Building a shed you can work from home in
Is it still a shed if it has skirting boards?
I cope with uncertainty by starting ambitious projects. During the early months of the pandemic I became a father for the 3rd time, changed job and built a shed.
I am not a DIY enthusiast, I had not made anything from wood since design & tech in secondary school. Watching hours of YouTube videos gave me the false sense of confidence I needed.
If you have the financial means (£10-£15k) I would strongly advise having a professional build your shed. The warm fuzzy feeling of building something myself ran out on the second day of digging foundations. The remaining months of physical exertion (and occasional trigonometry) were only sustained through the dopamine hits of social media attention as I tweeted pictures of my slow progress.
Planning
I’m from a military family and have had the 7 P’s drilled into me from childhood — prior preparation and planning prevents piss poor performance. Having rebelled against this advice for 39 years (and similar missives on admin and timekeeping), I decided to sit down and sketch out my thinking. Never one to miss an opportunity for procrastination, my pencil sketches became a perfectly rendered 3D model.
You probably don’t need to go into the detail of colour matching the materials, but this was a helpful exercise. I was struggling to visualise 2D plans and validate the amount of materials I would need. This approach helped me understand the trade offs between different roof designs, types of timber and how the placement of structural joists/studs related to the sheet materials.
It is at this point you should also check that everything is within your local planning rules. I am not a professional planner, so you’ll need to seek your own advice. The main restriction for my build was keeping the top of the flat roof less than 2.5m above the nearest adjacent bit of land.
The tools and materials that I used
I didn’t have any of the tools I needed. I bought most of these from Amazon or Screwfix:
- Mitre saw and stand
- Track saw and 2.8m rails
- Impact driver and electric drill
- Extra batteries for driver and drill
- Jigsaw
- Electric planer
- Nail gun and air compressor (optional)
- Clamps
- Rubber mallet
- Staple gun
- Special saw for cutting celotex insulation
- Large spirit level
- Small spirit level
- Saw horses
- Plastering hawk and trowels
- Paint brushes
- Stanley knife and blades
- Scissors
The materials will depend a bit on how you build and finish, but I needed:
- Concrete blocks
- Aggregate
- Concrete
- Weed proof membrane
- Treated structural timber (various sizes and large quantity)
- Oriented Strand Board (OSB 3)
- Shiplap cladding
- Rubber roofing kit
- Door and window
- Celotex insulation board
- Mineral wool insulation
- Plasterboard
- Floorboards
- Skirting boards
- Ceiling lights
- Cables, switches and RCD board
- 1000’s of screws & nails, various hangers & brackets, electrical stuff, plastering stuff, paints, glues and other DIY stuff I didn’t know existed.
All told, there was about £4000–5000 worth of stuff needed to build the shed.
Foundations
If you’re lucky you will have a level site, with some solid ground on which to build your shed. I was using my shed to level out a large drop at the end of the garden. I quickly dismissed building a retaining wall and filling a 5m x 4m x 0.6m hole with the required 30 tonnes of material. Instead, my shed was going to balance on high density concrete blocks.
The digging out, compacting, concreting and levelling of all the things took five times longer than expected and two skip loads of material removed from the garden.
Much much later into the process I was grateful for the effort here. Having a level base to work from is incredibly important. Something else to think about here is airflow and drainage, you don’t want your building sitting on the ground or it will quickly rot away.
If you have level ground you can think about making a concrete slab. This would be the foundation for the structure and the floor of the building. A concrete slab wasn’t an option for me, which means some extra carpentry.
Timber floor
This is a point of the build where being precise is going to help you later. The more square the timber floor frame is, the easier it will be to do the walls and then the roof.
Materials
I had a bit of a steep learning curve here. Doing a self design and build means being responsible for the structural integrity of the shed. A 3m x 4m timber clad building is going to be very heavy. My concrete piers meant I needed to pay attention to the gap between supports and what rating & size of timber could manage that span (including the weight of flooring, me being in the shed and anything else I would keep in it… like a 300kg motorcycle). You’ll want to familiarise yourself with:
- Span tables — to help calculate the size and type of timber for spanning gaps
- Timber grading — the difference between C16, C24 and other types of timber. Be careful here, some timber is not meant to be exposed to the elements
- Joist and stud “on centre” spacing — you will be attaching sheet materials to the frames you build, planning your spacing will mean less cutting down sheet materials (less waste and less ££). As far as I can tell this is the original spaces vs. tabs debate, there are loads of explanations on the internet
- Suppliers — you’ll be buying a lot of material, don’t go to B&Q. Your local timber merchant is going to be substantially cheaper. I was paying 50% of the price of a highstreet DIY store for higher rated timber
- Screws — buy good ones, in bulk. I used Turbogold PZ Double-Countersunk screws of various sizes (from Screwfix or Toolstation)
- Joist hangers, brackets and metalwork — buildersmetalwork.com
I can’t emphasis enough — when you’re buying materials, avoid the big DIY chain stores. I was nervous about going to a building supplies and timber merchant, but they were super helpful and gave me loads of advice. They were usually able to deliver the next day too. Similarly, Screwfix or Toolstation are the place to get all the consumable items you’ll need.
Framing the timber floor
There are a lot of videos on YouTube about how to construct a timber frame. How you build the floor will affect the roof height, how walls and floor materials attach, the amount and type of insulation you can use etc.. so make sure you’ve planned ahead.
I built the floor in ladder sections, that then sat inside an outer frame. I over-engineered this part of the shed. I was worried about spanning gaps between pillars and the potential total weight of the building. My foundations were below the level of the adjacent ground, so I had height to play with and could use thicker joist beams than I needed.
The mitre saw and stand did all the cutting, an impact driver and screws fixed things together and a rubber mallet persuaded some reluctant beams into place.
The final floor frame had double beams between each section and around the outside. I put damp proof material between each pier and any timber. It was then concrete bolted to the piers using angle brackets.
The main beams were attached to the frame sections with joist hangers and square twist nails, then noggins were screwed between all the beams. A small block of wood was nailgunned to the bottom of each beam, so that the celotex insulation didn’t fall out the bottom. When all the celotex was in any gaps were filled with foam and exposed timber was painstakingly covered in aluminium tape to make a thermal and vapour proof layer.
Next I laid OSB3 sheets onto the floor frame. This is where planning the spacing on the timber joists is important — with minimal cutting, the sheet material gets screwed onto the joists (roughly 6" spacing on the edges and 12" spacing in the “field”). I then treated the whole deck to a coat of weatherproof decking stain, because I was building during the British summer and there was no way the roof would be on before it rained.
The walls
Building the walls is a lot like the floor.
Making things square using Pythagorean Theorum
This was my first application of Pythagorean Theorem since GCSE maths. Making square buildings out of wood means lots of checking that things are at 90 degree angles. We can do that using the a2+ b2 = c2 formula, or an even simpler heuristic — the 3, 4, 5 rule. On one side of a corner measure out 3 feet and on the other side measure out 4 feet. The line between these two points is the hypotenuse. Jiggle things about until that distance is 5 feet and you know the corner is square. Repeat for all the corners, when you’re happy the wall frame is square use batons to make the frame rigid.
Lifting the walls
Bring a friend, you don’t have enough hands. Lifting heavy timber, making it level and screwing it to the floor is a team sport.
Planning ahead for flat roof design and internal walls
A flat roof isn’t completely flat. Depending on the roofing material you’re using it will need between a 1:80 and a 1:40 slope. How you will achieve this depends on your roof design. I went with a rear wall that was lower than the front (you could use firring strips on top of beams).
The way that the corners of your walls connect will have an impact on the internal stud work, fixing sheet materials and thermal efficiency. This is another YouTube rabbit hole to disappear into. I went with the California Corner method.
Flat roof design
At the planning stage you will have decided if you’re using a warm roof or cold roof design. There are pros and cons to each. For shed building where you’re staying under 2.5m the hardest thing to manage is keeping the internal height useable. I chose a cold roof design, that let me keep a bit more headroom within the overall height of the building. Pay close attention to the design of the airflow gaps and use of vapour barriers — getting this wrong will leave you with a damp and mouldy roof.
Roof joists
Literally and metaphorically a high point of the project. This job was done in blazing sunshine, I was gaining confidence in building things and it was starting to look like a building.
You’ll need to check span tables again and do the maths to decide what size and grade of timber you need for the roof joists. There’s a lot of measuring and checking involved at this point and it’s worth making a jig to maintain spacing between joists. Each end of the joists will also need to be trimmed at an angle to account for the slope of the roof — so you can keep the ends of the joist flat for fixing a fascia board later.
The joists need to overhang the front, rear and sides of the building. Even a modest overhang will give the building a lot of protection from rain water.
Sheet materials
Like the floor, I used OSB3 to cover the roof. You’ll want the smaller size of OSB so that you can lift it onto the roof without cutting it down. Again, your early planning will have made sure the joist spacing is correct for the sheet material you’re planning to use.
Screw everything down well, add the fascia boards around the outside and check that there’s nothing that could snag or tear the roofing material.
EDPM rubber roof
Order a rubber roofing kit from Rubber4Roofs. Enter the dimensions and they will guide you through ordering all the adhesives and trims you need to lay down a roof that will last 50 years.
You will need to pick a day when it’s dry to do this job, me and my brother in law just managed to get it done before a huge downpour tested our workmanship.
Windows, doors and cladding
Framing windows and doors
I built the frames for the windows and doors after the walls were up. This is a job you could do before the walls go up.
There are loads of videos on YouTube that explain how to do this. It’s important to get the details right here because the load of the roof will go through the framing. Get it wrong and the door or window frames could be damaged. If you’re planning fancy bifold doors the lintel will need to be steel, i was on a budget so some doubled-up horizontal joists were more than enough.
Wrapping in a breathable membrane
The building needs to be covered in housewrap. There’s some science here on managing how moisture leaves the structure. This breathable layer goes outside the frame and insulation. Secured with stainless steel staples and a staple gun, with some gaffa tape to seal where it overlaps.
When the whole thing’s wrapped you cut away for the door and windows, leaving enough housewrap to pull through the opening. This needs to be taped over with a specialist sealing tape to make the frame air and watertight.
Hanging a door and windows
I found some mismatched UVPC double glazed units at a local salvage yard for a few hundred pounds. I followed the instructions, used some plastic window spacers and made sure everything was level. Attaching the frame is done by screwing large screws through the plastic frames and into the timber.
If you’re using expensive units, probably best to have a professional fit them.
Cladding
Cladding material costs vary enormously. My dreams of a cedar-clad garden room were quickly forgotten when I saw the cost of the wood. It would have added an extra £2000. I’ve used treated redwood shiplap cladding on the front and treated feather edge board on the sides and back. The cheapest supplier I could find was Ruby Group.
The cladding is mounted to batons to keep an air gap between the membrane and the cladding.
Insect mesh is used at the bottom, top and in between any joins in the cladding. That air gap would be a lovely spot for bees and wasps to build nests.
Did I mentioned the nail gun yet?
You could nail the cladding down by hand. It would take a very very long time and you wouldn’t get to use a nail gun.
Interior
Insulation
With the exterior cladding complete the building is properly weatherproof. My local electrician ran some armoured cable from the house and fitted the internal wiring.
I used celotex to insulate the ceiling (note the air gap for the cold roof design) and cheaper mineral wool for the walls.
This is slow and fiddly work, but effort to plug every gap with material will pay off later. The thermal efficiency of your building is determined by how well you do this.
Plastering
I wanted a finish that felt more like an office than a shed (or a 70’s sauna), so chose to plasterboard and paint the room.
Before the plaster goes up, you need to make an impermeable vapour barrier. This is so that moisture from breathing doesn’t get into the insulation and the timber. The breathable layer on the outside will let moisture escape faster than you add it from the inside. Fix the vapour barrier with flexible sealant and stainless steel staples. Overlap the joins by a few feet, use sealant and then tape for good measure.
Again, there are loads of YouTube videos on how to fit plasterboard. I did miss that a plasterboard lifting machine is a thing. Lifting entire boards by yourself, even with a T-Shaped pole 😂, and fixing them to the ceiling is all kinds of hard work. Use the machine.
Once the boards are up, you use a jointing compound and some paper tape to cover the joins. American YouTube videos will refer to this stuff as ‘mud’. Start with the wall that’s most likely to be hidden from view and by the final wall you’ll have the technique dialled.
The plug sockets were from the middle at Lidl and were £8 each. The 3000 lumen ceiling lights were £20 each on Amazon. All the electrics were done by a professional and have been signed off. I ran and armoured Ethernet cable down the garden too.
A few coats of paint and some laminate flooring. Done 🙌🎉
The sockets are halfway up the wall because I will add some workbenches later. The desk is an old MOD officer’s eBay find. For the internet I’ve got an Ethernet cable going from a mesh WiFi hub in the house to a mesh WiFi hub in the shed.
