garden room interior

How to build a modern garden room (on a budget)

Today I’m going to take you through, step-by-step how I built this beautiful garden room for under £5.5k. It’s a fully functioning insulated garden room with electrical sockets, lighting, double glazing, a decking area and a proper interior finish. We use it as a multi-purpose space. Somewhere we can work, exercise and relax away from the noisy family house.

garden room interior

This building can be constructed on your own but I had a little help from an electrician and a plasterer. I hired these two professionals as I’m not qualified to sign off the electrical work and I’m no good at skimming walls with plaster. I wanted to make sure the space was finished to a high standard.

DIY garden room for less than £6k

Modern log cabin garden room design

This building design style is a modern twist on the traditional log cabin look. It’s part of a range of garden rooms from BillyOh or Garden Buildings Direct. This specific model is the Kent garden office. It comes in kit form for DIY construction at home. You could hire someone to build it for you but it’s much more fun doing it yourself.

The kit comes as a basic shell which includes the floor, walls, roof, windows and doors. You can customise it by size, wall thickness, floor and roof thickness, and the type of windows and doors you want. (single or double glazing, modern or traditional)

I have taken this basic shell and converted it into a fully functional garden room. To do this I’ve added electrics, laminate flooring, cladding ceiling, insulation and plasterboard. It’s all been skimmed with plaster inside with a painted finish to make it look and feel like a real interior.

Here’s a list of materials I used for the main structure and some links to where I purchased them:

BillyOh Kent garden office kit1
Foil-backed insulation roll – 14m1
C24 Kiln Dried Regularised Sawn Treated Timber 47mm x 150mm x 4.8m4
C16 Kiln Dried Regularised Sawn Treated Timber 47mm x 150mm x 3.6m9
Treated Incised UC4 Fence Post Green 100mm x 100mm1
Blue Circle Ready to Use Postcrete 20kg4
Gravel and Shingle Trade Pack 20mm4
4Trade Creocote Dark Brown 4L1
Bullet Gold Wood Screw 5.0 x 100mm Box of 2001

Here is how I built this garden room in a step-by-step guide.

Budget DIY garden room construction guide

Step 1. Location

Step 2. Building the wooden frame base

  • The wooden frame was bigger than the size of the garden room as I wanted a small decking area around the building.
  • I used 150x47mm construction timber for the frame. These were cut to size and screwed together.
  • The frame was supported by several 100x100mm posts.
  • The posts were set in Postcrete about 600mm into the ground. Gravel was placed at the bottom of each post hole to add a strong footing. The posts were treated with Creosote to prevent rotting.
  • The frame was covered with weed protective material. This can be done under the frame or over the frame.

Step 3. Setting the bearers for the building

  • The kit comes with bearers but I double up the number to help support the walls and flooring on this wooden frame base. (25x50mm timber)
  • The bearers were laid out in equal lengths from each other.
  • I screwed the bearers to the wooden base to prevent movement whilst building the walls.

Step 4. Building the walls

  • The first wall sections are fitted to the floor.
  • It’s very important to refer to the technical drawings and make sure the walls are spaced out correctly, especially the door opening width.
  • The walls all need to be set at right angles from each other.
  • Once the first wall sections have been placed the rest simply slot into each other.
  • The window frames come pre-constructed and should easily slot into the openings.

Step 5. The flooring

  • About halfway up the wall construction I decided to lay the flooring. This would make it easier to manoeuvre around the building to complete the rest of the build. (Rather than balancing over the bearers.)
  • I first added a layer of foil backed bubble insulation over the bearers. (Not included in the kit.)
  • The 18mm floorboards were then nailed into place over the insulation.
  • I cut a hole in one of the floorboards for the electrical wire to feed through.
flooring with insulation

Step 5. The roof construction

  • With the walls completed the roof rafters are fitted first and secured into place with screws.
  • I placed a layer of foil-backed insulation over the rafters. (Not included in the kit.)
  • The 18mm roof boards can then be screwed into place. I used a ladder for the first 10 or so boards and I then climbed onto the roof to complete the rest.
  • The roof was covered with roofing felt which is provided with the kit. This can be upgraded to shingles when purchasing the kit. Or you can upgrade to you own personal preference. Rolls of roofing felt are the cheapest option.
roof rafters

Step 6. Fitting the doors and windows

  • You’ll need a little carpentry skill to fit the door furniture. A hammer and chisel will be required to fit the locking mechanism.
  • The hinges, handles and locks are all secured to the frames with screws.
  • Take your time to ensure a good fit here.
  • The doors are heavy and you might require some help here to support them whilst screwing in place.
doors and windows for garden room

Step 7. Fitting the fascia boards and painting the outside

  • The fascia boards will need to be cut to length.
  • They can be nailed or screwed into place. I prefer a screw but a nail looks neater.
  • Finish off the exterior with 2 or 3 layers of paint. Ensure you get good coverage to protect the building for as long as possible.

Step 8. The decking around the garden room

  • Adding decking provides a good platform around the building for easy entrance and an outdoor seating area.
decking for garden room

This completes the main structure of the garden room.

garden room structure complete

The next task is to insulate, add electrics and finish the interior. For this you will need the following materials:

25x50mm timber battens – 4.8m15
25mm Celotex insulation boards12
12.5mm plasterboard – 2440x1220mm11
50mm drywall screws200
11m interior cladding12m2
Paint – 10L1
Laminate flooring – 12m square1
Flooring underlay – insulated – 1x15m1
Skirting of your choice – 14m1
Electrical Materials
Electrical cable 3 core 2.5mm (sockets) – 10m1
Electrical cable 3 core 1.5mm (lighting) – 10m1
Electrical junction box1
Light switch1
Light fittings – your choice2
SocketsUSB socketsany
Metal consumer unit – 2 way1
Armoured cable – size and length dependant on requirements
(Speak to an electrician about your garden room)

How to insulate your garden room

Step 9. Adding a timber frame for the insulation and plasterboard

  • To support the plasterboard over the insulation I first add a timber frame around every corner of the building. Use the 25x50mm timber for this.
  • These are simply cut to length and screwed onto the wall using wood screws.
  • It’s best to pre-drill holes so that the wood doesn’t split.
garden room interior works

Step 10. Fitting the insulation boards

  • The insulation boards can now be cut using a sharp knife and placed onto the walls. A hot glue gun can be used to help secure the boards to the walls.
  • Complete this on all the walls first.
  • Save any off-cuts for the ceiling later on.
garden room insulation

Step 11. Installing the electrics

  • Now is the perfect time to add all the electrical wiring for the project. Electrical safety is of utmost importance here.
  • If you are unfamiliar with this, please hire a professional electrician.
  • I cut small trenches into the insulation boards to run the wires.
  • The consumer unit can be placed anywhere, but the back wall was perfect for this.
  • The light switch is located by the door and controls a wall light at either end of the room. you can choose what kind of lighting you want for this project.
  • Make sure you leave enough length on the electrical cable to wire up the sockets and lighting fixtures.

Step 12. Fixing the plasterboard

  • Fitting the plasterboard over the electrical cable and insulation is next.
  • Cut the boards to size and fix using the drywall screws.
  • Cut the holes for the electrical sockets, switches and lighting fixtures.
  • Pull the electrical cabling through the holes.

Step 13. Skimming the walls with plaster

  • I hired a plasterer for this job. It took him about 5 hours to complete the job.
  • I let the plaster dry for about a week

Step 14. Fitting the ceiling cladding

  • The first job was to cut and place insulation in the ceiling. I used the same 25mm Celotex boards as the walls. (including any off-cuts from the walls)
  • I ran 25x50mm timber down each of the rafters to support the cladding.
  • I then cut and nailed the cladding boards into place.

Step 15. Painting the interior

  • Starting with a watered-down emulsion paint I completed a layer. I mixed the paint/water 50/50. this is to prevent the paint from drying on the fresh plaster and cracking.
  • Then completed a second layer
  • And a third

Step 16. Fitting the laminate flooring and skirting

  • I used a roll of gold foil-backed underlay for this job.
  • The laminate flooring was then cut to size and fitted leaving a 10mm gap around the edge. Take a look at Flooring Hub for an extensive range of laminate flooring. We found the perfect flooring at the right budget for this build.
  • The final step was to fit the skirting board around the edges.

All that’s left to do is add some furniture.

BillyOh garden office interior

This completes the build. Hopefully, I have provided enough information here for you to complete your own DIY garden room. You can take a look at my in-depth guide on this other article.

DIY garden office

You’ll save a load of money by completing this job yourself and buying the BillyOh log cabin kit.

This build has proven to be a great project so far. The insulation seems to be doing the trick although I’ve only been able to test it in the summer so far. It keeps the whole room nice and cool even in the hottest weather. The real test will come this winter. Update to follow.

Final word

If you are looking for a garden room for your property, this is a great way to accomplish it on a budget. Hiring a garden building company will cost you more than double for something the equivalent size. This DIY garden room can be accomplished by anyone who has the interest and desire to build their own unique outdoor building.

My full guide and review of this build can be found here if you require a little more detail. Also, Feel free to leave a comment in the section below and I’ll do my best to respond asap.

Good luck with your project. Why not try one of my other garden-building ideas to transform your outdoor living space? Any of these projects will add value to your property and create a beautiful outdoor space that can be enjoyed all year round, whatever the weather.


  1. Hi Ben, thanks for sharing – this is so helpful, as we’ve ordered a BillyOh kit and planning to insulate and finish interior ourselves. Just wondering how the insulation held up over the winter months? Did the cabin stay warm? Thanks!

    • Hi Naomi. The cabin stays warm up until mid/late Nov but Then it needs a heating source to keep it warm. I’m looking to install a mini log burner soon for comfortable use all year round. If you plan on using yours all year round I’d also advise installing some slightly thicker insulation (50mm at least) and 100mm under the floors to ensure a warm cabin throughout the winter. Hope this helps. Ben

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