Can you insulate your garden shed kit?
Yes, and most owners who spend real time in their shed insulate the roof and the floor. Here is exactly how each one is built up, what to buy, and why the walls are a different story.
In a hurry?
The short version
Your shed is solid wood, 1 1/8" to 1 3/4" thick, single wall, and it does not come insulated. The wood alone buffers enough that a space heater keeps it comfortable down to around 40°F. If you want more than that:
Insulate the floor
The insulation goes between the floor joists as the floor goes in, then floorboards on top, with an optional plywood subfloor between. Two slightly different methods depending on your foundation.
Insulate the roof
A grid of 1x2, 2x3 or 2x4 studs on top of the roof boards, insulation in the cavities, plywood over the lot, then your roofing. Deeper stud, thicker insulation.
Leave the walls
Roof and floor together get you roughly 20°F to 100°F, and at this size wall insulation is usually unnecessary. It can be done, but only after the building has settled.
Everything below is the detail: the two floor methods, the roof build-up including what happens at the fascia, the wall procedure for those who want it, and honest numbers on what insulation actually changes.
First, the one thing that governs everything
Your shed is alive
There is no stud frame in these buildings. The walls are machined tongue and groove boards that stack and interlock, and they are meant to float: through the year the wood takes on and gives off moisture, and a wall moves vertically by roughly 1/2" to 2" as it does.
That single fact is why the floor and the roof are straightforward to insulate and the walls are not. The floor sits below the movement and the roof sits above it, so both can be built up freely. Fix a rigid grid across the wall boards, though, and the wall can no longer settle, so gaps open between the courses instead.
It is the same reason we ask you to use flexible conduit for any electrical run through a wall. Nothing rigid should ever span the courses.
What this means in practice
Floor and roof insulation are part of the build, done as the shed goes up. Wall insulation is a separate job for later, after the structure has settled, and most people never need it.
Part one
Floor insulation
The insulation always ends up in the same place, in the cavities between the floor joists. How you get a surface for it to rest on is what changes with the foundation.
The simplest case
On a concrete slab or pavers
- Lay out the floor joists exactly as the assembly manual shows.
- Fill the cavities between the joists with your insulation.
- Either install the floorboards directly over the joists and insulation, or add a layer of plywood as a subfloor first and fasten the floorboards to that.
Two things worth doing because you are insulating. Lay a vapor barrier over the concrete before the joists go down. Better still, run pressure treated 2x4s perpendicular under the floor joists and set the joists on top, which keeps air moving under the building the way a bare floor does. Those 2x4s add about 1.5" to the overall height of the shed, and they do not raise the floor inside.
Blocks, piers or similar
On a treated wood grid
- Cover the treated wood grid with plywood, so the insulation has a surface to rest on. If you are using foam board, brackets fixed to the foundation beams are enough to carry it instead.
- Fill the cavities with insulation.
- Install the floorboards directly over the foundation beams and insulation, or add a plywood subfloor first and fasten the floorboards to that.
If it is easier, cover the wood grid with plywood to make one solid platform and then follow the concrete method above. It comes to the same thing.
Part two
Roof insulation
The roof boards that come with your kit stay exactly where they are. Everything else is a sandwich built on top of them, and it all goes on before your roofing material does.
Build the grid
Frame a grid of studs across the whole roof surface, on top of the roof boards supplied with the kit.
Fill the cavities
Pack every bay of the grid with your insulation.
Close it up
Cover the whole surface with plywood or other wood boards, then install the roofing material of your choice on top.
Stud size is your insulation thickness. Use 1x2, 2x3 or 2x4 lumber for the grid. Each one allows incrementally more insulation than the last, so choose the size that matches the thickness you want rather than the other way round.
What happens at the fascia. Insulation up to 2" thick is still covered by the fascia boards supplied with the kit, so use them as they come. If you go thicker than 2", the kit fascia will no longer cover the edge, so buy a wider appearance board locally, a 1x6 or 1x8 depending on your insulation thickness, and swap it for the front and back fascia provided.
Two things people ask next
Roofing nails. Normally you size the nail to the roof board plus two overlapping layers of shingle. Once there is insulation and plywood up there, nail length stops being critical, because any extra simply runs into the build-up. Almost any sensible length works.
Roofing material. If your shed sits in strong sun and heat, a metal roof with insulation underneath is the combination that reflects the most heat. Asphalt shingles are not the best choice in that climate.
Part three
The walls, and why they wait
Most owners never insulate the walls. Between the thickness of the wood itself and an insulated roof and floor, the space is usually small enough that it simply is not needed. But it can be done, and this is how.
Wait before you touch the walls. Give the building at least 3 months to compress, settle and acclimate, and a full year if you are in a four season climate. Framing the walls before that stops the structure settling and opens gaps between the boards.
After the waiting period
- Frame the walls with 2x2 studs or furring strips, screwed into every single wall board height-wise, so the boards are locked and can no longer float.
- Add the insulation layer between the framing.
- Install siding over it.
- Frame and flash around the doors and windows.
Do it from the outside if you can. Once the boards are locked in place they can no longer adapt by floating up and down, so working from the exterior leaves them less exposed to the swing in climate. It also keeps your spruce interior exactly as it is.
Honest numbers
What insulation actually buys you
Based on what owners report back to us, across a lot of climates.
| How it is built | Comfortable range | What that means |
|---|---|---|
| No insulation, space heater | Down to about 40°F | Fine year round in the Pacific Northwest, the Southeast and similar moderate climates. |
| Roof and floor insulated | About 20°F to 100°F | The usual choice for an office, studio or workshop that gets used all year. |
| Walls insulated as well | Beyond that range | Often unnecessary at this size. Worth it only in genuinely severe climates, and only after the building has settled. |
In deep winter areas an uninsulated shed is best thought of as a three season space. Insulate the roof and floor, add a heat source, and it becomes a year round one.
A word on skill level. These alterations are relatively easy to do, but they are still carpentry, and you need at least average handyperson skills to carry them out. SolidBuild is not liable for injuries or damage to the product that may occur during such installation.
Common questions
Frequently asked questions
Do the sheds come insulated?
No. The walls are solid wood, 1 1/8" to 1 3/4" thick, single wall construction. There is no insulation in the kit, though the wood itself gives a useful amount of natural thermal buffering.
What size studs do I need for the roof grid?
1x2, 2x3 or 2x4, each allowing incrementally more insulation thickness. Pick the size that matches the insulation you want to fit.
Will I need to replace the fascia boards?
Only if your insulation is thicker than 2". Up to 2" the fascia supplied with the kit still covers the roof edge. Above that, buy a wider appearance board locally, a 1x6 or 1x8 depending on the thickness, and swap it for the front and back fascia provided.
Can I insulate the floor and roof after the shed is already built?
The floor insulation goes in as the floor goes down, so it belongs to the build. The roof build-up sits on top of the roof boards and under the roofing, so it needs to happen before the roofing goes on, or the roofing has to come off again.
Why can't the walls be insulated straight away?
The wall boards float. They expand and contract through the year, moving roughly 1/2" to 2" vertically, and the building needs time to compress and settle. Anything rigid fixed across the boards before that stops the settling and opens gaps between the courses.
How long do I have to wait to insulate the walls?
At least 3 months, and a full year is best in a four season climate.
Is roof and floor insulation enough on its own?
For most owners, yes. It takes the building to roughly 20°F to 100°F with a heat source, and at this size wall insulation is often unnecessary.
Does insulating change the height of the building?
The roof gets thicker by the depth of the stud grid you choose. The floor does not rise, because the insulation sits between joists that are already there. If you add pressure treated 2x4s under the joists for airflow, they lift the whole building about 1.5" without raising the floor inside.
Can I run electrical at the same time?
Yes, and it is far easier to plan it before assembly. The one rule that matters here is the same one that governs insulation: use flexible conduit for anything routed through a wall, because the wall moves.
Anything we have not covered? Email info@solidbuildwood.com and we will answer it, and add it here.
Insulating is optional. Plenty of owners run their shed exactly as it arrives, with a space heater in the cold months, and are perfectly happy. If you are planning an office, a studio or a workshop you will use all year, insulate the roof and the floor while the building goes up, and leave the walls unless your climate really demands them.
These are alterations you or your contractor carry out, so results depend on materials, workmanship and local conditions, and local building rules always apply.