600mmRoof supports5£55.25
Plasterboard screws3.5x35mmSecure plasterboard1000£6.54
3m Shiplap cladding119×14.5mmCladding outer wall44£231.88
12.5mm Plasterboard2440x1220mmInternal walls25£190
Rockwool RWA45 insulation1200x600mmWalls & roof insulation8 packs£259.94
80mm screws5mm x 80mmStud walls & flooring300£12.57
Water vapour barrier4m x 25mWalls and roof1£15
90mm posts90x90mmx2.4mCorner posts2£30.60
Felt roofing (green)10m x 1mRoofing2£40
TOTAL (so far)£1877.17

The above completes the build to date but I intend on adding a window to the left hand wall and also want to extend the space further to have an L shape office. I will cover these details another time.

Save more money with Cashback

I always use a cashback site like Top Cashback when buying on line. It’s a great way to save money on builds like this and all your everyday shopping needs. My wife and I have generated over £2200 in a couple of years so it’s worth having a look at before you start buying materials and tools.

I’ve added the Top Cashback browser extension so that I don’t miss any potential cashback offers. It works on both Chrome and Firefox.

top cashback

Tools

If you’re not fully tooled up yet then consider the following to make this job both quicker and easier. I’ve been buying recently from Tooled Up due to their competitive prices and extensive stock listing. They also have great cashback offers.

  • Combi drill driver and impact driver – Make quick work of screws and pilot holes with these two drills.
  • Mitre saw – The 90 degree saw cut made easy with this essential tool.
  • Circular saw – Ideal for cutting sheet materials.
  • Jigsaw – handy for cutting complicated shapes out of sheet materials.
  • Tape measure – 5m should be plenty for this job but go for 8m if your build is bigger.
  • Panel saw – Cut the tops off the corner posts.
  • Orbital sander – consider a sander to clean off rough edges
  • Sealant gun – sealant and caulking
  • General tool kit – Hammers, screwdrivers, drill bits and more. You’ll likely need a general tool kit to help you through this build.

It’s worth checking Tooled Up clearance ranges as they often have some great deals and you can save a fair bit getting end of line products.

Step by step guide

Ground works

Let’s kick things off with the ground works for your garden office. I already had a reasonably flat surface with which to start the build. As mentioned above this office is to be an extension of my original DIY shed which I will also be insulating and boarding inside.

garden office build
Levelling the ground and placing the support slabs
how to build your own shed - base
The original space before I made the first structure

View my original post to see a full guide to building a base.

I used some left over type 1 MOT to provide a tough base with which to build on. I then laid out the 4 corner plinths to my required dimensions. I was a little restricted here due to an existing structure so the overall dimensions for the base were 3250mm x 3000mm.

The floor frame

Using one of the 3m C16 timber pieces I was able to dig out the ground and level the slabs using a large 1.8m spirit level.

garden office build
Screwing the frame together

As you can see I’ve built the frame directly off the original structure. Using 80mm screws to join the frame pieces together. Drilling pilot holes before inserting the screws. The spacing between each timber support is in intervals of 610mm which is half of the 1220mm wide 18mm MDF boards that will be fitted on top.

To protect the outer frame from water and possible rotting I wrapped each edge with the plastic sheeting. I simply stapled the plastic sheet to the wood with a staple gun.

It’s also at this point I made sure the frame was squared off, with each corner a right angle, by measuring diagonally (corner to opposite corner) and gently adjusting the frame until both lengths were exactly the same.

garden office build

It’s now time to add some more supports to ensure there is sufficient strength for the floor. You can see I’ve added additional slabs so the floor doesn’t flex when additional weight is added. This required further digging and shifting of the MOT.

garden office build
Additional support for the frame

With the correct measurements the 2440x1220mm 18mm thick MDF boards should fit neatly over this frame with suitable support. Make sure there is enough space so that the boards can be screwed into the frame alongside the other boards. Secure the boards down using 40mm (4mm wide) screws.

garden office build

To finish off the base and floor I added another full board and cut the remaining two to fit using a circular saw. If you have a good square base everything should line up nicely down the edges. I made sure the boards go right up to the edge of the frame because I’ll cover the lot with some waterproof material. This will protect the flooring from being breached by water and causing it to rot.

Insulating the floor

You might want to consider insulating the floor before going any further with your garden office. I decided not to insulate at this point due to my budget but I will add insulation afterwards. There is a great video below which demonstrates insulating the floor but you will need to consider this early on in the build process.

I have decided to insulate the floor retrospectively using something like this cork acoustic and thermal insulation roll. It won’t be as effective as the insulation in the above video and it will raise the floor by about 10mm but I’m happy with this.

The walls and roof

Building the wall frame is very straight forwards. I started by adding the 90mm posts to the corner and measuring the distance in-between. I then built another frame with the CLS timber measuring 2m tall and the correct length of the building. Struts were added in 600mm intervals to allow for the insulation to fit snuggly between. Nogins were added 1200mm up from the base timber. (again for the insulation to fit nicely.)

garden office build wall

I made two of these the same. For the original structure I made the rear wall the same (to the correct width) and added the roof supports afterwards.

I haven’t added any windows to my office yet but it’s at this point you should probably think about building a suitable frame if you’d like to add one (or more). They can be added after but it’s a little more difficult. Try follow this structure if you intend to add a window.

garden office build wall
Windowed wall frame

You can find cheap windows on Facebook Marketplace or Gumtree, especially if you’re not fussed with the size. If you want something a little more specific try Wickes or B&Q for windows. B&Q have matching grey windows here.

The wall frames were then screwed into the base using 80mm screws and screwed into the corner posts using 60mm screws.

To add additional strength to the structure it’s a good idea to insert diagonal supports on some of the frame. This will prevent the frame from leaning should you ever add weight to the interior walls.

garden office build

I then measured out my door frame and cut the lengths of CLS to fit. The above picture demonstrates how I’ve constructed this. My door measured 1190mm x 2090mm but I made sure the frame was about 3-5mm wider than this. This allowed me enough space to slide the door into the frame easily. The door comes with packers which fill any space and allows you to square up the door. It is crucial that the door is perfectly square or it won’t open and close properly. I took my time on this part to ensure the timber frame was spot on.

Here is a cross section diagram of the correct wall construction. You can also swap the 9mm OSB for 18mm OSB for a stronger more insulated wall.

garden office build wall cut through

The roof

For this I opted for a dual pitched roof supported by lengthways rafters running from end to end. Different to my original structure. Move the slider below to see the differences.

Both roof structures provide enough strength to take my full body weight. This is important as I needed to get on the roof to fit the felt. Visit my original post for the construction of the right hand image.

I used the five 70x45mm C16 for the roof rafters. These were all screwed in using 80mm screws. As you can see above I used the door frame to support the mid rafters. The side walls were used to support the outer rafters and a purlin at one end was used to support the rest.

Here is a picture of the original building as I started to add the roofing OSB boards.

how to build your own shed - the roof
Original building

Between the two I would say the original roof was stronger. The next job was to add the roof boards to the extension. This was a simple cut to length and lift onto the roof. I cut the boards using a circular saw then used the ladders to screw each board into place using 35mm screws.

garden office build

Once I had all the 9mm OSB 3 boards fixed I decided to add a waterproof barrier. This would protect the structure whilst I finished things off. I used the same plastic sheeting as before. The roof will eventually be finished off with felt.

garden office build

My next job was to remove all the cladding from the original structure and add 9mm OSB 3 boards which will help strengthen and insulate the building. I cut the boards to size with my circular saw and screwed them onto the original CLS timber frame. I then covered the boards with a waterproof plastic sheet (recommended you use a breathable membrane) and then added the cladding back over this.

I skipped this stage to save a little money but ideally you should fit 23mm x 44mm battens over the membrane, that run from the top of the wall to the ground. The cladding is then secured to these battens, also known as furring strips. These would be fitted about 500mm apart and will allow air to circulate between the water barrier and the cladding.

I then continued this process around the rest of the new extension.

garden office build

In the above image you can see that I’ve started to add the frame for the door.

I then returned to the original structure to complete the insulation and thicker walls. I started by removing all the cladding from one wall. I then cut and fitted the 9mm OSB 3 boards to the outer side of the wall. As you can see the space is quite busy with my hoardings so I had to work around all this.

garden office build

I then sealed any gaps with silicone sealant to create a water and air tight barrier. Another layer of waterproof plastic sheeting was then added over the top of this. (on the outside). I could then add the cladding back on top of this.

garden office build

Here I have returned to the original structure as sealed any gaps with silicone sealant. I wanted the structure to be as sound proof as possible and this would help. Whilst I am taking every care to seal the structure I’m also mindful that there needs to be some airflow through the building to prevent moisture build up which leads to damp and mould growth. For this reason I will be adding a window with air vents at a later date.

garden office build

With the exterior wall completed I turned my attention to the interior.

The interior

I started to think about where I wanted power in the garden office. I used 2.5mm twin & earth cable for the sockets and 1.5mm twin and earth for the lighting. I also purchased a small 2 way garage consumer unit to run the power. I’m only running the cable but I will have an electrician in to wire and test everything.

Cables can be fed through the CLS timber frames. Simply drill holes and feed the cable. Try following a cable diagram like this for some help. You can wire everything up but it will all need to be signed off by a qualified electrician before you start using it.

garden office build

I’ve also started adding the insulation at this point. Most of the insulation sheets fit directly into the gaps but for some I had to cut with a knife to fit.

garden office build electrics

The wiring has been folded in the locations I intend to add sockets. Here is a shopping list for the electricals.

ItemSizeQuantityCost
3 core 2.5mm (twin and earth) (sockets)50m1£28
Sockets – double 13A switchedNA5£22
35mm Double Pattress box35mm5£6
63A 4 way Consumer unitNA1£37
3 core 1.5mm² Twin & earth cable (lighting)25m1£12.50
10A 1 way White Single Light SwitchNA1£2
White Batten strip light 43W 4400lm1.2m2£72
TOTAL£179.50

I then returned to the new part of the structure to start adding the insulation.

garden office build insulation

Again this was a simple push in to fill the gaps. Some pieces were cut to fit with a Stanley knife. The noggins are located 120cm up so that one insulation board fit nicely. The CLS timber is 63mm thick and the insulation is 50mm thick which is fine. It’s good to have a small air gap in the wall as this traps warm air and limits sound movement between the layers.

I’m now adding the plasterboard directly over the timber frame. Ideally you should add another layer of 9mm oSB 3 boards before this but I am skipping this part to save money. These should be fitted using plasterboard screws only and screwed into the CLS timber. Boards can easily be cut to shape using a sharp Stanley knife on one face and then snapping the board. I used some of the CLS timber to cut long straight lines. Here is a quick video to demonstrate.

The ceiling was the tricky part. To make things easier ensure the insulation fits snuggly into the gaps and it shouldn’t fall back out. Failing this you can use some masking tape to hold them in whilst you add the plasterboard on top.

Because I worked on my garden office on my own it was very difficult lifting an entire piece of plasterboard onto the ceiling and screwing it in so I either cut the boards a bit smaller or I constructed a T shaped holding device out of the CLS timber. This allowed me to hold the plasterboard to the ceiling hands free whilst I added all the screws.

With all the plasterboards securely fixed in place I then when back and started filling all the gaps and holes. It’s a good idea to go over all the gaps with a jointing tape and fill holes with a standard wall filler.

garden office build

This takes you up to my current progress on the build.

I will be continuing this garden office over the next couple of months so check in shortly for the finishing touches. Thanks for reading so far.

My next jobs will be taken on when the weather warms up a bit. I hope to have things finished off by April 2021. Here is the remaining job list:

  • Install window or two
  • Insulate the floor
  • Complete the insulation and plasterboard inside
  • Complete electrics and have them signed off by a qualified electrician
  • Install guttering and water collection point
  • Paint inside
  • build furniture

Update May 2021

I’ve made a little progress but not as much as I’d like. I’ve added the felt roof, completed the cladding, added facia boards and painted the outside. Here’s a couple of pics.

garden office build
garden office build

Have a look at some of my other home DIY projects:

How to build a garden office from scratch - on a budget

One comment

  1. Thanks very much for posting this guide, exactly what I’m looking for in terms of building a workshop to replace an old shed that is beyond repair. I was considering block built, but this has convinced me that a decent timber frame structure should be ample.

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