Building a prefabricated shed might seem a little daunting for some, but don’t worry, I’m going to show you the step-by-step methods I use when erecting wooden sheds. I was recently hired to build this 7x4ft shed for a customer, so I’ll show you how I achieved this in under 3 hours on my own. If you are still deciding whether a prefab shed is the right option, I’ve also broken down whether it is cheaper to buy a shed or build your own.
In this guide, I’ll show you how to build a prefabricated wooden shed in under 3 hours.
Before you start, it’s also worth checking whether you need planning permission for a shed in your area, especially if you are placing it near a boundary or planning a larger structure.
Prepare a Solid Shed Base
I can’t stress this enough, your base needs to be raised, levelled, and provide suitable drainage. A base isn’t normally supplied with a pre-fab shed, so you will likely need to supply or build your own. Do not build your shed directly onto grass, turf or soil.
This is one of the most common mistakes people make, and it can seriously reduce the lifespan of your shed if done incorrectly. I’ve covered more common DIY mistakes that shorten your shed’s lifespan in another guide.
This customer arranged for a sleeper surround with a hardcore base to be built in preparation for this shed. All I had to do was level it slightly.
What You’ll Need
Before you start the shed build, collect all your materials and open all the packaging. Identify all the components and familiarise yourself with the instructions. Check that all pieces are present before starting the build.
Time required – Allow 3-6 hours to build a pre-fabricated shed like this.
I’m a seasoned shed builder with lots of experience, which is why this build took me just under 3 hours. But there’s no reason why you can’t achieve a similar goal in under 4 hours. Or this could be a half-day job for a couple who are new to DIY.
Can I build a shed on my own? Two people are advantageous on a build like this, but you can manage alone with a few tips listed below.
Difficulty: Beginner–Intermediate
If you are looking to take on a bigger project, I’ve also put together a full guide on how to build a garden workshop from scratch.
What Tools Do You Require?
Here’s a list of tools I’ve used for this job. One tool I would highly recommend to complete this job more easily is a couple of F-clamps. These are like an extra set of hands, Ideal for when you are working alone.
Complete Tool List
- Combi drill – I use a DeWalt DCD776, which is perfect for this job
- Impact driver – I recommend the DeWalt DCF887
- Tape Measure
- Spirit level
- F-clamps – Find good quality f-clamps here
- Hammer
- Utility knife
- Screwdrivers
- Step ladder
Optional Extras:
- Gloves – Protect your hands from splinters etc.
- Wood treatment (paint or stain) – Prolong the life of your shed.
- Clear silicone and silicone gun – Seal windows
How to Build a Pre-Fabricated Wooden Shed – Step-by-Step Instructions
Constructing the Floor
As with all garden buildings, we start with the floor, which is normally made of an OSB or chipboard. This shed came with the floor in three sections, which are located on bearers. The bearers are needed to raise the floor off the floor, preventing it from getting wet. The Bearers are normally treated with a rot-resistant treatment for a long-lasting raised floor.
The best method for constructing the floor base is as follows:
- Lay out the three boards and bearers to find the correct orientation
- Starting from the left, secure the first bearer to the edge of the board.
- Use the correct size nails and a hammer to secure the board to the bearer.
- Align and secure the next bearer to the other side of this board.
- Repeat this process for each board.
Top Tip – As you cannot see through the board to align the centre bearer, use another bearer or a tape measure to line up the nails.
- With each of the bearers in place you can now join all the boards to form one large floor base.
- Attach each section together through the bearer with 60mm screws.
- Ensure the base is moving into the best position, allowing for access around the shed and ensuring the roof will not overhang a neighbouring property.
Top Tip – Use some Creocote Timber Treatment on the bottom side of the bearers to extend the life of the most vulnerable part of your shed. Use a brush to apply a coat of Creocote before continuing the build. This will prevent moisture from damaging the floor of your shed.
Securing the Shed Walls
The next stage is to secure the four walls. It’s important to align and join each wall before we secure them to the floor. this is where a level and flat base makes all the difference. An uneven base will make it difficult to align the walls with each other and the base. When the walls are in place, if there are any gaps, you will need to adjust the floor again to level it.
Top Tip – align and join all walls before securing them to the floor. A flat and level base will ensure good alignment with no gaps.
- Start with the right and rear wall and align them to the base first. (do not secure to the base yet)
- Ensure the cladding over hangs the base. See image.
- Bring the two walls together and hold them in place with one of the F-clamps.
- Secure the two walls together using the screws provided. Usually 50 or 60mm
- Secure in three places.
- Check to ensure there are no gaps between the floor.
- Complete the other two walls with the same technique.
- Align and secure each wall to the next.
- Complete a final check to ensure each wall is aligned to the next and there are no gaps between the walls and the floor.
Top Tip – If there are any gaps between the walls or floor, adjust the base to suit and use an F-clamp to bring the gaps together.
Finally, to finish the wall construction, we will add the corner trim. hammer these into the four corners to provide a water-tight barrier.
Fitting the Shed Roof
The roof for this shed came pre-made, which is a great time saver. I was able to lift this into place myself but ask for help if you can’t manage on your own. These can be the heaviest parts.
- Lift the roof into place
- Ensure all edges align nicely with the walls
- Align the overhang equally on all sides
- Using a step ladder, use the provided screws to secure the roof to the walls from above.
Using an impact driver can save lots of time. See my complete guide to using an impact driver.
Top Tip – Ensure the screws are flush with the roof board to avoid damaging the roof felt when it’s installed.
- With the roof in place, it’s now time to secure all the walls to the floor.
- Using the screws provided, secure the walls from the interior.
How to Fit Shed Roofing Felt
This roofing felt came cut to size in two rolls, but you might need to trim your felt to size. This can easily be done by measuring the roof width, adding 40mm to each end and cutting the felt with a utility knife.
Here is the process:
- Measure and cut the felt to the correct length if required. A utility knife and a straight edge can be used.
- With the felt at the correct length, roll it up again and lift it onto the roof.
Top Tip – it’s much easier to lift the felt onto the roof when rolled up. Trying to lift the felt onto the roof when it’s flat can be difficult and can cause damage to the felt.
- Starting on the lower edge of the roof, roll out the felt and position it equally, ensuring there is a 40mm overhang on all edges.
- Tack the felt into place, using ~60mm spacing between each nail.
- Folder the corners as per below image and tack into place.
- Repeat the same steps for the next piece of felt, ensuring a good overlap between the pieces.
- Tack the felt down the overlap.
Fitting Fascia Boards
Fitting the fascia boards will finish the aesthetic of the shed roof and protect the felt from lifting in high winds.
- Lift each board into place using an F-clamp to help support one end when working alone.
- Secure each board in several locations with either nails or screws.
Finishing the Shed
The final stage of this build was to fit the doors, windows and security fittings.
Fitting the Door to the Shed
- Check the door orientation to atain which way up it fits.
- Lie the door down on the floor.
- Secure the door hinges to the correct side of the door.
- Lift the door into place and secure the hinges to the shed. This can be tricky on your own, but use a wedge to help lift it into place.
Top Tip – A wedge or block of wood can help to lift the door into place when working solo. Ensure the door is high enough in the doorway to cover any gaps. Especially at the top.
- The window perspex panels simply fit into place. Remove the protective plastic layer and slot them into the opening.
- Use the provided trim to secure the panels from the inside. Use the small nails provided.
- Seal the windows from the outside using some clear silicone sealant. (Not provided)
Protecting Your Shed
I’d strongly advise protecting your shed with a wood stain or paint to extend its life. I recommend using this Cuprinol Ducksback 5-year shed paint. It will provide up to 5 years of protection for the wood on your shed.
Final Thoughts
If I am being honest, builds like this are much easier than they first appear. Most of the work comes down to preparation and taking your time with the basics. A level base and properly aligned walls will make everything else fall into place.
This one took me just under 3 hours working on my own, but I have done plenty of these over the years. If this is your first time, do not worry about the time. Take it step by step and focus on getting each stage right. Even if it takes you half a day, you will still end up with a solid shed that will last for years.
Working alone can feel a bit awkward at times, especially when lifting panels or lining things up, but simple things like clamps or a small wedge of wood make a big difference. I still use those little tricks on every job.
Once everything is built, it is well worth taking the extra time to treat the timber properly. It not only improves the look but also protects your shed from the weather, which is what really makes it last.
Hopefully this guide has shown you that building a prefabricated shed is something you can absolutely do yourself. With a bit of patience and the right setup, it is a really satisfying job to complete.
If you are planning your own build and have any questions, feel free to reach out. I am always happy to help.
Discover more from HandymanBen
Subscribe to get the latest posts sent to your email.
