Hello and welcome to my free garden room plans for this 5x4m build. I’ve spent hours drawing up these garden room plans to share with like-minded DIY enthusiasts like you. These self build garden room plans have been carefully designed for DIY enthusiasts who want a professional-quality garden room without paying contractor prices. If you have basic tools, some spare time, and a reasonable budget, this step-by-step guide will walk you through the entire build process from foundations to finished interior, using proven construction methods for a strong, durable, and long-lasting garden room.
You can also find loads of free guides that take you through the entire build process on my DIY Garden Room Resource page. It’s full of free information that will ensure you get your garden room built to a very high standard.
Table of Contents
- What’s Included in These Free Garden Room Plans?
- Try the Paid Plans
- 5×4.5m (16x14ft) Insulated Garden Room Build – Full instructions, Plans & 3D SketchUp Model
- Access Interactive 3D Models
- What You Get Free vs Paid
- How Much Will it Cost to Build This 5x4m Garden Room?
- Download the Free 16-page PDF Garden Room Build Guide
- How to Build a Garden Room Base
- Building the Base Frame
- Building the Garden Room Walls
- Building the Garden Room Roof
- Adding the Wall Boards, Doors and Windows
- Electrics for Your Garden Room
- Breather Membrane
- Furring Strips for Cladding
- Cladding the Garden Room
- The Window and Door Framing
- Fitting the Waterproof Roofing Material
- Finishing the Interior
- Materials List for this 5x4m Self-Build Garden Room
- Common Mistakes to Avoid When Building a Garden Room
- Do You Need Planning Permission for This Garden Room?
- Garden Room Plans FAQ
What’s Included in These Free Garden Room Plans?
Within this article, I will show you a step-by-step guide to complete this garden room. I’ll also include a list of tools, materials and some detailed drawings and plans so you can see some of the finer detail in the creation of this amazing building. Before getting started on your garden room build, be sure to check if you need planning permission.
What’s not included in the free version:
- Access to the interactive 3D model.
- A full material and cut list for each stage of the build.
- A full printable materials list and quantities for the whole project. (To send to suppliers for up to date cost quotations).
- A printable garden room plan PDF document, guide and instructions.
- Detailed step-by-step instructions for each stage of the build process.
- Email support. If you get stuck or have questions about the build you can contact me for guidance.
Try the Paid Plans
5×4.5m (16x14ft) Insulated Garden Room Build – Full instructions, Plans & 3D SketchUp Model
Save 50% on build costs (up to £20,000) with these detailed instructions, plans and 3D models. Exact measurements: 497cm X 446cm (5×4.5m) All measurements are metric. (m, cm & mm)
These self-build garden room plans are ideal if you:
- Want to build your own garden office or studio
- Have basic DIY tools
- Want professional-grade construction without contractor costs
- Prefer downloadable PDF plans
Access Interactive 3D Models
What You Get Free vs Paid
Free Plans vs Full Paid Guide
| Feature | Free | Paid |
|---|---|---|
| Drawings | ✔ | ✔ |
| Step-by-step Instructions | Basic | Full |
| PDF Plans | ❌ | ✔ |
| Cut Lists | ❌ | ✔ |
| Interactive 3D model | ❌ | ✔ |
| Complete Materials List | ❌ | ✔ |
| Email Support | ❌ | ✔ |
How Much Will it Cost to Build This 5x4m Garden Room?
Before I scare you will the cost for this garden room, please bear in mind the total cost will include:
- Foundations and ground works
- Timber (Framework, sheet materials and cladding)
- Windows and doors
- Insulation
- Electrics (Sockets and lighting)
- EPDM roofing
- Internal finishing (Plaster, flooring and painting)
I’d also like to point out the potential savings here on labour. If you decide to take on this challenge yourself, then you will save roughly 50% of the total cost. For a garden room of this size and professional quality finish, you should expect to pay between £10,000 and £15,000. Hire a professional garden room company, and you could be in the region of £30,000. That’s a saving worth considering. That’s why I think my paid guide is worth considering. It’ll give you everything you need to complete this build on your own.
Download the Free 16-page PDF Garden Room Build Guide
Get started with this free 16-page PDF guide. Enter your email and I’ll send you the guide free of charge. It’ll get you on course to building your very own garden room office or studio in no time.
If you’re on a budget, check out my budget garden room build guide, where you can build an insulated garden room for under £6k.
5m x 4m Garden Room – Project Overview
| Feature | Specification |
|---|---|
| External Size | 5m x 4m (16ft x 13ft) |
| Internal Use | Office, studio, gym, hobby room |
| Wall Thickness | 140mm insulated |
| Roof Type | Cold flat roof |
| Cladding | Cedar / treated timber |
| Foundation Type | Timber base on pads/screws |
| Build Time (2 people) | 7-14 days DIY |
| Skill Level | Intermediate DIY |
How to Build a Garden Room Base
There are a number of ways to achieve this but I’m going to show you how to build a wooden frame base that will be suitable for most builds. Whether your plot is on a slope or even surface this will provide a good solid base to support your garden room.
- Start by clearing the ground where your garden room will be situated. Remove debris, plants and any type of vegetation. Leave a suitable 500mm gap between any boundaries and obstacles.
- Measure the area and mark the four corners of your building plot. You can use sticks, bricks or spray paint to achieve this.
- Use string and spikes to mark out the perimeter of the building. Adjust the corner spikes by measuring equal distances from corner to corner.
- Once the foundations are in place use a weed protective barrier to cover the floor. This will prevent invasive plants from growing into your building.
Garden Room Foundations
You can build the wooden frame on one of these foundation types:
Ground screws
These can be screwed into the ground and adjusted according to the required level.
Breeze block or concrete block pillars
These can be useful for gardens with sloping terrain.
Wooden post supports
These are the quickest and cheapest option for your garden room foundation but must be treated with creosote to protect from rot. You’ll also need to ensure good runoff and drainage. I personally would recommend another option as the life expectancy of this method will be far less than the other methods.
Building the Base Frame
The timber frame is constructed from a kiln-dried 47x150mm C24 construction timber. Spacing between rafters will be about 400mm. The timbers are 4.8m and 4.2m long joined with 3 large 100mm screws. The top is finished with 18mm OSB boards or if you want a higher standard finish, 22mm Egger Protect boards.
Insulating the base
I’d recommend using a 100mm thick insulation board. These can be cut using a panel saw and pushed between the joists. I recommend using these Celotex insulation boards:
Finishing the base with flooring boards
The final job for the garden room base is to secure durable flooring. The are two options here. The cheaper 18mm OSB board or a slightly more expensive TG4 chipboard flooring. I would recommend TG4 for a garden room.
or
Building the Garden Room Walls
Once the foundations and base are complete, it’s time to construct the walls. We’ll use 38x89mm CLS timber. Again, the spacing between timbers will be 400mm. A steel hollow beam is used above the large bi-fold doors to ensure the roof’s weight can be supported without impacting the doors.
The front walls are 100mm taller than the back walls to ensure there is suitable water run off on the roof. The window openings are set 5mm wider (in each direction) than the window frames to allow for easy installation.
Building the Garden Room Roof
Due to the large roof span and height restrictions (2.5m) we need to double up some 47x150mm C24 timbers. The timbers will be bolted together using 100x8mm nuts and bolts located in equal spacing along the beam.
Noggins and an outer frame can be added once the main support beams are in place.
Now, the roof boards can be secured onto the roof frame. For this, we use 18mm OSB T&G boards that measure 2400x600mm. The boards can be secured using 50mm screws in several locations.
Adding the Wall Boards, Doors and Windows
The walls need to be boarded using 18mm thick OSB3 boards. Simply attach the boards to the exterior walls and secure in place with 50mm screws. Cut out sections for windows and doors as required using a jigsaw or circular saw.
The doors and windows can be added at this stage and secured to the wall frames. Read the supplier’s installation instructions for the correct fitting. Use tech screws to secure the doors to the steel beam. Tech screws are self-tapping screws designed for easy installation into steel.
Electrics for Your Garden Room
Now is the ideal time to consider installing the electrical system in your garden building. If you’re not confident or qualified to handle tasks like wiring sockets and lighting, it’s safest to hire a professional electrician. Make sure to bring them in before you begin installing insulation and interior wall panels.
Breather Membrane
With all the boards in place on the walls it’s now time to cover them with a breathable membrane. (On the outside) This will prevent moisture from reaching the OSB boards and allow air circulation.
The breather materials can simply be stapled onto the boards. Ensure a 100mm overlap between layers. Normally available in 1.5m x 25/50m rolls.
Furring Strips for Cladding
In the next step of this guide, we’ll focus on furring strips, which are crucial for supporting the cladding and ensuring proper ventilation between the boards.
For vertical cladding, furring strips are installed in two layers: one set vertically and the other horizontally. If you’re installing horizontal cladding, you’ll only need vertical furring strips. It’s important to avoid attaching horizontal furring strips directly to the breather membrane, as this can trap moisture and lead to issues over time.
Cladding the Garden Room
The first step in cladding your garden room is choosing the right material. There are plenty of options available, so your decision will largely depend on your budget.
If your budget allows, Western Red Cedar is an excellent choice. It’s a naturally oily wood with outstanding moisture-resistant properties. While it will still require treatment, it tends to last much longer than other materials.
For a more budget-friendly option, pressure-treated pine is a solid choice. It comes in both loglap and shiplap styles, offering a durable and cost-effective solution.
The Window and Door Framing
Using a 22mm thick timber, measure and cut four pieces to fit into the window frame for a tidy finish.
Fitting the Waterproof Roofing Material
To achieve a watertight roof, you’ll need to install an EPDM rubber roofing system. These systems are available as kits that typically include a large rubber sheet, adhesive, and edge trim for securing the perimeter. For the best results, follow the manufacturer’s installation guidelines carefully. Here’s a helpful example video that clearly demonstrates the installation process.
Materials and Tools Needed
- EPDM roofing kit (rubber membrane, adhesive, and edge trim)
- Soft-bristle broom
- Roller and brush for adhesive
- Utility knife
- Measuring tape
- Protective gloves
Step 1: Prepare the Roof Surface
- Clean the surface – Ensure the roof deck is clean, dry, and free of debris. Sweep it thoroughly with a broom.
- Inspect the deck – Check for any loose boards, nails, or damage, and repair as needed. The surface must be smooth and secure.
Step 2: Measure and Cut the EPDM Membrane
- Unroll the EPDM membrane over the roof, allowing it to overhang the edges by at least 150mm (6 inches).
- Leave it to rest for 30 minutes to relax and reduce any wrinkles.
- Trim the membrane to size using a utility knife, but keep the overhang intact.
Step 3: Apply the Adhesive
- Fold back half of the membrane to expose the roof surface.
- Apply the adhesive evenly across the exposed roof deck using a roller or brush, following the manufacturer’s instructions.
- Allow the adhesive to become tacky (as per guidelines) before carefully laying the membrane back into place.
- Smooth the membrane with a soft-bristle broom, working from the center outward to remove any air bubbles.
- Repeat the process for the other half of the roof.
Step 4: Secure the Edges
- Apply adhesive to the edges and fold the membrane over, ensuring a tight seal.
- Attach the edge trim supplied in the kit to secure the membrane along the perimeter of the roof.
Step 5: Finishing Touches
- Trim any excess membrane with a utility knife.
- Inspect the entire roof for any wrinkles or air pockets, smoothing them out as needed.
- Check the edges and seams to ensure they are fully adhered and sealed.
Tips for a Successful Installation
- Perform the installation on a dry day with mild temperatures.
- Avoid stretching the membrane too tightly; it should be laid flat but not under tension.
- Follow all manufacturer instructions for adhesive curing times and application techniques.
Finishing the Interior
So far we have learnt how to build a garden room structure and make it water tight, but now it’s time to turn your attention to the interior. Hopefully, you now have all the electrics installed and can start fitting the insulation and plasterboard.
For the insulation, I’d recommend using two types. The first has great thermal protective properties whilst the second is great for acoustic insulation.
- Celotex insulation board – GA5040
- Rockwool RWA45 40mm
To help demonstrate how the entire wall looks I have created this cross section diagram.
This cross section view from the interior shows the following materials. Starting from the outside:
- Western red cedar cladding
- Furring strips (horizontal)
- Furring strips (vertical)
- Breather membrane
- 18mm OSB 3 board
- CLS timber frame (38x89mm)
- Celotex GA4050 (50mm thick)
- Rockwool RWA45 (40mm thick)
- Polythene vapour barrier
- Plasterboard (12.5mm thick)
- Skimmed plaster
- Paint of your choice
The same type of insulation can be used for the roof. The polythene vapour barrier is essential to stop any moisture reaching the plasterboard and plastered walls. This is available in large sheets and can be stapled to the walls and ceiling.
Electrical wiring can be cut into the insulation allowing for socket backboxes etc.
Materials List for this 5x4m Self-Build Garden Room
Here are all the materials required to complete this build. Use the links to find current stockists.
I’ve managed to cover a high level of information in this guide which should give you enough to plan and start your project.
Self Build Plans vs Garden Room Kits
| Self Build Plans | Prebuilt Kits |
|---|---|
| Much cheaper | Expensive |
| Customisable | Fixed sizes |
| Learn skills | No learning |
| Upgrade anytime | Locked design |
Common Mistakes to Avoid When Building a Garden Room
Over the years, I’ve seen a few common mistakes crop up when people attempt to build their own garden room. I’ve even seen this first-hand when my neighbour built his garden room. The structure looked great from the outside, but a few hidden shortcuts caused problems later on. Taking the time to get these details right from the start will save you money, frustration, and repairs down the line.
Skipping a vapour barrier
A vapour barrier is essential on the warm side of the insulation to stop moisture from reaching plasterboard and internal finishes. Without it, condensation can build up inside the walls and ceiling, eventually leading to damp, mould, and damaged materials.
Using undersized joists
Trying to save money by using smaller timber than recommended can result in sagging floors, bouncy walkways, and long-term structural issues. Always follow proper span tables and use correctly sized joists for the floor and roof to ensure strength and rigidity.
Poor drainage around the base
Water pooling around the base of a garden room is a recipe for rot. Make sure the ground slopes away from the building, install adequate drainage where needed, and avoid trapping moisture beneath the structure.
Do You Need Planning Permission for This Garden Room?
All of my garden building designs keep within the permitted development height and size restrictions. To check if you need planning permission for your specific house and garden visit me comprehensive guide: Do You Need Planning Permission for a Garden Room?
I hope you found this guide and information helpful. Please consider buying me a coffee to help support more free content on my site.
Thanks for reading. Please feel free to ask any questions in the comments section and I’ll respond ASAP.
What you get from my full paid guide:
- Access to the interactive 3D SketchUp model.
- A full material and cut list for each stage of the build.
- A full printable materials list and quantities for the whole project. (To send to suppliers for up to date cost quotations).
- A printable garden room plan PDF document, guide and instructions.
- Detailed step-by-step instructions for each stage of the build process.
- Email support. If you get stuck or have questions about the build you can contact me for guidance.
Thanks for your support
Garden Room Plans FAQ
Can I download these garden room plans as a PDF?
Yes. These free garden room plans include a downloadable PDF with the key drawings and dimensions for the 5m x 4m build. If you want printable cut lists, full quantities, and detailed step-by-step instructions, those are included in the paid version.
Are these garden room plans really free?
Yes — the core plans and guidance in this article are free to use. The optional paid upgrade includes extras like the interactive 3D model, full materials and cut lists, and printable documents you can send to suppliers for quotes.
What size is this garden room build?
This design is a 5m x 4m (approximately 16ft x 13ft) garden room. It’s ideal as a garden office, studio, gym, or hobby space and is designed to be fully insulated for year-round use.
Are these self build garden room plans suitable for beginners?
If you’re confident using basic tools and you’re happy measuring, cutting, and building accurately, you can follow this guide as a DIY project. It’s best suited to an intermediate DIY level, but many beginners succeed by working slowly, keeping everything square, and getting help for heavy lifting and electrics.
Do I need planning permission to build this garden room?
Many garden rooms can be built under permitted development rules, but it depends on factors like height, location in the garden, boundaries, and whether your property has restrictions. Always check current guidance for your area before you start.
What foundations work best for a garden room?
Common options include ground screws, concrete block piers, or a timber base supported on pads or posts. The best option depends on your soil type, slope, access, and drainage. The key is a level base with good airflow and water runoff.
Are garden room plans the same as summer house plans?
Not usually. Many summer house plans are designed for occasional use, while this garden room build focuses on insulation, vapour control, and weatherproofing for year-round comfort — more like a garden office or studio.
How much does it cost to build a 5m x 4m garden room?
Total costs vary depending on cladding, glazing, insulation level, electrics, and interior finish. As a rough guide, a DIY build is often significantly cheaper than hiring a contractor, especially if you already own tools and can do most of the labour yourself.
