How to Build a Garden Office From Scratch – On a Budget

In the era of widespread remote work, the demand for a dedicated workspace at home has intensified. Establishing a garden office has emerged as a solution to address distractions from daily life. This secluded workspace offers a focused environment, whether as an independent structure or a practical extension.

This guide is aimed at individuals with basic DIY skills and a modest budget. It offers insights into determining the viability of creating a garden office. Discover how I built my own garden office from scratch, providing firsthand experience and practical advice.

DIY Garden Office Designs

Whilst I’ve designed and built three garden offices over the past few years this article focuses on my budget garden office build and fitout, which cost around £4500. You can read all about my other two garden office builds in these articles:

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You can download the full step-by-step build instruction for the above garden room here.

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Now, I’ll jump straight into the build for this DIY budget garden office. This build covers a combination of my DIY shed which I extended and insulated to make this garden office.

Step-By-Step Guide for Building a Budget Garden Office

Ground Works

Let’s kick things off with the groundwork for your garden office. I already had a reasonably flat surface with which to start the build. If your surface isn’t flat, you may want to invest in some landscaping. As mentioned above, this office is to be an extension of my original DIY shed, which I will also be insulating and boarding inside.

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

I used some leftover 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 for the Garden Building

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.

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.

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.

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.

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 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 Garden Office Walls

Building the wall frame is very straightforward. 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 snugly between. Nogins were added 1200mm up from the base timber. (again for the insulation to fit nicely.)

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.

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 or a local glazing company.

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 frames. This will prevent the frame from leaning should you ever add weight to the interior walls.

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 allow 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.

Materials in order, starting from the inside:

1. Plasterboard
2. 9mm OSB or ply board
3. CLS timber frame
4. insulation
5. Breathable membrane
6. Furring strips
7. Cladding

To save money on my project I decided not to have the inner 9mm OSB/ply. I simply attached the plasterboard directly onto the CLS timber frame. This will save a reasonable amount of money but reduces the thermal properties of the structure.

The Garden Room 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.

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.

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.

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, which 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.

In the above image, you can see that I’ve started to add the frame for the door, which I purchased here on Wickes. It was the cheapest double-glazed exterior door I could find at the time.

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.

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.

Here I have returned to the original structure and sealed any gaps with silicone sealant. I wanted the structure to be as soundproof 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.

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

The Garden Office 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 on by a qualified electrician before you start using it.

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.

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

Item	Size	Quantity	Cost
3 core 2.5mm (twin and earth) (sockets)	50m	1	£28
Sockets – double 13A switched	NA	5	£22
35mm Double Pattress box	35mm	5	£6
63A 4 way Consumer unit	NA	1	£37
3 core 1.5mm² Twin & earth cable (lighting)	25m	1	£12.50
10A 1 way White Single Light Switch	NA	1	£2
White Batten strip light 43W 4400lm	1.2m	2	£72
TOTAL			£179.50

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

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. 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

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. I’ve recently built another garden office using a flat pack kit from Garden Buildings Direct. This can simplify the self-build process, saving you time, but it will cost a little more. This DIY garden office and the virtual office mean I can work from home, whilst also feeling like I’m at the office.

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 for the overall construction.

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.

Planning

Location Considerations Before You Build

Head into the garden with a tape measure and sketch out possible locations. Keep these points in mind:

• Is the ground level, or will groundwork / a base frame be needed?
• Check for obstacles (trees, drains, pipes, cables).
• Consider door position and sun direction.
• Leave access around all sides (aim for 50cm minimum) for building and future maintenance.
• Will you need a path to avoid mud in wet weather?
• Avoid building under trees if possible (leaves and debris cause extra maintenance).
• Plan size around standard sheet materials (2440 × 1220mm) to reduce waste.
• Think about electrics early; longer cable runs from the house increase cost.

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 on which to build.

• 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

Do you want to build your garden office on a slope or uneven ground?

Take a look at my recent guide, where I show you how to build a shed or garden office base on a sloped garden. This in-depth guide covers everything you need to know, from levelling ground to building a wooden-framed base on a steep slope.

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 I would recommend:

• 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 an 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 this shiplap cladding from Wickes. 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 instructions below for this style of 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 overhang you want on the roof. A roof with a decent-sized overhang will provide more protection from rain than a small overhang. My roof overhangs each edge by about 30cm, which is a little more than most sheds, but it protects the walls from the elements.

Materials

I’ve listed the materials I used, but feel free to upgrade or downgrade to suit your needs. For example, I chose higher-grade insulation for soundproofing and a more basic breathable membrane, which you may want to upgrade.

Why use a breathable membrane?
It keeps the weather out while letting moisture escape, helping prevent damp and mould.

Using reclaimed materials can significantly cut costs, though sourcing takes time. Search for local reclaimed wood suppliers or “wood recycling project” in your area.

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. If you don’t have a suitable vehicle for collecting large items, then you’ll need to hire a van, which can cost as little as £75 a day. I buy most of these materials from Travis Perkins, but you can shop around for the best prices.

Material	Size	Application	Quantity	Cost
18mm OSB 3 board	2440x1220mm	Flooring	4	£82
9mm OSB 3 board	2440x1220mm	Walls and roof	20	£310
CLS studwork 2.4m	38x63x2400mm	Flooring, walls & roof	40	£100
CLS studwork 3m	38x63x3000mm	Flooring & walls	8	£54
Upvc french doors	1190x2090mm	Doors	1	£480
C16 stick timber	95x45x3600mm	Roof ridge	1	£9.39
C16 stick timber	70x45x3600mm	Roof supports	5	£55.25
Plasterboard screws	3.5x35mm	Secure plasterboard	1000	£6.54
3m Shiplap cladding	119×14.5mm	Cladding outer wall	44	£231.88
12.5mm Plasterboard	2440x1220mm	Internal walls	25	£190
Rockwool RWA45 insulation	1200x600mm	Walls & roof insulation	8 packs	£259.94
80mm screws	5mm x 80mm	Stud walls & flooring	300	£12.57
Water vapour barrier	4m x 25m	Walls and roof	1	£15
90mm posts	90x90mmx2.4m	Corner posts	2	£30.60
Felt roofing (green)	10m x 1m	Roofing	2	£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.

Tools

If you’re not fully tooled up yet then consider the following to make this job both quicker and easier.

• 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.

You don’t necessarily need all of these tools, but they will help you build with higher quality and speed. I have recommended some of my favourite tools, which are Dewalt. I think this is a good quality brand alongside Makita. But it’s up to you what you use.

Planning Permission

Most garden offices fall under permitted development, but rules do apply. Always check the UK Planning Portal, your property deeds (for covenants), or your local planning authority before building. Getting it wrong could mean having to remove your structure.

Key permitted development rules (summary):

• Not allowed on listed buildings or in front of the house
• Not allowed to the side of a house on designated land
• Must not cover more than 50% of your garden (including other extensions/outbuildings)
• Must be single storey
• Max height: 4m (dual pitched), 3m (other roofs), or 2.5m if within 2m of a boundary
• Cannot be self-contained living accommodation
• Extra limits apply in National Parks, AONBs, World Heritage Sites & the Broads

👉 Read the full planning guide here: Do You Need Planning Permission for a Shed?

How Much Does it Cost to Build a Garden Office?

Professionally installed garden offices of this size will cost on average £15,000 to £20,000, depending on where you live. You can also self-build a professional-quality garden room with my detailed plans and instructions. By removing the labour costs of a build, you save about 50% of the price.

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.

More About my Professional Quality Garden Room

The download includes access to detailed drawings and cross-sections.

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Did you enjoy this post about my garden office build? Have a look at some of my other home and garden DIY projects:

• How to build a shed base on uneven ground
• How to build your own decking area
• How to build a veranda
• How to lay porcelain tile patio
• Build a scaffold board walkway
• BillyOh Kent Log Cabin review and step by step build guide